Influence of Damping Sistems on Bueldings Structures

Influence of Damping SystemsOn Building Structures Subject to Seismic Effects Julius Marko May 2006 ii Abstract In order to control the vibration response of high rise buildings during seismic events, energy absorbing passive damping devices are most commonly used for energy absorption. Today there are a number of types of manufactured dampers available in the market, which use a variety of materials and designs to obtain various levels of stiffness and damping. Some of these include friction, yielding, viscoelastic and viscous dampers. These dampers are usually installed between two load bearing elements (walls or columns) in new buildings. In existing buildings, which require retrofitting, they could be installed in cut-outs of shear walls, as evidenced from recent investigations. An effective damping system can result in higher levels of safety and comfort, and can also lead to considerable savings in the total cost of a building. This thesis treats seismic mitigation of multistorey buildings using embedded dampers. Three types of damping mechanisms, viz, friction, viscoelastic, and combined friction-viscoelastic were investigated. Finite element methods were employed in the analysis using the program ABAQUS version 6.3. A direct integration dynamic analysis was carried out to obtain the damped and undamped responses of the structure in terms of deflections and accelerations at all storeys in order to evaluate the effectiveness of the damping system in mitigating the seismic response. The damping mechanisms have been modelled as (i) a linear spring and dash-pot in parallel for the viscoelastic damper, (ii) a contact pair with friction parameter for a friction damper and (iii) a hybrid damper consisting of both a viscoelastic and a friction damper. The earthquake events used in this study have been applied as acceleration time-histories at the base of the structure in the horizontal plane. Concrete material properties were chosen to represent the model as many high-rise buildings are constructed by using reinforced concrete. Several medium and high-rise building structures with embedded dampers in different configurations and placed in various locations throughout the structure were subjected to different earthquake loadings. Influence of damper type and properties, configuration and location were investigated. Results for the reduction in tip deflection and acceleration for a number of cases demonstrate the feasibility of the technique for seismic mitigation of these structures for a range of excitations, even when the dominant seismic frequencies match the natural frequency of the structure. Results also provide information which can be used for optimal damper placement for seismic mitigation. Keywords Seismic response; Friction damper; Viscoelastic damper; Damping; Configuration i Influence of Damping Systems on Building Structures Subject to Seismic Effects Publications International Refereed Journal Papers: “Influence of Damping Systems on Building Structures Subject to Seismic Effects” Journal of Engineering Structures 26, November 2004, 1939-1956. “Mitigating Seismic Response of Shear Wall Structures Using Embedded Dampers” Institution of the Structural Engineer (UK), January 2006. “Study of Viscoelastic and Friction Damper Configurations in the Seismic Mitigation of Medium-Rise Structures” Journal of Mechanics of Materials and Structures, Accepted in April 2006 for Publication in 2006. International Refereed Conference Papers: “Influence of Damping Systems on Building Structures Subject to Seismic Effects” Proceedings of the Ninth International Conference on Civil and Structural Engineering Computing, Egmond-aan-Zee, The Netherlands, September 2003. “Comparative Study on the Efficiency of Friction and Viscoelastic Dampers within Shear Walls” Proceedings Second International Conference on Structural Engineering Mechanics and Computations, Cope Town, South Africa, September 2004. “Seismic Response of Building Structures Using Embedded Dampers” Australian Earthquake Engineering in the New Millenium -Where to from Here? Proceedings of the Conference, Mt. Gambier, South Australia, November 2004. ii Influence of Damping Systems on Building Structures Subject to Seismic Effects Contents Abstract Keywords Publications Contents List of Figures List of Tables Notations Statement of Original Authorship Acknowledgements i i ii iii vi xvii xvii xx xxi 1.1 1.2 1.3 1.4 1.5 1.6 CHAPTER 1 INTRODUCTION Background to the Study Problem Researched Aims and Objectives Method of Investigation Scope of Research Layout of Thesis 1 2 5 6 6 7 8 2.1 2.2 2.3 2.3.1 2.3.2 2.4. 2.4.1 2.4.1.1 2.4.1.2 2.4.2 2.4.3 2.4.4 2.4.5 2.5 2.6 2.7 2.8 2.8.1 2.8.2 CHAPTER 2 LITERATURE REVIEW Introduction Seismic Design Concept Analysis Procedures Static Analysis Procedures Dynamic Analysis Procedures Passive Energy Dissipation Devices Hysteretic Energy Dissipation Devices Metallic Dampers Friction Dampers Viscoelastic Dampers Dynamic Vibration Absorbers Phase Transformation Dampers Hybrid Dampers Use of Energy Dissipation Devices in Building Structures Research on Seismic Mitigation with Passive Dampers Configurations of Energy Dissipation Devices Conclusion to the Literature Review Summary of the Literature Review Proposed Research 10 11 12 15 15 15 17 19 20 24 28 33 36 37 38 44 49 54 54 54 3.1 3.2 3.3 3.3.1 CHAPTER 3 MODEL DEVELOPMENT & VERIFICATION Introduction Finite Element Modelling Loading and Boundary Conditions Boundary Conditions 56 57 58 58 58 iii Influence of Damping Systems on Building Structures Subject to Seismic Effects 3.3.2 3.4 3.4.1 3.4.2 3.4.3 3.5 3.5.1 3.5.2 3.6 3.6.1 3.6.2 3.7 3.8 3.9 3.10 3.10.1 3.10.2 3.10.3 3.10.4 3.10.5 3.10.6 3.11 3.11.1 3.11.2 3.11.3 3.11.4 3.11.5 3.12 3.13 3.14 3.15 3.15.1 3.15.2 3.15.3 3.15.4 Material Properties Damper Models Friction Damper Model Viscoelastic Damper Model Hybrid Damper Model 18-Storey Frame-Shear Wall Structure Description of 18-Storey Frame-Shear Wall Structure Damper Placement in 18-Storey Frame-Shear Wall Structure 12-Storey Frame Shear Wall Structure Description of 12-Storey Frame-Shear Wall Structure Damper Placement in 12-Storey Frame-Shear Wall Structure Shear Wall Structure 24-Storey Frame-Shear Wall Structure 18-Storey Frame Structure Dampers within 18 and 12-Storey Frame-Shear Wall Structures Structural Model with Friction Damper-Diagonal Configuration Structural Model with Viscoelastic Damper-Diagonal Configuration Structural Model with Friction Damper-Chevron Brace Configuration Structural Model with Viscoelastic Damper-Chevron Brace Configuration Structural Model with Hybrid Friction-Viscoelastic Damper Structural Model with Viscoelastic Damper-Lower Toggle Configuration Dampers within Shear Wall Structures Structural Model with Friction Damper-Diagonal Configuration Structural Model with Viscoelastic Damper-Diagonal Configuration Structural Model with Friction Damper-Chevron Brace Configuration Structural Model with Viscoelastic Damper-Chevron Brace Configuration Structural Model with Hybrid Friction-Viscoelastic Damper Dampers within 24-Storey Frame-Shear Wall Structures Dampers within 18-Storey Frame Structures Input Earthquake Records Verification of Results Results of Benchmark Model Testing Results of Analytical Investigation of Benchmark Models Effectiveness of Damper Configurations Results of Analytical Investigation of Damper Configurations 4.1 4.2 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.3.6 CHAPTER 4 RESULTS – HIGH RISE STRUCTURES Introduction Seismic Response of 96 m High Shear Wall Structure Seismic Response of 24-Storey Frame-Shear Wall Structure Damping Properties of Viscoelastic Dampers Frame-Shear Wall Structure Type T1 Frame-Shear Wall Structure Type T3 Frame-Shear Wall Structure Type T1-3 Parameters of Viscoelastic Dampers - Summary of Finding Response of T Structure under Five Earthquake Excitations iv 59 59 60 60 60 61 61 61 62 62 63 64 64 65 66 67 68 69 70 71 72 73 74 75 76 77 77 78 79 80 82 84 85 87 89 92 93 93 104 104 104 109 114 119 121 1 6.1 7.6 7.8 CHAPTER 6 RESULTS – 12-STOREY STRUCTURES Introduction Seismic Response of 12-Storey Frame-Shear Wall Structure Undamped Structure Diagonal Friction Dampers Diagonal Viscoelastic Dampers Chevron Brace Friction Dampers Chevron Brace Viscoelastic Dampers Hybrid Friction-Viscoelastic Dampers Lower Toggle Viscoelastic Dampers Summary of Findings in 12-Storey Structure 194 195 195 199 200 207 214 221 227 235 241 7.2.1 6.2.4 6.2 5.2.2 5.2.2.2.2.2.1 5.8 5.1 5.2.2.5 6.3 6.1 7.2 7.2.2.7 5.2.5 7.4 7.2.6 5.2.3 5.5 5.2.3 CHAPTER 7 CONCLUSIONS AND RECOMMENDATIONS Scientific Contribution from this Research Discussions 96 m High Shear Wall structure 24-Storey Frame-Shear Wall Structure 18-Storey Frame-Shear Wall Structure 18-Storey Frame Structure 12-Storey Frame-Shear Wall Structure Conclusions Recommendations for Further Research 252 253 254 255 255 257 259 259 261 262 LIST OF REFERENCES APPENDIX Tables of Results of 18-Storey and 12-Storey Structures 263 279 279 v .6 6.2 6.2 7.2.2.2.3 CHAPTER 5 RESULTS – 18-STOREY STRUCTURES Introduction Seismic Response of 18-Storey Frame-Shear Wall Structure Undamped Structure Diagonal Friction Dampers Diagonal Viscoelastic Dampers Chevron Brace Friction Dampers Chevron Brace Viscoelastic Dampers Hybrid Friction-Viscoelastic Dampers Lower Toggle Viscoelastic Dampers Summary of Findings in 18-Storey Structure Seismic Response of 18-Storey Frame Structure 126 127 127 131 132 139 146 153 159 166 172 182 6.2 6.3 7.2.2.7 6.2.Influence of Damping Systems on Building Structures Subject to Seismic Effects 5.4 5. 10 Figure 2.7 Figure 2.16 Figure 2.27 Figure 2.9 Figure 2.19 Figure 2.12 Figure 2.15 Figure 2.17 Figure 2.21 Figure 2.22 Figure 2.Influence of Damping Systems on Building Structures Subject to Seismic Effects Figures 4 Figure 1.13 Figure 3.4 Figure 2.2 Figure 3.6 Figure 2.4 Figure 3.15 vi 62 63 63 63 64 65 65 66 66 67 68 69 .8 Figure 3.1 Figure 2.12 Figure 3.1 Example of Typical Passive Energy Dissipating Devices Figure 2.23 Figure 2.29 Global Maps of Earthquake Events from Last 30 Years Base Isolation Example of Semi-Active Control System Idealized Force-Displacement Loops of Hysteretic Devices Examples of X-Shaped Plate Dampers Triangular Shaped Damper and Its Hysteretic Loops Yielding Steel Bracing System Examples of Lead Extrusion Devices Pall Friction Damper Uniaxial Friction Damper Installation of Uniaxial Friction Damper in Steel Frame Energy Dissipating Restraint Three Examples of Slotted Bolted Connections Idealized Force-Displacement Loops of VE Devices Typical VE Solid Damper Idealized Force-Displacement Loops of Viscous Devices Viscous Damping Wall Systems Orificed Fluid Damper Elastomeric Spring Damper Pressurized Fluid Damper Model of SDOF Structure and TMD Building with a TLD and a TLCD Tuned Liquid Column Dampers within Shear Wall Stress-Strain Response of Shape Memory Alloys Hybrid Friction-VE Damper Viscous Damping System – Construction Scheme Effectiveness of Damper Configuration in Frame System Application of the Damper with Lower Toggle Brace Assembly Toggle Specimen Model 11 14 18 19 20 21 22 23 24 25 26 27 27 29 29 28 31 32 32 33 33 35 35 36 38 43 50 51 52 Figure 3.2 Figure 2.3 Model Location of Applied Acceleration 18-Storey Frame-Shear Wall Structure Placement of Single Damper within 18-Storey Frame-Shear Wall Structure Placement of Three Dampers within 18-Storey Frame-Shear Wall Structure 12-Storey Frame-Shear Wall Structure Placement of Single Damper within 12-Storey Frame-Shear Wall Structures Placement of Two Dampers within 12-Storey Frame-Shear Wall Structures Placement of Dampers within Shear Wall Structures Placement of Dampers within 24-Storey Frame-Shear Wall Structures Placement of Single Damper within 18-Storey Frame Structures Placement of Three Dampers within 18-Storey Frame Structures Damping Systems Installed in Medium-Rise Structures Structural Details of Diagonal Friction Damper Detail of MPC Connection between Shear Wall and Damper Structural Details of Diagonal VE Damper 58 61 62 Figure 3.9 Figure 3.24 Figure 2.10 Figure 3.5 Figure 2.26 Figure 2.11 Figure 3.14 Figure 3.18 Figure 2.3 Figure 2.25 Figure 2.13 Figure 2.11 Figure 2.28 Figure 2.20 Figure 2.6 Figure 3.14 Figure 2.8 Figure 2.5 Figure 3.1 Figure 3.7 Figure 3. 22 Figure 3.13 Figure 4.2 Figure 4. Diagonal and Lower Toggle Configuration Tip Deflection of the Undamped Frame and the Frame Fitted with Viscous Damper of Lower Toggle Configuration 70 71 72 73 74 74 75 76 77 78 79 80 81 81 81 82 82 84 86 Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal Friction Damper under the El Centro Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal VE Damper under the El Centro Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Chevron Brace Friction Damper under the El Centro Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Chevron Brace Friction Damper under the El Centro Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Hybrid Friction-VE Damper under the El Centro Earthquake Tip Deflection Reductions for Five Types of Damping Systems Tip Deflection Reductions for Different Damper Location Tip Deflection Reductions under Different Earthquake Excitations Tip Acceleration Reductions for Five Types of Damping Systems Tip Acceleration Reductions for Different Damper Location Tip Acceleration Reductions under Different Earthquake Excitations Percentage Reductions in Tip Deflection of All Shear Wall Structures Percentage Reductions in Tip Acceleration of All Shear Wall Structures Percentage Reductions in Tip Deflection of Structures Type T1 Percentage Reductions in Tip Acceleration of Structures Type T1 Percentage Reductions in Tip Deflection of Structures Type T3 Percentage Reductions in Tip Acceleration of Structures Type T3 Percentage Reductions in Tip Deflection of Structures Type T1-3 Percentage Reductions in Tip Acceleration of Structures Type T1-3 94 vii 88 89 95 95 95 96 97 97 99 99 100 100 102 103 107 109 110 112 115 117 .25 Figure 3.16 Figure 4.21 Figure 3.Influence of Damping Systems on Building Structures Subject to Seismic Effects Figure 3.7 Figure 4.16 Figure 3.15 Figure 4.27 Figure 3.10 Figure 4.9 Figure 4.4 Figure 4.19 Structural Details of Chevron Brace Friction Damper Structural Details of Chevron Brace Viscoelastic Damper Structural Details of Hybrid Friction-Viscoelastic Damper Structural Details of Lower Toggle Viscoelastic Damper Damping Systems installed in Shear Wall Structure Details of Diagonal Friction Damper within Structure Type W Details of Diagonal Viscoelastic Damper within Structure Type W Details of Chevron Brace Friction Damper within Structure Type W Details of Chevron Brace Viscoelastic Damper within Structure Type W Details of Hybrid Friction-Viscoelastic Damper within Structure Type W Details of Diagonal Viscoelastic Damper within Structure Type T Details of Diagonal Viscoelastic Damper within Structure Type F The El Centro Earthquake Record and Its Dominant Frequencies The Hachinohe Earthquake Record and Its Dominant Frequencies The Kobe Earthquake Record and Its Dominant Frequencies The Northridge Earthquake Record and Its Dominant Frequencies The San Fernando Earthquake Record and Its Dominant Frequencies Elevation and Plan View of Five-Storey Benchmark Model Tip Deflection and Acceleration of the Undamped Benchmark Model and Benchmark model Fitted with Three Stiffness Dampers Undamped Frame and Frame with Damper of Chevron Brace.17 Figure 4.8 Figure 4.20 Figure 3.17 Figure 3.19 Figure 3.31 Figure 3.18 Figure 3.35 Figure 3.11 Figure 4.28 Figure 3.1 Figure 4.32 Figure 3.23 Figure 3.3 Figure 4.26 Figure 3.6 Figure 4.33 Figure 3.36 Figure 4.34 Figure 3.30 Figure 3.5 Figure 4.14 Figure 4.18 Figure 4.24 Figure 3.29 Figure 3.12 Figure 4. 13 Figure 5.1 Figure 5.17 Figure 5.9 Figure 5.16 Figure 5.6 Figure 5.11 Figure 5.7 Figure 5.20 Percentage Reduction in Tip Deflection of 24-Storey Frame-Shear Wall Structure in Terms of Damper Placement Percentage Reduction in Tip Deflection of 24-Storey Frame-Shear Wall Structure under Five Earthquake Excitations Percentage Reduction in Tip Acceleration of 24-Storey Frame-Shear Wall Structure in Terms of Damper Placement Percentage Reduction in Tip Acceleration of 24-Storey Frame-Shear Wall Structure under Five Earthquake Excitations 118 Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal VE Damper under the El Centro Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal VE Damper under the Hachinohe Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal VE Damper under the Kobe Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal VE Damper under the Northridge Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal VE Damper under the San Fernando Earthquake Tip Deflection and Acceleration Response of Structures fitted with Diagonal Friction and VE Dampers under the El Centro Earthquake Tip Deflection and Acceleration Response of Structures fitted with Chevron Brace Friction and VE Dampers under the El Centro Earthquake Tip Deflection and Acceleration Response of Structures fitted with Hybrid Friction-VE Damper and Lower Toggle VE Dampers under the El Centro Earthquake Interstorey Drifts of Undamped Structure under Five Earthquake Excitations Tip Deflection and Acceleration Response of the structures with Different Placement of the Diagonal Friction Dampers under the El Centro Earthquake 18-Storey Structure Fitted with 1 Diagonal Friction Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 1 Diagonal Friction Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 3 Diagonal Friction Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 3 Diagonal Friction Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 1 Diagonal Friction Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 1 Diagonal Friction Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements 18-Storey Structure Fitted with 3 Diagonal Friction Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 3 Diagonal Friction Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Tip Deflection and Acceleration Responses of the structures with Different Placement of the Diagonal VE Dampers under the El Centro Earthquake 18-Storey Structure Fitted with 1 Diagonal VE Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 128 viii 122 123 123 128 128 129 129 130 130 131 132 133 133 134 135 136 136 137 137 138 139 140 .10 Figure 5.5 Figure 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects Figure 4.19 Figure 5.2 Figure 5.22 Figure 4.14 Figure 5.15 Figure 5.18 Figure 5.20 Figure 4.8 Figure 5.21 Figure 4.4 Figure 5.12 Figure 5.3 Figure 5.23 Figure 5. 25 Figure 5.26 Figure 5.22 Figure 5.38 Figure 5.23 Figure 5.31 Figure 5.29 Figure 5.21 Figure 5.43 18-Storey Structure Fitted with 1 Diagonal VE Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 3 Diagonal VE Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 3 Diagonal VE Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 1 Diagonal VE Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 1 Diagonal VE Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements 18-Storey Structure Fitted with 3 Diagonal VE Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 3 Diagonal VE Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Tip Deflection and Acceleration Responses of the structures with Different Placement of the Chevron Brace Friction Dampers under the El Centro Earthquake 18-Storey Structure Fitted with 1 Chevron Brace Friction Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 1 Chevron Brace Friction Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 3 Chevron Brace Friction Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 3 Chevron Brace Friction Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 1 Chevron Brace Friction Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 1 Chevron Brace Friction Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements 18-Storey Structure Fitted with 3 Chevron Brace Friction Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 3 Chevron Brace Friction Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Tip Deflection and Acceleration Responses of the structures with Different Placement of the Chevron Brace VE Dampers under the El Centro Earthquake 18-Storey Structure Fitted with 1 Chevron Brace VE Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 1 Chevron Brace VE Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 3 Chevron Brace VE Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 3 Chevron Brace VE Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 1 Chevron Brace VE Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 1 Chevron Brace VE Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements ix 140 141 142 142 143 144 144 146 147 147 148 149 149 150 150 151 153 154 155 155 156 157 157 .41 Figure 5.36 Figure 5.24 Figure 5.37 Figure 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects Figure 5.27 Figure 5.42 Figure 5.34 Figure 5.28 Figure 5.32 Figure 5.33 Figure 5.40 Figure 5.35 Figure 5.30 Figure 5.39 Figure 5. 47 Figure 5.52 Figure 5.53 Figure 5.44 Figure 5.65 18-Storey Structure Fitted with 3 Chevron Brace VE Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 3 Chevron Brace VE Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Tip Deflection and Acceleration Responses of the structures with Different Placement of the Hybrid Friction-VE Dampers under the El Centro Earthquake 18-Storey Structure Fitted with 1 Hybrid Friction-VE Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 1 Hybrid Friction-VE Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 3 Hybrid Friction-VE Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 3 Hybrid Friction-VE Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 1 Hybrid Friction-VE Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 1 Hybrid Friction-VE Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements 18-Storey Structure Fitted with 3 Hybrid Friction-VE Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 3 Hybrid Friction-VE Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Tip Deflection and Acceleration Responses of the structures with Different Placement of the Lower Toggle VE Dampers under the El Centro Earthquake 18-Storey Structure Fitted with 1 Lower Toggle VE Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 1 Lower Toggle VE Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 3 Lower Toggle VE Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Structure Fitted with 3 Lower Toggle VE Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 18-Storey Structure Fitted with 1 Lower Toggle VE Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 1 Lower Toggle VE Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements 18-Storey Structure Fitted with 3 Lower Toggle VE Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 18-Storey Structure Fitted with 3 Lower Toggle VE Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Average Percentage Tip Deflection Reductions for All Damping Systems in All (1 Damper) Placements Average Percentage Tip Deflection Reductions for All Damping Systems (1 Damper Placement) under Different Earthquake Excitations x 158 158 159 160 161 161 162 162 163 163 164 166 166 167 167 168 169 169 170 170 172 173 .62 Figure 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects Figure 5.57 Figure 5.63 Figure 5.45 Figure 5.51 Figure 5.64 Figure 5.59 Figure 5.56 Figure 5.46 Figure 5.49 Figure 5.58 Figure 5.61 Figure 5.50 Figure 5.60 Figure 5.48 Figure 5.55 Figure 5.54 Figure 5. 80 Figure 5.75 Figure 5.77 Figure 5.71 Figure 5.73 Figure 5.69 Figure 5.76 Figure 5.83 Figure 5.78 Figure 5.66 Figure 5.74 Figure 5.84 Figure 5.68 Figure 5.85 Figure 5.81 Figure 5.82 Figure 5.87 Figure 5.67 Figure 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects Figure 5.86 Figure 5.88 Average Percentage Tip Deflection Reductions for All Damping Systems in Terms of Damper Placements Average Percentage Tip Deflection Reductions of All Systems under Different Earthquake Excitations Average Percentage Tip Deflection Reductions for All Damping Systems in All (3 Dampers) Placements Average Percentage Tip Deflection Reductions for All Damping Systems (3 Dampers Placement) under Different Earthquake Excitations Average Percentage Tip Deflection Reductions for All Damping Systems in Terms of Damper Placements Average Percentage Tip Deflection Reductions of All Systems under Different Earthquake Excitations Average Percentage Tip Acceleration Reductions for All Damping Systems in All (1 Damper) Placements Average Percentage Tip Acceleration Reductions for All Damping Systems (1 Damper Placement) under Different Earthquake Excitations Average Percentage Tip Acceleration Reductions for All Damping Systems in Terms of Damper Placements Average Percentage Tip Acceleration Reductions of All Systems under Different Earthquake Excitations Average Percentage Tip Acceleration Reductions for All Damping Systems in All (3 Dampers) Placements Average Percentage Tip Acceleration Reductions for All Damping Systems (3 Dampers Placement) under Different Earthquake Excitations Average Percentage Tip Acceleration Reductions for All Damping Systems in Terms of Damper Placements Average Percentage Tip Acceleration Reductions of All Systems under Different Earthquake Excitations Tip deflection and Tip Acceleration Responses of the Undamped Structure and the Structure Fitted with 3 Diagonal VE Dampers and Structure Fitted with 1 Friction and 1 VE Damper under the El Centro Earthquake Tip deflection and Tip Acceleration Responses of the Undamped Structure and the Structure Fitted with 3 Diagonal VE Dampers and Structure Fitted with 1 Friction and 1 VE Damper under the Hachinohe Earthquake Tip deflection and Tip Acceleration Responses of the Undamped Structure and the Structure Fitted with 3 Diagonal VE Dampers and Structure Fitted with 1 Friction and 1 VE Damper under the Kobe Earthquake Tip deflection and Tip Acceleration Responses of the Undamped Structure and the Structure Fitted with 3 Diagonal VE Dampers and Structure Fitted with 1 Friction and 1 VE Damper under the Northridge Earthquake Tip deflection and Tip Acceleration Responses of the Undamped Structure and the Structure Fitted with 3 Diagonal VE Dampers and Structure Fitted with 1 Friction and 1 VE Damper under the San Fernando Earthquake Tip Deflection and Acceleration Responses of Undamped Frame Structure and Frame Structure Fitted with Diagonal VE Dampers under the El Centro Earthquake Tip Deflection and Acceleration Responses of Undamped Frame Structure and Frame Structure Fitted with Diagonal VE Dampers under the Hachinohe Earthquake Tip Deflection and Acceleration Responses of Undamped Frame Structure and Frame Structure Fitted with Diagonal VE Dampers under the Kobe Earthquake Tip Deflection and Acceleration Responses of Undamped Frame Structure and Frame Structure Fitted with Diagonal VE Dampers under the Northridge Earthquake xi 174 174 174 175 175 175 176 177 177 177 178 178 178 179 179 180 180 180 181 182 183 183 183 .72 Figure 5.79 Figure 5.70 Figure 5. 96 Figure 5.1 Figure 6.8 Figure 6.89 Figure 5.9 Figure 6.99 Figure 6.95 Figure 5.97 Figure 5.93 Figure 5. 18-Storey Frame Structure – Percentage Reductions in Tip Deflection under Different Earthquake Records 18-Storey Frame-Shear Wall Structure vs.Influence of Damping Systems on Building Structures Subject to Seismic Effects Figure 5.6 Figure 6.90 Figure 5.94 Figure 5.5 Figure 6.10 Tip Deflection and Acceleration Responses of Undamped Frame Structure and Frame Structure Fitted with Diagonal VE Dampers under the San Fernando Earthquake 18-Storey Frame Structure Fitted with Diagonal VE Damper – Percentage Reduction in Tip Deflection under Different Earthquake Records 18-Storey Frame Structure Fitted with Diagonal VE Damper – Percentage Reduction in Tip Deflection for Different Placements 18-Storey Frame Structure Fitted with 3 Diagonal VE Dampers – Percentage Reduction in Tip Deflection under Different Earthquake Records 18-Storey Frame Structure Fitted with 3 Diagonal VE Dampers – Percentage Reduction in Tip Deflection for Different Placements 18-Storey Frame Structure Fitted with Diagonal VE Damper – Percentage Reduction in Tip Acceleration under Different Earthquake Records 18-Storey Frame Structure Fitted with Diagonal VE Damper – Percentage Reduction in Tip Acceleration for Different Placements 18-Storey Frame Structure Fitted with 3 Diagonal VE Dampers – Percentage Reduction in Tip Acceleration under Different Earthquake Records 18-Storey Frame Structure Fitted with 3 Diagonal VE Dampers – Percentage Reduction in Tip Acceleration for Different Placements 18-Storey Frame-Shear Wall Structure vs. 18-Storey Frame Structure – Percentage Reductions in Tip Acceleration under Different Earthquake Records 184 Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal Friction Damper under the El Centro Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal Friction Damper under the Hachinohe Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal Friction Damper under the Kobe Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal Friction Damper under the Northridge Earthquake Tip Deflection and Acceleration Response of Undamped Structure and Structure Fitted with Diagonal Friction Damper under the San Fernando Earthquake Tip Deflection and Acceleration Response of Structures fitted with Diagonal Friction and VE Dampers under the El Centro Earthquake Tip Deflection and Acceleration Response of Structures fitted with Chevron Brace Friction and VE Dampers under the El Centro Earthquake Tip Deflection and Acceleration Response of Structures fitted with Hybrid Friction-VE Damper and Lower Toggle VE Dampers under the El Centro Earthquake Interstorey Drifts of Undamped Structure under Five Earthquake Excitations Tip Deflection and Acceleration Response of the structures with Different Placement of the Diagonal Friction Dampers under the El Centro Earthquake 196 xii 185 185 186 186 187 187 188 188 190 191 196 196 197 197 198 198 199 200 201 .91 Figure 5.92 Figure 5.7 Figure 6.4 Figure 6.3 Figure 6.98 Figure 5.2 Figure 6. Influence of Damping Systems on Building Structures Subject to Seismic Effects Figure 6.11 Figure 6.12 Figure 6.13 Figure 6.14 Figure 6.15 Figure 6.16 Figure 6.17 Figure 6.18 Figure 6.19 Figure 6.20 Figure 6.21 Figure 6.22 Figure 6.23 Figure 6.24 Figure 6.25 Figure 6.26 Figure 6.27 Figure 6.28 Figure 6.29 Figure 6.30 Figure 6.31 Figure 6.32 Figure 6.33 Figure 6.34 12-Storey Structure Fitted with 1 Diagonal Friction Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 1 Diagonal Friction Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 2 Diagonal Friction Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 2 Diagonal Friction Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 1 Diagonal Friction Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 1 Diagonal Friction Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements 12-Storey Structure Fitted with 2 Diagonal Friction Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 2 Diagonal Friction Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Tip Deflection and Acceleration Responses of the structures with Different Placement of the Diagonal VE Dampers under the El Centro Earthquake 12-Storey Structure Fitted with 1 Diagonal VE Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 1 Diagonal VE Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 2 Diagonal VE Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 2 Diagonal VE Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 1 Diagonal VE Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 1 Diagonal VE Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements 12-Storey Structure Fitted with 2 Diagonal VE Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 2 Diagonal VE Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Tip Deflection and Acceleration Responses of the structures with Different Placement of the Chevron Brace Friction Dampers under the El Centro Earthquake 12-Storey Structure Fitted with 1 Chevron Brace Friction Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 1 Chevron Brace Friction Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 2 Chevron Brace Friction Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 2 Chevron Brace Friction Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 1 Chevron Brace Friction Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 1 Chevron Brace Friction Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements xiii 201 202 203 203 204 204 204 205 208 208 209 209 210 210 211 212 212 214 215 215 216 216 217 218 Influence of Damping Systems on Building Structures Subject to Seismic Effects Figure 6.35 Figure 6.36 Figure 6.37 Figure 6.38 Figure 6.39 Figure.6.40 Figure 6.41 Figure 6.42 Figure 6.43 Figure 6.44 Figure 6.45 Figure 6.46 Figure 6.47 Figure 6.48 Figure 6.49 Figure 6.50 Figure 6.51 Figure 6.52 Figure 6.53 Figure 6.54 12-Storey Structure Fitted with 2 Chevron Brace Friction Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 2 Chevron Brace Friction Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Tip Deflection and Acceleration Responses of the structures with Different Placement of the Chevron Brace VE Dampers under the El Centro Earthquake 12-Storey Structure Fitted with 1 Chevron Brace VE Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 1 Chevron Brace VE Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 2 Chevron Brace VE Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 2 Chevron Brace VE Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 1 Chevron Brace VE Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 1 Chevron Brace VE Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements 12-Storey Structure Fitted with 2 Chevron Brace VE Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 2 Chevron Brace VE Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Tip Deflection and Acceleration Responses of the structures with Different Placement of the Hybrid Friction-VE Dampers under the El Centro Earthquake 12-Storey Structure Fitted with 1 Hybrid Friction-VE Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 1 Hybrid Friction-VE Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 2 Hybrid Friction-VE Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 2 Hybrid Friction-VE Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 1 Hybrid Friction-VE Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 1 Hybrid Friction-VE Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements 12-Storey Structure Fitted with 2 Hybrid Friction-VE Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 2 Hybrid Friction-VE Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements xiv 218 221 221 222 222 223 223 224 224 225 226 228 228 229 230 230 231 231 232 233 Influence of Damping Systems on Building Structures Subject to Seismic Effects Figure 6.55 Figure 6.56 Figure 6.57 Figure 6.58 Figure 6.59 Figure 6.60 Figure 6.61 Figure 6.62 Figure 6.63 Figure 6.64 Figure 6.65 Figure 6.66 Figure 6.67 Figure 6.68 Figure 6.69 Figure 6.70 Figure 6.71 Figure 6.72 Figure 6.73 Figure 6.74 Figure 6.75 Figure 6.76 Figure 6.77 Figure 6.78 Figure 6.79 Figure 6.80 Tip Deflection and Acceleration Responses of the structures with Different Placement of the Lower Toggle VE Dampers under the El Centro Earthquake 12-Storey Structure Fitted with 1 Lower Toggle VE Damper – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 1 Lower Toggle VE Damper – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 2 Lower Toggle VE Dampers – Percentage Reductions in Tip Deflection under Different Earthquake Records 12-Storey Structure Fitted with 2 Lower Toggle VE Dampers – Percentage Reductions in Tip Deflection for Different Damper Placements 12-Storey Structure Fitted with 1 Lower Toggle VE Damper – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 1 Lower Toggle VE Damper – Percentage Reductions in Tip Acceleration for Different Damper Placements 12-Storey Structure Fitted with 2 Lower Toggle VE Dampers – Percentage Reductions in Tip Acceleration under Different Earthquake Records 12-Storey Structure Fitted with 2 Lower Toggle VE Dampers – Percentage Reductions in Tip Acceleration for Different Damper Placements Average Percentage Tip Deflection Reductions for All Damping Systems in All (1 Damper) Placements Average Percentage Tip Deflection Reductions for All Damping Systems (1 Damper Placement) under Different Earthquake Excitations Average Percentage Tip Deflection Reductions for All Damping Systems in Terms of Damper Placements Average Percentage Tip Deflection Reductions of All Systems under Different Earthquake Excitations Average Percentage Tip Deflection Reductions for All Damping Systems in All (2 Dampers) Placements Average Percentage Tip Deflection Reductions for All Damping Systems (2 Dampers Placement) under Different Earthquake Excitations Average Percentage Tip Deflection Reductions for All Damping Systems in Terms of Damper Placements Average Percentage Tip Deflection Reductions of All Systems under Different Earthquake Excitations Average Percentage Tip Acceleration Reductions for All Damping Systems in All (1 Damper) Placements Average Percentage Tip Acceleration Reductions for All Damping Systems (1 Damper Placement) under Different Earthquake Excitations Average Percentage Tip Acceleration Reductions for All Damping Systems in Terms of Damper Placements Average Percentage Tip Acceleration Reductions of All Systems under Different Earthquake Excitations Average Percentage Tip Acceleration Reductions for All Damping Systems in All (2 Dampers) Placements Average Percentage Tip Acceleration Reductions for All Damping Systems (2 Dampers Placement) under Different Earthquake Excitations Average Percentage Tip Acceleration Reductions for All Damping Systems in Terms of Damper Placements Average Percentage Tip Acceleration Reductions of All Systems under Different Earthquake Excitations Tip deflection and Tip Acceleration Responses of the Undamped Structure and the Structure Fitted with 2 Diagonal VE Dampers and Structure Fitted with 1 Friction and 1 VE Damper under the El Centro Earthquake xv 235 236 237 237 238 239 239 240 240 241 241 241 242 242 242 243 243 244 245 245 245 246 246 246 247 248 Influence of Damping Systems on Building Structures Subject to Seismic Effects Figure 6.81 Figure 6.82 Figure 6.83 Figure 6.84 Tip deflection and Tip Acceleration Responses of the Undamped Structure and the Structure Fitted with 2 Diagonal VE Dampers and Structure Fitted with 1 Friction and 1 VE Damper under the Hachinohe Earthquake Tip deflection and Tip Acceleration Responses of the Undamped Structure and the Structure Fitted with 2 Diagonal VE Dampers and Structure Fitted with 1 Friction and 1 VE Damper under the Kobe Earthquake Tip deflection and Tip Acceleration Responses of the Undamped Structure and the Structure Fitted with 3 Diagonal VE Dampers and Structure Fitted with 1 Friction and 1 VE Damper under the Northridge Earthquake Tip deflection and Tip Acceleration Responses of the Undamped Structure and the Structure Fitted with 3 Diagonal VE Dampers and Structure Fitted with 1 Friction and 1 VE Damper under the San Fernando Earthquake 249 249 249 250 Tables Table 2.1 Table 3.1 Table 3.2 Table 3.3 Table 3.4 Table 4.1 Table 4.2 Table 4.3 Table 4.4 Table 4.5 Table 4.6 Table 4.7 Table 4.8 Table 4.9 Table 5.1 Table 5.2 Table 6.1 Table 6.2 Damper Location Seismic Response of Benchmark Models Seismic Response of Analytical Models Results of Frame Deflection (after Marcelin) Results of Frame Deflection (ABAQUS) Tip Deflection and Acceleration of the Undamped Structure Percentage Reductions in Tip Deflection of the All Models Percentage Reductions in Tip Acceleration of the All Models Percentage Reductions in Tip Deflection of Structure Type T1 Percentage Reductions in Tip Acceleration of Structure Type T1 Percentage Reductions in Tip Deflection of Structure Type T3 Percentage Reductions in Tip Acceleration of Structure Type T3 Percentage Reductions in Tip Deflection of Structure Type T1-3 Percentage Reductions in Tip Acceleration of Structure Type T1-3 Tip Deflection and Tip Acceleration of the Undamped 18-Storey Structure Percentage Tip Deflection and Acceleration Reduction of the Structure Fitted with 1 Diagonal Friction Damper and 1 Diagonal VE Damper Tip Deflection and Tip Acceleration of the Undamped 12-Storey Structure Percentage Tip Deflection and Acceleration Reduction of the Structure Fitted with 1 Diagonal Friction Damper and 1 Diagonal VE Damper xvi 42 85 87 89 90 94 102 103 106 108 111 113 116 118 131 181 199 251 Influence of Damping Systems on Building Structures Subject to Seismic Effects Symbols A Ag C Cd Cc CM C0 D f fc fe f c’ Ec F FD FM Fvd G G’ G” h h I J K kd m M p Q t t T u ud ug U Ů Ü Shear Area Tributary Area of the Slab Structural Damping Matrix Damping Coefficient of VE Damping Device Damping Coefficient of the Corrector Damping Coefficient of the Main Spring Zero Frequency Damping Coefficients Control Force-Location Matrix Magnification Factor Vector of Forces in the Supplemental Device External Excitation Vector Compressive Strength Young’s Modulus Overall Force Force along the Axis of the Damper Force in the Main Spring Force in the Device Gravity Load Viscoelastic Damper Shear Storage Modulus Viscoelastic Damper Shear Loss Modulus Participation Matrix which Consists of Vector of Floor Masses Height above the Structural Base of the Structure to Level x Importance Factor Optimal Placement and Design of the Control System Structural Stiffness Matrix Axial Stiffness of Damping Device Lumped Mass Total Mass Matrix of the Structure Contact Pressure Live Load on the Structure Temperature Thickness of Viscoelastic Material Natural Period Interstorey Drift Vector Damper Relative Displacement Earthquake Ground Displacement Vector of Displacement of Structure Vector of Velocity Vector of Acceleration U id Real Value of Displacement Response Associate with the Modal Shape U iv Real Value of Velocity Response Associate with the Modal Shape xvii Influence of Damping Systems on Building Structures Subject to Seismic Effects V W x X Δci γ μ ρ τ τ max υ ω ψ id ψ iv ζ Velocity Weight Displacement of Damper Modal Response Damping Coefficient of the Damper Installed at the i Floor Deflection Shear Coefficient of Friction Damper Angle Density (kg/m3) Shear Stress Maximum Shear Stress Poisson’s Ratio Circular Frequency Displacement Mode Shape Velocity Mode Shape Modal Damping Ratio Abbreviations ADAS ASCE EDD EDR EDS FEA FEM FEMA FVED LCVA LED MCEER MDOF MTMD PGA OCT SDOF TDA TLD TLCD TMD SMA VDS VE Added Damping and Stiffness American Society of Civil Engineers Energy Dissipation Device Energy Dissipating Restraint Energy Dissipation System Finite Element Analysis Finite Element Method Federal Emergency Management Administration Friction-Viscoelastic Damper Liquid Column Vibration Absorber Lead Extrusion Damper Multidisciplinary Center for Earthquake Engineering Research Multi Degree of Freedom Multi Tuned Mass Damper Peak Ground Acceleration Optimal Control Theory Single Degree of Freedom Transient Dynamic Analysis Tuned Liquid Damper Tuned Liquid Column Damper Tuned Mass Damper Shape Memory Alloy Viscous Damping System Viscoelastic xviii To the best of my knowledge and belief.Influence of Damping Systems on Building Structures Subject to Seismic Effects Statement of Original Authorship The work contained in this thesis has not been previously submitted for a degree or diploma at any higher education institution. Signature: ______________________________________ Date: _______________________________________ xix . the thesis contains no material previously published or written by another person except where due reference is made. xx . deserves grateful appreciation. even amidst his heavy pressure of work throughout the entire period of study. His immense patience and availability for comments whenever approached. David Thambiratnam for his enthusiastic and expertise guidance. Finally. It is pleasure to thank fellow post-graduate students and friends for their support and contribution to this research. I would also like to thank the Physical Infrastructure Centre and the Faculty of Build Environment & Engineering for providing financial support. Without such assistance this study would not have been what it is. necessary faculties and technical support. Nimal Perera. encouragement. Adjunct Professor. I wish to express my appreciation to my wife Jana for her support.Influence of Damping Systems on Building Structures Subject to Seismic Effects Acknowledgements I am extremely grateful and deeply indebted to my supervisor Prof. I would like to thank Queensland University of Technology and the Centre for Environment and Engineering Research for providing Postgraduate Research Scholarship to carry out my research project. is to be mentioned with thanks for kindly agreeing to serve as associate supervisor. encouragements throughout the course of this study and the valuable assistance in many ways. constructive suggestions. and patience. Influence of Damping Systems on Building Structures Subject to Seismic Effects xxi . Chapter 1 Introduction i . Also buildings. The ideal aspects of a building form are simplicity. They are one of man’s most feared natural phenomena due to major earthquakes producing almost instantaneous destruction of buildings and other structures. Some of the major problems relating to earthquake design are created by the original design concept chosen by the architect. Additionally. About 10-20% of these earthquakes occur mid ocean. it has now risen to two in three and this upward tend shows no signs of abating. Unfortunately as the population of the earth increases the chances of this happening also increases. bridges and other works of man.iris. No engineer can truly transform a badly conceived building into an earthquake resistant building. less than one in three large earthquakes killed someone. which are tall in comparison to their plan area. the damage caused by earthquakes is almost entirely associated with man made structures.edu). The problem occurs when an earthquake hits highly populated areas. At the start of the century. will generate high overturning moments while buildings with large plan areas may not act as expected due to differences in 2 . On average about 200 large magnitude earthquakes occur in each decade (www. earthquakes also cause death by the damage they induce in structures such as buildings. Others occur in the areas away from towns and cities and so similarly cause few problems. regularity and symmetry in both elevation and plan. dams. at least in certain locations of the structure. Unfortunately many of earthquakes give very little or no warning before occurring and this is one of the reasons why earthquake engineering is complex.Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 1: Introduction 1. These properties all contribute to a more predictable and even distribution of forces in a structure while any irregularities are likely to lead to an increased dynamic response.1 Background to the study Earthquakes are one of nature’s greatest hazards to life on this planet and have destroyed countless cities and villages on virtually every continent. and hence cause no problems for human settlements. As in the cases of landslides. The damages which have occurred during earthquake events clearly demonstrate that the shape of a building is crucial to how they respond. which are not always predictable. which are most promising and on which this study concentrated. Once again cost is a factor as neither of the concepts can be justified by cost alone. dampers with active control 3 . This causes different parts of the building to be shaken differently creating obvious problems. There are two types of structural control provided by the addition of mechanical devices. For this reason. which will reduce the amount of seismic forces transmitted. the method of structural isolation is very efficient. Active control requires a power supply to activate the dampers and hence may be undependable during seismic events where the power supply could be disrupted. They absorb the energy from the earthquake reducing the effects on the critical components of the structure (FEMA 274). isolation. These plastic hinges. 2005). This is done by the insertion of energy absorbing material between the substructures and superstructures. energy absorption at plastic hinges and use of mechanical devices to provide structural control. The principle behind isolation is to change the natural period of the structure. are replaced leaving the building undamaged. Torsion from ground motion could be of great concern due to eccentricity in the building layout. substantially decouple a structure from the ground motion input and therefore reduce the resulting inertia force the structure must resist. which do not themselves support the structure. which suffer inelastic deformation are generally concentrated at the beam-column joints and are thus associated with damage to the primary structural elements. After the earthquake these absorbers. do as their name suggests. installations of mechanical energy absorbers. active and passive control. plastic hinges are provided. three methods can be identified as being practical and efficient. For instance if the centre of mass (gravity) is not in the same position as the centre of resistance a torsional moment about a vertical axis will be created which will have to be designed for. In traditional structures. On the other hand.Influence of Damping Systems on Building Structures Subject to Seismic Effects ground behaviour. but expensive and difficult to carry out (Di Sarno et al. These are. subjected to random and/or unpredictable loads. In order to achieve satisfactory earthquake response of a structure. The first type.. Influence of Damping Systems on Building Structures Subject to Seismic Effects have been tested on tall buildings subjected to wind induced loading rather the more unpredictable cyclic loading caused by earthquakes. Sadek (1999) and Soong and Spencer (2002). The characteristic of VE and viscous dampers are that. T. along with the potential for structural damage (FEMA 274). Constantinou et al. passive energy dissipation systems have emerged as special devices that are incorporated within the structure to absorb a portion of the input seismic energy. Fig. Symans and Constantinou (1999).1 Example of typical passive energy dissipating devices (Based on Soong T. These dampers have been reviewed in Soong and Dargush (1997). These use a variety of materials to obtain various levels of stiffness and damping. As a result.. viscous fluid. they dissipate energy at all levels of deformation and over a broad range of excitation frequencies. 1. the energy dissipation demand on primary structural members is often considerably reduced. Friction 4 . These dampers have different dynamic characteristics and so will affect the seismic response of structures differently. 1997) The idea of utilizing separate passive energy dissipating devices within a structure to absorb a large portion of the seismic energy began with the conceptual and experimental work of Kelly et al. (1998). (1972). et al. Some of these include viscoelastic (VE). On the other hand. friction and metallic yield dampers. Today there are various types of manufactured passive dampers available “off the shelf”. a linear spring and dash-pot in parallel for the VE damper. In conjunction with this program MSC / PATRAN Version 2004 was used as the pre-processor for generating the geometry. and a hybrid damper consisting of both a friction and a VE damping mechanism. For this reason the aim of this research is to investigate the behaviour of multi-storey frame-shear wall building structures under earthquake loads with damping devices strategically located within the cut outs of the shear wall The research will evaluate the influence of different damping systems on the overall seismic response of the structure. while investigations on use of damping devices within cut outs of shear wall is still very limited. thermal and electrical response of systems. 1. the use of passive energy dissipation devices has become very popular in the recent years. on the other hand. boundary conditions and loading conditions. the program selected for the numerical analysis was ABAQUS / Standard version 6. The damping mechanisms were modelled as a contact pair with friction parameter for a friction damper. However. and hybrid friction-VE damping mechanisms of different size. A combination of these dampers can be used within the structural system to effectively damp out the high and low frequency content of earthquakes. Finite element techniques with time history analysis were employed to investigate the effect of these damping systems under seismic loading of five different earthquake excitations. Metallic yield dampers dissipate energy through the inelastic deformation of the material. dynamic. Friction.2 Research Problem As mentioned in the previous section. For the purposes of this study.Influence of Damping Systems on Building Structures Subject to Seismic Effects dampers. This is commonly referred to as a hybrid system. element mesh. This is a general purpose finite element program that has been designed to solve a wide range of linear and non-linear problems involving static.3. VE. and as the post-processor for viewing 5 . dissipate energy only when the slip force is reached and exceeded. the vast majority of applications was realised within frame structures. configuration and placed at various locations were treated. 1. This analysis assembles the mass. To study the effectiveness of the damping systems in mitigating the seismic response.4 Method of investigation ¾ This research was carried out using computer simulations. and generating graphs of the response of buildings.3 Aims and objectives The main aim of this project is to generate fundamental research information on the seismic performance of building structural systems having passive damping devices installed within shear walls. the tip displacements and accelerations of each structure were acquired from the results of the analysis and compared with those of undamped structure. damping and stiffness matrices and solves the equation of dynamic equilibrium at each point in time. Finite element models of the shear wall of buildings was set up and analysed under five earthquake excitations ¾ The damping mechanisms were modelled as a linear spring and dash-pot in parallel for the VE damper. The response of the structure was obtained for selected time steps of the input earthquake accelerogram. A direct integration dynamic analysis was selected to obtain the response of the structures under earthquake loading. Additional objectives are: ¾ Create computer models of building structures – damper systems for investigation ¾ Study the effects of important parameters such as damper properties. a contact pair with friction parameter for a friction damper and a hybrid damper consisting of both a VE and a friction damping mechanism 6 . 1. locations and configuration of the dampers and earthquake types ¾ Use the research findings to propose more effective damping system for seismic mitigation.Influence of Damping Systems on Building Structures Subject to Seismic Effects the results of the analysis. Influence of Damping Systems on Building Structures Subject to Seismic Effects ¾ Size and material properties of the structure. and earthquake types. 7 . The scope of this investigation is as follow: -Building structures ¾ Frame shear wall structure is the range of height 48 m to 96 m ¾ The structures have natural frequencies within the range of dominant frequencies of the earthquakes treated here -Damping mechanisms ¾ Friction. chevron braced. configuration and location of dampers. viscoelastic and combined friction-viscoelastic dampers are considered -Damper configurations ¾ Diagonal. combined diagonal-chevron braced and lower toggle configurations are used -Damper locations ¾ Across the height of the structures with the dampers installed in one. The comprehensive investigation treating all the above parameters will provide results. which can be used to establish: ¾ The feasibility of using embedded dampers in seismic mitigation and ¾ Placement of dampers for the best results for different structures. 1. damping properties.5 Scope of research This research investigates seismic response of building structures with embedded dampers. were parameters in this investigation and the influence of these was studied ¾ Evaluation of results and reporting major findings. The main response parameters are tip deflection and tip acceleration of the structure. each with different duration of strong motion and range of dominant frequencies were used. two or three at a time -Seismic records ¾ Five different earthquakes. All the seismic records were scaled to have the same peak ground accelerations to facilitate comparison and to suite Australian (low) seismic conditions. Evaluation of results and application of findings to establish damping systems for best results. Chapter 2 Literature Review Highlights a review of previous literature published on the behaviour of a passive energy dissipation devices used in building structures under seismic loading. embedded with five types of damping systems obtained under variety of earthquake excitations are presented. Chapter 6 Results – 12-Storey Structures The results of finite element analyses of 12-storey frame-shear wall structures embedded with six types of damping systems obtained under different earthquake excitations. Chapter 4 Results – High-Rise Structures The results of finite element analyses of high-rise frame-shear wall structures. They are the following: Chapter 1 Introduction Presents the background and introduction to the topic. Chapter 7 Conclusions and Recommendations Highlights the major results and the main contributions of this research and makes some recommendations for further research. The development of finite element models and some model calibration are also presented.Influence of Damping Systems on Building Structures Subject to Seismic Effects 1. Chapter 5 Results – 18-Storey Structures The results of finite element analyses of 18-storey frame-shear wall structures embedded with six types of damping systems obtained under variety of earthquake excitations. states the aims and objectives and outlines the method of investigation used in this research project. Evaluation of results and application of findings to establish best damping model. 24 storey high. defines research problem. Chapter 3 Model Development and Verification of Results This chapter describes the method of investigation and the building structures and damping systems used in this research project. It then identifies the need and scope of the present research.6 Layout of thesis The material contained in this thesis is presented as seven chapters. 8 . Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 2 Literature Review 9 . breaks and moves to a new position. sinking at the boundaries.Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 2: Literature Review 2. The motion between them is not confined entirely to their own boundaries.1 Introduction The surface of the Earth consists of 12 solid and rigid plates 60-200 km thick. These plates are floating on top of a more fluid zone. Large and small earthquakes can also occur on faults not previously recognized. variations in temperature and strength within plates. Tectonic plates are somewhat flexible. In some parts. the vibration. when the stress exceeds the strength of the rocks. These seismic waves travel outward from the source of the earthquake along the surface and through the Earth at varying speeds and frequency depending on the material 10 .S. 2005) An earthquake is in technical terms. The crust may first bend and then. Geological Survey. resulting in many tiny shocks and a few moderate earth tremors. generated by a sudden dislocation of segment of the crust. In the process of breaking.1 Global maps of earthquake events from last 30 years (After U. constantly moving. and being regenerated. This movement build up large tectonic stresses. Fig. These earthquakes are mostly caused by localised stresses. vibrations called seismic waves are generated. 2. strain can build up for hundreds of years. Earthquake motion also occurs away from plate boundaries. producing great earthquakes when it finally releases. 2 Seismic design concept In conventional seismic design. the earthquakes of large magnitude do not necessarily cause the most intense surface effects. it may cause many deaths. injuries and extensive property damage. Body waves are of two types. Compressional waves. Shear waves. which travel through the Earth. and body waves. Both types pass from the focus of an earthquake to distant points on the surface. The earthquake's destructiveness in a given region depends on local surface and subsurface geologic conditions.Influence of Damping Systems on Building Structures Subject to Seismic Effects through. These factors include the focal depth. constructions in the area shaken by the quake and the design of building structures. the distance from the epicentre. which they move. In addition to magnitude and the local geologic conditions level of destruction depends on other factors. and they ordinarily reach the surface later. the density of population. 2. Instead of affecting material directly behind or ahead of their line of travel. Surface waves usually have the strongest vibrations and probably cause most of the damage done by earthquakes. However. which travel along the Earth's surface. called “P wave” travel at great speeds and push tiny particles of Earth material directly ahead of them or displace the particles directly behind their line of travel. An area underlain by unstable ground is likely to experience much more noticeable effects than an area equally distant from an earthquake's epicentre but underlain by firm ground such as granite. shear waves displace material at right angles to their path and therefore sometimes called "transverse" waves. called “S waves” do not travel as rapidly through the Earth's crust and mantle as do compressional waves. If the earthquake occurs in a populated area. but only compressional waves travel through the Earth's molten core. The two general types of vibrations produced by earthquakes are surface waves. acceptable performance of a structure during earthquake excitation is based on the lateral force resisting system being able to absorb and dissipate energy in a stable manner for a large number of cycles 11 . compressional and shear. These protective systems are in the form of: 1) Seismic isolation systems: ¾ Elastomeric bearings ¾ Lead rubber bearings ¾ Combined elastomeric and sliding bearings ¾ Sliding friction pendulum system ¾ Sliding bearings with restoring force 2) Supplemental energy dissipation devices: Passive energy dissipation Semi-active and Active systems ¾ Metallic dampers ¾ Active bracing systems ¾ Friction dampers ¾ Active mass dampers ¾ VE solid dampers ¾ Variable stiffness and damping systems ¾ VE or viscous fluid dampers ¾ Smart materials ¾ Tuned mass dampers ¾ Tuned liquid dampers Conventional design approach. special precautions need to be taken in safeguarding against damage of important secondary system. The method of structural isolation deflects or filters out the earthquake energy by interposing a layer with low horizontal stiffness between the structure and the 12 . Over the past couple of decades the astounding developments in alternate design strategies have been made.Influence of Damping Systems on Building Structures Subject to Seismic Effects (Constantinou et al. seeks to prevent occurrence of inelastic deformations by allowing structural members to absorb and dissipate the transmitted earthquake energy by inelastic cyclic deformations in specially created regions. which incorporate. possibly to the extent that the structure is no longer repairable. In such cases. Furthermore. 1998). the structure must be designed with sufficient strength to minimize the inelastic deformations. Conventional design approach is not applicable in situations when a structure must remain functional after earthquake. however.. earthquake protective systems in the structure. This strategy implies that some damage may occur. in such structures. this approach is very expensive. which are needed for continuing serviceability. 2 Base isolation (Based on Shustov V. and whose dominant modes are within a certain frequency range. However.Influence of Damping Systems on Building Structures Subject to Seismic Effects foundation.. 13 . Displacement reduction is achieved by adding either stiffness and/or energy dissipation to the building structure. Los Angeles. The structural isolation system includes wind resistant and tie down system and also includes supplemental energy dissipation devices to transmit force between the structure above the isolation system and the structure below the isolation system. Marina Apartments San Francisco). Tohoku Electric Power Company. These mechanical energy dissipating devices have been found to be quite promising and their applications form the focus of this study. it is not possible to provide sufficient flexibility for the reflection of the earthquake energy. The primary reason for introducing energy dissipation systems into building frames is to reduce the displacement and damage in the structure. 1994) Another approach to improving earthquake response performance is that of supplemental energy dissipation systems. in an earthquake rich in long period components. University of Southern California Teaching Hospital. 2. mechanical devices are incorporated into the frame of the structure and absorb the energy from the earthquake reducing the drift as well effects on the critical components of the structure. The structural isolations are suitable for a large class of structures that are short to medium height. Several building and bridges have now been installed with base isolation systems (for example Tokyo Port Terminal. In these systems. Fig. even though nonlinear response to strong ground shaking may be anticitated. also the linear dynamic procedure uses the same linearly-elastic structural model. Second. Fagan. similarly to linear static procedure. First. the evaluation of a nonlinear deformations should be carried out using nonlinear procedures that explicitly account for nonlinear deformations in deformed components. nonlinear dynamic.3. Hence.1 Static analysis procedures A static analysis is a quick and easy way to obtain an approximate response of a structure. 1992). this method determines the distribution of the earthquake base shear force. however. Krinitzsky et al.3 Analysis procedures Today. are described in great details in FEMA 273/274. According linear static procedures. non-linear static. static lateral forces are applied to the structure to obtain design displacements and forces (FEMA 273/274). On the othe hand. 1993. As an option. it is implied that an adequate measure of designactions can be obtained using a static analysis. in given direction. linear dynamic. it is simpler to express acceptability in terms of internal forces rather than internal deformations (FEMA 273/274). namely linear static. 2. Generaly. it does not explicitly account for effect of nonlinear response. 1987. the guidelines permit evaluation to be carried out using linear procedures. in 14 .2 Dynamic analysis procedures Similarly as the linear static. when using linear procedures. The linear dynamic procedure provide greater insight into the structural response. eved though seismic response is dynamic. throughout the height of a structure. In a linear procedure.3.. The guidelines provides also criteria to determine when nonlinear procedures are required as an alternative. there is direct relation between internal forces and internal deformation for all types of loading. Preferebly. there are a number of methods available for building structures subjected to seismic loading (Newmark and Hall. Four of them. 2.Influence of Damping Systems on Building Structures Subject to Seismic Effects 2. it is implied that an adequate measure of design actions can be obtained using a linearly-elastic model. The method is based on two important assumptions. all these results are combined by using established rule to calculate total response quantities (FEMA 273/274). Modal superposition is only suitable for linear analysis. The following approximations are made in this method: 15 . The time history analysis determines the response of a structure due to forces.C. which is implicit and unconditionally stable. U.Influence of Damping Systems on Building Structures Subject to Seismic Effects the case of nonlinear dynamic procedure. T. 1987). The direct integration utilize a step-by-step solution of equation of motion. fist is direct integration and the second. obtained by changing the structural properties. the modal frequencies and shapes are used to establish spectral demands. 1975). F(t) is the vector of applied forces. respectively. Using standard mathematical procedures (Clough and Penzien. modal superposition (Clough and Penzien. There are two types of this method. storey shears and base reactions for each mode of response considered. forces. There are two general types of dynamic analysis to choose from for structures subjected to seismic ground motions. velocity and acceleration vectors. which is generaly described as: MU&& + CU& + KU = F (t ) (2. and U&& are the displacement. the damping.K are the mass. velocities or accelerations that vary with time.1) where. which may varied with time. U& . 1993) and a response spectrum corresponding to the damping in the structure. respectively. with damping to the dynamic motion of force (Newmark and Hall. The response spectrum requires dynamic analysis of a structure to establish modal frequencies and mode shapes. Consequently. whereas direct integration can be used also for nonlinear analysis. M. which are the response spectrum and type history analysis. The spectral demands are then used to calculate displacements. the nonlinear load-deformation behaviour of individual components and elements is modeled directly in the mathematical model. The response spectrum is defined as a graphical relationship of the maximum acceleration response of a SDOF elastic system for various values of natural period. The most popular integration scheme is the Newmark-β method. and the stiffness matrices. displacements. 2) {U }t + dt = {U }t + {U& }dt + ⎛⎜⎜ ⎛⎜ 1 − β ⎞⎟{U&&}t + β {U&&}t + dt ⎞⎟⎟(dt )2 ⎝⎝ 2 ⎠ ⎠ (2.25 is used. however. These devices. but usually a value of 0. systems that require no externally supplied power and systems that require minimal externally supplied power to operate. an active control system develops motion control forces.4 Passive energy dissipation devices The function of Seismic Isolation and Energy Dissipation System is to reduce structural response due to earthquake. However. Passive control system develops control forces at the points of attachment of the system. dt is the time step of the analysis. the magnitude and direction of these forces are determined by a controller based on information from sensors and control strategy and supplied by the active control system. For this reason.3) where. reducing energy dissipation demand on the primary structural members. 2. The term control systems denotes what was previously termed energy dissipation system. and thus reducing the structural deflection and nonstructural deformations. respectively. in principle provide for more versatile response control. The relative motions of these points of attachment determine the amplitude and direction of the control forces. can absorb part of the energy induced in the structure. wind and other dynamic loads. 16 . they require a power supply to be activated and hence may be undependable during seismic events where the power supply could be disrupted. The power needed to generate these forces is provided by the motion of the points of attachment during dynamic excitation. and β is the structural damping depend on an amplitude decay factor. An active control system should. which are also known as motion control system. On the other hand. dampers with active control have been tested on tall buildings subjected to wind induced loading rather than the more unpredictable cyclic loading caused by earthquakes. whereas the terms passive and semiactive denote.Influence of Damping Systems on Building Structures Subject to Seismic Effects {U& } t + dt dt = {U& }t + ({U&&}t + {U&&}t + dt ) 2 (2. Power source required for the semi-active control system is typically very small and remotely related to the power output of the system. 2. 1995) In the last two decades. variety of energy dissipation devices (EDD) has been developed to enhance safety and reduce damage during earthquake excitations. Energy dissipation may be achieved either by the transformation of kinetic energy to heat or by the transferring of energy among vibrating modes.3 Example of semi-active control system (Based on Kobori et al. 17 . Fig. These devices utilize a wide range of material and technologies as a means to increase the damping. stiffness and strength characteristics of structures..Influence of Damping Systems on Building Structures Subject to Seismic Effects A semi-active Control System generally originated from passive control systems. orificing of fluid or sliding friction). which was modified to allow for adjustment of their mechanical properties (shearing of viscous fluid. The mechanical properties of semi-active control systems may be adjusted by a controller. 4. hysteresis devices have high resistance to fatigue. 2. exhibit substantial rate dependence. while VE or viscous devices involving deformation of VE solids or viscous fluids and those employing fluid orificing. in contrast. Fig.1 Hysteretic energy dissipation devices A variety of hysteretic energy dissipation devices has been proposed and developed to enhance structural protection. The simplest models of hysteretic behaviour involve algebraic relation between force and displacement. 1997) In general. 2. number of load cycles. which. which indicates that behaviour of friction dampers is close to that of Coulomb friction. and friction dampers that generate heat through dry 18 . 2. hysteretic systems are often called displacement dependant. hysteresis devices dissipate energy through a mechanism that is independent of the rate of load frequency.Influence of Damping Systems on Building Structures Subject to Seismic Effects The first mechanism includes either hysteretic devices. In addition. Hence. Most of these devices generate rectangular hysteresis loop (Fig. or variation in temperature. Hysteresis devices include metallic dampers that utilize the yielding of metals as the dissipative mechanism.. The second mechanism consists of re-centering devices that utilize either a preload generated by fluid pressurization or internal springs. or a phase transformation to produce modified force-displacement response that includes a natural re-centering component.4). which dissipate energy without considerable rate dependence.4 Idealized force-displacement loops of hysteretic devices (Based on Soong et al. Hysteretic devices operate on principles such as yielding of metals and frictional sliding. and VE or viscous devices. that the force output does not scale with the displacement. that means. The parallel metallic plate used to be installed within a frame bay between a chevron brace and the overlying beam. Disadvantages of these devices are their limited number of working cycles and their non-liner response. Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects sliding friction. The non-linearity of hysteretic devices must be considered in structural analysis as well as in design. The most desirable characteristic of these devices are their stable hysteretic behaviour. 1991) X-shaped plate dampers are probably the most popular among the metallic dampers. Consequently.. consequently. and relative insensitivity to change in temperature.1. the dampers 19 . low-cycle fatigue property.1 Metallic dampers Metallic dampers utilize the hysteretic behaviour of metals in the inelastic range. and significant path dependence is apparent. A wide variety of damping devices that utilize shear. these devices are relatively inexpensive and their properties will remain stable over the long lives of structures. It should also be noted that energy dissipation occurs only after a certain threshold force is exceeded.4. 2. depend on the nonlinear stressstrain characteristics of the metallic material. The both types of devices are inherently non-linear. long term reliability. The resisting forces of the dampers. In addition. flexure and material deformation in the plastic range have been developed and tested.5 Two examples of X-shaped plate dampers (Based on Whittaker et al. 2. There are also several interesting alternatives to the modified Newton-Raphson algorithm. The results of these studies showed that the X-shaped plate dampers exhibited good performance and proved to be stable under large axial loads in the device. Later.. they were also used in buildings.. The tapered shape of the plates generates nearly uniform yielding over the entire plate surface. after experimental work carried out by Tsai and Hong (1992). Italy and USA. Beyond a certain level of force.. the plates yield and hence provide substantial energy dissipation. (1987) and Whittaker et al. (1993). Jara et al. Variations of the steel cross-bracing dissipaters have been developed in New Zealand. Fig. Some applications of non-linear structural analysis to building frames incorporating metallic dampers can also be found in Xia and Hanson (1992). 2. (1991).6 Triangular shaped damper and its hysteresis loops (Based on Tsai et al. X-shaped plate dampers consisting of multiple X-shaped steel plates were introduced by Bechtel Power Corporation.Influence of Damping Systems on Building Structures Subject to Seismic Effects primarily resist the horizontal forces related to inter-storey drift via flexural deformation of the individual plates. Comprehensive experimental studies of these dampers have been carried out by Bergman et al.. Device similar to the triangular plate 20 . Triangular steel yielding devices have also been used in Japan. 1997) Triangular plate dampers were originally developed in New Zealand and used in several base isolation applications. 1985). Another device.7. 1980. which should be addressed to insure that the dampers can sustain a sufficient number of cycles of deformation without premature fatigue. as shown in Fig. The process of extrusion consists of forcing a lead piston through a hole or an orifice. thereby changing its shape.. which should be worked out carefully. 2. Fig. 1985) All these metallic yielding dampers may be effective in reducing the response of structures to earthquake loading.. as a passive energy 21 . Lead extrusion damper (LED) represents another class of dampers. The post-yielding deformation range of these dampers is a major concern.7 Yielding steel bracing system (Based on Tyler et al. 1991). which utilized the hysteretic energy dissipation properties of metal. Tyler.. is the stable hysteretic behaviour of the dampers under repeated inelastic deformation. 1992). LEDs were first suggested by Robinson et al. a yielding damper consisting of a short lead tubes loaded to deform in shear was developed for developed by Sakurai et al. Several modifications of the steel cross–bracing dissipater have been developed and installed in Italy (Ciampi. Energy is dissipated by inelastic deformation of the rectangular steel frame in the diagonal direction of the tension brace.. 2. (1987). Yielding steel bracing systems fabricated from round steel bars for cross-braced structure have been developed in New Zealand (Skinner et al.Influence of Damping Systems on Building Structures Subject to Seismic Effects dampers was developed by Obayashi Corporation (Soong and Constantinou. Another problem. 1994). The first device consists of a thick-walled tube and a co-axial shaft with a piston. There is a constriction on the tube between the piston heads and the space between the piston heads is filled with lead. As the shaft moves. the lead must extrude through the orifice formed by the bulge and tube.8. the piston moves along the tube and the lead is forced to extrude back and forth through the orifice formed by the constriction of the tube. 1987) The second type of LED is similar to the first one. the hysteretic behaviour of LED is essentially rectangular. there are two types of LEDs introduced by Robinson.Influence of Damping Systems on Building Structures Subject to Seismic Effects dissipation device for base isolated structures in New Zealand. As it can be seen from Fig. 2.. The load deformation relationship of LED is stable and unaffected by the number of loading cycles. Similar to most friction devices. except that the extrusion orifice is formed by a bulge on the central shaft rather than by a constriction in the tube. The central shaft extends beyond one end of the tube. Fig. When external excitation occurred. 2. The shaft is supported by bearings which also serve to hold the lead in place. They have a long life and do not have to be replaced or repaired after an earthquake excitation since the lead in the damper returns to its 22 .8 Two examples of lead extrusion devices (Based on Robinson et al. Consequently.2.Influence of Damping Systems on Building Structures Subject to Seismic Effects undeformed state after excitation. this is only valid if the slippage of the device is sufficient to completely straighten any buckled braces. However. number of load cycles. (1982). the tension brace induces slippage at the friction joint. the four links force compression brace to slip. 2. Friction dampers can provide mechanism for dissipation of large amount of energy and they have good performance characteristics and their behaviour is less affected by the load frequency. which is a more detailed model for the device in which each member of the bracing-damper system is represented by element reflecting 23 .1.2 Friction dampers A wide variety of friction dampers has been developed and installed in building structures. When load is applied to this damper.9 Pall friction damper (Based on Pall and Marsh. Fig. Friction damper exhibit rigid-plastic behaviour and force response is modelled by Coulomb friction. the braces in a moment resisting frame incorporated frictional devices. Energy is dissipated in both braces even though they were designed to be effective in tension only. In this type of damper. The lead extrusion devices are insensitive to environmental conditions and aging effects.4. X-braced damper was proposed by Pall et al.. or changes in temperature. 1982) Bracing-damper system. . Uniaxial friction damper (Fig.10 Uniaxial friction damper (Based on Sumitomo Metal Industries Ltd 1992) 24 .10) manufactured by Sumitomo Metal Industries Ltd. made obvious. but offers some advantages in terms of ease of manufacture and assembly. This helps to maintain a consistent coefficient of friction between the pads and the inner surface of the stainless steel casing. operation and damper force of the improved damper were compared with those of the original Pall friction damper. but buckle elastically in compression was proposed by Filiatrault and Cherry (1987). which provides dry lubrication. The authors conducted some physical experiments from which. 2. Bending stiffness is included to maintain stability of the damper mechanism. utilizes a slightly more sophisticated design. Hence the improved damper replicated the mechanical properties of the original damper. The structural braces are assumed to yield in tension. (2005). The construction details. Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects its individual axial and bending characteristics. The analyses and validation experiment carried out by authors showed that the resisting forces generated by these two dampers were identical with identical frictional forces. These copper alloy friction pads contain graphite plug inserts. 2.. The pre-compressed internal spring exerts a force that is converted through the action of inner and outer wedges into a normal force on the friction pads. that seemingly minor fabrication details can significantly affect the overall performance at the friction damper. Improved Pall friction damper was developed by Wu et al. or ambient temperature on damper response was reported as insignificant. Sumitomo friction damper was investigated by Aiken and Kelly (1990). the effect of loading frequency and amplitude. however. The performance of the friction dampers was outstanding. number of cycles. However. since this device also includes an internal spring and wedges encased in a steel cylinder. The EDR utilizes steel and bronze friction wedges to convert the axial spring force into normal pressure 25 .. there are some novel features of the EDR that produce very different response characteristics. Furthermore. The placement of the dampers did not influence base shears significantly. 2. The hysteresis loops showed very consistent. Inc. The design of this friction damper is superficially similar to the Sumitomo damper.12 was manufactured by Fluor Daniel. depend on the input ground motion because friction dampers are not activated and do not dissipate energy for forces smaller than threshold. nearly ideal Coulomb behaviour throughout the duration of the test and approximately 60% of the input energy was dissipated in the dampers. Fig. The reduction in displacements. 2.Influence of Damping Systems on Building Structures Subject to Seismic Effects Aiken and Kelly (1990) indicated that the response of these dampers is extremely regular and repeatable with rectangular hysteresis loops. 1992) Energy Dissipating Restraint (EDR) shown in Fig. The authors performed experimental and numerical examinations of this damper installed on 1/4-scale 9 storey steel frame in conjunction with chevron brace assembly.11 Installation of uniaxial friction damper in steel frame (Based on Sumitomo Metal Industries Ltd. Influence of Damping Systems on Building Structures Subject to Seismic Effects acting outward on the cylinder wall. Therefore, the frictional surface is created by the interface between the bronze wedges and the steel cylinder. Internal stops are installed within the cylinder in order to create the tension and compression gaps. The length of the internal spring can be changed during operation to provide a variable friction slip force. Fig. 2.12 Energy dissipating restraint (Based on Fluor Daniel, Inc., 1993) Slotted bolted damper, proposed by Fitzgerald et al., (1989) can be seen in Fig. 2.13. This damper allows slip to occur in slotted bolted connections. The connection consists of gusset plate, two back to back channels, cover plates, and bolts with washers. The sliding interface consists of steel. Fig. 2.13 Three examples of slotted bolted connections (Based on Fitzgerald et al., 1989, Grigorian et al., 1993, and Constantinou 1991) 26 Influence of Damping Systems on Building Structures Subject to Seismic Effects Grigorian and Popov (1993), introduced and tested a slotted bolted damper with the sliding interface consisted of brass and steel. A frictional characteristic of modified interface were a significantly more stable than those of steel interface. Earthquake simulator tests of a three-storey steel building model with the slotted connection have been carried out by Grigorian and Popov who showed the effectiveness of the device in reducing the seismic response. Utilizing of graphite impregnated bronze plates proposed by Constantinou et al., (1991), is another alternative to improve the frictional characteristic of the slotted bolted damper. Rotating slotted bolted friction damper with inclined slotted holes has been successfully proposed and tested by Butterworth (1999). Concentrically braced frame proposed by Yang and Popov (1995) is representative of another type of friction dampers. Concentrically braced frames offer one of the most efficient lateral loads resisting system available, which combine strength, stiffness, low weight and simple construction. Unfortunately, under seismic loading the applying of light tension-only tends to leads to ‘soft storey’ failure due to irrecoverable tensile yielding. To remedy this disadvantage, the authors suggested the used of specially detailed sliding plates moving in the vertical plane. 2.4.2 Viscoelastic dampers VE dampers have force displacement characteristics that are function of either the relative velocity between the ends of the damper or the frequency of the motion. However, the response of these devices may also be a function of relative displacement. VE devices exhibit stiffness and damping coefficients, which are frequency dependant. Moreover, the damping force in these devices is proportional to velocity, that the behaviour is viscous. Research and development of the VE dampers for seismic applications began in the early 1990s. Over the last few years extensive experimental program has been designed and carried out for steel frames and lightly reinforced concrete frames. VE dampers are mostly used in structures where the damper undergoes shear deformations. 27 Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig. 2.14 Idealized force-displacement loop of VE devices (Based on Soong et al., 1997) Solid VE dampers are constructed from constrained layers of acrylic polymers or copolymers and designed to produce damping forces through shear deformations in the VE material. When deformed, the VE materials exhibit the combined features of an elastic solid and viscous liquid i.e. they return to their original shape after each cycle of deformation and dissipate a certain amount of energy as heat. Fig. 2.15 Typical VE solid damper (Based on Chang et al., 1995) Several shake table tests of large-scale steel frames and reinforced concrete frames with added VE dampers have been carried out by Ashour et al., (1987), Fujita et al., (1991), Aiken et al., (1994), Chang et al., (1995), Foutch et al., (1993) and Min et al., (2004). In each of these experimental studies, VE dampers 28 Influence of Damping Systems on Building Structures Subject to Seismic Effects were found to significantly improve the response of the frame and reduce interstorey drifts and storey shears. These results have led to the development of design procedures for structures fitted with supplemental VE dampers. Bitumen rubber compound VE damper developed by Showa and Shimizu corporations induces large damping forces to shear deformation and can sustain shear strains of about 300%. The test results indicated a 50% reduction in the seismic response of the frame. Super-plastic silicone rubber VE shear damper developed and tested by Kumagai-Gumi Corporation at the top connection of a wall panel to the surrounding frame. Tests of ½ scale 3-storey steel frame show response reductions of up to 60%. Fluid VE devices, such as viscous shear walls, operate by shearing VE fluids. They possess the response characteristics similar to solid VE dampers, except that the fluid VE dampers do not exhibit stiffness when loads with low frequencies are applied (Fu and Kasai, 1999). The dampers, which utilise the viscous properties of fluids have been developed and used in several structural applications. Forcedisplacement loop of viscous damping devices is shown in Fig.2.16. Fig. 2.16 Idealized force-displacement loop of viscous devices (Based on Soong et al., 1997) Viscous-damping wall system was developed by Sumitomo Construction Company in Japan. The device consists of an outer steel casing attached to the lower floor, filled with a highly viscous fluid. An inner moving steel plate hanging from the upper floor is contained within the steel casing. The viscous damping force is induced by the relative velocity between the two floors. Arima et 29 Influence of Damping Systems on Building Structures Subject to Seismic Effects al., (1988) conducted experimental test on a full scale 4-storey steel frame with and without viscous damping walls. The results of frame fitted with viscous walls revealed response reductions of 66 to 80%. A 4-storey reinforced concrete building with viscous damping walls was constructed in Tsukuba, Japan and has since been monitored for earthquake response. The viscous damping walls installed in the 78 m high steel frame building in Shizuoka City, Japan, provided 20 to 35% damping and reduced the building response up to 70 to 80% (Miyazaki and Mitsusaka, 1992). Fig. 2.17 Viscous damping wall system (Based on Sumitomo Construction Company, 1996) Fluid viscous dampers operate on the principle of fluid flow through orifices. Viscous dampers can dissipate large amount of energy over a wide range of load frequencies. The main advantage of viscous dampers is that, they can reduce building deflection and stress at the same time. This is because the force from the dampers is completely out of phase with stresses due to flexing of the structure. Viscous dampers are relatively insensitive to temperature changes. However, these dampers are not suitable for stiff structures due to high damper force requirement. Fluid viscous dampers, which operate on the principle of fluid flow through orifices, are installed in a number of structural applications (some of them can be seen from Figs. 2.18-2.20). 30 Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig. 2.18 Orificed fluid dampers (Based on Constantinou et al., 1998) Viscous dampers of varieties of materials and damping parameters were proposed and developed for seismic protection. These dampers possess linear viscous behaviour when force response of viscous dampers is proportional to velocity, so structural design is generally straightforward. Comprehensive experimental and analytical studies of buildings fitted with viscous dampers manufactured by Taylor Devices, Inc. have been carried out by Lee and Taylor (2002). They affirmed that the addition of currently available viscous dampers into a structure could provide damping as high as 35% critical. Fig. 2.19 Elastomeric spring damper (Based on Taylor Devices, Inc., 1998) In a study conducted by Pong, (1994) indicated that the major disadvantage of using fluid dampers as energy absorbing devices is that the peak structural response cannot be reduced significantly if it occurs in the early stages of excitation because of the dependence of the damper’s resisting force on the velocity. To overcome this shortcoming, Pong suggested using a combination of tapered-plate energy absorber and fluid dampers. 31 stiffness and damping.21. The most popular representatives of this category of devices are Tuned Mass Damper (TMD) and Tuned Liquid Damper (TLD). The TMD usually experience large displacements. Their dynamic characteristics must be tuned to those of the primary structure..20 Pressurized fluid damper (Based on Taylor Devices. 2. the kinetic energy is transferred from the structure to the TMD and is absorbed by the damping component of the device. Fig. 1998) TMD consists of a mass. 1998) 2.Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig. In order to reduce input of seismic energy. 2. 2.3 Dynamic vibration absorbers Dynamic vibration absorbers have been examined in a several numerical and experimental studies. As a result. which moves relative to the structure and is attached to it by a spring and a viscous damper in parallel..21 Models of SDOF structure and TMD (Based on Abbas et al. 32 . Inc. as shown in Fig. The structural vibration generates the excitation of the TMD. the dynamic vibration absorbers involve mass.4. The optimum tuning and damping ratios that result in the maximum absorbed energy have been studied by several investigators.22) consist of rigid tanks filled with liquid. TLDs (Fig. Energy is dissipated by the movement of the liquid in the tube through an orifice.Influence of Damping Systems on Building Structures Subject to Seismic Effects TMD incorporated into a structure where the first mode of the structural response dominates. is expected to be very effective. which are: ¾ Reducing the motion in two directions simultaneously. where the energy is absorbed by the sloshing motion and dissipates it through viscous action of the liquid. 2. However. TLCDs are relatively simple to 33 . The tuned liquid damper (TLD) and tuned liquid column damper (TLCD). As a result. TLCD contain liquid-filled tube-like containers. similarly to a TMD impact indirect damping to the system and thus improve structural response. ¾ No activation mechanism is required. there is not a general agreement about the effectiveness of TMDs for seismic applications. TMDs have been found effective in reducing the response of structures to wind and harmonic loads and have been installed in a number of buildings. the relatively small mass of fluids compared to the large mass of TMDs requires larger spaces to achieve the same damping effect. In the case of TLCD. 1989). TLDs have several advantages over the previously described TMDs. Numerical and experimental results reveal that the effectiveness of TMDs on reducing the response of the same structure under different earthquake excitations or of different structures under the same earthquake is considerably different. TLD systems are not very sensitive to the actual frequency ratio between primary and secondary system. ¾ Minimum maintenance cost. A TLD dissipate energy by means of viscous actions of the fluid and wave breaking. The vibration frequency of the device can be adjusted by changing the liquid column length (Sakai. energy is dissipated by the passage of liquid through an orifice with inherent head loss characteristics. ¾ Do not require large stroke lengths. which are rigidly attached to the structure. the optimum parameters of TLCDs for seismic applications depend on the results of a deterministic response analysis of a series of SDOF structures to earthquake ground accelerations.23 Tuned liquid column dampers within shear wall (Based on Sumitomo Construction Company. Damping is increased by adjusting the orifice opening. Fig. Fig .2.Influence of Damping Systems on Building Structures Subject to Seismic Effects implement in existing buildings since they do not interfere with vertical and horizontal load paths. 1999) 34 . The results of this study indicate that the use of the optimum parameters reduces the displacement and acceleration responses up to 47% (mass ratio of 0.04).22 Building with a TLD and a TLCD (Application in the Crystal Tower Building of Chicago) In a study conducted by Sadek (1999). 2. TLCDs do not require the space for large stroke lengths. Influence of Damping Systems on Building Structures Subject to Seismic Effects 2. 2. for moderate earthquakes. the structure behaves elastically. Fig. The results of the testing included two types of behaviour of special interest: large strain behaviour and cyclic superelastic behaviour. Since most structures deal with low frequency content. it is possible to take advantage of these metals without much compromise. Some of the most promising characteristics of the martensitic and superelastic modes of SMA behaviour are: ¾ High stiffness for small strain (elastic loading) ¾ Reduced stiffness for intermediate strain (due to formation of martensite) ¾ High stiffness at large strain (elastic loading of martensite) Since the superelastic state ideally displays a hysteretic effect with zero residual strain.24 Stress-strain response of shape memory alloys (Based on Li. an energy absorbing device made of this material would theoretically provide a self-centering mechanism. which include a new class of materials referred to as shape memory alloy (SMA).4 Phase transformation dampers Phase transformation dampers are energy dissipating devices. and Samali. J. The advantage of this behaviour is that. 2000) Aiken (1992) incorporated small loops of Nitinol to study possibility of using this material as a passive energy dissipation device for structures. for low seismic excitation.. and their excellent fatigue and corrosion resistance properties. the 35 . B.4. Other attractive properties associated with SMA include their insensitivity to environmental temperature changes when properly heat treated. These metals are capable to produce large control forces despite its slow response time. This damper combines the 36 . Shao et al. due to a variety of practical problems. while remaining elastic. 2. A combination of these damping mechanisms can be apply within the structure to efficiently dampen out broad range of frequency content of seismic excitations (Hisano et al. The frictional element does not. Since these difficulties.5 Hybrid dampers The characteristics of VE and viscous dampers are that they dissipate energy at all levels of deformation and over a broad range of excitation frequencies (Chang et al. Yielding dampers dissipate energy through the uniform deformation of the steel (Tsai et al... however. When the VE material dissipates energy. intensive research and experimental work were undertaken by Samali and Wu (2000). However.4. so at a certain point the frictional element is not pushed hard enough to slip. As example of such problems can be used hybrid friction-VE damper. 2000. it heats and softens. The results of these investigations are more than encouraging. Such device is commonly referred to as a hybrid damping system. 1992). the most popular representative of this category. development and utilizing of hybrid damping systems is still rather limited. friction dampers dissipate energy only when the threshold force is reached and exceeded (Aiken et al. While no actual structural applications have taken place.... the structure stiffens and again dissipates large amounts of energy. Ribakov 2004. For these reasons. a careful design is necessary for all implementations of SMA in structural control. in the case of large earthquakes. only a limited number of hybrid damping systems have found practical application. On the other hand. these results also revealed that SMA is very sensitive to earthquake excitation type and can produce change in stiffness and consequently change the first natural frequency of the structure toward the earthquake dominant frequency.24. Hybrid friction-VE damper developed by company Damptech (2000) is probably. 1999). 1993).Influence of Damping Systems on Building Structures Subject to Seismic Effects Nitinol dissipate large amount of energy. 1991). 2. Behaviour of Nitinol during a moderate earthquake can be seen in Fig. Finally. The effective damping is usually formulated by applying device on a single degree of freedom (SDOF) system. 37 .Influence of Damping Systems on Building Structures Subject to Seismic Effects advantages of pure frictional and pure VE energy dissipation mechanisms. Fig. The damper consists of friction pads and VE polymer pads separated by steel plates as shown in the Fig. A prestressed bolt in combination with disc springs and hardened washers is used for maintaining the required clamping force on the interfaces as in the original FD concept.25 Hybrid friction-VE damper (Based on Damptech. Intensive testing is still underway with different VE materials. It has been experimentally confirmed that well designed friction-VE damper develop less than the half of peak response displacement of its non-damped counterpart and is also capable of dissipating 75%-90% of seismic input energy. however. As it was described in Section 2. 2. the guidelines for building structures subjected seismic loading identify four types of analysis.25. 2. is not taking in account the complex structure-device interaction. The most common method is linear procedures. and taken as the damping ratio of the first mode (FEMA 273/274). there are no clear design procedures for their implementation to building structures. which require modifying the seismic excitation on the structure with the respect of the added damping. 2000) 2.3. This oversimplified procedure.5 Implementation of supplemental devices to building structures Since the Energy dissipation devices (EDDs) are relatively new in the structural design and were introduced to the market by the individual producers. in the form of the estimate effective damping. The optimisation algorithm search the best device configuration from all the possible device location and combinations based criteria. For the device configuration with optimal seismic response reduction. including the natural frequencies. Since the added damping device often bring non-proportional damping into the system. However.Influence of Damping Systems on Building Structures Subject to Seismic Effects In order to investigate the effect of implementation of EDDs on buildings response. These analyses show that the most effective device distributions very much depend on the configuration of the structure and the building performance indices. acceleration or element force. sometimes. the structure has to be analysed carefully first. under design spectra compatible earthquakes. To better understand the effect of added non-proportional damping to the system. As a result of implementation of damping devices into the building structure. By this procedure. the dynamic properties of the original structural system are changed. the most common retrofit design procedure using EDD is to specify a damping ratio first before the design. several buildings have been studied. it is possible to design device configurations with acceptable building seismic response. which are displacement. an optimal device distribution is generated. both theoretical formulation and numerical simulation can be used. based on its characteristics and the defined performance index. A mathematically equivalent state space method can be used to obtain the structural characteristics and seismic response. After that. Currently. Subsequently. due to the oversimplification of the 38 . or under a varied range of earthquakes (FEMA 273/274). The overall effect of additional damping from the supplemental devices is generally investigated by applying the damping matrix into the original equation of motion. such as minimum response under seismic excitation. the devices are added to the structural system to increase the damping ratio to the specified value. The structure response is then checked for reduction. mode shapes and modal damping ratios. The seismic response reductions depend on the structure and its performance requirement. the dynamic characteristics can not be solved by using orthogonal property of the mode shapes so that the multi degree of freedom (MDOF) system is transformed into a set of SDOF modal systems. and identify for each configuration. This search is based on: ¾ Increase model damping for a particular mode ¾ Modify a particular mode shape ¾ Modify the total modal contribution to a particular mass point 5. For mass point of interest. which natural frequencies contribute most in the response and examine each corresponding steady state response vector to identify the largest contribution vector.. combined response) 3. The common practice of EDD design procedure based on maximum effective damping. the neglected higher mode might play an important role in the structural response (Lee et al. it is necessary to calculate characteristics of each potential configuration. natural frequencies and damping ratios. velocity. which can be applied to all type of structure. These comparisons reveal the most important modes in the response of the structure. 2001).Influence of Damping Systems on Building Structures Subject to Seismic Effects original system. the retrofitting design of using additional EDD is not a straightforward matter and there is no general rule. 39 . Search for optimal configuration of the EDD. Constantinou et al. (2001) defined a design procedure as follows: 1. not always lead to most effective design. the dynamic characteristics of structure need to be analysed carefully to fulfil the performance objective of the design. To find the effective configuration. compare these with the original structural characteristics. The largest added damping should not necessarily guarantee the best response reduction. Validation While following this procedure. so that the most effective device location is found and the devices are placed at those positions. The higher modes contributing to this response also need to be analysed. Structural analysis and simplification 2. acceleration. Hence. Definition of the constraints of added EDDs 4. Performance index (displacement. The comparisons should be made among modal shapes. loading factors. the designer should be aware that optimal distributions of damping devices throughout the building cause the structure to be non-proportionally damped.. the designers should check. the displacement response is further reduced (Uriz and Whittaker. The conventional modal analysis routine of fast calculation is employed in this approach and the damping effects can be clearly explained by using structural dynamic parameters. higher damping ratios could. To study the damping effects on MDOF building structures. displacements are reduced as the effective damping ratio is increased. the damped mode shape is not orthogonal to the damping matrix in the n-dimensional physical domain. For non-proportionally damped MDOF systems. The response of an MDOF non-proportionally damped system damping can be affected by many factors. The double modal superposition approach developed by Gupta and Law (1986) is used in some analysis. natural frequencies and damping ratio. therefore. The complex mode shapes are orthogonal in the state-space domain. For structures with added EDDs. increase the seismic response. such approach can only be accurate for proportionally damped or SDOF structures.Influence of Damping Systems on Building Structures Subject to Seismic Effects In addition. because the 40 . which include modal shape. However. in several cases. modal response. in the case of acceleration response. The displacement response is dominated by main modes. where real value cannot be directly applied” (Constantinou et al. the damping is no longer proportional or negligibly small. Many designers believe that fitting more dampers at the level of maximum inter-storey drift will achieve optimised structural response. where the response is the superposition of modal displacement and modal velocity. As mentioned previously. 2001). the analysis method must consider the effects of non-proportional damping. nor the complex system modes. The damping ratio and natural frequency in these equations are determined by the state vector eigen-value solution. It has been shown by Uriz and Whittaker (2002) that for MDOF systems. The state vectors for different supplemental damping devices are different. On the other hand.. the response is increasing. with a higher damping ratio and higher modal participation factor. 2002). which includes even higher mode contribution. These modes are not the undamped system modes. the damping distribution is very different if the optimisation target is chosen as the displacement or acceleration. are not constant. 7 and 12 became 99% when the ratio was increased to 30%. that the system response is not always reduced when the damping ratio is increased. The dampers were arranged in 13 different damper configurations (Table 2. the research team at Buffalo University (2001) analyzed a four DOF frame structure embedded with linear viscous dampers. Table 2. It can be concluded. 10%. damping ratio and modal shape.1). 4. the complex damping ratio remained nearly the same. 7. with four damping ratios (5%. However.Influence of Damping Systems on Building Structures Subject to Seismic Effects natural frequency. when the damping ratio was increased to 10%. Lastly. different damper configurations resulted in different response reductions even though they may achieve the same effective damping ratio value. while the other cases stayed unchanged. 7 and 12) in the fundamental mode collapse.1 Damper location (After Lee et al. dramatic changes resulted (in cases 1. except for the case 4. 41 . as the damping ratio became higher. Case 3. as the controlling damping ratio was higher than 15%. however.. the second mode shape turned into dominant in the system response. Consequently. 4. 3. 3. 2001) Placement/Case 1 1st storey x 2nd storey 3rd storey 4th storey 2 3 4 5 6 7 x x 8 9 x x x x x x x x 10 11 x x x x x x 12 13 x x x x x x x x x The results of first complex modal damping ratio for small damping ratios (5%) showed. the first complex damping ratio for cases 1. the response decreased as the damping ratio increased. and 12 have very different values when the controlling ratio increased to 20%. 10. 4. To demonstrate how system characteristic change due to added damping. 20% and 30%). The results revealed that. a dramatic change were observed in case 4. As regards to the relationship between the maximum displacement response and the controlling effective damping. which can be inconvenient and expansive. simulations of 7-storey shear framed structure with stiff beams were carried out. 2. Fig. based on response history analysis for all non-proportionally damped structures.. The results show a promising method of using off-the-shelf viscous dampers in VDS. (2001) to design the linear passive viscous dampers in accordance to the deformation and velocity. Optimal control theory (OCT) using a linear quadratic regulator is adapted in study conducted by Ribakov et al.26 Viscous damping system . The main difficulty in optimal design of passive viscous damped structures is that the optimal solution requires different levels of damping at each storey. The aim of this research. 2001) To investigate the effectiveness of the proposed design technique. was to obtain the required properties of the optimal viscous devices by using the OCT. Reductions up to 50% in the peak displacements and 60% in the peak accelerations were obtained.construction scheme (Based on Ribakov et al. The results of numerical simulation showed that its performance with VDS including standard dampers was close to the optimal design. where the angle between the damping correctors and the vertical plane was chosen so that the viscous damping system (VDS) consisting of standard viscous dampers produced optimal control forces. Thus.26. 2.. the 42 . Detail of the viscous damping system can be seen from Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects The authors emphasize the limitations of using the damping ratio as the key seismic response reduction measurement and they recommended evaluation of performance. (1997) proposed method of the optimal placement of viscous dampers for a building with specified storey stiffness. Several studies introduced complex mathematical formulations to optimise the performance index based on ‘optimal control theory’. (1992). These studies.. which utilize a fully populated optimal gain matrix. The results from these analyses showed that dampers should be placed in the lower storeys of the building if they are of uniform storey stiffness. 2. and Wu et al. This 43 . (1992) developed parametric optimization analyses to determine the optimum damping coefficient for the supplemental dampers to establish the effect of different damper distributions throughout the building hight.. were created by minimising a quadratic performance index and the parameters related to the supplemental damper coefficients were derived by approximations.. There are also sequential approaches to obtain the optimal damping coefficients distribution and capacity of the devices. This method is based on the intuitive criterion that additional damper is placed sequentially on the storey with the maximum inter-storey drift and as a result the damper is optimally installed if placed at a position of largest relative displacement across the damper.Influence of Damping Systems on Building Structures Subject to Seismic Effects damping at each floor is controlled and provides an improved behaviour of the structure during an earthquake.. Chang et al. Hahn et al. (1993) investigated the seismic behaviour of steel frame structure with added VE dampers and developed design guidelines based on obtained results.. (1996). Zhang et al. and De Silva (1981) proposed optimal control theory to establish the optimum damping coefficient and most effective damping coefficients distribution for viscous dampers under random earthquake ground motion.6 Research on seismic mitigation with passive dampers Though there is a lack of comprehensive guidelines implementing effects of energy dissipation devices on the structural dynamic behaviour. Gluck et al. it is still possible to find some partial studies. (1987) suggested that the optimal distribution of the supplemental devices should be at locations.. defining different forms of performance functions. The optimal distribution of friction dampers was obtained 44 . Consequently. Ashour et al. the authors extended this theory to design of MDOF VE and elastoplastic systems. They suggested that the distribution of the friction load should be similar to the storey stiffness.. which maximise the damping ratio of the fundamental mode. However. According Gurgoze et al. Kasai and Watanabe (1998) proposed a simplified theory to predict and compare the seismic performance of VE and elastoplastic passive dampers. Closed-form expressions for an equivalent period and an equivalent damping constant for these systems were suggested by idealizing them as linear SDOF systems. In a study conducted by Pong. Tsuji and Nakamura (1996) developed algorithms to reduce objective functions step by step. whose study included investigation of the effect of earthquake excitation frequencies content. such distribution should significantly reduce the structural displacement. As a result. Singh and Moreshi (2002) used a generic algorithm to determine the optimal size and location of viscous and VE dampers. The results showed that the addition of fluid dampers to the first floor of a building absorb more energy than those at the upper floors. (1992) optimal placement of viscous dampers should be based on an energy criterion. Yang et al. Natke (1993) carried out topological optimization to obtain optimal layout of the structure equipped with VE dampers. because this mode contribution to the structure’s response is the most significant.. such distribution can be less efficient in reducing the acceleration near the top of the structure.. (2002) proposed two optimal design methodologies for passive energy dissipation devices based on active control theories leading to the determination of the optimal damper placements and their capacities. Hanson et al.Influence of Damping Systems on Building Structures Subject to Seismic Effects approach was further developed by Shukla et al. (1993) studied influence of placement of supplemental friction dampers on seismic performance of structures. (1999).. (1994) a finite element model for fluid dampers was introduced and used in the analysis of a ten-storey frame. the first storey mass contributed less to the dominant mode of the system response.Influence of Damping Systems on Building Structures Subject to Seismic Effects from a nonlinear dynamic analysis (Filiatrault et al.. The building had been designed with 120 supplemental dampers. The design of friction damped frames was studied by group of researchers at University of California at Berkeley (Bhatti et al. respectively. Better results were obtained when most of the dampers from the first storey were removed. while a performance index to calculate response reduction was defined as a function of the strain energy of the undamped and damped structural systems. The analysing was formulated as a constrained optimization problem and nonlinear technique was applied to define the best results for various objective functions. Henry et al. 1985). With this optimised distribution.. It was shown that this approach yields similar behaviour of a structure with optimal viscous dampers and ADAS devices. and number of damper was gradually decreasing as the storey height increased. 1981. Dampers with smaller gains are eliminated first. 24 dampers were placed on the first storey.. 1990). 45 . A design method for metallic yielding dampers ADAS devices by utilizing optimal control theory was developed by Ribakov et al. Austin et al. and added to the 6th to 11th storeys. If the performance index was selected as optimal storey drift. the total system damping was increased by 4%.. as their effect on the building’s response is insignificant.. In this work the optimal properties of ADAS devices were proposed to be obtained b assuming equal dissipation in viscous and elasto-plastic actions of the linear viscous and nonlinear ADAS devices. Dampers are then eliminated in parts on their gains and their effect on the building’s response. (2001) introduced a new method to simultaneously determine the number of necessary dampers and the optimal placements and design of these dampers needed to retrofit existing structures. An 11-storey steel frame building structure was used as an optimal design example. (1999). He suggested starting with assumption that dampers are placed between every storey of the structure. Dampers with large gains are eliminated according to the building’s response with and without those dampers. (2001) was concentrated on using dampers within tall buildings that contain shear walls to enhance their seismic response. some of the viscous dampers were replaced with the hysteretic dampers. Therefore. the two different types of dampers (displacement dependant hysteretic lead damper and velocity dependant viscous damper) were used independently. firstly. The research undertaken by Madsen et al. The theory behind this being the rigid and highly damped lower part of a multi-storey building modulates the dynamic excitation resulting from strong ground motions more effectively. According to results of this project. the most effective position for the dampers is in the lower storeys. This has also the effect of reducing the stiffness at the base of the structure. there is only very limited number of publications concentrated of effective utilizing of combined energy dissipation systems.. was applied to high-rise building. In the other case. if the performance index was selected as acceleration. some studies are very promising. which involves both types of the dampers. the combined damping system. Due to some practical problems. (2002) studied and analysed the effects of vibration reduction control by combined hysteretic-viscous damping system on high-rise building. Hisano et al. the damping ratio of the dominant mode was increased by 19%.. which occurred in the 6th floor. Nevertheless. The number 46 . was reduced by an average of 11% for a series of spectra-compatible earthquake. was obtained. In one case. it was shown that it is more effective to place VE dampers in the lowest storeys. which could absorb a design energy earthquake vibration in the viscous damper. Subsequently. In the planning of the structure. while the total number of the dampers remained unchanged. and the largest storey drift. This new method of retrofitting buildings involves the use of VE dampers located within the shear wall of the building structure. the number of dampers.Influence of Damping Systems on Building Structures Subject to Seismic Effects Furthermore. However. increasing the natural period and so reducing the amount of seismic energy that is attracted to it. The effects of vibration reduction were analysed in two different cases. the optimal distribution would be different. The internal damping of the building was assumed to be proportional to the instantaneous stiffness of h = 2%. During preliminary study several damping systems were selected and studied for seismic retrofit. The results from the analysis showed that the deflection and acceleration responses obtained from the combined damping system were somewhere between those obtained from the case where only viscous damper was used independently and those obtained from the case where only lead dampers were used independently. A 12-storey concrete building was considered for retrofit by a number of engineers. Performance comparisons of earthquake response parameters were analysed. was examined under the Hachinohe and El Centro earthquake excitations. viscous dampers with supplemental friction dampers would have 25% lower floor acceleration responses over friction damping system. 1999). However. Shao and Miyamoto (Shao et al. who were also involved in the study. The building equipped with viscous dampers. The results of this study revealed that the best performance was achieved by the combination of nonlinear viscous dampers with supplemental friction devices. suggested that passive dampers could be the most cost-effective solution. These higher floor acceleration responses could increase the cost of the tile wall strengthening.Influence of Damping Systems on Building Structures Subject to Seismic Effects of the combined dampers was determined by considering the effects of lead dampers on the periodic characteristics of the building. Linear and non-linear time history analyses were performed. In contrast. All these studies have made some contributions to optimal use of energy dissipation devices. Based on these results the authors suggested that combination of a nonlinear viscous damper system with friction damper revealed great potential for the further seismic retrofit. Friction damping system had significant saving over the viscous damping system due to the damper unit price difference. lead dampers and the hybrid damping system respectively. none of them address the performance requirements sufficiently so that engineers can design an optimal damper placement based on particular performance index of a particular building.. These systems met the performance target with great saving over the previously proposed retrofit schemes. 47 . which utilize innovative mechanisms. while the required damping forces are large. which amplify damper displacements or velocities was developed. or in terms of architectural considerations such as open space requirements. These new configurations offer certain advantages.Influence of Damping Systems on Building Structures Subject to Seismic Effects 2. In recent years.7 Configurations of passive energy dissipation devices As it can be seen from previous sections. To amplify displacement and hence lower input force demand in energy dissipation devices the team of researchers at Buffalo University developed several new configurations.27 illustrates various damper configurations in a framing system and expressions for the magnification factors f. These configurations are more complex in their application since they require more care in their analysis and detailing. either in terms of cost of the energy dissipation devices. The following is a brief description of these new configurations and comparison with the typical chevron brace and diagonal configurations. 2. which resulted in increased cost. In addition. cannot be installed in certain areas due to open space requirements. several new configurations. Fig. (2001) and Constantinou and Sigaher (2000). 48 . are generally installed in diagonal or chevron brace configurations. a number of energy dissipating devices have been employed to provide enhanced protection for new and retrofit buildings. In the case of stiff structures treated under seismic or wind loads. These new configurations include the toggle-brace and the scissor-jack energy dissipation system. energy dissipation devices of diagonal or chevron brace configuration. which are made of varieties of materials and utilize different damping mechanisms. in many cases. The toggle-brace and scissor-jack are systems. structure experience only small displacement. which magnify the damper force through shallow truss configurations and consequently release the magnified force to the structural frame. The theory and development of these systems has been described in Constantinou et al. These devices. To address this larger damping devices were installed. 2001) It can be seen that: u D = f . W. FD. uD. On the other hand. is force along the axis of the damper and f. for which: FD = C 0 u& D (2. et al. M. This means.2. C0 is damping of the viscous damper.. is damper relative displacement.27 were confirmed by physical testing in laboratories at the Buffalo University. C.. u is interstorey drift. 2. u& D is relative velocity between the ends of the damper. the conventional chevron-brace and diagonal configurations have magnification factors less than or equal to unity.u (2. is weight of the frame and T is fundamental period. F. Example of 49 . The damping ratio under elastic conditions for a single-storey frame is: β= C 0 f 2 gT 4πW (2.FD (2. The formulas of the magnification factors introduced in Fig.7) where. The significance of the magnification factor can be clearly demonstrated in the case of linear viscous dampers.5) where.4) F = f .27 Effectiveness of damper configuration in framing system (Based on Constantinou.6) where. is magnification factor. is force exerted on the frame.Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig. the viscous damper in toggle-brace and scissor-jack configuration can achieve magnification factors f = 2 to 3 without any significant sensitivity to changes in the geometry of the system. the damping ratio is proportional to the square of the magnification factor. As results. Similarly for the maximum displacement.Influence of Damping Systems on Building Structures Subject to Seismic Effects instalment of energy dissipating device with lower toggle brace assembly in structural frame is shown in Fig. 50 . 2. the toggle brace damper configurations are evidently more efficient energy dissipation systems.28 Application of the damper with lower toggle braced assembly (Based on Taylor Devices Inc. Fig. 2. The results from this parametric study showed that the toggle brace configurations are capable of reducing both the maximum and root mean squared displacement of the buildings response. The reduction in root mean squared displacement for the toggle brace system was 34 %. as compared to 42 % and 47% for the lower and upper toggle brace system. while only 12% reduction for the chevron system. when the chevron and diagonal system had a reduction of 20% and 23% respectively. when yet again the toggle systems were about twice as effective as the conventional configurations. nevertheless. 2001) The numerical examples of the upper and lower toggle configurations were conducted by Marcelin (2003) on a 1-storey structure equipped with an upper and lower toggle viscous dampers. The results from this study revealed that the conventional diagonal and chevron configuration are capable of reducing the building response. similar trends were noted for the velocities.28.. In addition. 2000) The model was subjected to loading with sinusoidal waves and input earthquake waves. these small 51 . damper and auxiliary masses. As a result. The proposed model (Fig.. (2001) proposed and developed another type of the toggle damping mechanisms. A comparison between the acceleration response ratios of this model and a normal single-degree-of-freedom viscous damping system showed that the resonance magnification of the model by shown experiment was around 1. The lower arms of the toggle mechanism were connected to the frame with uni-axial pins so that the auxiliary mass could not vibrate in the out-of-plane directions. which is a kind of amplifier device with lever mechanisms. The pins of the upper arms were composed of universal joints to absorb the out-of-plane vibration and torsional vibration of the main frame mass and installation accuracy errors. The experiment results agreed well with the theoretical magnification and input-reducing effects.2.. which corresponds to a damping of approximately 40% when evaluated as a normal single-degree-of-freedom system. The model was composed of a frame whose columns were made of flat springs to confine the deformation in the in-plane directions.Influence of Damping Systems on Building Structures Subject to Seismic Effects Hata et al. 2.29) was a portal frame mounted on a unidirectional shaking table incorporating an obtuse-type toggle mechanism having viscous dampers. Fig.5 times. The main object of his experimental work was to develop toggle damping mechanism.29 Toggle specimen model (Based on Hata et al. when the structure experienced a horizontal drift at the top storey. a lever arm connected by means of hinges and to the storey diaphragm and the chevron brace. Even more. 2003) further developed a method for design of passively controlled structures using optimal control and viscous dampers with the dampers connected to the structure through lever arms. (2003) conducted a numerical simulation of 7-storey steel structure equipped with this damping system under varieties of seismic excitations. At the time. respectively. 52 . A connection of chevron brace and lever arm was realized through steel plates. In order to reduce the control forces and energy required for control. and as a result a magnified displacement and drift velocity were transferred to the damper placed at the bottom of the lever. 2003). they proposed also magnifying configurations for connecting semiactive and active dampers (Gluck and Ribakov 2000. Ribakov et al. Ribakov et al.. the large damping without changes in structural stiffness can be very valuable for retrofit of existing structures (Ribakov et al.. Ribakov 2000). Reduction in peak displacement in the range from 40 to 75% compared to the uncontrolled structure was achieved with this damping system. A proposed damping system yields significantly higher energy dissipation in the structural system with smaller devices.Influence of Damping Systems on Building Structures Subject to Seismic Effects dampers were considered to have a significant potential of providing large damping for buildings. (2000. which are transferred to the dampers. The system consisted of a chevron brace. Gluck (1996) proposed the utilizing of lever mechanisms to improve the damping characteristics of a structure by magnifying the drifts and drifts velocities. the lever arm rotated around hinge. These lever arm system was then used to magnify efficiency of damping devices.. A number of strategies and recommendations of effective use of passive dampers.8. 53 . The results from this research are presented in the next chapters. The reviewing was followed by recent research on seismic mitigation using passive dampers installed mostly in lower–rise structures. To further extend understanding of damping devices embedded within cut outs of shear walls. Finally. yielding of metals. whereas the research of damping devices placed within cut outs of shear walls is still very limited. as well as numerical and experimental results is described. It aims to carry out a comprehensive investigation on seismic mitigation of high and medium-rise structures with different damping devices embedded within cut outs of shear walls at different locations across the height of each structure. 2. shearing VE fluid or flow of viscous liquid through orifices. shear deformation of VE materials.2 Proposed research The main aim of this research project is to bridge existing knowledge gaps by undertaking comprehensive investigation of several high and medium-rise structures with different damping devices embedded within cut outs of shear walls. some of the possible configurations of dampers are presented. It briefly described the analysis methods currently in use and assumes their suitability. The vast majority of applications of damping devices presented in this literature review was realised within frame structures. Seismic mitigation principles are discussed next. The research will address the needs of local industries.8 Conclusions to the literature review 2.1 Summary of the literature review This literature review looked at the background of seismic activity and seismic effect on building structures. these structures are treated under a variety of different earthquake excitations and the results are compared in order to capture their advantages in creating efficient damping systems.Influence of Damping Systems on Building Structures Subject to Seismic Effects 2. followed by a description of a number of available passive energy dissipation devices using a range of material and damping mechanisms that work on principles such as frictional sliding.8. Influence of Damping Systems on Building Structures Subject to Seismic Effects 54 . Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 3 Model Development 55 . boundary conditions and loading conditions of the model. namely the displacement dependant friction part. The dynamic procedure in ABAQUS/Standard 56 . the second damping mechanism involves the use of VE damper and the third damping mechanism involves the use of a hybrid system consisting of friction and VE damper. and the velocity dependant VE part. which has the capacity to manage even small deformation can allow effective control of the building’s vibration response.Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 3: Model Development 3. the program selected for the numerical analysis has been ABAQUS Standard Version 6. analyse and investigate the effects of the six types of damping devices on the seismic response of structures. 96m high shear wall models and 18-storey frame models with embedded damping systems have also been treated. This analysis assembles the mass. 3. which has the capacity to manage large deformation.3. The first damping mechanism involves the use of friction damper. In order to further validate the feasibility of the procedure used in this study.1 Introduction This study comprehensively investigates the seismic response of 18 and 12 storey frame-shear wall structures with dampers located within cut-outs. and as the post-processor for viewing the results of the analysis. The response of the structure is obtained for selected time steps of the input earthquake accelerogram. For the purpose of this study. A direct integration dynamic analysis was selected to obtain the response of the structure under seismic loading.2 Finite element analysis Finite Element (FE) methods have been employed in this research to model. element mesh. namely 24-storey frame-shear wall structural models. three additional structural models. The use of both components of the hybrid damper. stiffness and damping matrices and solves the equations of dynamic equilibrium at each point in time. In conjunction with this computer program. MSC/PATRAN 2003 has been used as the pre-processor for generating the geometry. Three types of damping mechanisms were investigated. 1 Boundary conditions The earthquake events used in this study were recorded as time-history accelerations in the horizontal plane. ρ of 2500 kg/m3. Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects uses implicit time integration. Young’s modulus.2. thereby allowing only the x-direction translation. 3. To study the effectiveness of the damping system in mitigating the seismic response of the buildings in this study. 3. f′c of 32 MPa. and rotation about the z-axis. and density.Model location of applied acceleration 3.3.2 Material properties Concrete material properties were chosen for the models since many multi-storey buildings in Australia are constructed by using reinforced concrete.1 .000 MPa. 3. υ of 0. The support at the base of the structure was restrained against translation in the y-direction. No internal 57 . as shown in Figure 3. Poisson’s ratio. the maximum displacements and accelerations at the top of the structures are obtained from the results of the analysis and compared with those of the undamped building structure. Ec of 30. which reflects an assessment assuming predominantly elastic response with little cracking.3. The concrete had a compressive strength. The acceleration was applied in the xdirection at the base of the structure.3 Loading and boundary conditions.1. the direction of frictional slip must lie in the plane. Ec of 207. Some structural details are explained later in this chapter. The initial focus of this research was on the development of a model.4. f′c of 350 MPa.3 and density. and p . The extended version of the classical isotropic Coulomb friction model is provided in the computer program ABAQUS. The contact problem is therefore in linear range.000 MPa. Structural steel was used to model friction dampers and hybrid dampers with yield strength. which is proportional to the contact pressure in the form: τ crit = μ. 58 .4 Damper models 3. 3. In twodimensional contact problems.1 Friction damper model The first damping mechanisms employed in this study have been represented by friction dampers. is the coefficient of friction. μ . which slide one inside the other. there are only two options: slip to the right or left. This task was achieved by modelling the frictional contact between two tubes. (the program available to the author) for use with all contact analyses. is the contact pressure. Poisson’s ratio υ of 0. two contacting surfaces can carry shear stresses up to certain magnitude across their interface before they start sliding relative to one another.Influence of Damping Systems on Building Structures Subject to Seismic Effects damping was considered for the concrete since it was assumed small in relation to the damping provided by the damping devices. since all the states are governed by linear equations and nonlinearity is introduced only through the inequalities that trigger changes of state. The Coulomb friction model assumes that no relative motion occurs if the equivalent frictional stress is less than the critical stress. p (3. In the basic form of the Coulomb friction model. which represents the real behaviour of friction dampers.1) where. and Young’s modulus. and hence. ρ of 7700 kg/m3. which was considered sufficiently accurate for the purposes of this study.20 e (73.5 and 3.46 Temp ) (3. experimental results conducted by Chang et al.4. γ  is the shear strain.51γ −0. Abbas & Kelly (1993) define the stiffness and damping coefficients as follows: kd = G ′A t (3.23 e (72. and G” is the shear loss modulus.5ω 0..4) G ′′ = 18. A.6.3 Hybrid friction-viscoelastic damper model The third damping mechanisms employed in this study is represented by hybrid dampers consisting of both a VE and a friction damper model in series. ω. (1992) have shown that variation in the damper temperature due to dynamic excitation become negligible after several loading cycles as an equilibrium temperature is reached between the surroundings and the damper.89 Temp ) (3.3) where. Dampers are modelled as a linear spring and dash-pot in parallel (known as the Kelvin model) where the spring represents stiffness and the dashpot represents damping. However. the temperature of VE material significantly influences its mechanical characteristics. The following equations were used to obtain the moduli of the VE material as defined by Abbas and Kelly (1993): G ′ = 16. 59 . As it can be seen from equations 3.2 Viscoelastic damper model The second damping mechanisms employed in this study are represented by VE dampers.Influence of Damping Systems on Building Structures Subject to Seismic Effects 3.51γ −0. This model approximates the behaviour of a VE damper under vibratory loading to within 10%. is the shear storage modulus. 3. In the present study the temperature was kept constant at 21°C during the entire investigation. t. G’. is the thickness of the VE material.5) where.0ω 0.4.2) Cd = G ′′A ωt (3. is the loading frequency of the VE damper. is the shear area of the VE material. 5 18-storey frame-shear wall structure.0 m. These 60 . The dimensions of the shear walls were 6m wide and 0.1 Description of 18-storey frame-shear wall structure The structural models.0 m. as seen in Fig. 3. The columns and beams were located on either side of the wall. After the preliminary convergence study.Influence of Damping Systems on Building Structures Subject to Seismic Effects 3.18-storey frame-shear wall structure 3. The first set of models designated by H0 represents two-dimensional 18-storey frame-shear wall structures.2 Damper placement in 18-storey frame-shear wall structure One of the main aims of this study was to investigate the efficiency of energy dissipating dampers in vibration control for variety of placements under different earthquake loads.75 x 0. Fig. A lumped mass of 20.5. the concrete shear walls were constructed from 2016 S4R5 shell elements using shell elements of designation S4R5.4 m thick. 3. The height between storeys was set at 4.0 m. 3.000 kg at each beam-column and beam-shear wall junction was used to account for mass transferred from slabs and beams. treated in this thesis have been predominantly represented by two types of frame-shear wall structures.5.2 and had cross-sectional dimensions of 0.45 m respectively.75 x 0. and the beam spans were 6.2 .75 m and 0. which made the overall height of the structures to be 72. For this purpose twelve different damper placements were used to study the influence of location on the seismic response of these models. having 4 nodes per element and 5 degrees of freedom at each node. 6. The shear walls were constructed from 1344 S4R5 shell elements of the same parameters as in the previous models.6x0. 3.6 m and 0. H9 and H11 for single damper placements and by H1-3. H3. H4-6. and columns and beams with cross-sectional dimensions reduced to 0. 3. 3. 3. 3. H5. H13-15 and H16-18 for three dampers placement within the models. H7.Placements of three dampers within 18-storey frame shear wall structures 3.3 and 3. H10-12. The undamped structure (Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects models were designated by H1. Fig.3 .5).6 12-storey frame-shear wall structure 3.1 Description of 12-storey frame-shear wall structure The second set of models was represented by 12-storey frame-shear wall structure designated by M0 (Fig.6x0.4.2) was also analysed in order to compare results. As can be seen in Figs.4 .Placements of single damper within 18-storey frame-shear wall structures Fig.45 m respectively. the designating numbers correspond to location of the storey at which dampers were placed.0 m and the height between storeys 61 . H7-9. The spans of the beams were 6. M7-8.7 .Influence of Damping Systems on Building Structures Subject to Seismic Effects was 4. 3. Fig. Lumped masses of 20. M3-4.5 .6) and by M1-2. M3.0 m gave overall height 48. Fig.7).6 .12-storey frame-shear wall structure 3.3.6.2 Damper placement in 12-storey frame-shear wall structure In the 12-storey structural models twelve different damper placements were used to study the influence of location on the seismic response. 3. M5-6. M7. M5. M9 and M11 for single damper placement (Fig.3. M9-10 and M11-12 for placement of two dampers within these models (Fig. 3.Placements of two dampers within 12-storey frame-shear wall structures 62 . These placements are designated by M1.000 kg at each beamcolumn junction of the frames were used as before.0 m.Placements of single damper within 12-storey frame-shear wall structures Fig. 9 x 0. as shown in Fig. Lumped masses at each beam-column junction of the frames to account for mass transferred from slabs were 25. Placement of dampers and cut-out details were as in the study with shear wall models. The second structural types were represented by 24-storey frame-shear wall structures of designation T0. middle.9 m and 0. 3. The shear walls were modelled as before. 3. modelled using 2560 two-dimensional shell elements.8. The dimensions of the shear wall were 96 m high. W3 and W1-3 in which the damper was placed in the lower.8 24-storey frame-shear wall structures. 63 . as shown in Fig. upper and all three parts of the structure. and the spans were 8 m.8 . W2. respectively. Fig.9 x 0.45 m respectively. These were designated by W1. while the columns and beams of the frame had cross-sectional dimensions of 0.9. 3.000 kg.7 Shear wall structure In order to further demonstrate the feasibility of this study and if necessary extend the technique to taller structures three additional types of structural models with embedded dampers were also investigated.Placement of dampers within shear wall structures 3.Influence of Damping Systems on Building Structures Subject to Seismic Effects 3.5 m thick. A total of four different damping placements were used to study the influence of location on the seismic response of these models. The first of these structures chosen to test the feasibility of this technique was the shear wall designated W0. 15 m wide and 0. 75 x 0. F4.75 x 0. Fig.45 m respectively. 3.3. 3.11). The lumped masses at each beam-column junction were 20.75 m and 0. 3.Placement of dampers within 24-storey frame shear walls structures 3. F13-15 and F16-18 for placement of three dampers within these models (Fig. 3. Twelve different damper placements were used.10) and by F1-3.000 kg.9 . F10. where the columns and beams of the frame had cross-sectional dimensions of 0.10 . F7-9.9 18-storey frame structures The third structural types investigated in this study were represented by 18-storey frame structures designated by F (Figs.10. and the spans were 6 m.Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig. 3. These placements are designated by F1.11). F13 and F16 for single damper placement (Fig.Placement of single damper within 18-storey frame structures 64 . F4-6. F7. F10-12. Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig.11 .rise structures 65 . Fig. 3. Four different configurations of the dampers namely. chevron brace. lower toggle and a hybrid configuration consisting of the friction damper oriented horizontally and the VE damper mounted diagonally were considered.Placement of three dampers within 18-storey frame structures 3. 3. The undamped structure was also analysed in order to compare results.12 .Damping systems installed in medium.10 Dampers within 18 and 12-storey frame-shear wall structures Fig. Furthermore. diagonal. 3. which were primarily proposed and studied for medium-rise structures designated by H (18-storey) and M (12storey). Seismic analyses of these frame-shear wall structures were carried out with one type of damping system at a time.12 shows a six different damping systems. twelve different damper placements were used in each set of models to study the influence of location on the seismic response of these models. 71 m2 and the coefficient of friction between the tubes was assumed to be 0.75 m was modelled using 252 S4R5 shell elements.75 m was modelled using 264 S4R5 shell elements.25. the contact area in the unloaded state was 3. Fig. The connection between each tube and the shear wall was modelled using a MPC (Multi-Point Constraint) Pin type connecting element. and with one tube placed within the other. if these exist.1 Structural model with friction damper – diagonal configuration Details of the diagonal friction damper located within shear wall of the frameshear wall model can be seen in Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects 3.5 m high wall section was cut out and replaced by the damper. This MPC makes the displacement of the two nodes equal but allows the differential rotations. 3.10.Structural details of diagonal friction damper 66 . This MPC keeps a node on a straight line defined by two other nodes such that the node can move along the line. 3.5 m wide by 3. which provides a pinned joint between two nodes.13 . and the line can also change length.13 where a 3. A MPC Slider type connecting element was chosen to ensure frictional sliding between the tubes in a determined direction. This damper was modelled as a pair of diagonal tubes each with a thickness of 50 mm. The radial clearance between the tubes was 1mm. independent of each other. ¾ The inner tube having an outer diameter of 198 mm and length 3. ¾ The outer tube having an inner diameter of 200 mm and length 3. Kobe.05 Hz). The results for both structure were evaluated and in order to facilitate comparisons. In a similar manner.10.850 mm by 300 mm by 10 mm and the values G’= 900.000 Pa. 3.000 Pa and G”= 300.614 Hz.14 . 3. which corresponded to the fundamental frequency of this structure model.14 shows the details of the MPC connection between the damper and shear wall in the computer model.Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig. The values for this structure had kd = 10 x 106 N/m and cd = 38 x 106 Ns/m with dimensions of 1. Fig. Hachinohe. 67 .Details of MPC connection between shear wall and damper The response of this model as well as all others were investigated under the El Centro.670 mm by 300 mm by 10 mm and the values G’ = 950. The properties of the damper for 18-storeys models were at first calculated as kd = 10 x 106 N/m and cd = 63 x 106 Ns/m based on double layer damper in parallel with dimensions of 1. These moduli were calculated using the loading frequency f = 0. Detail of the diagonal VE damper located within the cut out of the shear wall can be seen in Fig. Northridge and San Fernando earthquake excitations described later in this chapter.2 Structural models with VE damper – diagonal configuration The concrete frame-shear wall was modelled using the same FE mesh. 3.15.000 Pa and G” = 450. were calculated. material properties and dimensions as in the previous models. 3. damping properties of VE dampers located in the 12storeys models (with f = 1.000 Pa. where one tube was placed within the other.5 m high. Based on the geometric orientation of the chevron bracing system. were used in all the subsequent analyses. In the case of the chevron brace. Fig. where θ is the damper angle to the horizontal. which was reduced to 3. the relative displacement along the direction of the damper was equal to the inter-storey drift of the floors between which it was connected. The only difference was in the size of the cut out. 3.3 Structural model with friction damper – chevron brace configuration The concrete frame-shear wall model was created using the same FE mesh.Influence of Damping Systems on Building Structures Subject to Seismic Effects approximate average values of kd = 10 x 106 N/m and cd = 50 x 106 Ns/m. 3. the value of the magnification factor f =1. Fig. The friction damper was modelled as a pair of horizontal tubes.Structural details of diagonal VE damper 3. The ratio between inter-storey drift and relative damper displacement was related through the magnification factors.16 shows the details of the frame-shear wall model with a friction damper of chevron brace configuration.10. 68 .5 m wide by 2. whereas in the case of the diagonal brace the magnification factor is f = cosθ.15 . material properties and dimensions as before. 16 . 3. While comparing to 69 . the chevron brace friction dampers was constructed as described below. the outer diameter of this tube was 198 mm and its length was 2. The connection between each tube and the shear wall was modelled using a MPC Pin type connecting element.10.8 m. The coefficient of friction between tubes was assumed to be 0.25.85 m. which represents 67% of the contact area for diagonal friction damper.Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig.49 m2. ¾ The outer tube was constructed from 264 S4R5 shell elements. 3. attached at one end directly to the left side of the shear wall and attached at the other end to the upper edge of the shear wall via an MPC Rigid connection. The thickness of both tubes was 50 mm. The details of the damper placed within the shear wall are shown in Fig. The damper was oriented horizontally in the upper part of the cut out. the radial clearance between the tubes was 1 mm and the contact area in the unloaded state was 2. the inner diameter of this tube was 200 mm and its length was 2.Structural details of chevron brace friction damper In order to create the chevron brace damper with approximately similar damping force to that of the diagonal dampers. ¾ The inner tube was constructed from 276 S4R5 shell elements. 3.4 Structural model with VE damper – chevron brace configuration The concrete frame-shear wall model was created as in the previous case. and a MPC Slider type connecting element was chosen to ensure frictional sliding between the tubes in a determined direction.17. with one tube placed within the other. The thickness of both tubes was 50 mm. The friction component of the hybrid friction-VE damper was modelled as a pair of horizontal tubes. 3. the radial clearance between the tubes was 1 mm and the contact area in the unloaded state was 1.17 . which represents 67% of the contact area for chevron brace friction dampers.485 m. material properties and dimensions as before.500 m. The direction of frictional sliding was determined by Slider type MPCs.18. which represented both spring and dashpot elements was oriented with one end attached to a brace assembly placed in the 70 .Structural details of chevron brace VE damper 3. 3. as shown in Fig. ¾ The outer tube was constructed from 384 S4R5 shell elements.Influence of Damping Systems on Building Structures Subject to Seismic Effects diagonal VE dampers. ¾ The inner tube was constructed from 155 S4R5 shell elements. the values of spring and dashpot remained the same. The VE part of the hybrid damper. the outer diameter of this tube was 198 mm and its length was 1. the inner diameter of this tube was 200 mm and its length was 1. Fig.25. whereas the overall length was reduced to 67% of length for diagonal VE damper.10. The coefficient of friction between the tubes was 0.67 m2.5 Structural model with hybrid friction-VE damper The concrete frame-shear wall models were modelled using the FE mesh. The only difference was in the size of the cut out.18 . which basically means that a magnification factor is more than two times greater than unity. the effect of the magnification factor on the damping force is notably higher.10. As it was mentioned previously the magnification factor for chevron brace represents f = 1 and for the diagonal bracing f = cosθ. material properties and dimensions as before. 3. and the other end attached to the lower left-hand corner of the cut out.Structural details of hybrid friction-VE damper 3. The reason is because in the toggle configuration the relative displacement of the dampers is 2-3 times the interstorey drift.5 m wide by 3. In the case of the lower toggle configuration. The values of damping and stiffness were kept the same as in the previous models.19.6 Structural model with VE damper – lower toggle configuration The concrete frame-shear wall models were created using the FE mesh. which represents 50% of length for the diagonal VE damper.Influence of Damping Systems on Building Structures Subject to Seismic Effects middle of the upper edge of the cut out. 71 . which was enlarged to 3. Detail of the lower toggle VE damper located within the cut out of the frame-shear wall model can be seen in Fig. This oriented the damper at 450 to the horizontal. where θ is the angle of damper to the horizontal. 3. while its length was 2.0 m high.475 m. Fig. The damper was oriented at 450 to the horizontal and had one end attached to the lower arm of the steel holder and the other end attached to the lower right-hand corner of the cut out.19 .Structural details of lower toggle VE damper Based on this. Furthermore.Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig.20 were investigated for shear wall structure designated by W. 3. the lower toggle VE damper was created with its length of 2. Seismic analyses of the shear walls were once again carried out with one type of damping system at a time. diagonal. All these structural models have natural frequencies. 3.11 Dampers installed within 96 m high shear wall structures Five different damping systems shown in Fig. which are connected to each other by MPC Pin and the connection to the shear wall was realised by 6 mm prebent plate. which represent 45% of the length of diagonal VE damper and the parameters of spring and dashpot were kept the same as previously. Three different configurations of the friction and VE dampers namely. 3.250 m. which match those of typical high rise buildings and hence enable a simple conceptual study for evaluating seismic mitigation. four different damper placements were used to study the influence of location on the 72 . chevron brace and a hybrid configuration consisting of the friction damper oriented horizontally and the VE damper mounted diagonally were considered. The arms of the brace assembly are created from 100 x 5 SHS. Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects seismic response of these models. 3. The undamped structure was also analysed in order to compare results.46 m high wall section was cut out and replaced by a diagonal friction damper. Fig. where a 12.21 . 3. 3.Damping systems installed in shear wall structure 3.21.1 Structural models with friction damper – diagonal configuration Details of the damper located within the shear wall can be seen in Fig.Structural details of diagonal friction damper within structure type W 73 .0 m wide by 12.11.20 . 22.25.240. and with one tube placed within the other. The radial clearance between the tubes was 1 mm.647 Pa and G” = 1.081 Pa. These moduli were calculated using the loading frequency 74 . The connection between each tube and the shear wall as well as the direction of frictional sliding was determined by Slider and Pin type MPCs 3. ¾ The outer tube having an inner diameter of 200 mm and length 14.4 m2 and the coefficient of friction between the tubes was 0.2 Structural model with VE damper – diagonal configuration Detail of the diagonal VE damper located within the cut out of the shear wall can be seen in Fig.11.Influence of Damping Systems on Building Structures Subject to Seismic Effects The damper was modelled as a pair of diagonal tubes each with a thickness of 50 mm.5 m was modelled using 239 S4R5 shell elements. 3. Fig. the contact area in the unloaded state was 16.Structural details of diagonal VE damper within structure type W The properties of the damper for model type W1 were at first calculated as kd = 80 x 106 N/m and cd = 107 x 106 Ns/m based on double layer damper in parallel with dimensions of 1. ¾ The inner tube having an outer diameter of 198 mm and length 15 m was modelled using 263 S4R5 shell elements.22 . 3.530 mm by 300 mm by 10 mm and the values G’ = 872. 11. The only difference was in the size of the cut out.735 Hz). were determined and used in all the subsequent analyses for the structures type W. and W1-3 (with f = 0.536 Hz) were calculated. damping properties of VE dampers located in the structure type W2 (with f = 0. which was reduced to 12. approximate average values of kd = 100 x 106 N/m and cd = 100 x 106 Ns/m.Influence of Damping Systems on Building Structures Subject to Seismic Effects f = 0. 3.125 m.23 . In a similar manner.Structural details of chevron brace friction damper within structure type W ¾ The outer tube was constructed from 311 S4R5 shell elements. The seismic responses of the structures were noticeably close when cd was within the range 40 x 106 to 140 x 106 Ns/m and kd within the range 30 x 106 to 120 x 106 N/m hence in order to facilitate comparisons. 75 .598 Hz).531 Hz. where one tube is placed within the other. W3 (with f= 0. 3. Fig. 3. ¾ The inner tube was constructed from 287 S4R5 shell elements. which corresponded to the fundamental frequency of this structure. The friction damper showed in Fig. respectively.3 Structural models with friction damper – chevron brace configuration The concrete shear wall was modelled using the same FE mesh. material properties and dimensions as before.0 m wide by 8.000 m.0 m high.23 was modelled as a pair of horizontal tubes. the outer diameter of this tube was 198 mm and its length was 11. the inner diameter of this tube was 200 mm and its length was 11. with one tube 76 . The parameters of the damper are presented in Fig.4 Structural model with VE damper – chevron brace configuration The concrete shear wall was modelled as in the previous case.2 m2 and the coefficient of friction between them was determined to be 0. The connection between each tube and the shear wall was modelled using a MPC Pin type connecting element. the radial clearance between the tubes was 1 mm.Influence of Damping Systems on Building Structures Subject to Seismic Effects The thickness of both tubes was 50 mm.25. 3.Structural details of chevron brace VE damper within structure type W 3. Fig.24 .11.11.23.24. 3.25 was modelled as a pair of horizontal tubes. and a MPC Slider type connecting element was chosen to ensure frictional sliding between the tubes in a determined direction.5 Structural model with hybrid friction-VE damper The concrete shear wall was modelled using the same FE mesh. The friction component of the hybrid damper shown in Fig. 3. 3. material properties and dimensions as before. The damper placed within the shear wall was oriented horizontally in the upper part of the cut out. attached at one end directly to the left side of the shear wall and attached at the other end to the upper edge of the shear wall via an MPC Rigid connection. The details of the MPC connection between the damper and shear wall in the computer model are also shown in Fig. 3. the contact area in the unloaded state was 13. Influence of Damping Systems on Building Structures Subject to Seismic Effects placed within the other. which corresponded to the fundamental frequency of the structure model type T1. In a similar manner.12 Dampers within 24-storey frame-shear wall structures Details of the diagonal VE damper located within the cut out of the shear wall of 24-storey frame-shear wall structure designated T are shown in Fig.25 . and the other end attached to the lower left-hand corner of the cut out. 3.4 m2. The contact area in the unloaded state was 5. except for length. damping properties of VE dampers located in 77 .26.Structural details of hybrid friction-VE damper within structure type W 3. while its length was 9. Damping and stiffness were kept the same as in the diagonal VE dampers.000 Pa. Fig.0 m. This oriented the damper at 400 to the vertical. The direction of frictional sliding was determined by Slider and Pin type MPCs. The properties of the damper for model type T1 were at first calculated as kd = 50 x 106 N/m and cd = 37 x 106 Ns/m based on double layer damper in parallel with dimensions of 980 mm by 300 mm by 10 mm and the values G’ = 850. 3. The material properties and dimensions.401 Hz. The VE part of the hybrid damper. were the same as in the chevron brace friction damper. These moduli were calculated using the loading frequency f = 0.000 Pa and G” = 250. which represented both spring and dashpot elements was oriented with one end attached to a brace assembly placed in the middle of the upper edge of the cut out. 9.586 Hz) were calculated. Fig. material properties as in the previous structures.Structural details of diagonal VE damper within structure type T 3.370 Hz).440 Hz.26 . 3. were determined and used in all the subsequent analyses for the structures type T. The properties of this damper embedded within the 18-storey frame structure were at first calculated as kd = 20 x 106 N/m and cd = 14 x 106 Ns/m based on double layer damper in parallel with dimensions of 706 mm by 300 mm by 10 mm and the values G’ = 850. 3. and T3 (with f = 0. These moduli were calculated using the loading frequency f = 0. Detail of the diagonal VE damper located within the frame can be seen in Fig. approximate average 78 . The seismic responses of the structures were noticeably close when cd was within the range 10 x 106 to 60 x 106 Ns/m and kd within the range 1 x 106 to 30 x 106 N/m hence in order to facilitate comparisons. approximate average values of kd = 50 x 106 N/m and cd = 40 x 106 Ns/m respectively. These frequencies would give varying values for kd and Cd but in order to facilitate comparisons. The dimensions of this structure are described in chapter 3.27.13 Dampers within 18-storey frame structures The concrete 18-storey frame structure designated by F0 was created using the same FE mesh.Influence of Damping Systems on Building Structures Subject to Seismic Effects the model type T1-3 (with f = 0.000 Pa and G” = 250.1.000 Pa. Duration of the strong motion and range of dominant frequencies were kept unchanged and were evaluated by Welch’s method (1967) based on Fast Fourier Transform Techniques. respectively.15 g for the medium-rise structures of designation H and M.3. which were selected to investigate the dynamic response of the models. duration of strong motion and ranges of dominant frequencies and therefore have different influences on the structure. Fig. using the computer program MATLAB Version 6. during which the strong motion took place. In order to ensure that the chosen mitigation procedure is effective under different types of excitations.14 Input earthquake records In general. The earthquake records.Structural details of diagonal VE damper within structure type F 3. five.27 . are: 79 . earthquakes have different properties such as peak acceleration. well-known earthquakes records were used in this study. For more consistent comparison. 3. These were all applied for the first 20 s of their duration. all earthquake records were scaled to peak ground acceleration (PGA) of 0. were determined and used in all the subsequent analyses for the structures type F.Influence of Damping Systems on Building Structures Subject to Seismic Effects values of cd = 50 x 106 Ns/m and kd = 10 x 106 N/m respectively.1 g for the taller structures of designation W and T and 0. 19 Hz.5 secs and dominant frequencies in the range 0. Fig.39-6.5 secs and dominant frequencies in the range 0.29 . 3.12 Hz. 3.5-7.5-5.5-12.5 secs and dominant frequencies in the range 0.Influence of Damping Systems on Building Structures Subject to Seismic Effects ¾ El Centro (1940) with duration of strong motion in the range of 1.30 .39 Hz. Fig.28 .29-1.Hachinohe earthquake record and its dominant frequencies ¾ Kobe (1995) with duration of strong motion in the range of 7. 3.Kobe earthquake record and its dominant frequencies 80 . Fig.19-2.El Centro earthquake record and its dominant frequencies ¾ Hachinohe (1994) with duration of strong motion in the range of 3. 5-9.5 secs and dominant frequencies in the range 0. in the case of medium or high-rise structure it is unrealistic.39 Hz.5-8. to conduct appropriate experimental tests. each proposed control strategy should be verified by experimental testing under conditions that are close to the realistic physical structure.07 Hz and Fig. A common guideline for the comparison of results from various algorithms and devices still does not exist. structural control research is generally greatly diversified in terms of specific applications and required objectives.14-1.15 Verification of results At the present time. Preferably. However.32 .31 . Fig. 81 .0 secs and dominant frequencies in the range 0.Northridge earthquake record and its dominant frequencies ¾ San Fernando (1971) with duration of strong motion in the range of 4. both logistically and economically.Influence of Damping Systems on Building Structures Subject to Seismic Effects ¾ Northridge (1994) with duration of strong motion in the range of 3. 3.San Fernando earthquake record and its dominant frequencies 3. 3.58-4. A committee of ASCE on Structural Control developed a benchmark study. Realising of these objectives allow implementation of innovative control approaches for dynamic hazard mitigation. et al. As it can be seen from previous sections of this chapter. namely in traditional diagonal and chevron brace and also in a relatively new lower toggle configuration. University of Technology. Spencer. similar model was created and treated under the same earthquake excitations in the computer program ABAQUS.Influence of Damping Systems on Building Structures Subject to Seismic Effects One of the available alternatives to examine the validity of research results is to use the analytical benchmark models proposed by the American Society of Civil Engineers (ASCE). In order to verify the validity of the present research project. Sydney participated in this benchmark project and have published several experimental works. Analytical results obtained with the computer program ABAQUS for all three damper configurations are also compared with those of Marcelin (2001) in the following sections. 1998 and Wu. confirmed by experimental testing of all three configuration used in present project. 1999). Smith. These damping systems were installed in three different configurations. six different damping systems were investigated in this study. Lu and Skelton 1997. 1997 Spencer. et al. which were conducted in their University’s laboratories. conducted analytical investigation. Marcelin (2001). The results are compared and evaluated with the results of experimental testing. Some of these testings were conducted on the five-storey benchmark model subjected to different earthquake excitations. Some of these algorithms have been experimentally confirmed at the Laboratory of University of Notre Dame’s (Baker. et al. et al. The primary objective of this project was to develop benchmark models to provide systematic and standardized means by which a variety of control methods can be examined. focusing on the comparisons of structural control algorithms for the benchmark structural control problems (Balas 1997. The researchers from Faculty of Engineering. 1997. et al. 82 . 1997). Fig. et al.15..0 g and Northridge (1994) scaled to a PGA of 0.. K2 =K3 =K4 =K5 = 10. (2000). from University of Technology. namely the El Centro (1940) scaled to a PGA of 0. Kobe (1995) scaled to a PGA of 1.5 Hz (BM5.5 g.5).. et al. respectively.26 x 106 N/m. Three types of earthquake motions. 3.066 x106 N/m and the stiffness of the damper was 1.33) was modelled as a lumped mass system in which the mass of each storey was concentrated at each floor level and passive viscous dampers were installed in the 1st. The mass of each storey was mi = 605 kg and 325 kg.33 Elevation and plan of the five-storey benchmark model (Based on Shi Lily D. Some of these results are used in present study in order to confirm validity of this research. The building (Fig.8 g were used as input earthquake excitations. Sydney conducted experimental work and numerical analysis of several types of damping systems installed in 5-storey benchmark models. The frame stiffness was K1 = 7. 2000) 83 .563 x 106 N/m.1 Benchmark model testing Shi Lily D.5 Hz. 3. 3rd and 5th storey.Influence of Damping Systems on Building Structures Subject to Seismic Effects 3. corresponding to frequencies of 5.5) and 7. The first natural frequencies of the two benchmark models without dampers for different storey masses were 5.5 Hz and 7.5 Hz (BM5. 5 Tip Deflection Tip Accelerations (mm) (g) Kobe El Centro Northridge Kobe El Centro Northridge 7.6) k f + kb The peak values of tip deflection and tip acceleration of experimental testing conducted on the BM7. f′c of 350 MPa.2 Results of analytical investigation of benchmark models The analytical model created in computer program ABAQUS was constructed of steel. The damper was expressed by the combination of damper stiffness (kf) and bracing stiffness (kb) joined in series..15.62 1.5 and BM5.90 1. 2000) Control No Control Passive Damping System Earthquake Type BM7.90 13. Nevertheless.00 1.5 than for BM7.09 BM5.60 14.38 1.18 The comparison of responses for undamped benchmark model and benchmark model fitted with viscous dampers showed that dampers were able to reduce peak values of tip deflection on the top of the structure without increasing floor accelerations by much.30 7. 3.40 15.50 1.60 7.22 1.60 1.10 1.31 2. deflection and acceleration reductions depend on the type of earthquake and structure. and 84 . The material properties were compressive strength.70 9.5 subjected to three earthquake excitations are presented in Table 3.88 1.60 9. The equivalent stiffness of the entire device (khi) was defined as: khi = k f kb (3.70 12.32 1.50 7. it has to be noted that tip acceleration and tip deflection of the damped models were in several cases higher then those of the undamped models.1 – Seismic response of benchmark models (After Shi Lily D.90 13. However. et al. This trend was evident in same of the models treated in this thesis.1 Table 3.5.Influence of Damping Systems on Building Structures Subject to Seismic Effects The damper used in this system consisted of a viscous damper connected to the bracing frame.43 1. The dampers performed significantly better for building model BM5.5 Tip Deflection Tip Accelerations (mm) (g) 17. in the case of the El Centro and 85 . in terms of tip deflection for BM7.5 and BM5.008 UN 1.2. Poisson’s ratio υ of 0. As it can be seen from these results.Influence of Damping Systems on Building Structures Subject to Seismic Effects Young’s modulus. The results of tip deflection and acceleration obtained by analytical models in computer program ABAQUS are presented below.5 and BM5.5 and 7.5 Hz.02 UN PD 0.6 -2 -0. On the other hand.34 – Tip deflection and acceleration response of the undamped BM5. the beams were made of steel profiles SHS 150 x 150 x 4 mm and floors were modelled of steel plate thickness of 12 mm. Time history responses of tip deflection and tip acceleration for the undamped BM7.5 and BM5. Ec of 207.012 1. The stiffness of the dampers installed in the 1st. 2 0.2 -0. reductions in tip acceleration and root mean squared acceleration were more substantial.008 0.8 -0.016 -1.6 Acceleration (m/s ) Deflection (m)- 0.4 0 5 10 15 20 -0.2 0. additional lumped mass was applied at each beam-column joint.8 g) are illustrated in Fig. On the other hand.02 Time (s) Time (s) Fig.8 2 0.004 0 -0. 3rd and 5th storeys resulted in decrease in tip deflection under the Kobe earthquake.012 -1. 3rd and 5th storeys was 1. To adjust natural frequencies to 5. the placement of the dampers in the 1st.016 15 PD 0.34.5. 3.004 0 5 10 -0. From this figure it can be seen that in terms of peak values of tip deflection and term root mean squared deflection only minor reductions were obtained.4 0 -0.3 and density. The columns were modelled from solid steel with cross-sectional dimensions of 30 x 30 mm.5 subjected to the same three earthquake excitations as it was for experimental testing are presented in Table 3.5 fitted with three stiffness dampers under the Northridge earthquake excitations (scaled to 0.000 MPa.26 x 106 N/m. ρ of 7700 kg/m3. 3.5 fitted with three viscous dampers The results of peak values of tip deflection and tip acceleration for the analytical models of the BM7. namely diagonal. whereas increase in acceleration was experienced under the El Centro earthquake. in the cases of BM7. in reasonably good agreement.5.47 1.5 Tip Deflection Tip Accelerations (mm) (g) Kobe El Centro Northridge Kobe El Centro Northridge 7.30 7.51 1.72 1. While comparing tip deflection and tip acceleration obtained from computer program ABAQUS with results from experimental testing (Tables 3. The dampers performed significantly better when installed in BM5.71 1.2 – Seismic response of analytical models Control No Control Passive Damping System Earthquake Type BM7. where the reductions in tip deflection were experienced under all three earthquake excitations.15. On the other hand.Influence of Damping Systems on Building Structures Subject to Seismic Effects Northridge earthquake excitations tip deflections were increased.2).90 14.57 1. In the cases of the BM5. the range of the results obtained from physical testing and from analytical computer model was slightly more open.5 Tip Deflection Tip Accelerations (mm) (g) 16. slight acceleration increase was recorded. 3.86 1.40 15.35) is capable of 86 .50 15. whereas under the El Centro earthquake.23 As regards to tip acceleration.49 1.42 1. once again. in terms of tip deflection the results were in reasonably good agreement and in all the cases followed similar trends.5 the dampers produced significant acceleration reductions under the Kobe and Northridge earthquake excitations.80 7.3 Effectiveness of damper configurations The damper fitted in three configurations. all the results were.60 13. 3.40 2.63 1. Table 3.80 14.90 8.70 8.26 BM5. the toggle brace configuration (Fig.5 the dampers produced significant reductions under the Northridge earthquake and small reduction was experienced also under the Kobe earthquake. chevron brace and lover toggle are investigated in present study.70 7. As regards to tip acceleration reduction.40 1. nevertheless. Traditional diagonal and chevron brace configurations restrict the amount of damping being applied to a structure.1 and 3.08 1. the elastic stiffness was k = 1. Numerical examples of the efficiency of varieties of configuration were highlighted in Section 2. The chevron and diagonal system had reductions of 15.3.Influence of Damping Systems on Building Structures Subject to Seismic Effects magnifying the damping effect of the damper on the structure response and allows the damping device to be used more efficiently.5-3 times the interstorey drift. diagonal and lower toggle brace configuration (Based on Marcelin S. in the case of the toggle brace configuration. the relative displacement along the direction of damper is 2.28 x 106 kNs/m and the external damping was c = 2. the larger the relative displacement.4% and 87 . the relative displacement along the direction of the viscous damper is either equal to (case of the chevron brace) or less than (case of the diagonal brace) the inter-storey drift of the floors between which they are connected. Therefore.458 x 104 kg. in terms of the tip deflection reduction.3. The results of peak values of tip deflection for the analytical models of the 1storey frame subjected to the El Centro earthquake excitations are presented in Tables 3.7.35 – Undamped frame and frame fitted with damper of chevron brace.. As shown in Table 3.27 x 104 kN/m. 2001) As referred in Section 2. On the other hand. the larger the damping force produced. The floor mass was m = 1.3. chevron brace and lower toggle configurations were examined by Marcelin (2001) on a 1-storey frame structure equipped with viscous damper fitted in three different configurations (one at time). Because of the geometric orientation of the chevron and the diagonal bracing systems. the frame fitted with the toggle brace system was twice as effective as the traditional configurations. The numerical examples of the diagonal.7. Fig. the force generated by a viscous damper is directly proportional to the relative velocity between each end of the damper. The floor mass was m= 1.Influence of Damping Systems on Building Structures Subject to Seismic Effects 12.04 0.3 – Results of frame deflection (after Marcelin) Brace Configuration Diagonal Chevron Uncontrolled Max. The material properties were compressive strength. 0.04 -0.36 illustrates the seismic responses of the undamped frame and the frame with viscous damper of the lower toggle configuration in terms of the peak values of tip deflection.000 MPa. 0.4 Results of analytical investigation of damper configurations The analytical model created in computer program ABAQUS was constructed of steel.06 TO Deflection (m) 0. However.3 and density.039 34.71 Lower Toggle 0.7 % respectively as compared to 34 % for the lower toggle brace system. f′c of 350 MPa.08 Time (s) Fig. Poisson’s ratio υ of 0.15. Ec of 207.08 UN 0.02 0 5 10 15 20 -0. Fig. 3. ρ of 7700 kg/m3.36 – Tip deflection of the undamped frame and frame fitted with viscous damper of lower toggle configuration.458 x 104 kg and the elastic stiffness was k = 1. The figure shows high performance of the lower toggle damper 88 . The results of this parametric study showed that the traditional diagonal and chevron configuration were capable of reducing the building response.02 0 -0.06 -0. Deflection % Deflection Red.052 12.28 x 106 kNs/m.059 0.050 15. Young’s modulus.75 3.42 0. The columns and beam were made of steel profiles SHS 750 x 500 x 5 mm and floors were modelled of steel plate thickness of 15 mm. the toggle brace damper configuration was significantly more effective. Table 3. 3. Despite this. The results revealed high tip deflection reduction experienced by all three dampers. These results are in good agreement with the results obtained from the parametric study described in previous section. both logistically and economically. Deflection % Deflection Red. Table 3.89 Lower Toggle 0.072 Brace Configuration Diagonal Chevron 0. in terms of root mean squared displacement the performance of the damper was even higher. the present computer results with viscous dampers agreed reasonably well with those from the literature study and confirmed the validity of the investigated method.061 15.27 0.4. The results for the frames fitted with the damper in all three configurations (one at time) compared with the undamped frame are presented in Table 3. 89 . It was not possible to exactly model the bench mark structures as some of the structural details were not available. However.78 As mentioned previously. to conduct appropriate experimental tests of medium or high-rise structures under seismic conditions.Influence of Damping Systems on Building Structures Subject to Seismic Effects with tip deflection reduction of 27.8%. the performance of the damper of lower toggle configuration was significantly higher.4 – Frame deflection (computer program ABAQUS) Uncontrolled Max. the validity of the method used in the present study was verified on benchmark models. For these reasons.052 27.062 13. 0. Furthermore. it is unrealistic. Influence of Damping Systems on Building Structures Subject to Seismic Effects 90 . Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 4 Results – High Rise Structures 91 . First type is represented by a 96 m high shear wall structure (described in the Section 3.High-rise structures 4. Working back from tip deflection to equivalent base shear and moment is one way of ‘averaging out’ the seismic effects of varying accelerations up the wall.2 Seismic responses of 96 m high shear wall structure There are various ways of assessing seismic response but computation of tip deflection is a reasonable measure of the overall effect of seismic response.7) embedded with five different damping systems (Section 3. The second type is represented by a structure. The undamped shear wall structural model was in this study created in order to compare its results with those of the shear wall structure embedded with five 92 . The results show that the value of reduction of tip deflection is dependent on the complex characteristics of the time histories used for assessment. Hence the benefits can only be legitimately assessed if the analysis is carried out for suite of time histories. Hence any reduction is worthwhile in overall seismic design force. Influence of the properties of the VE dampers on seismic mitigation with this structure was investigated under the five earthquake excitations.7. namely friction and VE diagonal dampers. This was the first structure treated in this research to determine feasibility of the procedure.1) Seismic analyses were caried out with one type of damper at one placement at a time. This analyssis was used to establish optimum damper properties. which includes the same shear wall with frames on both sides.1 Introduction The results from the finite element analyses of two types of high-rise structure are presented in this chapter.11). These damping systems were installed within cut outs of shear wall at four different damper placements (Section 3. friction and VE chevron brace dampers and hybrid friction-VE dampers. Efficiency of these damping systems was investigated under five different earthquake excitations.Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 4: Results . This structure was fitted with diagonal VE dampers embedded within the cut outs of the shear wall at four different damper placements. 4. Influence of Damping Systems on Building Structures Subject to Seismic Effects damping systems. The results of the tip deflection and tip acceleration of this structure obtained under five earthquake excitations are presented in Table 4.1. Table 4.1 - Tip deflection and tip acceleration of the undamped structure. Deflection(m) 2 Acceleration(m/s ) El Centro Hachinohe Kobe Northridge S.Fernando 0.161 0.356 0.168 0.143 0.141 4.87 5.33 5.96 5.57 4.42 The results for all the shear wall structural models obtained under each of the five earthquakes records are presented below. Figs. 4.1 to 4.5 illustrate tip deflection and tip acceleration under the El Centro earthquake excitations in this structural model of designation W1, which has the damper placed in the lower part of the structure, compared with the undamped structure. These figures clearly demonstrated that incorporation of the dampers to the structure reduced the peak values of tip deflections and tip accelerations under all five seismic loads. On the other hand, the performance of the dampers obtained under different excitations varied significantly. The highest tip deflection reduction was achieved for the diagonal VE damper, whereas the poorest results were obtained by the chevron brace friction damper. In terms of tip acceleration reduction the best results, once again, occurred for the diagonal VE damper, whereas the smallest reduction was recorded for hybrid friction-VE damper. Structure Fitted with Diagonal Friction Damper Structure Fitted with Diagonal Friction Damper 0.15 6 FR 2 0.05 0 -0.05 0 5 10 15 20 -0.1 UN 2 0 0 5 10 15 20 -2 -4 -0.15 -0.2 FR 4 UN Acceleration (m/s ) Deflection (m) 0.1 -6 Time (s) Time (s) Fig. 4.1 - Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal friction damper under the El Centro earthquake 93 Influence of Damping Systems on Building Structures Subject to Seismic Effects Structure Fitted with Diagonal VE Damper Structure Fitted with Diagonal VE Damper 0.15 6 VE 2 0.05 0 -0.05 0 5 10 15 VE 4 UN Acceleration (m/s ) Deflection (m) 0.1 20 -0.1 UN 2 0 0 5 10 15 20 -2 -4 -0.15 -6 -0.2 Time (s) Time (s) Fig. 4.2 - Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal VE damper under the El Centro earthquake Structure Fitted with Chevron Brace Friction Damper Structure Fitted with Chevron Brace Friction Damper 0.15 6 FR 2 0.05 0 -0.05 0 5 10 15 FR 4 UN Acceleration (m/s ) Deflection (m) 0.1 20 -0.1 UN 2 0 0 5 10 15 20 -2 -4 -0.15 -0.2 -6 Time (s) Time (s) Fig. 4.3 - Tip deflection and tip acceleration response of the undamped structure and the structure embedded with chevron brace friction damper under the El Centro earthquake Structure Fitted with Chevron Brace VE Damper Structure Fitted with Chevron Brace VE Damper 6 0.15 VE 2 0.05 0 -0.05 0 5 10 -0.1 15 20 UN 2 0 0 5 10 15 20 -2 -4 -0.15 -0.2 VE 4 UN Acceleration (m/s ) Deflection (m) 0.1 -6 Time (s) Time (s) Fig. 4.4 - Tip deflection and tip acceleration response of the undamped structure and The structure embedded with chevron brace VE damper under the El Centro earthquake 94 Influence of Damping Systems on Building Structures Subject to Seismic Effects Structure Fitted with Hybrid Damper Structure Fitted with Hybrid Damper 0.15 6 HY UN 0.05 0 -0.05 0 5 10 15 HY 4 Acceleration (m/s 2) Deflection (m) 0.1 20 -0.1 UN 2 0 0 5 10 15 20 -2 -4 -0.15 -0.2 -6 Time (s) Time (s) Fig. 4.5 - Tip deflection and tip acceleration response of the undamped structure and the structure embedded with hybrid friction-VE damper under the El Centro earthquake The reductions in tip deflection and tip acceleration obtained with all damper types, configurations and at all locations for each of the five earthquake records compared with that of the undamped structure are presented below. Fig. 4.6 illustrates the average percentage reduction in the peak values of tip deflections obtained by all the structural models compared with that of the undamped structure. Physical parameters of the diagonal VE dampers (spring stiffness, kd = 100 x 106 N/m, dashpot damping, cd = 100 x 106 Ns/m) and the diagonal friction dampers (friction coefficient, μ = 0.25 and the geometry of the sliding tubes) were determined after a preliminary analysis where each was acting with approximately the same damping force. The hybrid friction-VE damper was created to represent 52% of the damping force of the diagonal VE damper, and 33% of the damping force of the chevron brace friction dampers. Finally, the parameters of the chevron brace friction dampers and chevron brace VE dampers represent 67% of the damping force of the diagonal dampers, based on geometry. From this point of view, the results displayed good performance for all five types of damping systems. Overall, the highest reduction was achieved by models with hybrid friction-VE dampers with an average reduction of 22.2%. The second highest reduction was experienced by shear wall structure embedded with chevron brace friction dampers. It was followed by structures fitted with diagonal friction and diagonal VE dampers, which each showed relatively similar performance. 95 Influence of Damping Systems on Building Structures Subject to Seismic Effects Finally, the lowest performance was recorded for structures fitted with chevron brace VE dampers, with an average tip deflection reduction of 12.3%. Fig. 4.6 - Average tip deflection reductions for five types of damping systems. While comparing shear wall structures fitted with VE dampers and structure fitted with friction dampers, VE dampers performed better in nearly all cases in the lower and middle parts of the structure, while friction dampers performed obviously better in the upper part and throughout the structure. The hybrid damping system displayed the highest performance and the most reliable behaviour. Fig. 4.7 illustrates the average percentage tip deflection reduction of the models with respect to the damper locations. Fig. 4.7 - Average tip deflection reductions (experienced under five earthquakes) for different damper locations. 96 Influence of Damping Systems on Building Structures Subject to Seismic Effects The best performance was experienced in the shear wall structure of designation W1-3 with dampers placed in all three parts of the structure, with an overall reduction of 24.7%. Unexpectedly high performance with an overall reduction of 19.9% occurred for shear wall type W3 with dampers placed in the upper part of the structure. This was followed by an overall reduction of 19.1% for shear wall type W2 with dampers placed in the middle part of the structure. Considerably the lowest overall tip deflection reduction of 8.5% was obtained for shear wall type W1 representing dampers placed in the lower part of the structure. The efficiency of the damping systems under a variety of earthquake loadings was also evaluated and results can be observed from Fig. 4.8. Fig. 4.8 - Average tip deflection reductions (for five types of damping systems) under different earthquake excitations. It can be seen that the greatest average reduction in tip deflection of 26.3 %, was experienced under the Kobe earthquake excitation, which was characterised by a strongly narrow dominant frequency range (0.29-1.12 Hz). The second highest average deflection reduction of 19.8% occurred under the San Fernando earthquake, which, in contrast to the Kobe earthquake, had a wide band of dominant frequencies (0.58-4.39 Hz). The results of the shear wall structure obtained under the Northridge earthquake, which had a strongly dominant narrow frequency range (0.14-1.07 Hz), were slightly lower, with an average reduction of 19.2%. In the case of the El Centro earthquake excitation, which displays a wide band of dominant frequencies (0.39-6.39Hz), the efficiency of the models was slightly lower with an average reduction of 15.9%. The lowest performance of 97 Influence of Damping Systems on Building Structures Subject to Seismic Effects 11.2% occurred under the Hachinohe earthquake excitation, which had a moderate dominant frequency range (0.19-2.19Hz). The primary objective of this study was to investigate the tip deflection of the structure. However, the percentage reductions in the peak values of the tip accelerations were also studied and the results are presented in Figs. 4.9-4.11. Fig. 4.9 shows that all types of damping systems produced good results. Overall, the best result was achieved by the structure embedded with diagonal friction dampers, with an average tip acceleration reduction of 42.8%. The second highest reductions occurred for the shear wall structures embedded with diagonal VE dampers, this was followed by shear wall structures embedded with hybrid friction-VE dampers and structures embedded with the chevron brace VE damper. Finally, the poorest overall result was experienced by shear wall structures embedded with the chevron brace friction dampers, with an overall tip acceleration reduction of 18.1%. While comparing shear wall structures embedded with VE and friction dampers, it can be concluded that the greater tip acceleration reduction was achieved with VE dampers in the lower and middle parts of the structure, or with friction dampers in the upper part and throughout, though not as significantly as in the case of reduction in the tip deflection. Fig. 4.9 - Average tip acceleration reductions for five types of damping systems. 98 99 .10).4%. A noticeably lower overall reduction of 27. with an overall tip acceleration reduction of 42. 4. 3. Fig.10 .5% was achieved by structure type W1 representing the model with dampers placed in the lower part of the structure (Fig. The efficiency of the damping systems in reducing tip acceleration under a variety of earthquake loading is illustrated in Fig. 4.Influence of Damping Systems on Building Structures Subject to Seismic Effects In terms of damper placement (Fig. and lastly the poorest result was experienced by structure type W3 with the dampers placed in the upper part of the structure.8).11. with an overall tip acceleration reduction of 16.1% occurred for shear wall structure type W2 with the dampers placed in the middle part of the structure.Average tip acceleration reductions (for five types of damping system) under different earthquake excitations. with dampers placed in the all three parts of the structure. 4. Fig. displayed a reduction of 36. the best results. while type W1-3.Average tip acceleration reductions (under five earthquakes) for different damper locations.1%.11 . 4. responses under earthquakes with varying frequency content and strong motion duration have yielded a wide range of results and some interesting features.7% was achieved under the Hachinohe earthquake excitation and only slightly lower reduction of 35. using finite element techniques.8% was experienced under the El Centro earthquake excitation. The overall reduction occurred for the Northridge earthquake was lower with an average of 33. viz.1% was experienced under the San Fernando earthquake excitation. this study encountered resonant structural vibration.8% overall tip acceleration reduction for the Kobe earthquake and finally the lowest reduction with average value of 22. Three types of damping mechanisms. Hence. The natural frequencies of most of the shear wall structural models (with cut outs at different location) were within the frequency range of the dominant modes of the earthquakes. while friction dampers performed better in the upper parts of the structure and throughout. These structural systems was modelled and analysed under five different earthquakes. and has demonstrated the possibility of mitigating seismic response of structures by an appropriately embedded damping systems. configuration and location on the seismic response were studied. in most cases during the strong motion. VE. In terms of reduction in the tip deflection. while greatest reduction in the peak values of tip acceleration was achieved when dampers were placed in the lower level. VE dampers performed better than friction dampers in the lower and middle parts of the structures. The effects of damper type. 100 . However. the best performance was experienced when dampers were placed in the upper level. located within cut outs of shear walls. friction.Influence of Damping Systems on Building Structures Subject to Seismic Effects The highest overall tip acceleration reduction of 37.8%. to mitigate the seismic response of shear wall structures were investigated in this section. and hybrid friction-VE dampers. The results of this investigation confirmed that substantial reductions in deflection and acceleration of the structure could be achieved by all three types of dampers in all configurations and at all locations. Hybrid dampers were overall the most efficient and also had the most stable performance. this was followed by 26. 9 19.9 13.4 21.5 18.6 13.2 .9 34.5 9.9 26.7 32.8 17.6 8.Fernando Hybrid Chevron Friction VE Wall W1 10.8 3.5 11.4 31.4 37.9 15.1 8.8 -7.5 5.7 24.3 26.9 45.3 and in Figs.8 9.4 24.7 11.1 Wall W1-3 21.8 22.6 43.2 13.7 Wall W3 11.5 14.9 21.4 39.6 7.8 18.2 12.2 17.13 respectively.1 18.6 30.0 12.2 26.2 31.3 10.7 33.5 17.5 22.6 26.2 31.2 11.8 14.2 22.7 14.2 8.6 5.12 – Percentage reductions in tip deflection of all shear wall structures Table 4.Influence of Damping Systems on Building Structures Subject to Seismic Effects The complete sets of results in terms of percentage reductions in tip deflections and tip accelerations for the shear wall structures are presented in Tables 4.4 8.5 -1.5 3.9 19.8 35.Percentage reductions in tip deflection of the all models Records El Centro Hachinohe Kobe Northridge Configurations Devices Diagonal Friction VE Hybrid Chevron Friction VE Diagonal Friction VE Hybrid Chevron Friction VE Diagonal Friction VE Hybrid Chevron Friction VE Diagonal Friction VE Hybrid Chevron Friction VE Diagonal Friction VE S.0 -1.0 33.1 -2.6 2.9 12.2 12.6 28.4 30.7 21. Fig.6 14.9 7.4 9.6 19. 4.5 10.4 8.6 33.0 .8 17.12 and 4.7 32.2 13.9 -6.5 12.7 19.3 28.8 101 Wall W2 1.7 26.8 12. 4.2 and 4.7 1.5 22.6 42.2 10.3 33.0 1.9 44.7 22.4 16.1 37.6 17.3 10.1 8.6 11. 4.5 35.7 102 Wall W2 39.8 49.6 30.8 -9.8 20.8 52.2 10.5 65.6 29.1 28.7 44.9 31.1 22.6 2.9 39.2 21.8 28.7 61.2 31.7 54.1 46.9 28.3 25.9 47.3 25.8 31.8 49.3 2.13 – Percentage reductions in tip acceleration of all shear wall structures Table 4.Fernando Hybrid Chevron Friction VE Wall W1 51.8 51.6 7.8 29.4 6.0 26.5 29.0 52.1 14.3 -3.0 51.9 54.8 32.Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig.3 41.1 37 21.8 7.2 5.9 60.9 30.9 33.3 71.0 13.7 28.3 30.5 19.7 43.5 50.0 27.5 Wall W1-3 41.8 -0.8 53.0 27.4 -10.9 39.8 36.9 42.8 26.7 14.9 -5.4 21.5 32.7 29.6 .8 35.3 .2 28.5 35.9 9.5 25.9 12.3 34.1 36.9 47.8 40.8 17.4 30.4 20.Percentage reductions in maximum tip acceleration of the all models Records El Centro Hachinohe Kobe Northridge Configurations Devices Diagonal Friction VE Hybrid Chevron Friction VE Diagonal Friction VE Hybrid Chevron Friction VE Diagonal Friction VE Hybrid Chevron Friction VE Diagonal Friction VE Hybrid Chevron Friction VE Diagonal Friction VE S.3 11.1 38.1 38.7 39.1 59.3 20.7 11.2 Wall W3 8.0 18.7 39.7 5.8 58.1 36.7 38.1 28. namely T1 with the damper placed in the lowest part of the structure.Influence of Damping Systems on Building Structures Subject to Seismic Effects 4. had the large change in the natural frequency compared to undamped structure. 3.3.1 and 3. The natural frequencies of these models (with different cut-outs) ranged from 0.1 Damping properties of VE dampers The main aim of the following sections is to ilustrate the influence of the damping properties of the dampers on structural performance under earthquake load. as shown in Fig.9. which has damper positioned over the storeys 4 to 6. depending on the stiffness of the damper.8. This change in the natural frequency was anticipated.12.3 Seismic responses of 24-storey frame-shear wall structure In order to further demonstrate the feasibility of the procedure used in this study. the second type of high-rise structure represented by 24-storey frame-shear wall structure (discussed in Section 3. 4. when the natural frequency was reduced from 0. The peak values of tip deflection and tip acceleration for three of them.401 Hz to 0. T3 with the damper placed in upper part of the structure and T1-3 with the dampers placed in the all three parts of the structure were studied under the El Centro earthquake excitation. This structure.602 Hz to frequencies varying in range from 0. The results from the finite element analysis for the 24-storey frame-shear wall structures embedded with diagonal VE dampers are presented below.1) embedded with diagonal VE dampers was also investigated. 4. These structures included four different damper placements. since reducing the stiffness at the 103 . The dimensions and parameters of the shear walls were chosen as before and also diagonal VE dampers were embedded at locations similar to that in the study with shear wall structure.3.434–0. The seismic responses of the frameshear wall structures were analysed under the same five earthquake excitations.8.727 Hz and were within the frequency range of dominant modes of the earthquakes considered in this study.472 Hz.2 Frame-shear wall structure type T1 The design of structure designated by T1 was discused in details in sections 3. as described in Section 3.4 shows the percentage reductions in the peak values of tip deflections experienced by this structure compared with results of the undamped structure. while decrease in the performance was significant when value of the damper was moved out of this range. The best performance with the highest reduction of 38. The results of percentage reduction in tip deflection of the structure embedded with damper of varying properties display overall very high performance.28.4 and 4.Influence of Damping Systems on Building Structures Subject to Seismic Effects lowest part of the structure increases the ductality. The results reveal the high level of sensitivity of the structure to varying damping properties of dashpot. 3. A summary of the results of the seismic response of the structure embedded with these dampers is provided in Tables 4. The second highest reductions were recorded for dashpot with damping parameter of cd = 60 x 106 Ns/m. as it can be seen from Fig. Table 4.000 to 200 x 106 Ns/m.9% was recorded for dashpot with damping parameter of cd = 70 x 106 Ns/m.5 shows the percentage reductions in the peak values of tip acceleration experienced by the same structure. The damper was created as elastic spring and dashpot in parallel. it was followed by cd = 50 x 106 Ns/m and cd = 80 x 106 Ns/m with reductions only slightly lower. and thus considerably reduces the natural frequency of the structure.5. 104 . A dynamic analysis of this structure with damper placed over the storeys 4 to 6 were conducted under the El Centro earthquake excitation.000 to 200 x 106 N/m and values of dashpot to be in the range from 10. The range of the most dominant frequencies for the El Centro earthquake. In general. were in the range 0. The values of spring were after preliminary study determined to be in the range from 10.12. it can be stated that dashpot with the values of damping in the range from cd = 20 x 106 Ns/m to cd = 140 x 106 Ns/m experienced very high and stable performance. while Table 4.7 Hz what means that instalment of the damper partially detune the structure out of this range.5-0. 0 26.8 200 *Tip deflection of the undamped structure type T0 represents 0.5 33.5 34.5 38.4 -22.0 -1.9 36.7 37.1 28.0 24.1 36.7 28.0 10 20 30 40 50 105 60 80 100 120 200 1.5 30.7 31.9 30.9 35.5 35.4 305 31.8 19.0 9.2 19.8 19.2 25.7 25.1 31.1 31.1 25.9 37.0 31.2 -22.6 25.3 26.5 50 23.188 m 20.9 35.8 -3.1 26.0 4.9 80 38.5 36.3 37.6 7.4 1.3 25.3 33.8 19.2 19.7 34.3 35.2 1.6 -14.8 -0.7 28.6 12.9 37.8 19.7 25.4 35.8 3.9 40 Cd [106 Ns/m] Table 4.7 26.8 0.4 -14.3 26.5 28.6 -4.7 32.9 37.1 35.7 100 22.8 -9.7 32.7 28.3 28.3 34.1 25.3 35.3 36.3 35.7 28.5 37.4 -4.1 24.2 -6.6 -21.5 33.7 31.7 25.05 0.6 4.1 37.6 6.1 23.1 34.1 32.7 31.7 34.3 70 38.7 29.4 32.7 31.0 -6.4 24.2 0.5 34.4 34.5 36.7 35.05 Kd [106 N/m] -5.8 19.4 -12.1 37.0 24.5 25.3 35.1 31.7 20 28.5 31.5 36.7 35.0 1.3 28.7 36.3 32.7 34.7 33.5 35.5 33.8 19.7 28.1 34.4 3.3 35.6 32.1 37.9 35.9 35.1 25.2 1.1 37.0 24.9 32.1 27.1 31.4 .7 37.1 -22.1 28.2 19.5 31.0 9.3 26.6 12.1 36.8 19.3 35.5 22.0 -2.1 60 35.3 140 16.3.6 24.3 26.9 37.4 26.9 36.7 31.2 -22.5 33.3 31.9 35.1 27.2 5.5 10 18.4 9.7 34.0 6.Percentage reductions in tip deflection of structure type T1 Influence of Damping Systems on Building Structures Subject to Seismic Effects .1 31.9 23.2 32.7 23.1 30 35.0 -20.7 31.7 31.1 0.9 33.6 -2.8 19.6 -10.7 37.9 27.3 26.8 3.1 120 20.1 34.8 0.5 36.8 19.4 23.1 37. Percentage reductions in tip deflection of the structure type T1 With regards to the spring parameters. For convenience see also Fig.0 0.0 20.Influence of Damping Systems on Building Structures Subject to Seismic Effects Deflection reductions of the structure type T1 40.14. the level of sensitivity of the structure to varying damping properties of dashpot was noticeably high.1 1 10 20 30 40 50 60 70 80 100 120 140 200 -30. A summary of the results of the percentage reductions in tip acceleration for the same structure is shown in Table 4. It was followed by kd = 100 x 106 N/m. with the highest reduction of 64. The tip acceleration reductions for the dashpots with values from cd = 10 x 106 Ns/m to cd = 50 x 106 Ns/m were only slightly lower. as it can be seen from Fig. Outside this range. The best performance. 4. 4.0 30.4% was achieved by dashpot with damping parameter of cd = 20 x 106 Ns/m. kd = 120 x 106 N/m and kd = 60 x 106 N/m. Influence of the damper stiffness was insignificant in the range of values in which the dashpot displayed the highest performances. 106 . 4. However.14 . In general. the results make obvious that the tip deflection of the structure noticeably depend less on the change in the stiffness of the spring.0 % Reduction -10.0 -20.0 10. However.1 0 0 0.15. the decrease in tip acceleration reductions beyond this range was substantial.0 6 6 Cd [10 Ns/m] K d [10 N/m] Fig.0 200 120 100 80 60 50 40 30 20 10 1 0.5. the best results were recorded for the spring with stiffness of kd = 80 x 106 N/m. the results revealed the significant tip acceleration reductions. 2 10.6 64.8 80 41.1 36.0 30.8 14.1 42.4 43.9 64.1 39.6 31.1 44.8 50.4 54.7 37.6 10 47.6 23.7 35.9 58.0 60.9 63.5 53.1 47.6 200 *Tip acceleration of the undamped structure type T0 represents 2.9 54.8 50.6 60.2 54.9 57.9 30 62.6 21.3 60.6 58.1 38.8 47.2 60 48.1 0.6 31.3 64.0 36.9 58.4 39.6 46.1 39.2 54.7 39.7 37.9 56.0 30.5 55.0 25.7 0.2 57.4 39.1 47.9 59.8 10.5 -0.1 120 36.9 60.1 42.7 36.9 56.9 56.9 53.2 0.7 36.1 9.6 64.8 48.6 57.1 47.0 62.7 36.8 49.8 50.37.1 10.6 61.6 60.7 36.9 53.8 47.6 58.9 55.6 31.5 53.6 60.3 62.4 .7 36.0 37.5 15.3 38.9 60.1 48.7 39.0 60.Percentage reductions in tip acceleration of structure type T1 Influence of Damping Systems on Building Structures Subject to Seismic Effects .3 60.9 53.0 35.4 44.1 39.4 40.1 48.6 32.4 36.0 10 20 30 40 50 60 80 100 120 200 36.6 64.7 36.05 0.1 42.9 53.0 61.9 58.8 10.1 42.0 61.2 50.97 m/s2 61.8 107 Kd [106 N/m] 13.1 43.3 30.3 58.1 45.0 37.6 56.4 15.1 41.7 36.6 64.2 58.9 20.9 53.3 60.8 50.4 39.2 56.5 47.7 26.6 31.0 20 Cd [106 Ns/m] Table 4.6 62.7 38.0 32.0 31.8 1.4 43.2 50.9 56.6 31.5 50.0 37.5 53.05 58.6 31.1 30.6 53.6 31.4 43.9 17.6 59.0 35.0 62.6 55.8 45.3 61.8 14.3 1.9 56.1 39.8 50.8 42.6 63.3 32.6 47.6 50 52.2 56.9 60.8 50.3 34.4 39.3 59.1 47.5 47.8 50.9 58.9 55.9 58.1 100 38.2 54.0 64.1 47.9 58.7 0.1 47.5 63.8 50.8 70 45.9 56.7 140 31.6 31.3 40 55.9 58. Percentage reductions in tip acceleration of the structure type T1 With respect to spring parameter.1 0 0 0. The damper was created as elastic spring and dashpot in parallel. On the other hand.0 % Reduction 20.15 . the changes in spring parameters caused noticeably varied results.0 60.0 50. as described in Section 3.0 6 6 K d [10 N/m] Cd [10 Ns/m] Fig. depend on stiffness of the damper.3. 4.0 10. The parameters of spring and dashpot were determined to be the same as in the previous structure. when damping of dashpot was below these values. experienced the smaller change in the natural frequency compared to undamped structure.5-0.586 Hz to 0. the result illustrate low sensitivity to change of the spring stiffness in the cases when values of dashpot were equal or higher than cd = 10 x 106 Ns/m.8).1 1 10 20 30 40 50 60 70 80 100 120 140 200 -10.0 0.612 Hz.0 30.12.3 Frame-shear wall structure type T3 The frame-shear wall structure designated by T3 (discused in Section 3.602 Hz to frequencies varying in range from 0.0 200 120 100 80 60 50 40 30 20 10 1 0. 4. The highest tip acceleration reductions were recorded for spring of kd = 10 x 106 N/m this was followed by kd = 1 x 106 N/m and kd = 1 x 105 N/m.Influence of Damping Systems on Building Structures Subject to Seismic Effects Acceleration reductions of the structure type T1 70. hence this structure was treated at least partialy in resonant conditions. which has damper positioned over the storeys 19 to 21. when the natural frequency was altered from 0. These frequencies were within the range of the most dominant frequencies of the El Centro earthquake (0.7 Hz). A summary of the results of reductions in the 108 .0 40. in the case when the value of dashpot was lower than cd = 10 x 106 Ns/m the performance of the damper decreased considerably for the all spring parameters.6. In addition. 4.1% was recorded for dashpot with damping parameter cd = 30 x 106 Ns/m. However.0 6 200 120 100 80 60 50 40 30 20 10 1 0. The results illustrate high performance of the dampers.Percentage reductions in tip deflection of the structure type T3 109 . From the presented results it can be seen. In terms of spring parameter (Table 4. Consequent increase in stiffness of spring resulted in a gradual decrease in tip deflection reductions.0 20.0 0. The subsequent increase or decrease in damping of dashpot caused relatively regular decrease in tip deflection reductions. when the damping value of dashpot was less than cd = 10 x 106 Ns/m.0 6 Cd [10 Ns/m] Kd [10 N/m] Fig.0 25. Deflection reduction of the structure type T3 30.Influence of Damping Systems on Building Structures Subject to Seismic Effects peak values of tip deflections obtained by this structure compared with results of the undamped structure under the El Centro (1940) earthquake excitation is provided in Tables 4.1 1 10 20 30 40 50 60 70 80 100 120 140 200 -5. that the best performance with the highest tip deflection reduction of 28.0 % Reduction 5. this performance was more than 10% lower than in the case of previously studied structure T1.6).1 0 0 0. the highest deflection reductions were recorded for spring with values of kd = 10 x 106 N/m and kd = 1 x 106 N/m. The performance of the dampers was distinctly lower.0 15.16 .0 10. 0 4.0 16.2 1.6 15.0 21.1 4.0 24.3 26.0 6.8 200 *Tip deflection of the undamped structure type T0 represents 0.6 20.6 22.6 .6 140 15.05 24.8 21.8 19.4 10 13.6 21.0 5.6 18.2 19.4 24.0 21.8 20.2 19.6 20.4 20.4 19.3 26.8 17.4 16.8 22.4 6.0 21.0 21.6 22.8 5.2 16.8 12.2 -4.0 19.0 0.6 16.7 25.6 6.1 25.6 21.8 23.0 4.2 40 28.4 21.8 9.2 18.4 18.3 20.6 18.2 19.4 19.Percentage reductions in tip deflection of the structure type T3 Influence of Damping Systems on Building Structures Subject to Seismic Effects .2 16.4 22.0 21.8 21.2 4.2 18.8 16.1.6 3.6 24.8 18.6 15.6 6.7 25.8 19.7 26.6 6.0 100 17.0 16.4 13.4 1.1 25.4 0.7 60 17.2 16.05 0.2 16.8 16.8 20.8 16.2 4.0 24.5 27.2 10.2 -1.6 22.4 19.0 21.8 11.2 16.3 26.3 20 20.6 24.2 16.2 18.0 18.8 -2.8 20.6 13.6 18.6 17.2 22.4 19.6 22.7 25.4 21.6 21.4 -0.2 16.4 26.9 24.1 0.8 80 17.4 5.4 24.6 22.4 14.0 25.8 5.6 3.0 27.0 21.8 27.6 6.4 4.4 19.6 16.6 0.4 19.0 12.0 3.4 23.8 4.8 19.0 4.4 18.0 25.6 2.8 19.4 21.0 22.2 20.2 23.0 12.4 21.8 23.2 0.4 19.188 m 23.8 18.8 19.4 23.0 5.2 17.0 2.2 110 Kd [106 N/m] 9.4 24.0 17.0 26.8 30 Cd [106 Ns/m] Table 4.2 21.4 1.6 18.0 70 17.5 120 18.6 10.2 22.4 17.8 15.2 22.2 19.2 16.5 27.3 25.0 10 20 30 40 50 60 80 100 120 200 2.6 24.2 19.8 21.4 5.4 23.6 26.6 18.4 0.5 19.4 20.2 19.2 16.0 3.8 22.7 50 24.4 23.2 19.4 3.8 0.1 27. 0 -10. From these results it can be seen. Moreover the tip acceleration reductions of the structure became even insignificant when the value of the dashpot represented cd = 1 x 105 Ns/m on one side or cd = 200 x 106 Ns/m on the other side of the range.0 6 Cd [10 Ns/m] Fig. 4. Acceleration reductions of the structure type T3 50.0 -20.7 The tip acceleration reductions achieved by this structure were very high.0 40.0 60 0 0 0. that the highest tip acceleration reduction of 44.Influence of Damping Systems on Building Structures Subject to Seismic Effects A summary of reductions in the peak values of tip acceleration obtained by the structure with dampers embedded over the storeys 19 to 21 compared with results of the undamped structure obtained under the El Centro earthquake excitation is illustrated in Tables 4.0 10.0 30. respectively.0 % Reduction 0.4% occurred for dashpot with damping parameter cd = 10 x 106 Ns/m. The subsequent increase or decrease in the damping of dashpot caused relatively regular decrease in reductions.17 .1 1 10 20 30 40 50 60 70 80 100 120 140 200 20 1 6 K d [10 N/m] 40 100 200 -30.Percentage reductions in tip acceleration of the structure type T3 111 .0 20. values of the reductions were in average by 20% lower than it was for the structure with damper embedded in the lower storeys. nevertheless. 4 100 6.7 35.0 7.9 -2.7 2.7 -3.5 17.9 24.8 16.2 15.4 4.7 6.1 28.1 9.3 1.1 -3.4 -6.2 14.0 5.4 8.1 15.7 3.3 24.7 4.0 1.7 38.0 39.5 12.2 25.3 0.4 0.4 -12.4 11.2 22.0 33.2 19.8 14.7 1.9 -22.9 23.7 1.6 1.7 6.5 20.0 36.0 2.8 10.8 13.7 35.1 10.7 7.0 1.4 5.3 37.1 120 4.6 25.6 23.8 9.7 -7.4 16.2 17.4 7.4 41.1 6.1 0.7 2.5 19.4 8.4 10.2 24.8 11.7 42.8 15.97 m/s2 20.0 4.4 6.1 70 8.8 13.5 14.8 12.9 19.Percentage reductions in tip acceleration of the structure type T3 Influence of Damping Systems on Building Structures Subject to Seismic Effects .1 11.7 6.1 8.3 21.4 9.1 5.1 8.4 -15.4 44.9 40 13.1 6.5 17.9 27.4 34.1 5.2 15.2 24.3 0.3 43.1 4.7 6.4 7.5 13.1 5.8 50 11.9 25.6 23.3 34.2 19.9 20.9 19.0 10 20 30 40 112 50 60 80 100 120 200 -8.4 9.8 18.1 6.7 6.2 23.7 0.3 34.6 24.1 7.0 43.0 140 2.4 2.9 25.7 5.5 18.5 11.6 34.1 80 6.8 13.3 0.8 1.1 11.7 7.1 9.8 8.1 11.4 34.1 8.1 5.1 38.0 -13.3 200 *Tip acceleration of the undamped structure type T0 represents 2.8 8.4 37.1 10.2 24.8 10.1 33.8 9.1 7.8 10.8 60 9.9 24.7 1.3 20 42.05 0.05 Kd [106 N/m] 16.4 5.1 0.-11.4 6.2 30 Cd [106 Ns/m] Table 4.1 9.4 0.5 12.5 14.1 6.8 11.7 4.1 -19.8 16.3 10 17.4 8.0 2.3 40.2 23.1 32.7 5.6 22.9 22.4 14.2 24.5 17.7 .8 13.0 4.1 -9.4 5.4 6.7 5.1 12.1 36.4 26.4 10.4 4.1 13.5 17.2 -10.5 6.8 14.2 17. which has damper positioned over the storeys 4 to 6. 10 to 12 and 19 to 21.8.28.3.3% was achieved for dashpot with damping parameter of cd = 80 x 106 Ns/m.5-0. 4. The results reveal noticeably stable performance of dampers within the broad range of damping properties of dashpot. The performance of the dampers with dashpots within the range from cd = 20 x 106 Ns/m to cd = 200 x 106 Ns/m were only slightly lower. On the other hand.Influence of Damping Systems on Building Structures Subject to Seismic Effects As regards to the effect of the different spring parameters on tip acceleration reduction of the structure. as it can be seen in Fig. The best performance with the highest reduction of 41. depend on stiffness of the damper. while the results experienced out of this dashpot’s range were obviously irregular without any recognizable trend. 113 .602 Hz to frequencies in range from 0. however. The performance of dampers with dashpot cd = 10 x 106 Ns/m were considerable lower. 3. Nevertheless this statement is fully accurate only when the values of dashpots were from 10 x 106 to 80 x 106 Ns/m. the subsequent increase in stiffness of the spring caused a gradual decrease in tip acceleration reductions. The values of spring and dashpot were determined to be in the same range as it was in the previous case.12. the best results occurred for springs with stiffness of kd = 1 x 105 N/m and kd = 1 x 106 N/m. The diagonal VE dampers were created as elastic spring and dashpot in parallel.4 Frame-shear wall structure type T1-3 The design of structure designated by T1-3 was discused in details in sections 3.458 Hz. were in the range 0. when the natural frequency was reduced from 0. as described in Section 3.370 Hz to 0.5 and in Fig.7 Hz. 4.18. This structure. The instalment of dampers within the cut outs of shear wall detune structure from the range of the most dominant frequencies. experienced the large change in the natural frequency compared to undamped structure. which for the El Centro earthquake. A summary of the results of the percentage reductions in the peak values of tip deflections obtained by this structure compared with results of the undamped structure are presented in Table 4. 0 -20. Deflection reductions of the structure type T1-3 60. The similar tip deflections were also experienced when stiffness of spring was kd = 1 x 105 N/m and kd = 5 x 104 N/m.18 . For the damping of dashpot smaller than cd = 20 x 106 Ns/m the unfavourable increase in deflections were eliminated only in the case when the value of the stiffness of spring was equal or higher than cd = 80 x 106 Ns/m.0 -80. On the other hand. a subsequent increase in stiffness of the spring over the value kd = 1 x 106 N/m caused a gradual decrease in tip deflection reductions. the performances of the dampers with the dashpots under this value were unfavourable with high increase in tip deflections.0 20.0 6 6 K d [10 N/m] Cd [10 Ns/m] Fig.0 -60.0 40. On the other hand.1 1 10 20 30 40 50 60 70 80 100 120 140 200 -100. With respect to spring parameter. Table 4.Influence of Damping Systems on Building Structures Subject to Seismic Effects still adequately high. the highest reductions in tip deflection were recorded for the dampers with spring of stiffness kd = 1 x 106 N/m. 4.0 200 120 100 80 60 50 40 30 20 10 1 0.8 illustrates.0 % Reduction -40.1 0 0 0. that when values of dashpots were in the range from cd = 20 x 106 Ns/m to cd = 200 x 106 Ns/m.0 0.Percentage reductions in deflection of the structure type T1-3 114 . 3 38.9 35.6 18.1 -58.7 32.1 28.9 33.1 34.05 4.0 32.3 31.7 -36.6 -18.05 0.7 37.0 0.7 35.9 32.7 37.1 34.5 41.3 -55.6 -85.1 37.5 39.9 38.7 34.5 36.7 35.1 140 25.9 -58.9 35.9 32.7 31.9 27.5 37.9 38.1 120 29.9 38.7 34.3 38.7 37.3 38.1 27.8 -9.9 -50.5 38.5 30 30.5 39.5 30.1 37.3 28.5 28.7 37.8 .8 -6.9 35.2 -80.3 -71.9 38.1 40 Cd [106 Ns/m] Table 4.3 38.5 31.7 34.7 34.5 36.5 38.9 100 40.1 28.0 -74.1 34.3 32.0 10 20 30 40 115 50 60 Kd [106 N/m] 80 100 120 200 1.7 34.1 37.7 37.3 -80.9 36.5 27.188m 32.5 38.3 32.9 36.2 13.1 28.7 31.5 33.3 37.1 34.3 38.1 34..8 -84.3 35.7 37.1 -80.7 34.7 35.8 18.3 37.6 -34.2 15.8 2.1 28.1 0.3 38.Percentage reductions in tip deflection of the structure type T1-3 Influence of Damping Systems on Building Structures Subject to Seismic Effects .3 29.9 21.4 5.9 36.0 1.1 33.1 37.3 35.2 10 34.4 -0.3 37.1 80 31.1 30.7 34.7 38.7 -38.1 38.5 34.1 50 34.7 34.9 33.1 34.5 -19.3 60 35.9 29.5 34.9 70 38.1 37.5 39.1 37.4 -2.3 38.9 38.9 29.2.9 36.7 34.3 29.7 38.5 37.8 4.7 37.4 -14.9 32.1 -53.7 35.4 0.3 35.2 20 19.2 7.7 34.9 38.7 33.2 1.1 28.2 13.9 39.1 37.5 30.9 38.0 13.4 19.5 200 *Tip deflection of the undamped structure type T0 represents 0.0 33.4 -5.5 36.9 38.8 -1.9 29.8 19.1 34.4 -25.7 29.8 4.9 40.5 28.2 13.1 26.1 41.2 20.7 37.2 -4.8 -84.1 -58.3 36.1 1.7 37.7 34.9 35.3 37.1 28.9 35.8 -10.7 34.5 27.4 0.0 19.9 39.5 29. 0 0.19 .0 40. the highest tip acceleration reductions were recorded for the value of kd = 20 x 106 N/m.0 200 120 100 80 60 50 40 30 20 10 1 0.9. 4.0 % Reduction 20. In the case when the value of the dashpot was less than cd = 10 x 106 Ns/m the highest tip acceleration reduction was recorded for the springs kd = 50 x 106 N/m and kd = 60 x 106 N/m. The subsequent increase or decrease of the damping in dashpot resulted in relatively regular decrease in the tip acceleration reduction.4%. In terms of spring parameter it can be seen. The results revealed the significantly high tip acceleration reductions experienced for broad range values of spring and dashpot with the highest reduction of 69.0 10.Influence of Damping Systems on Building Structures Subject to Seismic Effects The results for percentage reduction in tip acceleration of the structure embedded with damper of varying properties under the El Centro earthquake excitation is provided in Tables 4.0 6 6 K d [10 N/m] Cd [10 Ns/m] Fig.0 30.1 0 0 0. Acceleration reductions of the structure type T1-3 70. As regards to influence of dashpot.1 1 10 20 30 40 50 60 70 80 100 120 140 200 -10. that while the damping of dashpot was within the range cd = 10 x 106 – 200 x 106 Ns/m the highest acceleration reductions were recorded for the spring kd = 10 x 106 N/m and kd = 1 x 106 N/m.0 50.0 60.Percentage reductions in tip acceleration for the structure type T1-3 116 . Further increase in stiffness of spring reasoned in slight decrease in the tip acceleration reductions. 9 53.0 38.1 43.4 63.3 61.1 45.0 10.8 44.8 41.3 64.3 60.4 44.5 55.8 1.7 41.7 38.4 117 38.0 50 53.1 45.3 63.6 57.3 64.1 0.9 54.9 59.3 62.4 37.0 38.3 59.9 67.05 0.9 60.3 62.2 56.5 23.0 30 66.9 61.1 41.1 48.0 69.0 64.1 10.9 56.41.2 53.5 48.8 48.0 38.2 38.8 42.1 43.6 65.3 62.1 120 39.9 60 51.5 56.0 65.9 54.6 66.6 64.2 57.2 54.7 64.9 80 44.5 47.5 50.5 53.4 34.3 34.0 62.8 48.3 64.4 42.0 20 68.2 51.8 100 41.1 45.3 20.0 Kd [106 N/m] 54.7 4.9 53.0 3.9 59.4 41.5 2.6 26.3 60.3 62.0 200 *Tip acceleration of the undamped structure type T0 represents 2.8 48.4 38.6 58.6 5.7 62.0 68.9 56.4 8.5 30.0 10 20 30 40 50 60 80 100 120 200 21.2 55.1 45.0 5.2 53.6 60.1 -4.9 53.0 69.4 34.6 63.3 59.9 56.9 58.4 38.4 140 35.3 61.6 64.4 29.4 65.8 45.6 56.9 52.6 56.7 4.9 52.6 58.7 31.0 24.1 46.8 45.5 8.3 58.9 56.3 33.0 62.4 0.6 62.0 62.9 58.4 64.3 64.0 66.1 48.4 38.0 68.Percentage reductions in tip acceleration for the structure type T1-3 Influence of Damping Systems on Building Structures Subject to Seismic Effects .8 48.0 63.9 20.6 10 Cd [106 Ns/m] Table 4.0 62.8 45.9 57.0 66.8 48.8 6.3 61.3 33.3 67.7 66.3 36.7 1.4 44.4 40.4 38.3 0.0 64.4 67.3 66.0 69.4 12.8 43.0 66.6 58.9 .4 38.0 38.4 39.4 24.0 6.3 1.4 4.9 66.8 41.8 48.2 28.9 53.4 43.5 53.4 65.7 66.4 38.2 56.8 44.4 43.9 70 48.2 56.1 45.3 40 66.05 66. 64.6 56.97 m/s2.7 1.8 47.6 58.3 64. the range of the parameters at which the damper achieved the performance close to the maximum values was noticeably wider. 118 .Influence of Damping Systems on Building Structures Subject to Seismic Effects 4. 4. While comparing these results with results recorded for the damper placed in the lower storeys. from the results it is evident.3. cd. In addition. to higher maximum tip deflection reduction. as it was expected.14 and 4. has clearly less impact on the response of the structure than the damping coefficient. occurred for the structure with the dampers placed in the all three parts of the structure. The performance of the damper embedded in the lower storeys was even higher with maximum tip deflection reduction of 38.Summary of finding The influence of the damping properties of the diagonal VE dampers on performance of the 24-storey frame-shear wall structure under earthquake load were investigated. The dampers experienced a high performance over the wide range of damping parameters.1% was achieved for dashpot with damping parameter cd = 30 x 106 Ns/m and spring with stiffness of kd = 10 x 106 N/m. The highest performance. kd. the fitting of these two additional dampers extended the range of the parameters at which the damper experienced the maximum performance.16. On the other hand. This reduction was obtained for dashpot with damping parameter cd = 70 x 106 Ns/m and spring with stiffness of kd = 1 x 106 N/m. However. that fitting of additional two dampers in the middle and upper parts of the structure produced only slightly increased in maximum deflection reduction. The subsequent increase or decrease in these parameters resulted in relatively regular decrease in tip deflection reduction. In the case of the structure with the damper embedded in the upper storeys the maximum tip deflection reduction of 28.5 Parameters of VE dampers . as it can be seen from Figs. The maximum tip deflection reduction of 41.9%. that the damper stiffness.3% occurred for the dashpot with damping parameter cd = 80 x 106 Ns/m and spring with stiffness of kd = 10 x 106 N/m. it is obvious. Influence of Damping Systems on Building Structures Subject to Seismic Effects In terms of tip acceleration. relatively insignificant. in a smaller scale conducted under the Hachinohe and Kobe earthquake 119 . the results imply that instalment of the damper in the middle and upper storeys had only small influence on the structural performance over the whole range of investigated dampers parameters. similarly to results for tip deflection reduction. while additional increase or decrease in damping resulted in noticeably decrease in tip acceleration reductions. The maximum reduction of 44. The tip acceleration reductions experienced for other values of dashpot were significantly lower. In the case of the structure with the damper embedded in the lower storeys the highest tip acceleration reduction of 64. While comparing the tip acceleration reductions experienced by all three structures.4% occurred for the dashpot cd = 20 x 106 Ns/m and spring kd = 10 x 106 N/m. yet again. The results for tip acceleration reduction. Influence of the damper parameters on seismic response of these structures was. The results for other values of damping revealed noticeably lower tip acceleration reductions. The highest tip acceleration reduction was experienced by the structure with the dampers embedded in all three parts of the structure. the significantly high reductions were experienced in all three damper placements. An influence of the change in the damper stiffness was.4% occurred for the damper with the dashpot cd = 10 x 106 Ns/m and spring kd = 1 x 105 N/m. An influence of change in the damper stiffness was less significant. The maximum reduction of 69. Tip acceleration reductions experienced by the structure with the damper embedded in the upper storeys was noticeably lower. The change in the damper stiffness did not considerably affect the results.4% was experienced for damper with dashpot cd = 20 x 106 Ns/m and spring kd = 10 x 106 N/m. reveal significantly higher efficiency of the damper positioned in the lower storeys. respectively were determined and used in all subsequent cases.20 illustrates the percentage reductions in the peak values of tip deflections experienced by the structures embedded with the dampers at four different placements. 14. The high average tip deflection reduction of 20. approximate average values of kd = 40 x 106 N/m and cd = 50 x 106 Ns/m.Influence of Damping Systems on Building Structures Subject to Seismic Effects excitations.3. A slightly lower average 120 . 17.1 30 Avg.6 50 20 40 30 Avg.6 Response of the structure under five earthquake excitations The 24-storey frame-shear wall structural model was further investigated under five earthquake excitations. Based on results reported in the previous sections it can be seen that the structures experienced the highest performance when Cd was within the range 10 x 106 to 100 x 106 Ns/m and kd within the range 1 x 106 to 60 x 106 N /m.0% was achieved by the structure with the damper placed in the lower storeys. The tip deflection and tip acceleration reduction occurred under these earthquake excitations were significantly different. Fig.20 – Percentage reduction in tip deflection of 24-storey frame-shear wall structure in terms of damper placements The results showed significant performance of the structures for all damper placements. 4. Tip Deflection Reduction Avg. Hence in order to facilitate comparisons. 20 % Deflection Reduction 50 20 10 10 0 EC HA KO NO SF Avg 0 T1 T2 T3 T1-3 Type of the Structure Fig. 4. 4. However. 31.8 40 Avg. the ranges of the most effective damping parameters were relatively close to those experienced under the El Centro earthquake. The reductions occurred under the Northridge earthquake excitation were also relatively high. while clearly the lowest reductions were experienced under the Hachinohe earthquake. Noticeably higher reduction of 26.22 shows the results of peak values in tip acceleration reduction experienced by the same structures.5 30 Avg.1% occurred for the structure T3.4% was experienced by the structure T2 with the damper placed in the middle storeys. while the lowest efficiency with still relatively high an average reduction of 14.21 – Percentage reduction in tip deflection of 24-storey frame-shear wall structure under five earthquake excitations Fig. which had the damper placed in the upper storeys. 4. 24. as it was expected. however the range of the particular results was noticeably wide. 4.8% occurred for the structure with the damper placed in the middle storeys.21. 16. was obtained by the structure with the three dampers placement.1 50 40 T1 30 T2 T3 20 10 10 0 T1-3 Avg 0 El Centro Hachinohe Kobe Northridge S. Clearly the highest tip deflection reductions were achieved by the structures T1.1% was experienced by the structure with the upper storeys damper placement. with the dampers placed in the lower. 26.6 Avg. the dampers achieved the highest tip deflection reductions under the El Centro earthquake excitation however the reduction experienced under the Kobe and San Fernando earthquakes were only slightly lower. which had the damper placed in the lower storeys and structure T13.2 % Reduction 40 50 Avg. middle and upper storeys. As it can be seen in Fig. which both 121 . 10. The average tip deflection reduction of 18.1 Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects tip deflection reduction of 17. Fernando Earthquake record Fig. Clearly the highest average tip deflection reduction. 4. The structures achieved significant overall tip deflection reduction. Tip Deflection Reduction 20 Avg. 27. 57. 35. Tip Acceleration Reduction Avg. recorded under the Hachinohe earthquake. 18.4 60 Avg.23 presents the same results in terms of tip acceleration reduction experienced under different earthquake excitations.22 – Percentage reduction in tip acceleration of 24-storey frame-shear wall structure in terms of damper placements Fig.9 Tip Acceleration Reduction Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects obtained relatively similar results under all earthquake excitations.4 80 Avg.1 40 Avg. 34. 25. Clearly the highest reductions were achieved under the San Fernando earthquake. Fernando Earthquake Record Fig. 4.1 40 60 EC HA Avg.7 % Reduction 80 80 60 T1 T2 40 T3 T1-3 20 20 0 Avg 0 El Centro Hachinohe Kobe Northridge S. 26.1 Avg.1 % Acceleration Reduction 80 40 KO NO SF 20 20 0 Avg 0 T1 T2 T3 T1-3 Type of the structure Fig. yet again.9 60 Avg. Avg. 51.4. It was followed by the reductions occurred under the Kobe and El Centro earthquakes. The reductions recorded under the Northridge earthquake were slightly lower and the lowest reductions were. 40. 4. 59. it can be suggest that in the case of the structure T1-3 the dampers placed in the middle and upper storeys were rather ineffective in reducing tip acceleration. Based on this.23 – Percentage reduction in tip acceleration of 24-storey frame-shear wall structure under five earthquake excitations 122 . 123 . While comparing the results from 24-storey frame-shear wall structure embedded with diagonal VE dampers with results obtained from 96m tall shear wall structure embedded with the same dampers.Influence of Damping Systems on Building Structures Subject to Seismic Effects The dampers demonstrate a high performance in the vast majority of cases. the dampers achieved clearly better results in both investigated parameters when placed in the lower storeys. where the dampers experienced the lowest reductions in both investigated parameters reverse trend was observed. surprisingly higher tip deflection and tip acceleration reductions were obtained by 24-storey frame-shear wall structure. In general. in the case of the Hachinohe earthquake. however. both types of structure revealed similar trends in both investigated parameters. Nevertheless. Influence of Damping Systems on Building Structures Subject to Seismic Effects 124 . 18-Storey Structures 125 .Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 5 Results . Though tip deflection is more important in assessing overall seismic response. namely friction and VE diagonal dampers.2). For this reason any reduction in tip deflection represents a worthwhile reduction in overall seismic design force. 5. First type is represented by an 18-storey frame-shear wall structure (described in Section 3. Seismic analyses were caried out with one type of damping system at one placement a time.1) embedded with six different damping systems (Section 3.10). These damping systems were embedded in cut outs of shear walls at tvelwe different damper placements (Section 3. except the shear wall is replaced by one bay of frame.1-5. 5. there are various ways of assessing seismic response. The second type is represented by an 18-storey frame structure of the same parameters as it was for an 18storey frame-shear wall.1 Introduction The results from the finite element analysis of two types of medium-rise structure are presented in this chapter. friction and VE chevron brace dampers. The efficiency of the dampers fitted in this structure ws investigated under the same five earthquake excitations.2 Seismic response of 18-storey frame-shear wall structure As it was mentioned previously.18-storey structure 5. This structure was fitted with diagonal VE dampers installed at 12 different placements. in most cases.Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 5: Results . computation of tip deflection is a reasonable measure of the overall effect of the earthquake. The efficiency of these damping systems were investigated under the five different earthquake excitations.5 illustrate the tip deflection and tip acceleration of the structure designated by H1-3 with the diagonal VE dampers fitted in the lowest three storeys compared with tip deflection and tip acceleration of the undamped structure obtained under five earthquake excitations.5.5. From these graphs it is evident that the dampers embedded into the cut-outs of shear walls. hybrid friction-VE dampers and VE lower toggle dampers. the reductions in the peak values of the tip accelerations at the top of the structure are also investigated. 126 . Figs. However. 1 -6 -0.15 Time (s) Time (s) Fig. 5.3 4 2 0 Acceleration (m/s ) UN 2 0 -2 -0. Tip deflection (El Centro earthquake) Tip acceleration (El Centro earthquake) VE UN VE UN 6 4 Deflection (m) 2 0.1 0 5 10 15 20 -0.5 -6 Time (s) Time (s) Fig.2 Acceleration (m/s ) 0.2 0 5 10 15 20 -4 -0.4 0 5 10 15 20 -4 -0.2 -0.1 6 Deflection (m) -0.Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal VE dampers under the Kobe earthquake 127 .2 4 2 Acceleration (m/s ) Deflection (m) 0.Influence of Damping Systems on Building Structures Subject to Seismic Effects significantly reduced the tip deflection and tip acceleration throughout the duration of the earthquakes.1 0.05 0 VE UN 6 UN 5 10 15 20 2 0 -2 0 5 10 15 20 -4 -0.15 0. 5.Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal VE dampers under the Hachinohe earthquake Tip deflection (Kobe earthquake) Tip acceleration (Kobe earthquake) VE 0.1 0 -0.3 .Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal VE dampers under the El Centro earthquake Tip deflection (Hachinohe earthquake) Tip acceleration (Hachinohe earthquake) VE UN VE 0.05 0 -0.1 0 5 10 15 20 2 0 -2 -0.3 0.2 .1 . 5.3 -6 Time (s) Time (s) Fig. 15 -3 Time (s) Time (s) Fig. advantage of the 128 .Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal VE dampers under the Northridge earthquake Tip deflection (San Fernando earthquake) 0.05 0 -0.6 shows the typical tip deflection and tip acceleration responses of structure embedded with diagonal friction and diagonal VE dampers.1 0 5 10 15 20 -2 -0.Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip deflection (Northridge earthquake) Tip acceleration (Northridge earthquake) VE VE 6 UN 0.05 VE 3 UN Acceleration (m/s ) Deflection (m) Tip acceleration (San Fernando earthquake) VE 0 5 10 15 20 1 0 -1 -0.6-5.2 UN 4 2 Acceleration (m/s ) Deflection (m) 0. In contrast. it was evident that the different damping properties of the friction and VE dampers resulted in significantly different seismic responses. Fig.1 0 -0.1 0 5 10 15 20 2 0 -2 0 5 10 15 20 -4 -0.3 Time (s) Time (s) Fig. 5. 5. 5. 5.4 . that the diagonal friction dampers surpassed the diagonal VE dampers in their ability to reduce the intensity of the initial strong motion. From these graphs.1 UN 2 2 0.8 illustrate tip deflection and tip acceleration responses of six damping systems embedded in the same structure under the El Centro earthquake excitation.Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal VE dampers under the San Fernando earthquake Figs.5 . It can be seen. as well as from numerous other results obtained with dampers at different placements.2 -6 -0.3 0. The structure embedded with the chevron brace friction dampers revealed tip acceleration response more typical for the structures fitted with friction dampers. 5.1 -0. 5. Chevron VE brace dampers 6 0.1 4 Deflection (m) 2 Acceleration (m/s ) 0.2 0 0 5 10 15 20 -0.2 2 0 0 5 10 15 20 -2 -4 VE VE -0. whereas.Tip deflection and tip acceleration responses of the structures embedded with diagonal friction and VE dampers under the El Centro earthquake Fig. Chevron brace friction dampers vs.2 -0.1 -0. On the other hand. 5. tip acceleration response of the structure fitted with the chevron brace VE dampers was more typical for the structure fitted with VE dampers. Diagonal VE dampers 6 0.7 compares the seismic responses of the same structure embedded with chevron brace friction and chevron brace VE dampers.3 -6 FR Time (s) FR Time (s) Fig.3 2 0 0 5 10 15 20 -2 -4 VE Time (s) VE -6 FR Time (s) FR Fig. their tip acceleration responses were more diverse.2 4 Aceleration (m/s ) 0. Both structures displayed relatively close tip deflection responses. Diagonal VE dampers 0.6 . respectively.3 0 0 5 10 15 20 -0.Influence of Damping Systems on Building Structures Subject to Seismic Effects diagonal VE dampers was in gradually decreasing the tip deflection and tip acceleration of the structure.8 . Chevron brace VE dampers Chevron brace friction dampers vs.Tip deflection and tip acceleration responses of the structures embedded with chevron brace friction and VE dampers under the El Centro earthquake 129 .1 2 Deflection (m) Diagonal friction dampers vs. Diagonal friction dampers vs. 72 Kobe 0. somewhere.130 2.95 S.163 4.275 5.1 -0.1 Table 5. the seismic responses of the lower toggle VE dampers were.1 .245 5. The seismic response of the structure fitted with hybrid friction-VE dampers was mostly.Tip deflection and tip acceleration of the undamped 18-storey structure. noticeably close to the seismic responses of the structure fitted with friction dampers. between the response of the chevron brace friction dampers and the diagonal VE dampers. are illustrated in Fig.1 4 2 Acceleration (m/s ) Deflection (m) Hybrid dampers vs.464 4.66 Hachinohe 0.2 0 0 5 10 15 20 -0.3 Time (s) -6 TG Time (s) TG Fig.9 shows the interstorey drifts of the undamped 18-storey structure under five earthquake excitations.Tip deflection and acceleration responses of the structures embedded with Hybrid friction-VE damper and VE lower toggle dampers under the El Centro earthquake 5. Deflection (m) Acceleration (m/s2) El Centro 0.8.2 2 0 0 5 10 15 20 -2 -4 HY HY -0.2.Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip deflection and tip acceleration responses of the structures embedded with hybrid friction-VE dampers and lower toggle VE dampers. The highest interstorey drifts. Lower toggle VE dampers 6 0. in the vast majority of cases. as expected. with the maximum 130 . The tip deflection and tip acceleration of this structure experienced under five earthquake excitations are presented in Table 5. Hybrid dampers vs.93 Northridge 0. 5. 5. On the other hand.1 Undamped structure The undamped structural model was in this study created in order to compare its results with the results of the structures fitted with six damping systems.72 Fig.Fernando 0. Lower toggle VE dampers 0. respectively.8 . 5. 0. Fig.03 14-15.0204 m and the Kobe earthquake with the maximum interstorey deflection of 0. 1-2 0. In these graphs.2.0221 m was recorded under the El Centro earthquake.01 6-7 7-8 13-14. which were placed in storeys 1 to 3 and 13 to 15 respectively.2 Diagonal friction dampers The results of the tip deflection and tip acceleration experienced by the structures embedded with diagonal friction damper are presented below.Fernando 15-16 16-17 17-18 Fig. In Fig.0221 Interstorey Drifts (m) 0.Influence of Damping Systems on Building Structures Subject to Seismic Effects interstorey deflection of 0.04 11-12.9 it can also be seen that the maximum interstorey drifts occurred between storeys 14 and 15. it can be seen. 12 and 13. This followed by the Northridge earthquake with the maximum interstorey deflection of 0.Interstorey drifts of undamped structure under the five earthquake excitations 5. The second highest interstorey drifts of 0. 0. then 15 and 16. 5.0128 m.0326 m occurred under the Hachinohe earthquake. that the dampers embedded 131 . 11 and 12. etc. 16 and 17. The lowest interstorey drifts were recorded under the San Fernando earthquake with the maximum interstorey deflection of 0.0100 m.10 illustrates time history responses of tip deflection and tip acceleration under the El Centro earthquake in the undamped structure and in the structures embedded with diagonal friction dampers.0204 5-6 14-15. 5.0100 16-17. This was followed by drifts between storeys 13 and 14.9 . 5. 0.05 3-4 4-5 0. 0.0128 0. 0.0326 2-3 8-9 9-10 10-11 11-12 12-13 13-14 14-15 0 El Centro Hachinohe Kobe Northridge Earthquake Records S.02 0. 5.58 % Deflection Reductions Avg.1 -0. -2.26 25 Avg -15 Earthquake Records Fig. 15. 5.3 -6 Time (s) Time (s) Fig. 15 Avg.48 16 -5 Avg. -4.9).Fernando Avg. the damper displayed extraordinary performance under the El Centro.1 0 0 5 10 15 20 -0. 5.10 Tip deflection and acceleration responses of the structures with different placement of the diagonal friction dampers under the El Centro earthquake The percentage reductions in the peak values of the tip deflection experienced by the structures fitted with the diagonal friction damper embedded at six different locations under five different earthquakes are presented in Fig. While working back to inter-storey drifts obtained by the undamped structure (Fig. 5. it is evident.Influence of Damping Systems on Building Structures Subject to Seismic Effects in the upper storeys (with higher interstorey drifts) produced clearly better results in both investigated parameters than the dampers fitted in the lowest storeys.2 2 0 0 5 10 15 20 -2 -4 -0. 14. Hachinohe and Northridge earthquake excitations.27 Avg. Tip Deflection (El Centro earthquake) Tip Acceleration (El Centro earthquake) 1-3 UN 0.11 – 18 storey structure embedded with 1 diagonal friction damper -percentage reductions in tip deflection under different earthquake records As it can be seen from this figure. 12.2 1-3 UN 6 13-15 0.04 20 1 4 10 7 5 10 13 0 -10 El Centro Hachinohe Kobe Northridge S.11.3 13-15 4 2 Acceleration (m/s ) Deflection (m) 0. that these three earthquake excitations caused 132 . in the cases of the Kobe and San Fernando earthquakes. that efficiency of the damper under the El Centro.09 15 Avg.95 10 Avg. in which the structure experienced noticeably lower inter-storey drifts. The results of the same structure in terms of tip deflection reduction at different damper placements are illustrated in Fig. unfavourable increase in average tip acceleration was recorded under the Kobe and San Fernando earthquake excitations. 7. The reductions experienced under the El Centro and Northridge earthquakes were slightly lower.85 % Deflection Reductions 20 EC HA KO NO SF 0 Avg -5 1 4 7 10 13 16 -10 -15 Placement of the Dampers Fig.12 – 18 storey structure embedded with 1 diagonal friction damper -percentage reductions in tip deflection for different damper placements The tip deflection reductions for the structure embedded with three diagonal friction dampers fitted at six different placements are shown in Fig. in the upper placements adverse increase in tip deflection was recorded. while in contrast. 5.13. In contrast. Hachinohe and Northridge earthquakes was directly related to an increase in inter-storeys drift.26%.Influence of Damping Systems on Building Structures Subject to Seismic Effects clearly the higher interstorey drifts. On the other hand. which caused noticeably lower interstorey drifts. 6. 7.10 Avg. The 133 . was obviously poor. the efficiency of the dampers occurred under the Kobe and San Fernando earthquakes. 6. The best performance occurred under the Hachinohe earthquake with average tip deflection reduction of 15. whereas.12.02 Avg. 25 5 Avg. This may be attributed to inadequate compensation for removed stiffness at cut out and/or partial resonance of the damped structure and insufficient push on the friction damper to make it fully operational. the dampers were effective when embedded in the 1st or 4th storey. 5. 5. 4. From these results it is evident.41 Avg. 9. 14 presents the results of tip deflection reduction in terms of different dampers placements. as it was expected. The results achieved under the El Centro. performance of the dampers under the Kobe and San Fernando earthquakes were. 23. The results displayed similar trends as it was for the structure embedded with one damper. in case of the Kobe and San Fernando earthquakes.13 – 18 storey structure embedded with 3 diagonal friction dampers -percentage reductions in tip deflection under different earthquake records Fig.99 Avg. once again. nevertheless. one again.Influence of Damping Systems on Building Structures Subject to Seismic Effects overall results were.64 Avg. an adequate efficiency was displayed only when the dampers were fitted in the lowest storeys. 5. the similar trends were experienced. unfavourable with noticeably increase in deflection. On the other hand. The reason may be. -1. The highest tip deflection reductions were obtained under the Hachinohe earthquake excitations and significantly high reductions also occurred under the El Centro and Northridge earthquakes. 134 . noticeably higher than for the structure embedded with one damper. -20. The highest average reduction was achieved by the structure with the dampers fitted in the top storeys.Fernando Avg. 5. attributed to inadequate compensation for removed stiffness at cut out and/or change in natural frequency of the structure. On the other hand. 18. while the lowest average reduction was recorded for the structures with dampers placed in storeys 10 to 12. Hachinohe and Northridge earthquakes fully support Hanson’s theory (1993). which recommends placement of friction dampers at levels of maximum interstorey drift. 30 1-3 4-6 0 7-9 Avg.97 10-12 13-15 16-18 -30 -45 El Centro Hachinohe Kobe Northridge S. 11.64 -15 Avg.97 % Deflection Reductions 15 Avg Earthquake Records Fig. 3.78 % Deflection Reductions 30 HA KO 0 -10 EC NO SF 1-3 4-6 7-9 10-12 13-15 16-18 Avg -20 -30 -40 Placement of the Dampers Fig.20 Avg.31 1 4 7 0 10 Avg. 7. 6. 12.67 10 Avg.95% was achieved under the Hachinohe earthquake. while the reductions occurred under the Kobe and especially under the San Fernando earthquakes were obviously unfavourable. The reductions recorded under the El Centro and Northridge earthquakes were clearly lower and rather inconsistent.14 – 18 storey structure embedded with 3 diagonal friction dampers -percentage reductions in tip deflection for different damper placements The percentage reductions in the peak values of the tip acceleration for the structures fitted with the diagonal friction damper are shown in Fig.95 30 Avg -30 Earthquake Records Fig. 3. -12. The highest average tip acceleration reduction of 11.61 20 Avg. 1.15.52 Avg. the increase in tip acceleration to a level lower than 10 m/s2 (in this case. 5 m/s2) did not represent any significant decrease in structural safety. The structure experienced a wide range of results. Nevertheless. 10 Avg. -2. 11. 5.48 -10 13 16 -20 El Centro Hachinohe Kobe Northridge S. 5.17 Avg. 7.15 – 18 storey structure embedded with 1 diagonal friction damper -percentage reductions in tip acceleration under different earthquake records 135 .Influence of Damping Systems on Building Structures Subject to Seismic Effects 40 Avg.57 Avg.43 % Acceleration Reductions 20 Avg. 5. 5.Fernando Avg. 5.05 20 Avg. clearly the poorest results. was experienced for the upper storeys placements. 2.22 1-3 4-6 7-9 0 10-12 13-15 -20 Avg.22 Avg.20 Avg.16). -16.20 % Acceleration Reductions 20 EC HA KO NO SF -10 Avg -20 1 4 7 10 13 16 -30 Placement of the Dampers Fig. whereas.07 Avg. -0. 5.43 60 -40 El Centro Hachinohe Kobe Northridge 16-18 Avg S.82 0 Avg. 18.17 – 18 storey structure embedded with 3 diagonal friction dampers -percentage reductions in tip acceleration under different earthquake records 136 . 17. in the case of the Hachinohe earthquake. with strong increase in tip acceleration. 6. 5. 1.35 10 Avg. Avg. 2. 30 Avg. The highest reductions for the Northridge earthquake was obtained when the damper was placed in the upper storeys.50 Avg.73 % Acceleration Reductions 40 Avg. In the cases of the Kobe and San Fernando earthquakes. -1. the highest reductions occurred when the damper was placed in the 1st or 10th storeys.Influence of Damping Systems on Building Structures Subject to Seismic Effects In terms of damper placement (Fig. tip acceleration reductions occurred under the El Centro earthquake were increasing when the damper was moved towards the top of the structure. 4.17. 5.16 – 18 storey structure embedded with 1 diagonal friction damper -percentage reductions in tip acceleration for different damper placements The tip acceleration reduction for structure embedded with three diagonal friction dampers are shown in Fig.Fernando -60 Earthquake Records Fig. 14. which caused transfer of acceleration to the ambient structural elements as well as decrease in stiffness of the top storeys due to the cut out in the shear wall. -17. 5. 3. 5. wide range of results was experienced.89 Avg. under the San Fernando earthquake excitation. The reductions experienced under the Kobe earthquake were rather inconsistent and the poorest result with tip acceleration increase by 16. 0. Clearly the worst results. In terms of efficiency of different damper placement (Fig. 19. This tip acceleration increase was mainly due to the operating principle of the friction dampers. The reductions under the El Centro and Northridge earthquakes were only slightly lower.16 Avg. tip deflection reductions were 137 . experienced by the structure with the dampers placed in the top storeys.37 % Acceleration Reductions 40 Avg. The tip acceleration reductions for the dampers placed in storeys 7 to 12 were rather inconsistent with some significant results. once again. with massive tip acceleration increases were.18) the greatest tip acceleration reductions occurred when the dampers were placed in storeys 1 to 6 and 13 to 15.57 20 Avg.73% was recorded. 21. yet again. In these excitations. The overall performance of the dampers was adequately high. nevertheless.39 0 Avg. Avg. 19.Influence of Damping Systems on Building Structures Subject to Seismic Effects The highest acceleration reduction of 18.78 60 EC HA KO NO SF -20 Avg -40 1-3 4-6 7-9 10-12 13-15 16-18 -60 Placement of the Dampers Fig.18 – 18 storey structure embedded with 3 diagonal friction dampers -percentage reductions in tip acceleration for different damper placements Diagonal friction dampers embedded in the 18-storey structure were investigated in this section. The dampers achieved a high performance in both investigated parameters under earthquake excitations. which caused high deflections.22% was achieved under the Hachinohe earthquake. respectively. 138 . This may be attributed to inadequate compensation for removed stiffness at cut out and/or partial resonance of the damped structure and insufficient push on the friction damper to make it fully operational.Influence of Damping Systems on Building Structures Subject to Seismic Effects gradually increasing when the dampers were moved towards the storeys with the highest interstorey drifts. Significant tip acceleration reductions were experienced when the dampers were placed in storeys 1 to 6 and 13 to 15.2. the results for other placements were relatively poor. 5. the diagonal friction dampers were noticeably less effective under the earthquake excitations. which caused transfer of acceleration to the ambient structural elements.3 Diagonal VE dampers The results of the tip deflection and tip acceleration experienced by the structures embedded with diagonal VE dampers are presented below. are illustrates in Fig. In contrast. the efficiency of the dampers was rather inconsistent without any obvious trends. Time history responses of tip deflection and tip acceleration under the El Centro earthquake excitation in the undamped structure and in the structures with the diagonal VE dampers placed in storeys 1 to 3 and 13 to 15. respectively.19. In contrast. The worst results with regard to increase in tip acceleration occurred for the uppermost storey placements. their even higher performance in terms of root mean square deflection and root mean square acceleration can be observed. The graphs show the high performance of the dampers embedded in the lowest storey. respectively. This was mainly due to the operating principle of the friction dampers. while their performance was clearly less significant when placed in the upper storeys. In terms of tip acceleration reduction. 5. which cause only small deflections. as well as decrease in stiffness of the top storeys due to the cut out in the shear wall. In addition to high tip deflection and tip acceleration reductions obtained by placing the dampers in the lowest storey. 61 7 10 13 Avg. 5. The structures experienced reasonable overall performance with a few significant results. The damper obtained the highest performance when was placed in the lowest storey.91 1 Avg. The average reduction for the El Centro earthquake was only slightly lower.35 6 Avg. 1.25 % Deflection Reductions 10 16 Avg 0 El Centro Hachinohe Kobe Northridge S.1 2 0 0 5 10 15 20 -2 -4 -0. 2. 5. 4. 5. 4. whereas. 8 Avg.19 – Tip deflection and acceleration responses of the structures with different placement of the diagonal VE dampers under the El Centro earthquake Fig. while it performance gradually decreased when was moved towards the top of the structure.Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip Deflection (El Centro earthquake) Tip Acceleration (El Centro earthquake) 1-3 UN 0.Fernando Earthquake Records Fig.3 Time (s) Time (s) Fig. 5. The highest average reduction of 4. 1. the reductions obtained under the Hachinohe. This trend was experienced under all earthquake 139 .1 0 0 5 10 15 20 -0.21.2 -6 -0.3 13-15 UN 13-15 0.91% occurred under the Kobe earthquake excitation.2 4 2 Acceleration (m/s ) Deflection (m) 1-3 6 0.20 – 18 storey structure embedded with 1 VE diagonal damper -percentage reductions in tip deflection under different earthquake records The results of the same structure with respect to damper placement are presented in Fig.20 shows the tip deflection reduction for the structure embedded with the diagonal VE damper.59 4 4 2 Avg. Northridge and San Fernando earthquakes were rather insignificant. 67 4 Avg. 8 EC HA KO NO 2 Avg. 36 12 1-3 4-6 6 7-9 Avg.95 Avg. 7. 19.22. The highest average reduction of 19. 5. the tip deflection reductions recorded for the Northridge and Hachinohe earthquakes were a noticeably poorer.07% occurred.Fernando -12 Earthquake Records Fig. under the San Fernando earthquake. 5.21 – 18 storey structure embedded with 1 diagonal VE dampers -percentage reductions in tip deflection for different damper placements The tip deflection reduction for the structure embedded with three diagonal VE dampers are illustrated in Fig.89 24 Avg. 5. 1. On the other hand.Influence of Damping Systems on Building Structures Subject to Seismic Effects excitations except for the San Fernando earthquake.27 % Deflection Reductions 30 13-15 16-18 Avg 0 -6 10-12 El Centro Hachinohe Kobe Northridge S. 15.03 6 Avg. 1. 4. The lowest average tip deflection reduction of 4. except for top placements.61 Avg. where the highest tip deflection reduction occurred when the damper was placed in the 7th storey.07 Avg. 7.26 Avg. 4.53 % Deflection Reductions 10 SF Avg 0 1 4 7 10 13 16 Placement of the Dampers Fig.68 18 Avg. 2.54 Avg. 3.22 – 18 storey structure embedded with 3 VE diagonal dampers -percentage reductions in tip deflection under different earthquake records 140 . 4. also significantly high.27% was obtained under the El Centro earthquake. similarly as it was in the case of one damper placements. The tip deflection reductions experienced under the Kobe earthquake were. EC HA 6 0 -6 1-3 4-6 7-9 10-12 13-15 KO Avg.21% was recorded under the Hachinohe earthquake.31 24 Avg. 5. 18. 13. 5. According to a study conducted by Ashour (1987).38 % Deflection Reductions 30 Avg. The results for the diagonal VE dampers were in accordance with Ashour’s study.Influence of Damping Systems on Building Structures Subject to Seismic Effects The results of tip deflection reduction in terms of damper placement are presented in Fig. the optimal placement of dampers should be the one that maximizes the damping ratio of the fundamental mode.23 – 18 storey structure embedded with 3 diagonal VE dampers -percentage reductions in tip deflection for different damper placements Fig. as this mode’s contribution to the structure’s overall response is always significant. while their subsequent repositioning towards the top storeys responded in a gradually decrease in tip deflection reduction under all earthquake excitations.24 shows the percentage reduction in tip acceleration for the structure embedded with the diagonal VE damper placed at 6 different locations.23.44 36 NO SF Avg 16-18 -12 Placement of the Dampers Fig.38 18 Avg. The best performance occurred when the dampers were placed in the lowest three storeys. whereas. San Fernando and El Centro earthquakes were rather insignificant. while the reductions obtained under the Kobe. when they were moved towards the top of the structure a gradual decreased in their efficiency was experienced. 141 .44 12 Avg. 8. 20.89 Avg. 4. 0. The reductions under the Northridge earthquake were also adequately high. The highest average reduction of 11. 5. The results experienced under the all earthquake excitations confirmed the best performance experienced by the dampers placed in the lowest storeys. 5.07 10 EC Avg.30 % Acceleration Reductions 20 10 13 16 Avg 0 -5 El Centro Hachinohe Kobe Northridge S. 25 Avg. In overall.12 15 Avg.39 Avg. whereas.29 10 4 Avg. 1.24 – 18 storey structure embedded with 1 VE diagonal damper -percentage reductions in tip acceleration under different earthquake records The results for percentage reductions in tip acceleration in terms of damper placement are shown in Fig. 11.21 1 5 7 Avg. 8. average reductions 142 .94 15 Avg. decrease in tip acceleration reductions was experienced as the damper was moved towards the top of the structure. 8. 2.37% was obtained under the Hachinohe earthquake. The highest average reduction of 22. 3.89 % Acceleration Reductions 20 SF Avg 0 1 4 7 10 13 16 -5 Placement of the Dampers Fig. 7. 2. The highest acceleration reductions occurred when damper was placed in the lowest storey.Influence of Damping Systems on Building Structures Subject to Seismic Effects 25 Avg.41 5 KO Avg.25 – 18 storey structure embedded with 1 diagonal VE damper -percentage reductions in tip acceleration for different damper placements The tip acceleration reductions experienced by the structure embedded with three diagonal VE dampers are presented in Fig. 4.48 Avg. Fernando Earthquake Records Fig. 11.26.37 HA NO Avg. 5.25. 5. 5. 5. the dampers obtained a very high tip acceleration reduction. However. 7.27). 5. experienced under the San Fernando earthquake.33 20 Avg.27 – 18 storey structure embedded with 3 diagonal VE dampers -percentage reductions in tip acceleration for different placements 143 .Influence of Damping Systems on Building Structures Subject to Seismic Effects occurred under the Northridge.56 30 Avg. 11.50 Avg.26 – 18 storey structure embedded with 3 VE diagonal dampers -percentage reductions in tip acceleration under different earthquake records In terms of tip acceleration reduction at different damper placements (Fig. 1-3 Avg. 5. yet again. the diagonal VE dampers achieved the highest reduction when placed in the lowest three storeys.46 15 Avg.17 HA Avg. 21. Kobe and El Centro earthquakes were also a comparably high. 22. EC Avg. -6. 15. 30. This trend was in agreement with previously investigated structure fitted with one diagonal VE damper. 13. 5.58 Avg. while their moving towards the top of the structure caused decreases in tip acceleration reductions. 14.51 % Acceleration Reductions 45 Avg.Fernando -30 Earthquake Records Fig.56 60 0 KO NO SF Avg 1-3 4-6 7-9 10-12 13-15 16-18 -15 -30 Placement of the Dampers Fig. Clearly the lowest tip acceleration reductions were.37 30 Avg.19 % Acceleration Reductions 40 Avg. 5.73 50 10 4-6 7-9 10-12 13-15 0 16-18 Avg -10 -20 El Centro Hachinohe Kobe Northridge S. 36. In terms of tip acceleration reductions. The best performance of the diagonal VE dampers was obtained when the dampers were fitted in the lowest storeys and gradually decreased as the dampers were moved towards the top of the structure.Influence of Damping Systems on Building Structures Subject to Seismic Effects The seismic responses of the 18-storey frame-shear wall structure embedded with one and three diagonal VE dampers. the performance of the diagonal friction dampers increased when the dampers were moved towards the storeys with higher interstorey drifts. while the reductions occurred under the Northridge and Hachinohe earthquake excitations were clearly lower. Based on the results presented in this section. the diagonal VE dampers were consistent under all earthquake excitations. when the best results occurred under the Hachinohe and Northridge earthquakes. In general. whereas. the range of particular results was relatively wide. the reductions under the Kobe and El Centro earthquakes were noticeably lower. as they were moved towards the top of the structure. In terms of tip deflection reductions. respectively. a reverse trend was experienced. the highest performance was obtained under the El Centro and Kobe earthquakes. As regards to tip acceleration reduction. in can be stated that the most characteristic feature experienced by diagonal VE dampers was their clearly highest performance when placed in the lowest storeys and a consequent decrease in efficiency. while diagonal VE dampers reached better results under other earthquakes. the acceleration reductions were regularly decreased as the dampers 144 . the diagonal VE dampers revealed a high and consistent performance. The poorest results in both investigated parameters were recorded under the San Fernando earthquake. In contrast. were investigated in this section. However. whereas. While comparing the results of tip deflection reductions for diagonal VE dampers with those of the diagonal friction dampers. the diagonal friction dampers were rather ineffective under the Kobe and San Fernando earthquakes excitations. diagonal friction dampers achieved better results under the El Centro earthquake. The both types of dampers produced the highest reductions when dampers were placed in the lowest storey. In the case of diagonal VE dampers. These graphs show moderate performance of the dampers. 5. respectively. 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects were moved towards the uppermost storeys. are illustrate in Fig. 5.1 -0. 5. The damper performed well.28 – Tip deflection and acceleration responses of the structures with different placement of the chevron brace friction dampers under the El Centro earthquake The results of the percentage reductions in the peak values of the tip deflection experienced by the structures fitted with the chevron brace friction damper are illustrated in Fig.2 2 0 0 5 10 15 20 -2 -4 1-3 1-3 UN -0. the dampers fitted in the upper storeys revealed slightly better results in both investigated parameters. The time history responses of tip deflection and tip acceleration under the El Centro earthquake in the undamped structure and in the structures with chevron brace friction dampers placed in storeys 1 to 3 and 13 to 15.2 0 0 5 10 15 20 -0. showing a high level of reliability and a slightly higher overall performance than it was for the structures fitted with the diagonal friction damper or the diagonal VE damper.4 Chevron brace friction dampers The results of tip deflection and tip acceleration experienced by the structures fitted with chevron brace friction damper are presented below. The highest average tip deflection reduction of 9.79% was obtained under the Kobe earthquake.28. Tip Acceleration (El Centro) 6 0. The seismic responses of the dampers in both placements was relatively close.2.29. while in the case of the diagonal friction dampers open range of the results was recorded.3 Time (s) UN -6 13-15 Time (s) 13-15 Fig.1 4 2 Acceleration (m/s ) Deflection (m) Tip Deflection (El Centro) 0. however. The average reductions experienced under the other earthquakes 145 . 5.62 6 Avg. the average tip deflection reductions obtained by the structure with the damper fitted in the other placements were within 1%. 5. 5. 3.95 Avg.48 % Deflection Reductions 12 EC HA KO NO SF 3 Avg 0 1 4 7 10 13 16 -3 Placement of the Dampers Fig. 9.Fernando -3 Earthquake Records Fig.30 – 18 storey structure embedded with 1 chevron brace friction damper -percentage reductions in tip deflection for different placements Tip deflection reductions occurred under the El Centro. 5. 5.95% occurred when the damper was embedded in the 13th storey.70 9 Avg. 5.14 Avg.00 % Deflection Reductions 12 4 7 10 13 16 3 Avg 0 El Centro Hachinohe Kobe Northridge S. Hachinohe and Northridge earthquakes increased as the damper was moved towards the 146 . 5.17 6 Avg. 4.26 9 Avg. Avg. as it can be seen in Fig. 5.62% under the Hachinohe earthquake to 5. However.63 Avg.79 15 1 Avg.30. 5. 15 Avg. 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects oscillated in range from 3.21 Avg.29 – 18 storey structure embedded with 1 chevron brace friction damper -percentage reductions in tip deflection under different earthquake records The best performance with an average tip deflection reduction of 5.70% under the San Fernando earthquake. 4. these two reverse trends resulted in extraordinary close average tip deflection reduction for all damper placements. whereas under the Northridge earthquake reverse trend can be observed. 6. two major trends can be observed. In the case of the Kobe earthquake.96% occurred under the Hachinohe earthquake to 9. The dampers obtained a high performance in the vast majority of cases. The average tip deflection reductions were confined in very narrow range from 6.31 illustrates the tip deflection reduction for the structure fitted with three chevron brace friction dampers.73% under the Northridge earthquake. The second trend. As it can be seen in Fig. observed under the El Centro.Fernando -4 Earthquake Records Fig.98 8 Avg.61 12 Avg. the damper was the most efficient in the lowest placements and the deflection reductions occurred for the middle and upper storey placements were constant. 5.32.73 Avg. 9. which was observed under the Kobe and San Fernando earthquakes imply the highest damper efficiency occurred when the dampers were placed in the lowest storeys and their efficiency rapidly decreased as they were moved toward the top of the structures. 147 . 7. Fig.31 – 18 storey structure embedded with 3 friction chevron brace dampers -percentage reductions in tip deflection under different earthquake records With respect to damper efficiency at different placements. 9. 20 Avg. 5. support the theory that the damper efficiency is increased when they are located in regions of large inter-storey drift. The first trend.61 % Deflection Reductions 16 1-3 4-6 7-9 10-12 13-15 16-18 4 Avg 0 El Centro Hachinohe Kobe Northridge S. 9.96 Avg. 5. Hachinohe and Northridge earthquake excitations.Influence of Damping Systems on Building Structures Subject to Seismic Effects uppermost storey. 58 Avg. 2. 0. 8. 8.47 10 Avg. 9. Avg. 5. 8. 5.46 Avg.98 Avg. 5. 8. -1. The poorest results with increase in tip acceleration were recorded under the Hachinohe and Kobe earthquakes.25 -4 -8 El Centro Hachinohe 16 Avg. 5.09 16 Avg.33 shows the tip acceleration reduction for the structure embedded with the chevron brace friction damper.34 % Deflection Reductions 15 EC HA KO NO 5 SF Avg 0 1-3 4-6 7-9 10-12 13-15 16-18 -5 Placement of the Dampers Fig.03 % Acceleration Reductions 12 Kobe Avg Northridge S. 8.09% was achieved under the El Centro earthquake.32 – 18 storey structure embedded with 3 diagonal VE dampers -percentage reductions in tip deflection for different placements Fig. -3.44 8 4 1 4 7 10 0 13 Avg.83 Avg. The highest average tip acceleration reductions occurred when the damper was placed 148 .33 – 18 storey structure embedded with 1 friction chevron brace damper -percentage reductions in tip acceleration under different earthquake records Fig.Fernando -12 Earthquake Records Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects 20 Avg. The highest average reduction of 10.34 shows the same results in terms of different damper placements. The reductions under the Northridge and San Fernando earthquake were inconsistent and less significant.74 Avg. 10. 35. 2. 1. 3. 5. 5.17 15 SF Avg -10 1 4 7 10 13 16 -15 Placement of the Dampers Fig. 4.34 – 18 storey structure embedded with 1 chevron brace friction damper -percentage reductions in tip acceleration for different placements The tip acceleration reduction for the structure embedded with three chevron brace friction dampers are illustrated in Fig.78 % Acceleration Reductions 25 El Centro Hachinohe Kobe Northridge Avg S.34 % Acceleration Reductions 10 Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects in the 4th storey.58 20 Avg. The poorest result.58 5 -5 EC HA KO 0 NO Avg. 8. 1. 30 1-3 Avg.78 Avg. The average reductions recorded under the El Centro and Hachinohe earthquakes were slightly lower.35 15 Avg.35% was experienced under the Kobe earthquake.26 Avg. -0. whereas the reductions under the San Fernando and Northridge earthquakes were in the vast majority of cases relatively insignificant. 9. 3. its repositioning towards the top or bottom of the structure caused increase in tip acceleration. while.34 Avg. The highest average reduction of 10.12 10 Avg.96 5 -5 -10 -15 4-6 7-9 10-12 13-15 16-18 0 Avg.Fernando Earthquake Records Fig. with small increase in average tip acceleration occurred when the damper was placed in the 1st storey.35 – 18 storey structure embedded with 3 friction chevron brace dampers -percentage reductions in tip acceleration under different earthquake records 149 . 5. Avg. 10. -1. excitations causing highest interstorey drifts (Fig. 5. the highest average tip acceleration reduction occurred when the dampers were placed in storeys 4 to 6.32 15 Avg. -2. Hachinohe and Northridge earthquakes i. revealed consistent and adequately high efficiency of the dampers under all earthquake excitations. The results for tip acceleration reductions were comparative to those of tip deflection reductions only under the El Centro and Hachinohe earthquake. Avg.13 20 Avg. 6. was directly related to increase in interstorey drift. by decrease of stiffness of the top storeys due to the cut-out in the shear wall.Influence of Damping Systems on Building Structures Subject to Seismic Effects As it can be seen from Fig.36.36 – 18 storey structure embedded with 3 chevron brace friction damper -percentage reductions in tip acceleration for different placements An 18-storey frame-shear wall structure embedded with one or three chevron brace friction dampers were investigated. This increase in tip acceleration was mainly due to the operating principle of the friction dampers and additionally. 17. in the case of the Kobe and San Fernando earthquakes.49 10 Avg. In terms of damper placements.63 % Acceleration Reductions 25 Placements of the Dampers Fig. 5. 6. 7. The tip acceleration reductions for the other damper placements were considerably lower and rather inconsistent. In the 150 .59 30 5 EC Avg.9).e. reverse trend can be observed. The poorest result. it can be seen. that performance of the dampers under the El Centro. with the increase in tip acceleration was experienced when the dampers were fitted in the highest storeys. On the other hand. 5.77 HA KO NO SF 0 Avg -5 -10 -15 1-3 4-6 7-9 10-12 13-15 16-18 Avg. which was the main investigated parameters. 3. The results for tip deflection reduction. The tip acceleration reductions occurred under the Northridge and San Fernando earthquakes were inconsistent and in average insignificant. whereas the diagonal VE dampers performed better under the Hachinohe. In the case of the Kobe and San Fernando earthquakes reverse trend occurred for the structures fitted with chevron brace friction dampers. Kobe and particularly under the El Centro earthquakes.Influence of Damping Systems on Building Structures Subject to Seismic Effects case of the Kobe earthquake. Hachinohe and Northridge earthquakes. With regards to damper placements. the chevron brace friction dampers performed better under the Northridge and San Fernando earthquakes. On the other hand. The highest difference in favour of the diagonal friction damper occurred under the Hachinohe earthquake excitation. the structure fitted with the chevron brace friction dampers experienced the 151 . the structure fitted with diagonal VE dampers experienced a gradual decrease in tip deflection reduction when the dampers were moved from the lowest to the uppermost storeys under all earthquake excitations. In comparison of the tip deflection reduction experienced by the structure fitted with the chevron brace friction dampers and the structure fitted with the diagonal VE dampers. while the results for the structure fitted with the diagonal friction dampers were rather inconsistent. significant tip acceleration reductions were obtained when the dampers were placed in the lower storey. both types of dampers revealed similar trends under the El Centro. in which increase in efficiency occurred when the dampers were moved towards the storeys with a higher interstorey drifts. whereas the diagonal friction dampers performed clearly better under the El Centro. the chevron brace friction dampers performed significantly better under the Kobe and San Fernando earthquakes. while the reductions for other damper placements were rather insignificant. While comparing the results of tip deflection reductions experienced by structure fitted with chevron brace friction dampers with those of the structure fitted with the diagonal friction dampers. 2.1 -0. are illustrates in Fig. 5. 5.38 shows the tip deflection reduction for the structure embedded with the chevron brace VE damper placed at 6 different locations. while the lowest reductions were recorded when the dampers were placed in the uppermost storeys.2 0 -0.1 4 2 Acceleration (m/s ) Deflection (m) Tip Deflection (El Centro) 0.37 Tip deflection and acceleration responses of the structures with different placement of the chevron brace VE dampers under the El Centro earthquake Fig. This was in agreement with the results of the diagonal friction and VE dampers. the results of the structure fitted with the chevron brace friction dampers revealed noticeably lower reductions than the structure fitted with the diagonal friction dampers and diagonal VE dampers.37. while under other earthquake excitations reverse trend occurred. 5. In terms of tip acceleration reductions.3 2 UN -6 13-15 Time (s) 13-15 Fig. The damper revealed a 152 . 5. Time history responses of tip deflection and tip acceleration under the El Centro earthquake in the undamped structure and in the structures with the chevron brace VE dampers placed in storeys 1 to 3 and 13 to 15 respectively. Tip Acceleration (El Centro) 6 0.5 Chevron brace VE dampers The results of the tip deflection and tip acceleration experienced by the structures fitted with chevron brace VE damper are presented below. The highest tip acceleration reductions occurred when the dampers were placed in the lower storeys.2 0 5 10 15 20 -2 1-3 UN Time (s) 0 -4 1-3 -0.Influence of Damping Systems on Building Structures Subject to Seismic Effects similar trend only under the Kobe and San Fernando earthquakes. The graphs revealed relatively close and rather insignificant performance of the dampers fitted in both placements. 5. 5. 5.07 % Deflection Reductions 10 7 10 13 16 Avg 2 0 El Centro Hachinohe Kobe Northridge S.39 shows the results of the same structure in terms of efficiency of the damper at different placements. 5.70% under the Hachinohe earthquake.12% occurred under the Kobe earthquake. the overall result followed the trend more typical for friction dampers i.Influence of Damping Systems on Building Structures Subject to Seismic Effects good performance and high reliability.Fernando Earthquake Records Fig.82 8 Avg. 5. The highest average reduction of 8.01 % Deflection Reductions 10 EC HA KO NO SF Avg 2 0 1 4 7 10 13 16 Placement of the dampers Fig.05 6 Avg.70 8 Avg. the highest tip deflection reduction occurred in storeys with highest interstorey drift and was decreased when the dampers were moved towards the 153 .39 – 18 storey structure embedded with 3 chevron brace friction damper -percentage reductions in tip acceleration for different placements Interestingly. 5. 5. 4. 4. 4. 4.63 Avg. 4.e.50 4 Avg.50 6 1 Avg. 8.17 Avg.07% under the El Centro earthquake to 4. 5.12 12 4 Avg. 4 Avg. while the deflection reductions for the other earthquakes were confined in narrow range from 4. Avg.39 Avg.38 – 18 storey structure embedded with 1 VE chevron brace damper-percentage reductions in tip deflection under different earthquake records Fig. 5. occurred under the San Fernando earthquake.93%.Influence of Damping Systems on Building Structures Subject to Seismic Effects bottom or the top of the structure. 8.40 – 18 storey structure embedded with 3 VE chevron brace dampers -percentage reductions in tip deflection under different earthquake records As it can be seen from Fig. 9. 4. Hachinohe and Northridge earthquakes were in agreement with the overall trend.37 12 Avg. This trend was in agreement with results of the structure embedded with the diagonal VE dampers. The tip deflection reductions occurred under the Kobe earthquake were consistent throughout all the placements. 8.Fernando -3 Earthquake Records Fig. Fig. while strong decrease in tip deflection was experienced when the dampers were moved toward the top of the structures. Hachinohe and Northridge earthquakes were also adequately high. Clearly the lowest performance. These two reverse trends resulted in remarkably narrow range of average tip deflection reductions at all placements. 10. in the cases of the Kobe and San Fernando earthquakes. reverse trend was experienced.19 Avg.40 shows the tip deflection reductions for the structure embedded with three chevron brace VE dampers installed at 6 different placements. with average reduction of 4. Hachinohe and Northridge earthquake excitations. 6 1-3 4-6 Avg. The results obtained under the El Centro. the reverse trend was experienced under the El Centro. 5. whereas in the case of the San Fernando earthquake. 154 .37% occurred under the Kobe earthquake.76 % Deflection Reductions 15 Avg. 5. the highest tip deflection reductions occurred when the dampers were placed in the lowest storeys. The highest average tip deflection reduction of 10.61 18 7-9 10-12 13-15 16-18 3 Avg 0 El Centro Hachinohe Kobe Northridge S.93 9 Avg. The average reduction obtained under the El Centro. On the other hand.41. 42 shows the results of tip acceleration reduction for the structure embedded with the chevron brace VE damper.Influence of Damping Systems on Building Structures Subject to Seismic Effects 18 Avg.61 13 Avg. The reductions obtained under the Northridge and San Fernando earthquakes were inconsistent and mostly insignificant. In the cases of the Hachinohe and Kobe earthquakes. 8. adequately high tip acceleration reductions occurred only for the uppermost storey placement.70% occurred under the El Centro earthquake. 5. 5. In the case of the El 155 . the highest tip acceleration reductions were obtained when the damper was placed in the 4th storey. In contrast. 8.95 Avg. -1. 5. 8.58 Avg. 6 1 4 7 3 10 0 -3 El Centro -6 Hachinohe Kobe Avg. 4. 16 Northridge S.21 % Deflection Reductions 15 EC HA KO NO 6 SF Avg 3 0 1-3 4-6 7-9 10-12 13-15 16-18 -3 Placement of the Dampers Fig. 8. 7.41 – 18 storey structure embedded with 3 chevron brace VE dampers -percentage reductions in tip deflection for different placements Fig. -1. the poorest result occurred when the damper was placed in the 1st storey.95 Avg.Fernando Avg -9 Earthquake Records Fig. 7.63 12 Avg. 4.87 9 Avg.63 Avg. 7.98 while in the other placements a slight increase in tip acceleration was experienced.70 12 Avg.43.12 % Acceleration Reductions 9 Avg. The highest acceleration reduction of 7. 5.42 – 18 storey structure embedded with 1 VE chevron brace damper-percentage reductions in tip acceleration under different earthquake records As can be seen from Fig. 23 Avg. 5. 3.28 5 Avg. this trend was mostly caused by changes of structural stiffness due to cut outs.77 Avg. 2.43 – 18 storey structure embedded with 1 chevron brace VE damper -percentage reductions in tip acceleration for different placements Fig.39 4 Avg.02 10 Avg. The worst results. with regular increase in tip accelerations from the uppermost to the lowest placement were obtained under the Hachinohe and Kobe earthquakes. 4.44 shows the results of tip acceleration reductions for the structure fitted with three chevron brace VE dampers. 10.02 Avg. 6. 3.Influence of Damping Systems on Building Structures Subject to Seismic Effects Centro. 0. Avg.46 % Acceleration Reductions 16 0 7-9 10-12 13-15 16-18 Avg -4 -8 El Centro Hachinohe Kobe Northridge S. while the damper was essentially ineffective throughout the all placements.60 8 Avg. 2. Nevertheless.Fernando -12 Earthquake Records Fig. Northridge and San Fernando earthquakes the results did not followed any apparent trends. 2. 5.94 20 1-3 4-6 Avg. -0. 5. Avg.87 % Acceleration Reductions 15 EC HA KO NO 0 SF 1 4 7 10 13 Avg 16 -5 -10 Placement of the Dampers Fig. 0.44 – 18 storey structure embedded with 3 chevron brace VE dampers -percentage reductions in tip acceleration under different earthquake records 156 .37 12 Avg. 7% of the damping force of the diagonal VE dampers.42 Avg. Nevertheless. rather reverse trend can be observed. the highest tip acceleration reduction occurred when dampers were placed in the lowest storeys. no particular trend was apparent under any earthquake excitations. 5. In the cases of the El Centro.06 Avg. whereas the reductions were gradually decreased when the dampers were moved towards the bottom of the structure.90 10 Avg. 20 EC Avg. 7. 1.78 Avg. 8. As it can be seen from Fig. however. The results of tip deflection reduction revealed consistent and adequately high efficiency of the dampers. Hachinohe and Northridge earthquakes. 5.45. Chevron brace VE dampers were created to represent 66.89 5 HA Avg.25 % Acceleration Reductions 15 0 -5 KO NO SF Avg 1-3 4-6 7-9 10-12 13-15 16-18 -10 Placement of the Dampers Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects A highest average reduction of 10.94% was achieved under the El Centro earthquake. 0. the highest tip deflection reductions were experienced when the dampers were placed in the uppermost storeys. The tip acceleration reductions experienced under the other earthquake exitations were mostly insignificant. In the cases of the Kobe and San Fernando earthquake excitations.45 – 18 storey structure embedded with 3 chevron brace VE dampers -percentage reductions in tip acceleration for different placements Chevron brace VE dampers embedded in 18-storey frame-shear wall structure were investigated in this section. their overall tip deflection reductions were 157 . 0. 2. while a decrease in deflection reduction was experienced as the dampers were moved towards the top of the structures. In terms of damper placements. In addition. 5. While comparing with other previously discussed damping systems. 5. the dampers embedded in both placements achieved only moderate reductions of the seismic responses. while the results obtained under the other earthquake excitations were mostly insignificant. while the lowest reductions were recorded when the dampers were placed in the uppermost storeys. respectively. The dampers placed in the upper storeys obtained slightly higher tip deflection reduction. tip acceleration reductions obtained by the chevron brace VE dampers were noticeably lower. This was in agreement with the results of diagonal friction and VE dampers.46 shows time history responses of tip deflection and tip acceleration under the El Centro earthquake in the undamped structure and in the structures with the hybrid friction-VE dampers placed in storeys 1 to 3 and 13 to 15.6 Hybrid friction-VE dampers The results of the tip deflection and tip acceleration experienced by the structures fitted with hybrid friction-VE dampers are presented below. outstanding performance of the diagonal dampers occurred under the El Centro and Hachinohe earthquakes was not achieved.2. With regards to tip acceleration reductions. As it can be seen from these graphs. high and consistent results occurred under the El Centro earthquake. the structure achieved the highest tip acceleration reductions when the dampers were placed in the lowest storeys and gradually decreased when the dampers were moved towards the top of the structure.Influence of Damping Systems on Building Structures Subject to Seismic Effects comparatively high. while the dampers placed in the lowest storeys obtained clearly better results in terms of tip acceleration reduction. The highest tip acceleration reductions occurred when the dampers were placed in the lower storeys. 158 . chevron brace VE dampers provided the higher reliability and readibility than the diagonal dampers. Fig. Nevertheless. 2 4 Deflection (m) 2 Acceleration (m/s ) 0. the tip deflection reductions occurred under the El Centro and Hachinohe earthquakes were mostly insignificant. 15 Avg. The reductions obtained under the Northridge and San Fernando earthquakes were also adequately high.Fernando -3 Earthquake Records Fig.56 9 Avg. 5.47.46 Tip deflection and acceleration responses of the structures with different placement of the hybrid friction-VE dampers under the El Centro earthquake The results of the tip deflection reduction for the structure embedded with the hybrid friction-VE damper are presented in Fig. 2.1 0 0 5 10 15 20 -0. 8. On the other hand.33 6 1 Avg. 5.2 2 0 0 5 10 15 20 -2 -4 1-3 1-3 UN -0. 3.48. whereas the tip deflection reductions 159 . Tip deflection reductions for the other placements were clearly less significant. 5.47 – 18 storey structure embedded with 1 hybrid damper -percentage reductions in tip deflection under different earthquake records As can be seen from Fig.3 Time (s) UN -6 13-15 13-15 Time (s) Fig.47 3 Avg. The highest average tip deflection reduction of 8. 5.29 Avg. the damper achieved clearly the best performance when placed in the 7th storey.47% occurred under the Kobe earthquake. The damper revealed adequately high and consistent performance.1 -0. 5. In the case of the Kobe earthquake. 4.04 % Deflection Reductions 12 4 7 10 13 16 Avg 0 El Centro Hachinohe Kobe Northridge S. consistent performance occurred at all placements.Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip Acceleration (El Centro) Tip Deflection (El Centro) 6 0. 3.11 Avg. 9. 8.93 % Deflection Reductions 15 Avg.68 6 Avg.98 Avg.79 Avg.45 15 EC HA Avg. Avg. whereas the reductions experienced under the El Centro and Hachinohe earthquakes were only moderate. 5.00 % Deflection Reductions 12 3 KO NO SF Avg 0 1 4 7 10 13 16 -3 Placement of the Dampers Fig. 3. 3. The highest average reduction of 9.92 10 Avg. 4.Fernando -5 Earthquake Records Fig. 5. 5 Avg.22 9 Avg. 6.Influence of Damping Systems on Building Structures Subject to Seismic Effects recorded under the other earthquake excitations were rather complex without any obvious trends.76 Avg.41 20 1-3 4-6 7-9 10-12 13-15 16-18 Avg 0 El Centro Hachinohe Kobe Northridge S. 5. 4. 9.48 – 18 storey structure embedded with 1 hybrid friction-VE damper -percentage reductions in tip deflection for different placements Fig. The dampers obtained adequately high and stable overall performance.92% was achieved under the Kobe earthquake. The deflection reductions occurred under the Northridge and San Fernando earthquakes were slightly lower.49 shows tip deflection reductions for the structure embedded with three hybrid dampers. 9. 4.49 – 18 storey structure embedded with 3 hybrid dampers -percentage reductions in tip deflection under different earthquake records 160 . from Fig. 5.50 – 18 storey structure embedded with 3 hybrid friction-VE dampers -percentage reductions in tip deflection for different placements The results of tip acceleration reduction for structure embedded with one hybrid friction-VE damper are presented in Fig. 1.83 30 1 4 7 20 0 El Centro Hachinohe Kobe Northridge 13 Avg.51. 5. while in the cases of the Kobe and San Fernando earthquakes.51 – 18 storey structure embedded with 1 hybrid damper -percentage reductions in tip acceleration under different earthquake records 161 .00 Avg. 50 Avg. 5.18 Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects As regards of efficiency of the dampers at different placements. Hachinohe and Northridge earthquakes the highest average reductions occurred for the dampers placed in storeys 13 to 15. 7.28 Avg.87 Avg. the highest average reduction occurred when the dampers were placed in the lowest storeys. 8.99 % Deflection Reductions 15 EC HA KO NO 5 SF Avg 0 1-3 4-6 7-9 10-12 13-15 16-18 -5 Placement of the Dampers Fig. 0. 5. 7. and no prefereable location was recognised. 3. 26. 7. In the case of the El Centro.62 10 Avg. 8. 20 Avg.77 % Acceleration Reductions 40 16 Avg S.54 10 Avg. 7.87 10 Avg.82 Avg.50 it can be observed that the average tip deflection reductions were confined within exceptionally narrow range. Fernando -10 Earthquake Records Fig. 2. 51 20 Avg.56 15 Avg. 3. 8. 9.Influence of Damping Systems on Building Structures Subject to Seismic Effects The best performance with the greatest average acceleration reduction of 26.54 Avg.09 Avg. The range of the particular results obtained from all damper placements was widely open and no particular trends were recognised.Fernando -10 Earthquake Records Fig. 5. the lowest reduction was recorded for the damper placed in the 1st storey. 5.09 % Accelration Reductions 40 13 NO SF Avg 16 Placement of the Dampers Fig.52) and in contrast. 4-6 Avg.15 KO Avg.30 25 7-9 10-12 13-15 16-18 0 Avg -5 El Centro Hachinohe Kobe Northridge S.52 – 18 storey structure embedded with 1 hybrid friction-VE damper -percentage reductions in tip acceleration for different placements Fig. -0. in contrast the reductions under the other earthquakes were in the vast majority of cases only miniscule. 14. 8.02 % Acceleration Reductions 20 Avg. 5. 2. 0. Clearly the highest average tip acceleration reductions occurred when the damper was placed in the 7th storey (Fig. 5. 50 EC 30 0 -10 1 4 7 10 Avg. 15.82 10 1-3 5 Avg. 6.53 shows the tip acceleration reduction of the structure fitted with three hybrid friction-VE dampers. 8.99 Avg.83% was obtained under the El Centro earthquake.83 10 HA Avg.53 – 18 storey structure embedded with 3 hybrid dampers -percentage reductions in tip acceleration under different earthquake records 162 . 5. the structure fitted with three hybrid dampers experienced a consistent performance under all earthquake excitations.08 10 EC Avg. while a gradual decrease in reductions was experienced when the dampers were moved towards the top or bottom of the structure.20 % Acceleration Reductions 20 KO NO SF Avg 0 -5 1-3 4-6 7-9 10-12 13-15 16-18 -10 Placement of the Dampers Fig. In terms of the tip deflection reduction. whereas the reductions occurred under the Northridge and San Fernando earthquakes were mostly inadequate. 5. Based on the results. The results for the 163 .54 Avg.54.30% was once again displayed for the El Centro earthquake excitation. 6. These results were in same cases rather reverse to results of tip acceleration reduction experienced by the structure fitted with one hybrid friction-VE damper.54 – 18 storey structure embedded with 3 hybrid friction-VE dampers -percentage reductions in tip acceleration for different placements 18-storey frame-shear wall structure embedded with the hybrid friction-VE dampers was investigated in this section. Relatively high average reductions were also experienced under the Hachinohe and Kobe earthquakes.23 5 HA Avg. 16. 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects The highest reduction of 15. Hachinohe and Northridge earthquakes the damper efficiency increased when the dampers were moved towards the storeys with higher interstorey drifts (only dampers placed in storeys 4 to 6 were slightly out of this trend). it can be seen that the expected high and reliable performance of the hybrid friction-VE dampers was achieved only partially. the highest tip acceleration reduction was obtained by the structure with the dampers placed in storeys 4 to 6. 8. 5. In the cases of the El Centro.19 25 Avg. In the cases of the Kobe and San Fernando earthquake excitations rather reverse trends can be observed. 1.59 15 Avg. Avg. As can clearly be seen in Fig. the best overall results and also the most consistent acceleration reductions occurred under the El Centro earthquake excitations. that average tip acceleration reductions of hybrid dampers were somewhere in the middle under all earthquake excitations. Their tip deflection reductions obtained under the Kobe and Northridge earthquakes were somewhere in the middle. As regards to tip acceleration reductions for the hybrid dampers. While comparing the hybrid friction-VE dampers with the other previously discussed damping systems. 164 . This means that whereas the friction component of the hybrid dampers operated appropriately.Influence of Damping Systems on Building Structures Subject to Seismic Effects structure fitted with one damper were in majority of cases inconsistent and significant reductions were recorded only for the damper fitted in the 7th storey. The results occurred under the Northridge and San Fernando excitations were inconsistent and mostly insignificant. that the structures embedded with a hybrid friction-VE dampers follow a trends close to these of the structures embedded with the chevron brace friction dampers. while the results for the others placements were only moderate. It is evident. the hybrid dampers surpass the others under the San Fernando earthquake excitations. the VE component of the hybrid dampers remained essentially ineffective. whereas in the cases of the El Centro and Hachinohe earthquakes the hybrid dampers were the least effective among all investigated damping systems. In the case of the Hachinohe and Kobe earthquakes the high acceleration reductions were experienced for lower storey placements. While comparing the tip acceleration reductions of the structures fitted with the hybrid dampers with reductions experienced by the structures fitted with other damping systems. it can be seen. the deflection reductions experienced under the El Centro and Hachinohe earthquakes were noticeably lower.3 15 -2 UN Time (s) -6 13-15 UN Time (s) 13-15 Fig.55 – Tip deflection and acceleration responses of the structures with different placement of the lower toggle VE dampers under the El Centro earthquake Fig. 5. On the other hand. 5.56 illustrates the tip deflection reductions for the structure embedded with the lower toggle VE damper placed at 6 different locations. The highest average reduction of 12. Time history responses of tip deflection and tip acceleration under the El Centro earthquake in the undamped structure and in the structures with the lower toggle VE dampers placed in storeys 1 to 3 and 13 to 15 respectively.7 Lower toggle VE dampers The results of the tip deflection and tip acceleration experienced by the structures fitted with lower toggle VE dampers are presented in this section.2 0 0 5 10 15 20 -0. The reductions occurred under the Northridge and San Fernando earthquakes were also an adequately high and relatively stable.1 -0.2 2 0 0 5 10 20 -4 1-3 1-3 -0.1 4 Deflection (m) 2 Acceleration (m/s ) 0. 5. Higher performance in both studied parameters was obtained by the dampers embedded in storeys 13 to 15.2.55. 165 . are illustrates in Fig. It is worth noticing that while the seismic responses of the structure with the dampers fitted in storeys 13 to 15 displayed features more typical for VE dampers. Tip Deflection (El Centro) Tip Acceleration (El Centro) 6 0. the seismic responses of the structure with dampers fitted in the lowest storeys were closer to typical response of the structure fitted with friction dampers.93% was obtained under the Kobe earthquake.Influence of Damping Systems on Building Structures Subject to Seismic Effects 5. without any apparent trends. 9. reverse trend was experienced. 5.57 – 18 storey structure embedded with 1 lower toggle VE damper -percentage reductions in tip deflection for different placements 166 . The tip deflection reductions obtained under the Hachinohe earthquake gradually increased when the damper was moved from the bottom to the top of the structure. while. 12.26 % Deflection Reductions 15 EC HA KO NO 6 SF Avg 3 0 1 4 7 10 13 16 -3 Placement of the Dampers Fig. Fernando -3 Earthquake Records Fig.56 – 18 storey structure embedded with 1 lower toggle damper -percentage reductions in tip deflection under different earthquake records As can be seen in Fig. 6.64 9 6 Avg. 5. 7. 18 Avg.52 9 Avg.77 Avg. 8. 4.81 Avg. 8. 7. the highest average tip defection reduction and the most consistent performance was obtained by the damper placed in the 13th storey.89 Avg.27 12 Avg.81 % Deflection Reductions 15 Avg. 5. The performance of the damper in the other placements was only slightly lower.Influence of Damping Systems on Building Structures Subject to Seismic Effects Avg.93 18 1 4 7 10 13 16 3 Avg 0 El Centro Hachinohe Kobe Northridge S. 6. The tip deflection reductions occurred under the other earthquakes were rather stable. 3.84 12 Avg.57.05 Avg. in the case of the San Fernando earthquake. 8. 15.58.Fernando -8 Earthquake Recrds Fig. 5. Northridge and San Fernando earthquakes were also significantly high and even the lowest average tip deflection reduction.90 Avg. A reverse trend occurred under the Kobe and San Fernando earthquakes.59 the highest average tip deflection reductions of 14.75% occurred under the Kobe earthquake. In the cases of the El Centro and Hachinohe earthquakes the highest average tip deflection reductions occurred when the dampers were placed in the uppermost storeys. the performance remained relatively consistent at all damper placements.54% occurred when the dampers were placed in the lowest three storeys. The tip deflection reductions for other placements were only slightly lower. The dampers displyed very high performance with the features similar to those of the structure fitted with one lower toggle VE damper.75 32 1-3 4-6 7-9 10-12 13-15 16-18 Avg 0 El Centro Hachinohe Kobe Northridge S. 5. 167 .58 – 18 storey structure embedded with 3 lower toggle dampers-percentage reductions in tip deflection under different earthquake records As it can be seen from Fig.92 Avg. recorded under the Hachinohe earthquake. was adequately high. 14. while a gradual decrease in deflection reduction was experienced when the dampers were moved towards the bottom of the structure. 18. 8 Avg. 5.19 % Deflection Reductions 24 Avg. 7. The highest average reduction of 18. In the case of the Northridge earthquake. The reductions obtained under the El Centro. 10.Influence of Damping Systems on Building Structures Subject to Seismic Effects The results for tip deflection reduction of the structure fitted with three lower toggle VE dampers are presented in Fig.71 16 Avg. 14. 13.00 -6. 4.00 Avg. The tip acceleration reductions obtained under the Northridge and San Fernando earthquakes were also adequately high. 24.52 Avg.79 Avg.59 – 18 storey structure embedded with 3 lower toggle VE dampers -percentage reductions in tip deflection for different placements The results of tip acceleration reduction for the structure embedded with the lower toggle VE damper (Fig.16 Avg. Consecutively. 11. 6. 5.60) were in contrast to results of tip deflection reductions.25 36.42 Avg.00 7 10 13 16 Avg 0. 13. Fernando -12.00 Avg.25% occurred under the El Centro earthquake.00 24.00 Earthquake records Fig. 14. 13. 5.22 18.62 16 Avg. while the acceleration reductions experienced under the Hachinohe and Kobe earthquake excitations were rather insignificant.60 – 18 storey structure embedded with 1 lower toggle damper -percentage reductions in tip acceleration under different earthquake records As can be seen from Fig.73 12. Avg. 5.00 Avg. The greatest average acceleration reductions of 24.00 El Centro Hachinohe Kobe Northridge S.Influence of Damping Systems on Building Structures Subject to Seismic Effects Avg. 5. 3. 6.35 32 EC HA KO NO 8 SF Avg 0 1-3 4-6 7-9 10-12 13-15 16-18 -8 Placement of the Dampers Fig.54 % Deflection Reductions 24 Avg. a slight decrease in acceleration 168 .23 % Acceleration Reductions 30.61 the highest tip acceleration reductions occurred when the damper was fitted in the 4th storey.00 1 4 6. 11. The highest average tip acceleration reduction of 21. 21.Influence of Damping Systems on Building Structures Subject to Seismic Effects reduction was experienced. 11.66 % Acceleration Reductions 24 6 KO NO SF Avg 0 1 4 7 10 13 16 -6 Placement of the Dampers Fig. 11.61 – 18 storey structure embedded with 1 lower toggle VE damper -percentage reductions in tip acceleration for different placements The results of the tip acceleration reduction for the structure embedded with three lower toggle VE dampers are presented in Fig. The tip acceleration reductions occurred under the El Centro earthquake were significantly high in all placements. 10. 9.62.15 Avg.80 Av.18 % Acceleration Reductions 45 1-3 4-6 7-9 10-12 13-15 0 El Centro Hachinohe Kobe Northridge S. 5. 30 HA Avg. 18.62 Av. still adequately high.24 15 Av.90 Avg. Av. The reductions obtained under the Kobe earthquake were also comparatively high. 5.62 – 18 storey structure embedded with 3 lower toggle dampers-percentage reductions in tip acceleration under different earthquake records 169 .18% occurred under the El Centro earthquake.59 30 Av. The tip acceleration reductions experienced under the other earthquake excitations were noticeably lower. 5.95 12 EC Avg. when the damper was moved towards the top or the bottom of the structure. 8. 6. 11. 6. nevertheless.39 18 Avg.78 Avg.Fernando 16-18 Av -15 -30 Earthquake Records Fig. while the reductions experienced under the other earthquake excitations were rather inconsistent. 12. In the cases of the El Centro and Hachinohe earthquakes the highest average tip deflection reductions occurred when the dampers were placed in the uppermost storeys and were gradually decreased when the dampers were moved towards the bottom of the structure.50 15 Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects The greatest tip acceleration reductions were achieved when the dampers were placed in storeys 13 to 15 and 1 to 6. In contrast. A reverse trend was experienced under the Kobe and San Fernando earthquakes. the best results were experienced under the El Centro earthquake. 27.03 Avg.63 – 18 storey structure embedded with 3 lower toggle VE dampers -percentage reductions in tip acceleration for different placements The results of the lower togle VE dampers embeded in the 18-storey structure were presented in this section. 9.81 Avg. The dampers revealed a very high performance in both investigated parameters and under all earthquake excitations. 20. 0 HA KO NO SF 1-3 4-6 7-9 10-12 13-15 16-18 Avg -15 -30 Placement of the Dampers Fig. while the reductions occurred under the other earthquake 170 . In the case of the Northridge earthquake the performance remained rather consistent for all placements. 5. The reductions for the other placements were only slightly lower. The highest tip deflection reductions of the structure embedded with three lower toggle VE dampers occurred when the dampers were placed in the lowest three storeys. -6. Similar trends were also experienced for the structure fitted with one lower toggle VE damper.5% was experienced when the dampers were EC Avg.37 repositioned towards the uppermost storeys. 25. respectively.96 % Acceleration Reductions 45 Avg. In terms of tip acceleration reduction. an increase in average tip acceleration by 6.64 30 Avg. The reductions under the Kobe earthquake were comparatively high. structures embedded with the lower toggle friction dampers were also analysed. its overall performance was noticeably higher and also more reliable. The results for the reduction in tip deflection followed similar trends to those of the structures fitted with chevron brace friction dampers. To provide extra comparisons. however.8 Summary of findings in the 18-storey structure The results from the 18-storey frame-shear wall structure embedded with the six different damping systems installed at twelve different placements were investigated in this chapter. In contrast. 5. The results revealed a noticeable level of similarity to those of the lower toggle VE dampers and for that reason are not presented in this study. The VE damper was created to represent only 42% of the damping force of the diagonal VE damper. With regard to reduction in tip acceleration the results comply with a trend. the time history graphs of both types of dampers make more obvious that amplifying force of toggle brace assembly altered damping response of friction (or VE) dampers to operate in a relatively similar way. This may be attributed to inadequate compensation for removed stiffness at cut out in location close to investigated point. Regards to placements. as it was expected. an increase in average tip acceleration was experienced when the dampers were embedded in the uppermost storeys. In general. the range of the results was considerably wide. the greatest tip acceleration reductions occurred when the dampers were placed in storeys 13 to 15 and great results were also experienced for the structure with dampers placed in storeys 1 to 6.Influence of Damping Systems on Building Structures Subject to Seismic Effects excitations were noticeably lower. However. for the lower toggle VE dampers.2. which is closest to that of the diagonal VE dampers. nevertheless. the dampers obtained substantial reductions in the peak values of the tip deflection and tip acceleration. The highest tip deflection reductions were recorded. The results of these dampers reveal high levels 171 . The most consistent performances in all placements and under all seismic excitations were displayed for both types of the chevron brace dampers. their efficiency considerably decreased when placed towards the top of the structure. 5.9 % Deflection Reductions 10 10 8 1 4 6 7 10 4 13 16 2 2 0 Avg 0 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle Damping Devices Fig. in the case of the San Fernando earthquake. which caused the highest structural deflections from all excitations. The hybrid damping system acted in a similar way to that of the friction chevron brace damper. Lastly. 5. which indicates that only the friction part of this damping system was working properly.64 -5. 5. involvement of the diagonal friction dampers was rather unfavourable.74 Avg. This may be attributed to inadequate compensation for removed stiffness at cut out and/or partial resonance of the damped structure and insufficient push on the friction damper to make it fully operational.94 6 Avg. The overall results for the all damping system embedded in the 18-storey frameshear wall structure in terms of reduction in the peak values of the tip deflection are illustrated in Figs. 4 Avg. On the other hand. 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects reliability under all excitations and when placed in all locations.64 . 2. 6. however.71 Avg. These dampers achieved the highest reductions under the Hachinohe earthquake. which caused the lowest structural deflection.45 8 Avg.Average percentage tip deflection reductions for all damping systems in all (1 damper) placements 172 .71. while the VE part remained rather ineffective. The reductions for the diagonal VE damping system were even higher for the lower storey placements. the results of diagonal friction dampers reveal the highest sensitivity to placement and also to variations in seismic excitations. 7.18 Avg. 4. 71 8 Avg. 6.32 Avg.88 Avg.67 .Fernando -5 Earthquake Records Fig. 6. 5.23 10 Avg.61 10 Avg.Average percentage tip deflection reductions for all damping systems in term of damper placements 10 Diag VE Chev FR Chev VE 5 Hybrid Toggle Avg 0 0 El Centro Hachinohe Kobe -5 Northridge S. 5.34 6 Avg. 4.45 16 Avg. 4. 5. 5. 5.72 Avg.94 16 Avg.Average percentage tip deflection reductions of all damping systems under different earthquake excitations 173 .96 10 Avg.90 % Deflection Reductions Influence of Damping Systems on Building Structures Subject to Seismic Effects Diag VE Chev FR Chev VE Hybrid Toggle EC HA KO NO SF Avg -4 -8 -8 Damping Devices 8 8 Avg. 7.66 . 5. 5. 2.63 Diag FR Avg. 5. 5. 5. 5.18 12 Avg.19 % Deflection Reductions Fig. 5.74 12 Avg. 5.04 Avg. 5.65 .Average percentage tip deflection reductions for all damping systems (1 damper placement) under different earthquake excitations Diag FR Diag VE 6 Chev FR Chev VE 4 4 2 2 Hybrid Toggle 0 Avg 0 1 4 7 10 13 16 Placement of the Dampers 20 20 15 15 5 Avg.8 4 4 0 0 -4 Diag FR Avg.43 % Deflection Reductions Fig. 26 9 Avg. 8.18 12 15 Avg. 7.Average percentage tip deflection reductions for all damping systems in terms of damper placements 174 . 5. 5.50 20 15 Avg. 7. 8.97 21 Avg.Average percentage tip deflection reductions for all damping systems (3 dampers placement) under different earthquake excitations 12 Diag VE Chev FR Chev VE 9 6 6 3 3 0 Diag FR Hybrid Toggle Avg 0 1-3 4-6 7-9 10-12 13-15 16-18 Placement of the Dampers Fig. 8.Influence of Damping Systems on Building Structures Subject to Seismic Effects 21 Avg. 5. 8.97 25 Avg.96 9 Avg.22 % Deflection Reductions Fig.39 % Deflection Reductions Fig. 6. 10. 6.78 25 Avg. 8.14 Avg.39 % Deflection Reductions 18 12 1-3 4-6 7-9 10-12 9 6 6 3 3 0 13-15 16-18 Avg 0 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle Damping Devices 15 10 10 EC 5 5 HA 0 0 -10 Avg.70 .21 15 Avg. 13. 10.37 12 Avg.37 -5 Avg.97 15 Avg. 9. 13. 8.68 . 10.69 . 11. 8.Average percentage tip deflection reductions for all damping systems in all (3 damper) placements -15 -20 -25 KO NO -5 SF -10 Avg -15 Diag FR Diag VE Chev FR Chev VE Hybrid -20 Toggle -25 Damping Devices 21 18 18 Avg.78 Avg.96 20 Avg.50 21 18 15 Avg. however. once again.20 15 15 10 10 5 5 0 0 Chev VE -5 Hybrid -10 Avg. 10. their reductions in the lower storeys were noticeably lower. Hachinohe and Kobe earthquakes. 10. while the reductions experienced under the Northridge and San Fernando earthquakes were quite small. The slightly lower overall tip acceleration reduction was attributed to their ineffectiveness in the uppermost storeys and poor results experienced under the San Fernando earthquake.Fernando -25 -20 -25 Earthquake Records Fig.49 25 Avg.29 % Deflection Reductions Influence of Damping Systems on Building Structures Subject to Seismic Effects -15 -20 -10 Diag FR Diag VE Chev FR Toggle Avg -15 El Centro Hachinohe Kobe Northridge S. 12.72-5. The diagonal friction dampers displayed. The average reductions for the lower toggle VE dampers were close to those of diagonal VE dampers.26 -5 Avg.79. The tip acceleration reductions of these dampers were greatest when placed in the lower parts of the structure. 5. The lowest tip acceleration reductions were obtained by the chevron braced VE dampers where adequate reductions were recorded only under the El Centro earthquake excitation. The overall results for all damping systems embedded in the 18-storey frameshear wall structure in terms of reduction in the peak values of the tip acceleration are illustrated in Figs. the highest reductions were recorded for the structures fitted with the diagonal VE dampers. The hybrid friction-VE dampers and the chevron brace friction damper followed similar trends with rather inconsistent acceleration reductions under the El Centro. 10. 3.03 25 Avg. 175 . the highest sensitivity to variation of the dampers placement and seismic excitations.71 .58 20 Avg. 5.Average percentage tip deflection reductions for all damping systems under different earthquake excitations As regards of the peak values of the tip acceleration for the same structures. 50 9 Avg.10 Avg. 1. 7.91 Avg. 1. 8.8 6 3 12 1 9 6 10 13 3 16 Avg 0 -3 4 7 Avg.66 15 Avg. 4.73 .97 15 Avg.72 .3 % Acceleration Reductions 12 0 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle -3 Damping Devices 25 20 20 5 Avg. 2.0 Avg. 2.64 6 Diag FR 9 Avg.04 9 Avg. 2.30 % Acceleration Reductions Fig. 7.97 25 Avg. 8. 3.91 15 Avg.80 30 Avg.04 30 Avg. 1. 5. 7.Average percentage tip acceleration reductions for all damping systems (1 damper placement) under different earthquake excitations Diag VE Chev FR 6 Chev VE Hybrid 3 Toggle Avg 0 -3 0 1 4 7 10 13 16 -3 Placement of the Dampers Fig. 6.74 .18 % Acceleration Reductions Fig. 5. 6.Average percentage tip acceleration reductions for all damping systems in all (1 damper) placements 15 EC KO 5 NO 0 -5 -5 -15 HA 10 0 -10 EC SF Avg -10 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle -15 Damping Devices 12 12 3 Avg.00 10 Avg.96 15 Avg. 6. 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects 15 Avg. 3. 1.Average percentage tip acceleration reductions for all damping systems in terms of damper placement 176 . 75 .77 . 6.89 % Acceleration Reductions Fig.90 % Acceleration Reductions Fig.14 30 Avg.Average percentage tip acceleration reductions for all damping systems under different earthquake excitations 1-3 20 4-6 7-9 10 10-12 13-15 0 0 16-18 Avg -10 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle -20 -10 -20 Damping Devices 15 10 10 5 5 KO 0 0 NO -5 -10 Diag VE Chev FR Chev VE Avg. 6. 3. 7. 7.89 15 Avg. 4.45 40 Avg.87 Avg.30 30 25 25 5 Avg. 5.55 30 Avg.76 .45 25 Avg. 14.64 25 Avg.23 10 Avg. 3. 4.14 20 Avg.Fernando -15 Avg -10 -15 Earthquake Records 10 Avg. 5.63 20 Avg. 7.91 % Acceleration Reductions Influence of Damping Systems on Building Structures Subject to Seismic Effects Diag FR 15 Diag VE 10 Chev FR Chev VE 5 Hybrid 0 0 Toggle -5 -5 -10 El Centro Hachinohe Kobe Northridge S. 15.71 15 20 Avg.55 20 Avg.Average percentage tip acceleration reductions for all damping systems (3 dampers placement) under different earthquake excitations 177 . 14.89 20 Avg.64 40 Avg. 15. 12. 0.Average percentage tip acceleration reductions for all damping systems in all (3 dampers) placements -15 -20 -5 EC HA SF Avg -10 -15 Diag FR Hybrid Toggle -20 Damping Devices Fig. 7. 0. 5. 30 20 Avg. 17.Fernando -20 Earthquake Records Fig. -5.80-5.Influence of Damping Systems on Building Structures Subject to Seismic Effects Diag FR 20 Avg.79 .17 Avg. 11. 7. In the case of the hybrid frictionVE dampers anticipated high and reliable performance was accomplished only partially. 1. the diagonal VE dampers obtained clearly the best results when placed in the lowest storeys.78 . 5.84 30 Avg.98 -10 Avg.Average percentage tip acceleration reductions for all damping systems in term of damper placements -15 -20 -10 Avg -15 Kobe Northridge S. 7. 4. 19. 12.36 -5 Avg.84 show the time history response of the 18-storey frame-shear wall structure fitted with this 178 . Based on this finding combined damping system consisting of the diagonal friction damper placed in the 16th storey and the diagonal VE damper placed in the 1st storey was also investigated. 5. 14.09 40 0 Diag VE Chev FR 10 Chev VE Hybrid 0 Toggle Avg -10 1-3 4-6 7-9 10-12 13-15 16-18 -20 -10 -20 Placement of the Dampers 25 25 20 20 15 15 10 10 Diag VE 5 5 Chev FR 0 0 Hybrid -5 Toggle Diag FR Hachinohe Avg.91 10 Avg. Figs.Average percentage tip acceleration reductions for all damping systems under different earthquake excitations The results presented in this chapter imply the diagonal friction dampers experienced the best performance when placed in the storeys with the highest interstorey drift.59 % Acceleration Reductions 30 40 Avg. 10. when the higher consistency was achieved at the expense of lower efficiency.05 Chev VE Avg. On the other hand. 5.33 % Acceleration Reductions Fig.58 El Centro Avg. 15 4 2 Acceleration (m/s ) Deflection (m) 0.1 Acceleration (m/s ) 4 0 0 5 10 15 20 -0.2 -4 -0.82 .Tip deflection and acceleration responses of the undamped structure and the structures fitted with three diagonal VE dampers and the structure fitted with one friction damper and one VE dampers respectively under the El Centro earthquake Tip Acceleration (Hachinohe earthquake) Tip Deflection (Hachinohe earthquake) VE 0.05 15 20 2 0 0 5 10 15 20 -2 -4 -0. 5. Tip Acceleration (El Centro earthquake) Tip Deflection (El Centro earthquake) VE 0.1 VE 6 UN UN CO CO 0 4 5 10 15 20 2 Acceleration (m/s ) Deflection (m) 0 -0.80 .15 -6 Time (s) Time (s) Fig.Tip deflection and acceleration responses of the undamped structure and the structures fitted with three diagonal VE dampers and the structure fitted with one friction and one VE damper respectively under the Kobe earthquake 179 .2 -0.1 -0.Influence of Damping Systems on Building Structures Subject to Seismic Effects combined damping system compared with responses of the undamped structure and structure with the diagonal VE dampers embedded in the lowest three storeys.05 0 0 5 10 -0.3 Time (s) Time (s) Fig.1 0.5 -6 Time (s) Time (s) Fig.2 VE 6 UN UN CO CO 0.3 VE 6 UN UN CO CO 0.1 2 0 0 5 10 15 20 -2 -0.4 -4 -0.2 Deflection (m) 2 0.Tip deflection and acceleration responses of the undamped structure and the structures fitted with three diagonal VE dampers and the structure fitted with one friction and one VE damper respectively under the Hachinohe earthquake Tip Deflection (Kobe earthquake) Tip Acceleration (Kobe earthquake) VE 0. 5. 5.81 .1 -0.3 2 0 0 5 10 15 20 -2 -0. 99 15. El Centro 26.16 15. % Accel.2.Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip Deflection (Northridge earthquake) Tip Acceleration (Northridge earthquake) VE 0.55 Hachinohe 19.2 -6 -0.2 .66 As can be seen from the graphs. Red.05 -2 -0. Red.15 VE 3 UN UN CO 0.1 2 0.84 .1 -4 -0. the combined damping system 180 .31 13.3 6 UN UN CO 0.05 1 2 Acceleration (m/s ) Deflection (m) CO 0 0 0 5 10 15 20 0 5 10 15 20 -1 -0.80 Northridge 25.2 4 0.3 Time (s) Time (s) Fig.1 -3 -0.28 S.Fernando 6. the structure fitted with the combined damping system obtained adequately high and consistent tip deflection and tip acceleration reductions under all earthquake excitations.18 25.1 2 2 Acceleration (m/s ) Deflection (m) CO 0 0 5 10 15 VE 20 0 0 5 10 15 20 -2 -0. 5.Percentage tip deflection and tip acceleration reduction of the structure fitted with one diagonal friction damper and one diagonal VE damper % Defl. 5.36 14. Table 5.92 8.82 Average 16.83 . In comparison with the responses of the structure fitted with the diagonal VE dampers.Tip deflection and acceleration responses of the undamped structure and the structures fitted with three diagonal VE dampers and the structure fitted with one friction and one VE damper respectively under the Northridge earthquake Tip Acceleration (San Fernando earthquake) Tip Deflection (San Fernando earthquake) VE 0.Tip deflection and acceleration responses of the undamped structure and the structures fitted with tree diagonal VE dampers and the structure fitted with one friction and one VE damper respectively under the San Fernando earthquake For convenience the results of the combined damping system are also presented in Table 5.15 Time (s) Time (s) Fig.85 Kobe 7. which had the same dimensions as the exterior bays. it should be point out that the combined damping system consist of only two dampers. except for substitution of the shear wall with an interior bay. while the advantage of the VE damper was in more gradual decreasing seismic response of the structure. it can be suggested. Northridge and San Fernando earthquakes.89 show tip deflection and tip acceleration under all five earthquake excitations in the structure of designation F1-3 with the diagonal VE dampers 181 . which include the diagonal friction damper fitted in the storey with maximum interstorey drift and the diagonal VE damper fitted in the storey the closest to the source of excitation can produce better and more reliable result than individual friction or VE dampers. From the results presented in this chapter it can be seen that the friction dampers in the vast majority of cases suppressed the VE dampers in their ability to reduce the intensity of the initial strikes.3 Seismic response of 18-storey frame structure As it can be seen in the literature review (Chapter 2). at the same time as in terms of tip acceleration reduction it was under the San Fernando earthquake. Its results were compare with results of the 18-storey frame-shear wall. 5. In the light of these. 5. that the combined damping system. In order to better comprehend the findings from this. The dimensions of the 18-storey frame structure were kept the same as for previously discussed 18-storey frame-shear wall structure. a number of studies have investigated the use of damping devices within frame structure. On the other hand. To emphasize these results. instalment of the dampers in the cut outs of the shear wall is a realtively new method with only limited investigation.85-5. study an additional structural model represented by the 18-storey frame structure (designated by F) embedded with diagonal VE dampers (described in the Section 3.9) was also investigated. While closely studying the time history responses of all damping systems it can be seen the combined damping system effectively involved the advantages of both damping mechanisms to obtain significant and consistent performance.Influence of Damping Systems on Building Structures Subject to Seismic Effects obtained the higher tip deflection reduction (which is more important parameter) under the Hachinohe. Figs. 5.1 0.86 – Tip deflection and acceleration responses of the undamped structure and the structures fitted with diagonal VE dampers under the Hachinohe earthquake Tip Deflection (Kobe earthquake) Tip Acceleration (Kobe earthquake) UN 0.4 -5 Time (s) Time (s) Fig.05 0 -0.87 – Tip deflection and acceleration responses of the undamped structure and the structures fitted with diagonal VE dampers under the Kobe earthquake 182 .15 3 0.15 UN 4 1-3 1-3 3 2 2 Acceleration (m/s ) Deflection (m) 0.2 5 10 15 20 -2 -3 -0.05 0 5 10 15 20 -0. 5.2 -4 Time (s) Time (s) Fig.3 -4 -0.1 2 0 Acceleation (m/s ) Deflection (m) UN 5 2 1 0 -1 0 -0.2 UN 4 UN 1-3 0. Tip Deflection (El Centro earthquake) Tip Acceleration (El Centro earthquake) 0. 5.05 -3 -0.85 – Tip deflection and acceleration responses of the undamped structure and the structures fitted with diagonal VE dampers under the El Centro earthquake Tip Deflection (Hachinohe earthquake) Tip Acceleration (Hachinohe earthquake) UN 0.Influence of Damping Systems on Building Structures Subject to Seismic Effects fitted in the lowest three storeys compared with the seismic responses in the undamped structure.1 2 2 Acceleration (m/s ) Deflection (m) 1-3 0.1 -0.05 0 0 5 10 15 20 1 0 -1 0 5 10 15 20 -2 -0.15 1 0 -1 0 5 10 15 20 -2 -3 -0.1 1-3 1-3 4 0 3 5 10 15 20 -0.1 -4 Time (s) Time (s) Fig. 1 -0. The high performance was also experienced under the El Centro earthquake.2 -3 -0.2 Deflection (m) UN 0. The greatest performance with an outstanding average reduction of 30.5% was achieved under the Northridge earthquake.1 1-3 1 0. 5. 5.90. deflection reductions. On the other hand. The results of peak values of tip deflection reduction for the 18-storey frame structure embedded with the diagonal VE damper are show in Fig. at the same time as the poorest performance was displayed under the Hachinohe earthquake.3 -4 Time (s) Time (s) Fig. The best performance can be observed under the Northridge earthquake. were insignificant. 5. 183 .Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip Deflection (Northridge earthquake) 0.1 1 0 -1 0 5 10 15 20 -2 -0.1 0 0 5 10 15 20 -0.05 15 20 0 5 10 15 20 -1 -0.3 Tip Acceleration (Northridge earthquake) UN 4 1-3 1-3 3 2 2 Acceleration (m/s ) 0.89 – Tip deflection and acceleration responses of the undamped structure and the structures fitted with diagonal VE dampers under the San Fernando earthquake From these graphs it is evident that the dampers embedded in the lowest storeys of the frame structure in most cases significantly reduced the tip deflection and acceleration of the structure throughout the duration of the earthquakes.15 0 -2 -3 Time (s) Time (s) Fig. which occurred under the other earthquake excitations.05 2 Acceleration (m/s ) Deflection (m) 1-3 0 0 5 10 -0.88 – Tip deflection and acceleration responses of the undamped structure and the structures fitted with diagonal VE dampers under the Northridge earthquake Tip Deflection (San Fernando earthquake) Tip Acceleration (San Fernando earthquake) UN 2 UN 0. 99 20 10 Avg. 3.4% occurred under the Northridge earthquake. 30 30 Avg. The reductions for the 4th storey.91 – 18 storey frame structure embedded with diagonal VE damper -percentage reductions in tip deflection for different placements The tip deflection reduction for the structure embedded with three diagonal VE dampers are presented in Fig. 5.49 50 1 30 4 7 Avg. 0 20 10 EC HA KO NO SF Avg 0 1 4 7 10 -10 13 16 -10 Damper Placements Fig. Clearly the higher average tip deflection reductions of 34. The dampers revealed similar trends as in the case of one damper placement. 11.Influence of Damping Systems on Building Structures Subject to Seismic Effects 50 Avg. 30. 5.70 Avg. 5.92. 5. 7th storey and 10th storey placement were comparatively high.26 % Deflection Reductions 40 0 20 10 13 10 16 Avg 0 El Centro Hachinohe Kobe Northridge S.94 30 Avg.91 illustrates the tip deflection reduction for the same structures with respect to damper placement.15 20 40 10 Avg. 12.20 % Deflection Reductions whereas the reductions for the upper storey placements were clearly lower. 7. 13.03 40 Avg. 3. 10.74 40 Avg. 5.83 50 Avg.90 – 18 storey frame structure embedded with diagonal VE damper -percentage reductions in tip deflection under different earthquake records Fig.2% occurred when the damper was fitted in the lowest storey. 3. The high tip 184 . 13. The highest average tip deflection reduction of 13.Fernando -10 -10 Earthquake Records Fig.24 50 Avg. Influence of Damping Systems on Building Structures Subject to Seismic Effects deflection reductions were also recorded under the El Centro earthquake. In contrast, the reductions obtained under the San Fernando earthquake were only moderate and the poorest performances occurred under the Kobe and Hachinohe earthquakes. 40 40 1-3 Avg, 17.19 4-6 7-9 10 20 Avg, 7.25 20 30 Avg, 3.95 30 Avg, 3.20 % Deflection Reductions 50 Avg, 36.42 50 10-12 13-15 10 16-18 Avg 0 0 El Centro Hachinohe Kobe Northridge S.Fernando -10 -10 Earthquake Records Fig. 5.92 – 18 storey frame structure embedded with 3 diagonal VE dampers -percentage reductions in tip deflection under different earthquake records The average tip deflection reductions for different placements were by some means varied by significant results obtained under the Northridge and El Centro earthquakes; nevertheless, the highest tip deflection reduction occurred in the majority of the cases when the dampers were placed in storeys 4 to 6 and 7 to 9, respectively. The deflection reductions for the other placements were decreased as 40 40 Avg, 9.34 10 Avg, 10.18 20 30 Avg, 12.35 30 Avg, 16.93 50 Avg, 18.44 50 Avg, 14.37 % Deflection Reductions the dampers were moved towards the top or bottom of the structure. 0 20 10 EC HA KO NO SF Avg 0 1-3 4-6 7-9 10-12 -10 13-15 16-18 -10 Damper Placements Fig. 5.93 – 18 storey frame structure embedded with 3 diagonal VE dampers -percentage reductions in tip deflection for different placements 185 Influence of Damping Systems on Building Structures Subject to Seismic Effects The results of peak values of tip acceleration reduction for the same structure embedded with the diagonal VE dampers are shown in Fig. 5.94. Greatest average reduction of 31.0% was achieved under the San Fernando earthquake. High average reduction was also obtained under the Hachinohe earthquake. On the other hand, acceleration reductions recorded under the other earthquakes were obviously less significant. 40 10 30 4 7 Avg, 8.69 Avg, 6.92 20 40 1 Avg, 16.52 30 Avg, 6.44 % Acceleration Reductions 50 Avg, 30.99 50 20 10 13 16 10 Avg 0 0 El Centro Hachinohe Kobe Northridge S.Fernando -10 -10 Earthquake Records Fig. 5.94 – 18 storey frame structure embedded with diagonal VE damper -percentage reductions in tip acceleration under different earthquake records The highest average tip acceleration reduction of 18.5% was obtained when the damper was placed in the lowest storey (Fig. 5.95). The average reduction for the uppermost placement was only slightly lower. The tip acceleration reductions for 20 Avg, 18.15 30 Avg, 8.74 40 Avg, 13.57 40 Avg, 13.23 50 Avg, 11.29 50 Avg, 18.49 % Acceleration Reductions the other placements were noticeably lower; nevertheless, still adequately high. 10 30 20 10 0 EC HA KO NO SF Avg 0 1 4 7 10 -10 13 16 -10 Damper Placements Fig. 5.95 – 18 storey frame structure embedded with diagonal VE damper -percentage reductions in tip acceleration for different placements 186 Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip acceleration reductions for the structure embedded with three dampers are presented in Fig. 5.96. The highest average tip acceleration reduction of 27.9% was, yet again, achieved under the San Fernando earthquake. The average reduction occurred under the Hachinohe earthquake was only slightly lower. The tip acceleration reductions recorded under the Northridge and El Centro earthquakes were also relatively high. On the other hand, reductions that occurred under the Kobe earthquake were, except for uppermost placement, relatively poor. 60 20 10 40 1-3 4-6 7-9 10-12 20 13-15 16-18 10 0 -10 50 30 Avg, 0.57 30 Avg, 13.31 Avg, 27.38 40 Avg, 16.18 % Acceleration Records 50 Avg, 27.94 60 Avg 0 El Centro Hachinohe Kobe Northridge S.Fernando -10 Earthquake Records Fig. 5.96 – 18 storey frame structure embedded with 3 diagonal VE dampers -percentage reductions in tip acceleration under different earthquake records Fig. 5.97 shows the tip acceleration reductions for the frame structure embedded 60 50 50 Avg, 12.15 Avg, 15.27 20 Avg, 19.40 30 Avg, 18.09 40 Avg, 26.45 60 Avg, 11.09 % Acceleration Reductions with three dampers at 6 different placements. 40 30 20 10 10 0 0 -10 1-3 4-6 7-9 10-12 13-15 16-18 EC HA KO NO SF Avg -10 Damper Placements Fig. 5.97 – 18 storey frame structure embedded with 3 diagonal VE dampers -percentage reductions in tip acceleration for different placements 187 Influence of Damping Systems on Building Structures Subject to Seismic Effects Interestingly, the results revealed some trends, which are in disagreement with those for the structures with one damper placement. The lowest tip acceleration reductions occurred when the dampers were placed in the lowest storeys. The tip acceleration reductions for structures with damper placed in storeys 13 to 15 and 10 to 12, respectively, were slightly higher. The tip acceleration reductions for the structures with the dampers placed in storeys 4 to 6 and 7 to 9, respectively, were noticeably higher. Clearly the highest tip acceleration reductions were obtained when the dampers were placed in the uppermost storeys. Diagonal VE dampers embedded in the 18-storey frame structure were investigated in this section. Overall, the dampers experienced a high performance in both investigated parameters. However, the range of the results was relatively wide. In terms of tip deflection reductions both types of the structure i.e. the structure fitted with one damper and the structure fitted with three dampers experienced similar trends. Clearly the highest deflection reductions were experienced under the Northridge earthquake. The tip deflection reductions recorded under the El Centro earthquake were also relatively high, whereas, the reductions occurred under the other earthquakes were only moderate. In both structures the dampers performed noticeably better when placed in the lower storeys, however, there was no particular placement with significantly the best results under all excitations. With regards to tip acceleration reduction, both structures (i.e. structure fitted with one and three dampers) experienced similar trends. The best results were recorded under the San Fernando and Hachinohe earthquakes. The reductions occurred under the Northridge and El Centro earthquakes were noticeably lower. The poorest results occurred under Kobe earthquake. The highest tip acceleration reductions were experienced when the dampers were placed in the uppermost storey. This was anticipated, since the placement of the dampers in the top storey increased the stiffness in the area of measurement. In the case of the lowest storey placements the lowest tip acceleration reductions were obtained. This was also anticipated, since the dampers fitted in the lowest storeys increased the stiffness at the base, and thus, decreased the ductility of the structure, which caused detuning 188 Influence of Damping Systems on Building Structures Subject to Seismic Effects of the structural natural frequency to the range of dominant frequencies of the earthquakes. While comparing the results of the 18-storey frame structure embedded with the diagonal VE dampers with the results of the 18-storeys frame-shear wall structure embedded with the same dampers, a number of different trends can be observed. In general, the dampers placed in the frame structure produced slightly better results in both investigated parameters. This was expected, because the structure did not experienced decrease of stiffness due to cut out of shear wall. For convenience the results of tip deflection and tip acceleration of both structures embedded with three diagonal VE dampers are, once again, shown in Figs. 5.98 and 5.99. 40 30 Avg, 3.95 Avg, 17.19 50 Avg, 7.25 10 Avg, 4.07 Avg, 15.95 F Structure Avg, 7.89 20 Avg, 7.68 % Reduction 30 Avg, 19.27 40 H Structure Avg, 3.20 50 Avg, 36.42 Tip Deflection Reductions in "H" and "F" Structures 20 1-3 4-6 7-9 10-12 10 13-15 16-18 0 -10 0 EC HA KO NO SF EC -20 HA KO NO SF Avg -10 -20 Earthquake Records Fig. 5.98 – 18-storey frame-shear wall structure vs.18-storey frame structure -percentage reductions in tip deflection under different earthquake records In Fig. 5.98 it can clearly be seen that the frame structure obtained the higher tip deflection reductions under the Northridge earthquake excitation and that slightly better results were also experienced under the San Fernando earthquake. On the other hand, the frame-shear wall structure performed better under the Hachinohe, Northridge and, the most noticeably, under the Kobe earthquakes. Generally, it can be stated that in terms of tip deflection reduction under different earthquake excitations, the better overall performance was achieved by the dampers placed in the frame structure. On the other hand, the performance of the dampers placed in the frame-shear wall structure was slightly more consistent. As regards to 189 Influence of Damping Systems on Building Structures Subject to Seismic Effects efficiency of the dampers in different placements, the dampers placed in frame– shear wall structure were highly effective in the lowest storeys and their efficiency was decreased when they were moved towards the top of the structure. In the case of frame structure, this trend was less obvious and the dampers revealed more stable performance throughout the all placements. Fig. 5.99 shows the results of tip acceleration reduction obtained by the same structures. The dampers fitted in the frame structure achieved clearly higher tip acceleration reductions under the El Centro, Hachinohe and San Fernando earthquakes, whereas, in the cases of the Kobe and Northridge earthquakes, clearly higher tip acceleration reductions were achieved by the dampers fitted in the frame-shear wall structure. On the whole, tip acceleration reductions obtained by the dampers fitted in the frame-shear wall structures were slightly lower, but, once again, more consistent. Tip Acceleration Reductions in "H" and "F" Structures Avg, 0.57 Avg, 27.38 Avg, 16.18 Avg, 7.33 15 Avg, 27.94 60 F Structure Avg, 21.73 Avg, 15.58 % Reduction 30 Avg, 11.19 45 Avg, 22.37 H Structure Avg, 13.31 60 45 30 1-3 4-6 7-9 15 10-12 13-15 0 0 16-18 Avg -15 EC HA KO NO SF EC -30 HA KO NO SF -15 -30 Earthquake Records Fig. 5.99 – 18-storey frame-shear wall structure vs.18-storey frame structure -percentage reductions in tip acceleration under different earthquake records The frame structure embedded with three diagonal VE dampers experienced the highest tip acceleration reductions when the dampers were placed in the uppermost storey and the similar result was experienced for the structure embedded with one damper. This trend was in contrast with the results obtained from all previously examined structures for which the diagonal VE dampers obtained the highest acceleration reductions when placed in the lowest storeys, 190 191 . The main reason for this tip acceleration increase. experienced by previously investigated structures. can be attributed to decrease in stiffness of the top storeys due to the cut-out in the shear wall.Influence of Damping Systems on Building Structures Subject to Seismic Effects whereas uppermost storeys placement caused an increase in tip acceleration. diversities in tip acceleration reductions obtained by the dampers in other placements were also obvious. Nevertheless. Influence of Damping Systems on Building Structures Subject to Seismic Effects 192 . Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 6 Results – 12-Storey Structures 193 . Figs. hybrid friction-VE dampers and VE lower toggle dampers embedded within cut outs of shear walls of the structure.10). 6. The efficiency of these damping systems were investigated under the five different earthquake excitations. namely friction and VE diagonal dampers. as it can be seen from the structural response recorded under the San Fernando earthquake excitation. were studied. friction and VE chevron brace dampers. 6. instalment of the dampers can in same cases increase the seismic response of the structure.1-6. These damping systems were placed within cut outs of shear wall at tvelwe different damper placements (Section 3.5. From these graphs.2 Seismic responses of 12-storey frame-shear wall structure The results presented in this section show the typical time history responses of the 12-storey structure embedded with different damping systems.1 was modelled and analysed. A 12-storey frame-shear wall structure described in Section 3.12.5 illustrate the tip deflection and tip acceleration under five earthquake excitations in the structure of designation M 9-10 with the diagonal friction dampers fitted in storeys 9 and 10.6. compared with tip deflection and tip acceleration in the undamped structure. as shown in Fig. it is evident that the dampers embedded into the cut-outs of shear walls can significantly reduce the tip deflection and tip acceleration throughout the duration of the earthquakes.12-storey structures 6.Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 6: Results . A total of six different damping systems (Section 3.2) Seismic analyses were caried out with one type of damping system at one placement a time.1 Introduction The results from the finite element analysis of the 12 storey structures embedded with the different damping systems installed at different placements are presented in the following sections. On the other hand. 3. 194 . 3 .1 0. 6.Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal friction dampers under the El Centro earthquake Tip acceleration (Hachinohe earthquake) Tip deflection (Hachinohe earthquake) UN 0.1 -0.Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip deflection (El Centro earthquake) Tip acceleration (El Centro earthquake) UN 0.05 0 -0.15 2 0 0 5 10 15 20 -2 -4 -0.Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal friction dampers under the Kobe earthquake 195 .2 4 2 Acceleration (m/s ) Deflection (m) 0.25 -6 Time (s) Time (s) Fig.05 UN 8 9-10 -6 -8 Time (s) Time (s) Fig. 6. 6.2 .05 UN 6 9-10 0 5 10 15 20 -0.4 Time (s) Time (s) Fig.15 -0.Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal friction dampers under the Hachinohe earthquake Tip deflection (Kobe earthquake) Tip acceleration (Kobe earthquake) UN 0.2 4 2 0 Acceleration (m/s ) Deflection (m) 0 2 0 -2 0 5 10 15 20 -4 -0.1 2 Acceleration (m/s ) Deflection (m) 9-10 4 0.15 9-10 6 0.2 -0.1 8 9-10 UN 9-10 6 5 10 15 20 -0.3 -6 -8 -0.1 -0.1 -0.1 .05 0 0 5 10 15 20 2 0 -2 0 5 10 15 20 -4 -0.15 0. 8 show tip deflection and tip acceleration under the El Centro earthquake excitation for the same 12-storey frame-shear wall structure embedded six different damping systems.1 0.1 -0. Fig. discussed in previous chapter. 6.05 UN -6 Time (s) Time (s) Fig. 196 .2 9-10 4 0.2 6 9-10 2 0. which were in agreement with the results for 18storey frame-shear wall structure. 6.05 -0. 6. demonstrated superiority of the diagonal friction dampers over the diagonal VE dampers when placed in the upper storeys.6 shows the tip deflection and tip acceleration responses of the 12-storey structure with the diagonal friction and diagonal VE dampers placed in storeys 9 and 10.Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip deflection (Kobe earthquake) Tip acceleration (Northridge earthquake) UN 0.05 9-10 4 Acceleration (m/s ) Deflection (m) 0. The results for the 18-storey structure. 6.6-6.05 0 -0.15 -6 Time (s) Time (s) Fig.15 Tip acceleration (San Fernando earthquake) UN 6 9-10 0. Fernando earthquake Figs.4 .Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal friction dampers under the S. the 12storey structure embedded with the same dampers treated under the El Centro excitations showed the results.1 -4 -0. As it can be seen in this figure.1 2 Acceleration (m/s ) Deflection (m) 0 0 5 10 15 20 2 0 0 5 10 15 20 -2 -0.5 .15 UN 0 5 10 15 20 2 0 0 5 10 15 20 -2 -4 -0.Tip deflection and tip acceleration response of the undamped structure and the structure embedded with diagonal friction dampers under the Northridge earthquake Tip deflection (San Fernando earthquake) 0.15 -0. 25 Time (s) FR -6 Time (s) VE VE Fig. these trends were in the case of the 12-storey structure. while advantage of the VE dampers was in gradually decreasing the tip deflection and tip acceleration of the structure.1 4 0.15 -0. as it can be observed from Fig. 6.7 and from many other results presented latter in this chapter. Chevron brace friction dampers vs Chevron brace VE dampers Chevron brace friction dampers vs Chevron braceVE dampers 6 0.6 . 6. 6. However.05 0 5 10 15 -0. The seismic responses of the dampers in both investigated parameters were relatively close.15 6 0.05 2 Deflection (m) 2 Acceleration (m/s ) 0. during the strong seismic excitation.Tip deflection and tip acceleration responses of the structures embedded with Friction and VE chevron brace dampers under the El Centro earthquake 197 .05 0 5 10 15 20 -0.7 .7 shows tip deflection and tip acceleration responses of the structures embedded with the chevron brace friction and chevron brace VE dampers under the El Centro earthquake excitation. The friction dampers performed slightly better in the first half of the excitation. The results discussed in the previous chapter. i. demonstrated the better ability of friction dampers to reduce the intensity of the initial strong motion.1 -0. while the VE dampers were better performing during smaller excitation.e.25 0 -2 -8 VE VE Time (s) Time (s) Fig.Tip deflection and tip acceleration responses of the structures embedded with diagonal friction and VE dampers under the El Centro earthquake Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects Diagonal fricton dampers vs Diagonal VE dampers Diagonal friction dampers vs Diagonal VE dampers 0.15 0 -0.1 Deflection (m) 2 Acceleration (m/s ) 4 0.1 2 0 0 5 10 15 20 -2 -0.2 20 0 5 10 15 20 -4 -6 UN UN FR FR -0. 6. noticeably less obvious.15 -4 -0.2 UN UN FR -0.05 0 -0. 2. El Centro Hachinohe Kobe Northridge S. Hybrid dampers vs Lower toggle dampers Hybrid dampers vs Lower toggle dampers 6 0. whereas the structure fitted with the lower toggle VE dampers achieved better results in terms of tip acceleration reduction.9 shows the interstorey drifts of the undamped 12-storey structure under five earthquake excitations. 6.05 0 -0.141 Acceleration (m/s2) 5. Both types of dampers achieved good overall performance.15 -4 -0.93 5.0396 m.15 0.61 6.2 -0.69 6.8. are illustrated in Fig. 6.8 .05 0 5 10 15 20 -0.1 Undamped structure The undamped structural model was created in order to compare its results with the results of the structures fitted with the damping systems.206 0.154 0. The second highest interstorey drifts were experienced under the El Centro 198 .1 .145 0.1 Table 6.Fernando Deflection (m) 0. The structure fitted with the hybrid dampers obtained slightly higher tip deflection reduction.1 2 0 0 5 10 15 20 -2 -0. The highest interstorey drifts were displayed under the Hachinohe earthquake with the maximum interstorey deflection of 0.374 0.Tip deflection and tip acceleration of the undamped 12-storey structure.51 Fig.76 3.Tip deflection and acceleration responses of the structures embedded with Hybrid damping systems and VE lower toggle dampers under the El Centro earthquake 6. 6. The results of the tip deflection and tip acceleration of this structure obtained under five earthquake excitations are presented in Table 6.25 UN UN HY Time (s) HY -6 Time (s) LT LT Fig.1 Deflection (m) 2 Acceleration (m/s ) 4 0.Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip deflection and tip acceleration responses of the structures embedded with the hybrid friction-VE dampers and the structure embedded with the lower toggle VE dampers respectively. 05 5-6 6-7 7-8 8-9 9-10 0.Interstorey drifts of undamped structure under the five earthquake excitations 6.06 9-10. 199 .0170 4-5 6-7. While comparing seismic responses for both damper placements.0149 m.0173 m and the San Fernando earthquake with the maximum interstorey deflection of 0. 0.0173 0.0396 3-4 0.02 10-11. 6. and 9 and 10.2. etc. 7 and 8. 6.0170 m.2 Diagonal friction dampers The results of the tip deflection and tip acceleration experienced by the structures embedded with the diagonal friction damper are presented below.03 2-3 10-11. the dampers embedded in the storeys 9 to 10 with higher interstorey drifts produced slightly better results in tip deflection.Influence of Damping Systems on Building Structures Subject to Seismic Effects earthquake with the maximum interstorey deflection of 0. 0.04 1-2 10-11. 0. respectively. 0. The lowest interstorey drifts occurred under the Northridge earthquake with the maximum interstorey deflection of 0. From the Fig.10 illustrates time history responses of tip deflection and tip acceleration under the El Centro earthquake excitation in the undamped structure and in the structures with the diagonal friction dampers placed in storeys 1 and 2. then 11 and 12. This was followed by the Kobe earthquake with the maximum interstorey deflection of 0.01 10-11 11-12 0 El Centro Hachinohe Kobe Northridge S.0149 0.9 . Fig. This was followed by drifts between the storeys 9 and 10.9 it can also be seen that the maximum interstorey drifts were displayed between storeys 10 and 11. 0. 6.0226 m.0226 Interstorey Drifts (m) 0. 0. 8 and 9.Fernando Earthquake Records Fig. In these graphs it can be seen that the dampers in both placement produced clearly better results than undamped structure. it is worth noticing.05 2 0 0 5 10 15 20 -2 -0. The performance of the damper achieved under the Kobe. that both responses remained generally in phase with responses of undamped structure. while in terms of tip acceleration. On the other hand. except for the lowest placement.11 illustrates the results of the percentage reductions in the peak values of the tip deflection obtained by the structures fitted with the diagonal friction damper at six different locations under five earthquake excitations.11 – 12 storey structure embedded with 1 diagonal friction damper -percentage reductions in tip deflection under different earthquake records 200 .36 % Deflection Reductions 23 Avg.10 Tip deflection and acceleration responses of the structures with different placement of the diagonal friction dampers under the El Centro earthquake Fig. 6.15 -4 -0. clearly the better result occurred for the dampers fitted in the lowest storeys.1 Acceleration (m/s2) Deflection (m) 0. also very high. 6. 10. 2.Fernando 11 Avg -15 -23 Earthquake Records Fig. 16.25 -6 Time (s) Time (s) Fig.15 UN 1-2 6 9-10 9-10 0.Influence of Damping Systems on Building Structures Subject to Seismic Effects which is the primary investigated parameter.2 -0.15 Avg. 1 3 5 7 0 9 El Centro Hachinohe Kobe -8 Northridge S.05 0 5 10 15 20 -0. 9.38 unexpectedly poor.1 4 0 -0. Northridge and San Fernando earthquakes were. the performance under the Hachinohe earthquake was 8 Avg. 6. The damper obtained the greatest performance under the El Centro earthquake.03 15 Avg. Tip deflection (El Centro earthquake) Tip Acceleration (El Centro earthquake) UN 1-2 0. In addition. 9.99 30 Avg. these trend were more complex. 5. 6. This trend was relatively regular under the Northridge and San Fernando earthquakes. 14. and a regular decrease in deflection reduction was experienced as the damper was moved towards the bottom of the structure.08 6.46 Avg. 6. In the case of the Hachinohe earthquake adequate tip deflection reductions occurred only for the lower storey placements. 30 EC 10 HA Avg. 6.Fernando -10 Earthquake Records Fig.64 % Deflection Reductions 20 NO SF Avg -20 -30 1 3 5 7 9 11 Placement of the Dampers Fig. whereas the trends occurred under the El Centro and Kobe earthquakes. 6.13 – 12 storey structure embedded with 2 diagonal friction dampers -percentage reductions in tip deflection under different earthquake records 201 . 15.37 -10 Avg.12 – 12 storey structure embedded with 1 diagonal friction damper -percentage reductions in tip deflection for different damper placements The percentage reductions in the peak values of the tip deflection obtained by the structures fitted with the three diagonal friction dampers are presented in Fig.99 % Deflection Reductions 30 Avg.05 Avg.90 KO 0 Avg. 18. 9.Influence of Damping Systems on Building Structures Subject to Seismic Effects In terms of damper placements (Fig.86 40 Avg. 5.13. 11. 27. 2. 20 10 Avg.80 Avg. 1-2 3-4 5-6 7-8 9-10 11-12 Avg 0 El Centro Hachinohe Kobe Northridge S. 13.12) the highest tip deflection reductions occurred when the damper was placed in the 11th storey.52 Avg.31 Avg. The results of tip deflection reduction in terms of efficiency of the dampers in different placements are illustrated in Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects The dampers display a very high efficiency in the vast majority of the cases. in the cases of the El Centro and Kobe earthquakes this trend was less obvious. 18.18 Avg. tip deflection reductions significantly increased as the dampers were moved towards the storeys with the higher interstorey drifts.79 20 Avg.15 shows the tip acceleration reduction for 12-storey structure embedded with the diagonal friction damper. while. while tip acceleration reductions occurred under the other earthquake excitations were 202 .70 Avg.14 – 12 storey structure embedded with 2 diagonal friction dampers -percentage reductions in tip deflection for different damper placements Fig. yet again. The reductions occurred under the Northridge and San Fernando earthquakes were also adequately high. The highest average tip deflection reduction of 27. 20. while tip deflection reductions experienced under the Hachinohe and Kobe earthquakes were clearly less significant. the results of the same dampers in terms of tip acceleration reductions were rather unfavourable. 10 Avg. 6. 19. 9. This trend was. 6. 4. 14.86% was achieved under the El Centro earthquake. While this structure revealed very good overall performance in terms of tip deflection reduction.72 % Deflection Reductions 30 Avg. only minor tip deflection reductions. The dampers placed in the lowest storeys produced in the majority of cases. High reductions were experienced under the El Centro and Kobe earthquakes.99 Avg.82 40 EC HA KO NO SF Avg 0 1-2 3-4 5-6 7-8 9-10 11-12 -10 Placement of the Dampers Fig. 6. On the other hand. relatively regular under the Northridge and San Fernando earthquakes.14. 12% was recorded under the San Fernando earthquake.76 Avg.64 Avg.93 % Acceleration Reductions 20 NO SF Avg -20 -30 -40 1 3 5 7 9 11 Placement of the Dampers Fig.63 30 Avg. 6.16 – 12 storey structure embedded with 1 diagonal friction damper -percentage reductions in tip acceleration for different damper placements The results of tip acceleration reduction for structures fitted with two diagonal friction dampers are illustrated in Fig.15 – 12 storey structure embedded with 1 diagonal friction damper -percentage reductions in tip acceleration under different earthquake records As can be seen from Fig. while its repositioning towards the storeys with higher interstorey drifts resulted in increase in tip acceleration reduction. 6.12 Avg.12 % Acceleration Reductions 20 Avg. 6. 12. 1.45 10 -10 EC HA KO Avg. -2. 4.21 -10 -20 9 Avg.77 Avg. On the other hand.16. 30 0 Avg. in the case of the El Centro and San Fernando earthquake excitations rather reverse trend can be observed.18 Avg. The highest tip acceleration reductions occurred under the El Centro earthquake.86 acceleration by 16.Fernando -40 Earthquake Records Fig. 12. 1.Influence of Damping Systems on Building Structures Subject to Seismic Effects mostly unfavourable. -16. This was followed by. -3. 0.17. 0. -30 El Centro Hachinohe Kobe Northridge 11 Avg S. still 203 . 6. the poorest result with increase in average tip acceleration occurred for the lowest damper placement. The poorest result with strong increase in average tip 10 1 3 5 0 7 Avg. 5. 6. 16. 6. while a gradual increase in tip acceleration occurred as the dampers were moved towards the top of the structure. 6. -9.98 20 % Acceleration Reductions Avg.98 10 1-2 3-4 5-6 0 7-8 9-10 -10 Avg. 11. acceleration reductions occurred under the Northridge and Kobe earthquakes. 10. 3.03 Avg. Both 204 .57 Avg. -20 El Centro Hachinohe Kobe Northridge 11-12 Avg S.23 30 0 EC HA KO NO SF -10 Avg -20 1-2 3-4 5-6 7-8 9-10 11-12 -30 Placement of the Dampers Fig. On the other hand. 13.51 Fernando earthquake excitations were unfavourable.18 – 12 storey structure embedded with 2 diagonal friction dampers -percentage reductions in tip acceleration for different damper placements The 12-storey frame-shear wall structure embedded with the diagonal friction dampers was investigated in this section.14 30 Avg. 6. The dampers obtained adequately high overall performance.17 – 12 storey structure embedded with 2 diagonal friction dampers -percentage reductions in tip acceleration under different earthquake records The highest tip acceleration reductions can be observed when the dampers were placed in the lowest storeys (Fig. 2. however.Fernando -30 Earthquake Records Fig.28 % Acceleration Records 20 Avg.08 Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects adequately high. 0. -8.98 10 Avg.80 Avg.18). the range of the results was relatively wide. the results recorded under the Hachinohe and San Avg. Avg. 7. on the other hand.11. 6. The highest tip acceleration reductions were achieved when the dampers were placed in the lowest storeys and were gradually decreased as the dampers were moved towards the top of the structure. The results for tip acceleration reductions were rather inconsistent.6. Northridge and San Fernando earthquake excitations. it was anticipated that the 12-storey structure fitted with the diagonal friction dampers should achieve a significant performance primarily under earthquake excitations with higher interstorey drifts. the biggest difference occurred under the Hachinohe earthquake. the results. While comparing these results with the results of the diagonal friction dampers fitted in the 18-storey frame-shear wall structure. when. In terms of tip deflection reduction. where high deflection reductions achieved by the dampers embedded 205 . the reductions occurred under the Hachinohe and San Fernando earthquakes were unfavourable. On the other hand. several different trends can be observed. in the majority of cases.Influence of Damping Systems on Building Structures Subject to Seismic Effects structures (with one damper placement and with two damper placement) experienced significantly high tip deflection reduction under the El Centro. confirmed previous finding. only minor tip deflection reductions. which imply that the diagonal friction dampers placed in the lowest storeys produced. Based on the results obtained from the 18-storey structure. However.14 the performance of dampers fitted in the12-storey structure under the Hachinohe excitations was rather insignificant. the reductions significantly increased. the dampers were moved towards the storeys with the higher interstorey drifts. as it can be seen from Figs. In terms of efficiency of the dampers in different placements. The diverse damper performance was also experienced under the San Fernando earthquake. while the reductions occurred under the Hachinohe and Kobe earthquakes were less significant. once again. The acceleration reductions experienced under the Northridge and Kobe earthquakes were also adequately high. The highest tip acceleration reductions were obtained under the El Centro earthquake excitations. Tip Deflection (El Centro earthquake) Tip Acceleration (El Centro earthquake) 0. Time history responses of tip deflection and tip acceleration under the El Centro earthquake excitation in the undamped structure and in the structures with the diagonal VE dampers placed in storeys 1 and 2 and 9 and 10. 6.Influence of Damping Systems on Building Structures Subject to Seismic Effects in the 12-storey structure were in contrast with massive increase in tip deflection experienced by the same dampers fitted in the 18-storey structure. In terms of tip acceleration reductions the highest difference in damper efficiency was.1 Deflection (m) 0 -0. while the dampers fitted in the 12-storey structure were rather ineffective. While 206 . the dampers placed in 18-storey structure experienced significant tip deflection reductions.2. respectively.2 -0.15 2 0 0 5 10 15 20 -2 -4 -0.25 Acceleration (m/s2) 4 0.05 0 5 10 15 20 -0. 6. when.1 -0. the trends experienced in the 12-storey and 18-storey structures were rather reverse under all earthquake excitations.15 6 0.19 – Tip deflection and acceleration responses of the structures with different placement of the diagonal VE dampers under the El Centro earthquake From these graphs it can be seen that the structures embedded with the diagonal VE dampers produced clearly better results than undamped structure.05 UN UN -6 1-2 Time (s) 9-10 Time (s) 1-2 9-10 Fig.19. experienced under the Hachinohe earthquake. 6. As regards to efficiency of the dampers in different placements. yet again. are illustrates in Fig.3 Diagonal VE dampers The results of the tip deflection and tip acceleration reduction experienced by the 12-storey structures embedded with the diagonal VE damper are presented below. was experienced by the dampers fitted in the lowest storeys. 2.47 36 1 Avg. while its repositioning towards the top or bottom of the structure resulted in decrease in tip deflection reduction. 0. 6. than clearly a higher efficiency. 207 .47% was achieved under the El Centro earthquake excitation. Avg.21 shows the damper efficiency in different placements. In general. The greatest average tip deflection reduction of 17.18 18 Avg. 17.Fernando 5 7 9 11 Avg -9 -18 Earthquake Records Fig.38 % Deflection Reductions 27 S. This trend can be observed under the Hachinohe.91 3 Avg. in both investigated parameters. while under the El Centro earthquake excitation rather reverse trend can be observed. In the case of the Kobe earthquake an efficiency of the damper was regularly increasing when the damper was moved from the lowest storey towards the top of the structure. Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects comparing an efficiency of the dampers embedded in the two different placements. 6. 2.43 9 0 El Centro Hachinohe Kobe Northridge Avg. The tip deflection reductions occurred under the other earthquakes were in the vast majority of cases only moderate. 6. Northridge and San Fernando earthquakes.20 – 12 storey structure embedded with 1 diagonal VE damper -percentage reductions in tip deflection under different earthquake records Fig. the highest deflection reduction occurred when the damper was positioned in the middle storeys. These results were in agreement with previous findings.20 shows the tip deflection reductions for the structure embedded with the diagonal VE damper. 0. 13 18 Avg.Fernando -9 Earthquake Records Fig.80 27 Avg.6% occurred under the El Centro earthquake.56 % Deflection Reductions 27 0 KO NO SF Avg 1 5 3 7 9 11 -9 -18 Placement of the Dampers Fig. The greatest average reduction of 29.80 9 3-4 Avg. 6. 1.44 Avg. The average tip deflection reduction obtained under the Kobe earthquake was also reasonably high. the reductions recorded under the San Fernando and Hachinohe earthquakes were only moderate. The poorest results with only small tip deflection reductions occurred under the Northridge earthquake. 29.Influence of Damping Systems on Building Structures Subject to Seismic Effects 36 EC HA Avg.22 – 12 storey structure embedded with 2 diagonal VE dampers -percentage reductions in tip deflection under different earthquake records 208 .21 – 12 storey structure embedded with 1 diagonal VE damper -percentage reductions in tip deflection for different damper placements Percentage reductions in tip deflection for the same structures fitted with two diagonal VE dampers are illustrated in Fig.26 Avg. 0.42 18 5-6 Avg. 7. 6. 17.55 45 1-2 Avg.87 9 Avg. 4. Avg. 3. 6.22. On the other hand. 6.79 Avg.02 % Deflection Reductions 36 7-8 9-10 11-12 Avg 0 El Centro Hachinohe Kobe Northridge S. 6. 1. 7. 72 Avg. 6.44 27 Avg. 6. -2. 45 EC Avg.07 10 Avg. 3.83 5 Avg.23 – 12 storey structure embedded with 2 diagonal VE dampers -percentage reductions in tip deflection for different damper placements Fig. 8. 15.56 HA KO Avg. the structure displayed only a small sensitivity to damper placements and tip deflection reductions for the lower and middle storeys placement were within an exceptionally narrow range.38 % Acceleration Reductions 15 1 3 5 7 9 11 Avg -5 El Centro Hachinohe Kobe Northridge S.05 Avg. 6.24 – 12 storey structure embedded with 1 diagonal VE damper -percentage reductions in tip acceleration under different earthquake records 209 . 14. 0 Avg.Fernando -10 Earthquake Records Fig. whereas placing the dampers in the uppermost storeys resulted in noticeably lower performance.40 9 NO Avg. 4. 7. In general.88 18 Avg.32 % Deflection Reductions 36 SF Avg 0 1-2 3-4 5-6 7-8 9-10 11-12 -9 Placement of the Dampers Fig. 6. 14. 4.12 Avg.24 shows the tip acceleration reduction for the structure embedded with the diagonal VE damper.23 shows high average tip deflection reductions for the structure with two diagonal VE dampers located in the lower and middle storeys. 2. 14.Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig. 6. Hachinohe and San Fernando earthquakes. the results obtained under the Kobe and Northridge earthquakes were rather complex and did not reveal any obvious trend. 3.26. 6. achieved under the El Centro earthquake.25 – 12 storey structure embedded with 1 diagonal VE damper -percentage reductions in tip acceleration for different damper placements The tip acceleration reductions obtained by the structure embedded with two diagonal VE dampers are presented in Fig.25 10 Avg.10% was.38% occurred under the El Centro earthquake. This trend can be observed under the El Centro. The poorest result with increase in tip acceleration was recorded under the Northridge earthquake excitation.76 Avg.83 % Acceleration Reductions 15 0 HA KO NO SF Avg -5 -10 1 3 5 7 9 11 Placement of the Dampers Fig. The highest average reduction of 18. yet again.Influence of Damping Systems on Building Structures Subject to Seismic Effects The highest average reduction of 7. the highest acceleration reduction occurred for the damper placed in the lowest storeys and a decrease in acceleration reduction occurred when the damper was moved towards the top of the structure. 1. 5. 4. The reductions obtained under the Kobe.79 Avg. 210 .25. EC Avg.70 Avg. whereas. 6. Hachinohe and San Fernando earthquakes were noticeably lower. 0. As can be seen in Fig. 2.63 5 Avg. while. the reductions obtained under the San Fernando earthquake were clearly lower. The reductions occurred under the Hachinohe and Kobe earthquakes were also adequately high. The poorest result and unfavourable increase in average tip acceleration was experienced under the Northridge earthquake. -1.64 Avg. 18. 6.33 30 Avg.27) the highest tip acceleration reductions occurred for the dampers placed in the lowest storeys.27 – 12 storey structure embedded with 2 diagonal VE dampers -percentage reductions in tip acceleration for different damper placements The diagonal VE dampers embedded in the 12-storey frame-shear wall structure were investigated in this section.74 23 1-2 Avg. while under the Kobe earthquake the reductions for the middle storey placements were the lowest. -2. 16. 10. 6.08 15 Avg.62 HA Avg. 9.Fernando -15 Earthquake Records Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects 45 Avg. 6.26 – 12 storey structure embedded with 2 diagonal VE dampers -percentage reductions in tip acceleration under different earthquake records In terms of damper placements (Fig. The poorest reductions occurred under the Northridge earthquake excitations. 7. 13. when the dampers were moved towards the top of the structure a gradual increase in tip acceleration was recorded.26 EC KO Avg.10 % Acceleration Reductions 38 8 0 5-6 7-8 9-10 11-12 Avg -8 El Centro Hachinohe Kobe Northridge S. In terms of tip deflection reductions the extraordinary performance was experienced under the El Centro earthquake. 6.14 % Acceleration Reductions 45 NO SF Avg 0 1-2 3-4 5-6 7-8 9-10 11-12 -15 Placement of the Dampers Fig. while.49 15 3-4 Avg. This trend can be observed under the El Centro and Hachinohe earthquakes. the highest reductions occurred for the middle storey placements. Avg. 6. In the case of the San Fernando earthquake. High 211 .58 30 Avg. 17.70 Avg. rather reverse trends were experienced. the poorest result with an increase in tip acceleration was experienced under the Northridge earthquake. in the cases of the Kobe and Northridge earthquakes. 212 . confirmed trends. in both types of structure the dampers clearly gave the highest tip deflection reductions under the El Centro and Kobe earthquakes. achieved under the El Centro earthquake excitation. Furthermore. which indicated that the highest tip deflection and tip acceleration reductions occurred when the dampers were placed in the lowest storeys and gradually decreased as the dampers were moved towards the top of the structure. while in contrast. while the reductions recorded under the other earthquakes were obviously less significant.Influence of Damping Systems on Building Structures Subject to Seismic Effects tip deflection reductions occurred also under the Kobe earthquake. The results for 12-storey structure embedded with the diagonal VE dampers. yet again. While comparing these results with the results of the diagonal VE dampers embedded in the 18-storey structure. In terms of tip acceleration reduction. The dampers embedded in the 18-storey structure obtained the highest tip deflection reductions when placed in the lowest storey and a regular decrease in deflection reductions occurred as they were moved towards the top of the structure. the best results were. In the case of the 12-storey structure consistency and regularity of this feature was less obvious. while the diagonal VE dampers embedded in the 18-storey structure achieved the higher tip acceleration reduction under the other earthquakes. the diagonal VE dampers embedded in the 12-storey structure achieved higher reductions under the El Centro earthquake. In terms of tip acceleration reductions. once again. The graph of tip deflection illustrates a high performance of the dampers placed in the upper storeys. The performance of the damper under the Hachinohe earthquake was unfavourable.2 -0. 6.1 4 Deflection (m) 0. 213 .Influence of Damping Systems on Building Structures Subject to Seismic Effects 6.4 Chevron brace friction dampers The results of tip deflection and tip acceleration experienced by the structures fitted with the chevron brace friction damper are presented below. The highest average tip deflection reduction of 13. respectively. the damper performed effectively and reliably under the other earthquake excitations.83% occurred under the Kobe earthquake and the average tip deflection reductions under the El Centro.29. yet again. Tip Deflection (El Centro earthquake) Tip Acceleration (El Centro earthquake) 6 0. 6.28 display the time history responses of tip deflection and tip acceleration under the El Centro earthquake in the undamped structure and in the structures with the chevron brace friction dampers placed in storeys 1 and 2. In terms of tip acceleration the better results were. Northridge and San Fernando earthquakes were only slightly lower. Nevertheless.25 UN 1-2 Time (s) 9-10 20 Acceleration (m/s2) 0.05 0 5 10 15 -0.15 2 0 -2 0 5 10 15 20 -4 -6 UN 1-2 -8 Time (s) 9-10 Fig.05 0 -0. the dampers fitted in both placements were not able to effectively reduced intensity of tip acceleration related to initial strong motions.28 – Tip deflection and acceleration responses of the structures with different placement of the chevron brace friction dampers under the El Centro earthquake The results of the percentage reductions in the peak values of the tip deflection experienced by the structures fitted with the chevron brace friction damper are illustrated in Fig. while the dampers placed in the lowest storeys were rather ineffective.2.15 -0. 6. Fig.1 -0. and 9 and 10. On the other hand. displayed for the dampers placed in the upper storeys. 11.31. 6.Influence of Damping Systems on Building Structures Subject to Seismic Effects 30 Avg. 6.5%. The lowest tip deflection reductions occurred when the damper was fitted in the lowest storey.64 10 Avg. 6.30 shows high performance of the damper in all placements. The greatest performance. -0. 14. 9.60 20 Avg.83 15 1 3 10 Avg. was obtained under the El Centro earthquake. 6. while a increase in reductions was experienced when the damper was moved towards the storeys with higher interstorey drifts. 6. 8.Fernando -5 Earthquake Records Fig.30 – 12 storey structure embedded with 1 chevron brace friction damper -percentage reductions in tip deflection for different placements The percentage reductions in tip deflection for the structures fitted with two chevron brace friction dampers are illustrated in Fig. This was followed by still adequately high reductions 214 . while the deflection reductions experienced under the Kobe earthquake were very consistent. 10. 8.51 % Deflection Reductions 25 KO NO SF Avg 5 0 1 3 5 7 9 11 -5 Placement of the Dampers Fig. This trend was displayed under the El Centro.26 EC HA Avg. Northridge and San Fernando earthquakes.42 5 0 El Centro 5 7 9 11 Avg. 13. 13.05 Avg. 30 Avg. 6.55 15 Avg.61 20 Avg.29 – 12 storey structure embedded with 1 chevron brace friction damper -percentage reductions in tip deflection under different earthquake records Fig. with an average deflection reduction of 21.02 Avg.55 % Deflection Reductions 25 Avg Hachinohe Kobe Northridge S. 31 – 12 storey structure embedded with 2 chevron brace friction dampers -percentage reductions in tip deflection under different earthquake records From Fig. 14.93 Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects recorded under the Kobe.29 20 Avg.32 – 12 storey structure embedded with 2 chevron brace friction dampers -percentage reductions in tip deflection for different placements 215 . yet again.24 25 Avg.50 1-2 15 Avg. 6. 10. Northridge and San Fernando earthquakes. 6. slight decreases in efficiency were experienced. 14. 17. 16. Conversely. displayed under the El Centro. 35 Avg.20 20 Avg. This trend was. 15. 35 15 10 Avg.89 Avg. 6. the reductions occurred under the Hachinohe earthquake were rather insignificant.83 Avg.91 25 3-4 5-6 7-8 9-10 11-12 10 Avg. 17.29 % Deflection Reductions 30 EC HA KO NO SF Avg 5 0 1-2 3-4 5-6 7-8 9-10 11-12 Placement of the Dampers Fig. Northridge and San Fernando earthquakes.32. 21.Fernando Earthquake Records Fig. while the deflection reductions occurred under the Kobe and Hachinohe earthquakes were rather constant. 2.68 % Deflection Reductions 30 5 Avg 0 El Centro Hachinohe Kobe Northridge S.49 Avg. it can be seen that the highest average tip deflection reduction occurred for the structures with dampers placed in storeys 7 and 8. 14. 6. As the dampers were moved towards the top or bottom of the structure. 71% occurred under the Kobe earthquake. 6. 16.34 shows the tip acceleration reductions experienced by the same structure in terms of efficiency of the dampers in different placements. On the other hand.45% was recorded under the San Fernando earthquake. The massive increase in average tip acceleration by 50. 6.20 -30 Avg. -25. Fernando -90 Earthquake Records Fig.33 – 12 storey structure embedded with 1 chevron brace friction damper -percentage reductions in tip acceleration under different earthquake records Fig. -50. In the case of the Kobe earthquake tip acceleration reductions were gradually increased when the damper was moved towards the storeys with higher interstorey drifts. 6.71 0 Avg.33. while the increase in tip acceleration to a level lower than 10 m/s2 (in this case 5 m/s2) did not represent any decrease in structural safety.Influence of Damping Systems on Building Structures Subject to Seismic Effects The results of tip acceleration reduction for the 12-storey structure embeded with the chevron brace friction damper are illustrated in Fig. The results obtained under the other earthquake excitations were unfavourable with an increase in tip acceleration. As mentioned previously. -5. in which strong increase in tip acceleration was recorded for all the placements. Overall results were strongly influenced by the results occurred under the El Centro and San Fernando earthquakes.60 % Acceleration Reductions 15 -60 -75 El Centro Hachinohe Kobe Northridge 11 Avg S. A significant average tip acceleration reductions of 16.45 -45 1 Avg. -7. the results displayed under the other earthquake excitations seem to be more influenced by decrease in stiffness due to cut-outs in shear wall than by an ability of the damper to decrease tip acceleration. 30 3 5 7 9 Avg. the reduction in structural tip deflection is primary purpose for incorporation of the dampers to the structure.88 -15 Avg. 216 . 97 % Acceleration Reductions 15 Avg -90 Earthquake Records Fig. -21. 6.36 an increase in tip acceleration was recorded for all damper placements. -54. 6.74 3 Avg. The results display relatively high acceleration reductions under the Kobe earthquake. 30 3-4 5-6 7-8 9-10 11-12 -60 -75 El Centro Hachinohe Kobe Northridge S. Clearly the worst results occurred under the San Fernando earthquake. -6. 6. where increase in average tip acceleration by 54.35 – 12 storey structure embedded with 2 chevron brace friction dampers -percentage reductions in tip acceleration under different earthquake records As can be seen from Fig. 9.01 -30 Avg. However.77 -20 1 Avg. even this increase (to 5. -10.Fernando Avg. -6. -17. -20.76 % Acceleration Reductions 20 NO SF Avg -60 -80 Placement of the Dampers Fig.6% was experienced. 6. -21. However.97 7 Avg.17 0 Avg.35.34 – 12 storey structure embedded with 1 chevron brace friction damper -percentage reductions in tip acceleration for different placements Percentage reductions in tip acceleration for the structure embedded with two chevron brace friction dampers are illustrated in Fig. -17.24 -40 9 11 KO Avg.27 -15 Avg. the reductions occurred under the other earthquakes were considerably poor.59 -45 1-2 Avg.44 m/s2 for uppermost placement) did not represent any decrease in structural safety. The lowest tip acceleration increase was recorded when 217 . -2.42 5 Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects 40 EC 0 HA Avg. On the other hand. The results for tip deflection reduction.31 KO Avg.25 -30 EC Avg. Nevertheless. In the case of the Kobe earthquake the performance was relatively consistent. 218 .22 Avg. more influenced by decrease in the stiffness due to cut-outs in shear wall than by ability of the dampers to reduce tip acceleration. Northridge and San Fernando earthquakes were also adequately high. yet again. the efficiency of the dampers under the Hachinohe earthquake was rather poor. -6. the tip acceleration reductions of chevron brace friction damper seem to be. while. -17. 30 0 HA Avg. The reductions obtained under the El Centro. The highest and the most consistent performance in terms of tip deflection reductions were achieved under the Kobe earthquake excitations.Influence of Damping Systems on Building Structures Subject to Seismic Effects dampers were placed in storeys 5 and 6. -16. However. -32. In terms of damper placements. revealed adequately high efficiency of the dampers. -11. -16. the performance of the dampers under the El Centro. In terms of tip acceleration reduction. the highest increase occurred when the dampers were placed in the uppermost storeys. the chevron brace friction dampers obtained very poor results.68 % Acceleration Reductions 15 -60 NO SF Avg -75 -90 1-2 3-4 5-6 7-8 9-10 11-12 Placement of the Dampers Fig. The tip acceleration reductions. which occurred under the Kobe earthquake excitations.34 -45 Avg. Northridge and San Fernando earthquakes regularly increased when the dampers were moved from bottom to the top of the structure.59 -15 Avg. 6. were adequately high and relatively consistent.36 – 12 storey structure embedded with 2 chevron brace friction dampers -percentage reductions in tip acceleration for different placements The chevron brace friction dampers embedded in the 12-storey frame-shear wall structures were investigated in this section. the dampers fitted in the 18-storey structure were obviously more effective under the Hachinohe earthquake. The overall reductions in tip deflection for chevron brace friction dampers were comparatively high to those of the diagonal friction dampers and diagonal VE dampers embedded in the 12-storey structure. While comparing the results of tip deflection reduction for chevron brace friction dampers embedded in the 12-storey frame-shear wall structure. 219 . the same dampers embeded in the 18-storey structure experienced relatively high tip acceleration reductions in the majority of the cases. In contrast. whereas no common trends were observed under the other earthquake excitations. In the case of the El Centro and Northridge earthquakes. On the other hand. even this increase in tip acceleration to the value of 5 m/s2.Influence of Damping Systems on Building Structures Subject to Seismic Effects the results obtained under the other earthquake excitations were considerably poorer. The worst results with strong increase in tip accelerations were recorded under the San Fernando earthquake. both structures revealed a regular increase in tip deflection reductions when the dampers were moved from the bottom towards the top of the stucture. As mentioned previously tip acceleration reduction for the 12-storey structures embedded with the chevron brace friction dampers were considerably poor with adequate results achieved only under the Kobe earthquake. the dampers fitted in the 12-storey structure were more effective under the other earthquakes. in terms of tip acceleration reduction. The dampers displayed a slightly lower level of sensitivity to the placement and a relatively higher consistency than the diagonal dampers. with the reductions experienced by the same dampers embedded in the 18-storey frameshear wall structure. In contrast. the efficiency of the chevron brace friction dampers was considerably poorer with a significant increase in tip acceleration in a majority of the cases. Nevertheless. did not represent any significant decrease in structural safety/performance and these dampers were efficient in reducing tip deflection and hence improve overal structural performance. Influence of Damping Systems on Building Structures Subject to Seismic Effects 6.15 20 Acceleration (m/s2) 0. once again.38. the dampers.15 Tip Acceleration (El Centro earthquake) 2 0 -2 0 5 10 15 20 -4 -6 -0. whereas. Northridge and San Fernando earthquakes were also adequately high. as it can be observed from this graphs. in both placements.25 -8 1-2 Time (s) 1-2 Time (s) 9-10 9-10 Fig. obtained by the dampers placed in the upper storeys.5 Chevron brace VE dampers The results of the tip deflection and tip acceleration reductions experienced by the structures fitted with the chevron brace VE damper are presented below.95% was obtained under the Kobe earthquake.05 0 -0.05 0 5 10 15 -0. are illustrated in Fig.1 -0. respectively.2. 6. This figure illustrate significant reduction in tip deflection experienced by the dampers fitted in the upper storeys. Time history responses of tip deflection and tip acceleration under the El Centro earthquake in the undamped structure and in the structures with the chevron brace VE dampers placed in storeys 1 and 2. The average tip deflection reductions occurred under the El Centro.2 UN UN -0. 6. and 9 and 10. Tip Deflection (El Centro earthquake) 6 0. however. 6. In terms of tip acceleration response the better results were.Tip deflection and acceleration responses of the structures with different placement of the chevron brace VE dampers under the El Centro earthquake The results of the percentage reductions in the peak values of the tip deflection experienced by the structures fitted with the chevron brace VE damper are illustrated in Fig. were not able to reduced intensity of tip acceleration related to initial strong motions. whereas the performance of the damper occurred under the 220 .1 4 Deflection (m) 0. the dampers remained rather ineffective when fitted in the lowest storeys. The highest average tip deflection reduction of 14.37. The damper revealed an adequately high overall performance.37. Fernando -4 Earthquake Records Fig. 6. 8. 8. This trend occurred under the El Centro.26 Avg. 6.38 – 12 storey structure embedded with 1 chevron brace VE damper -percentage reductions in tip deflection under different earthquake records Fig. -0.45 % Deflection Reductions 15 EC HA KO NO SF Avg 3 0 1 2 3 4 5 6 -3 Placement of the Dampers Fig. whereas in the case of the Kobe earthquake reverse trend can be observed.40. 9. 9. The best performance with 221 . 18 6 Avg. 6.51 12 Avg. 6. 7.95 20 1 Avg.82 Avg. Avg.61 8 3 5 7 9 Avg.39 – 12 storey structure embedded with 1 chevron brace VE damper -percentage reductions in tip deflection for different placements Tip deflection reductions experienced by the same structures fitted with two chevron brace VE dampers are displayed in Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects Hachinohe earthquake was obviously poor with insignificant results in all the placements. 8.96 Avg.56 9 Avg.39 shows relatively regular increase in damper efficiency when the damper was moved from bottom to the top of the structure. 6. 14. Northridge and San Fernando earthquakes. 5.37 Avg.98 12 Avg. 6.24 % Deflection Reductions 16 4 0 El Centro 11 Avg Hachinohe Kobe Northridge S. 17 20 Avg. This overall trend was clearly demonstrated under the El Centro. 9.97 Avg. 13. Northridge and San Fernando earthquakes were also reasonably high. whereas the tip deflection reductions obtained under the Hachinohe and Kobe earthquakes were rather constant throughout all the placements. 6. Avg. 30 Avg. 10. 11.98 1-2 Avg.37 % Deflection Reductions 21 Avg. 18. once again. 6. The reductions occurred under the El Centro.18% was achieved under the Kobe earthquake.04 Avg. Northridge and San Fernando earthquakes.13 % Deflection Reductions 25 EC HA KO NO SF Avg 5 0 1-2 3-4 5-6 7-8 9-10 11-12 -5 Placement of the Dampers Fig. 12. 6.Fernando -7 Earthquake Records Fig.33 Avg. 9. whereas the reductions recorded under the Hachinohe earthquake were.Influence of Damping Systems on Building Structures Subject to Seismic Effects an average reduction of 18.07 15 10 Avg. The dampers experienced a gradual increase in efficiency when were moved from the bottom to the top of the structures. 14. 2.18 28 7 3-4 5-6 7-8 9-10 11-12 Avg 0 El Centro Hachinohe Kobe Northridge S.41 shows the results of tip deflection reduction in the different damper placements.40 – 12 storey structure embedded with 2 chevron brace VE dampers -percentage reductions in tip deflection under different earthquake records Fig.23 14 Avg. only minuscule. 6.84 Avg. 14.41 – 12 storey structure embedded with 2 chevron brace VE dampers -percentage reductions in tip deflection for different placements 222 . Influence of Damping Systems on Building Structures Subject to Seismic Effects The results of tip acceleration reduction for the 12-storey structure embeded with the chevron brace VE damper are illustrated in Fig. -4.93 Avg. -21. in this case.90 Avg. 6.75 % Acceleration Reductions 15 NO SF Avg -45 1 3 5 7 9 11 -60 Placement of the Dampers Fig.02 30 EC KO Avg. the increase in tip acceleration to a level. -1. -7.Fernando Avg. lower than 5 m/s2 did not represent any decrease in structural safety/performance.58 0 Avg.25 % Acceleration Reductions 15 Avg -60 Earthquake Records Fig. However.19 -15 HA Avg.02 -15 -30 Avg. Avg.02% was experienced under the San Fernando earthquake. 6.66 0 Avg. The poorest results with a massive increase in average tip acceleration by 36.43 – 12 storey structure embedded with 1 chevron brace VE damper -percentage reductions in tip acceleration for different placements 223 .42 – 12 storey structure embedded with 1 chevron brace VE damper -percentage reductions in tip acceleration under different earthquake records Fig. -1. On the other hand.42. -20. 6. -36. unfavoreable results with increase in tip acceleration were recorded under the other earthquake excitations. The reductions occurred under the Kobe earthquake were very consistent and adequately high. 30 1 3 Avg.22 -30 Avg.36 5 7 9 11 -45 El Centro Hachinohe Kobe Northridge S. 17.43 shows the same results in terms of different damper placements. -14. -17. 6. 0. with an increase in the average tip acceleration by 36. 6. adequately high. while their repositioning towards the top or bottom of the structure caused gradual increase in tip acceleration.44 illustrates tip acceleration reduction for the 12-storey structure embedded with two chevron brace VE dampers. which occurred under the other earthquake excitations. were evidently poor. observed under the El Centro and San Fernando earthquakes. 6. whereas the reverse trend occurred under the Kobe earthquake. the results. -36. This pattern can be. The acceleration reductions under the Kobe earthquake were. nevertheless. when the damper was moved towards the top or bottom of the structure. 6. yet again. 30 3-4 5-6 7-8 Avg. However. -8. Fig. 14. this increase did not influence the level of the structural safety. This trend can be observed under the El Centro and San Fernando earthquakes. Clearly the poorest result.60 -45 1-2 Avg. -4. the trends experienced under the other earthquake excitations were more complex. Fernando -90 Earthquake Records Fig.55 0 Avg. was experienced under the San Fernando earthquake.6%.12 % Acceleration Reductions 15 -60 9-10 11-12 Avg -75 El Centro Hachinohe Kobe Northridge S.26 -15 Avg.45). this increase was the lowest when the damper was placed in the 3rd storey and a gradual increase was experienced. the lowest acceleration increase was recorded when the dampers were placed in storeys 5 and 6. In the cases of the Hachinohe and Northridge earthquakes no particular trend were recognised. yet again. 224 .44 – 12 storey structure embedded with 2 chevron brace VE dampers -percentage reductions in tip acceleration under different earthquake records In terms of damper placement (Fig. -14. whereas.16 -30 Avg. Nevertheless.Influence of Damping Systems on Building Structures Subject to Seismic Effects High increase in tip acceleration was recorded in the vast majority of placements. -1. -26. -8. However. In contrast.71 -30 EC Avg. yet again. 225 .45 – 12 storey structure embedded with 2 chevron brace VE dampers -percentage reductions in tip acceleration for different placements Chevron brace VE dampers embedded in 12-storey frame-shear wall structure were investigated in this section. In contrast. achieved under the Kobe earthquake excitations. The results of both investigated parameters were very close to those of chevron brace friction dampers.85 Avg. Prime such feature was a regular increase in performance when the dampers were moved from the bottom towards the top of the structure. -3. This can be observed under the El Centro. the highest and most consistent tip deflection reductions were.57 % Acceleration Reductions 15 -45 KO NO SF Avg -60 -75 1-2 -90 3-4 5-6 7-8 9-10 11-12 Placement of the Dampers Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects 30 HA Avg. 6.30 0 Avg. -12. the results obtained under the other earthquake excitations were an obviously poor. In terms of damper placement some features more common for friction dampers were experienced. The tip acceleration reductions occurred under the Kobe earthquake excitation were adequately high and consistent. were improving overal structural performance.23 -15 Avg. In terms of tip deflection reduction the dampers experienced a high overall performance. even this poor result did not influence the level of the structural safety and the dampers. The worst result with a strong increase in tip acceleration was recorded for the San Fernando earthquake. The results of tip acceleration reduction experienced by the 12-storey structure fitted with the chevron brace VE dampers were noticeably poorer. The dampers similarly to chevron brace friction dampers remained rather ineffective under the Hachinohe earthquake. -5.64 Avg. efficient in reducing tip deflection. Northridge and San Fernando earthquakes. The tip acceleration reduction obtained by the 18-storey structure embeded with the same dampers were. the dampers embedded in the 18-storey structure were obviously more effective under the Hachinohe earthquake. both structures revealed a regular increase in tip deflection reductions when the dampers were moved from the bottom towards the top of the stucture. under the other earthquake excitations no common trends were experienced. inconsistent and mostly insignificant. what was in contrast with a high acceleration reductions obtained by the diagonal dampers. In the cases of the El Centro and Northridge earthquakes. In contrast. evidently better than those of the12-storey structure. except for the El Centro earthquake.Influence of Damping Systems on Building Structures Subject to Seismic Effects Tip deflection reductions experienced by the chevron brace VE dampers embedded in the 12-storey structure were adequately high compared to those of the diagonal friction or diagonal VE dampers. 6.2. however. with the reductions recorded for the chevron brace VE dampers embedded in the 18-storey frameshear wall structures. 226 . chevron brace VE dampers were more consistent and less sensitive to damper placements. when adequate results occurred only under the Kobe earthquake. In terms of tip acceleration reduction. moreover. Tip acceleration reduction obtained by the 12-storey structure embedded with chevron brace VE dampers were unfavourable. On the other hand. While comparing tip deflection reductions experienced by the chevron brace VE dampers fitted in the 12-storey frame-shear wall structures. the chevron brace VE dampers experienced unfavourable results.6 Hybrid friction-VE dampers The results of the tip deflection and tip acceleration reductions experienced by the structures fitted with the hybrid friction-VE dampers are presented below. the dampers embedded in the 12-storey structure were more effective under the other earthquakes. 1 Defletion (m) 0 0 5 10 15 20 -0.69 3 Avg.46 shows time history responses of tip deflection and tip acceleration under the El Centro earthquake in the undamped structure and in the structures with hybrid friction-VE dampers placed in storeys 1 and 2. nevertheless. 6.1 Acceleration (m/s2) 4 0. however.Fernando -6 Earthquake Records Fig.Influence of Damping Systems on Building Structures Subject to Seismic Effects Fig. Tip Deflection (El Centro earthquake) 0. and 9 and 10.03 6 Avg. The best performance with average reduction of 11.47 – 12 storey structure embedded with 1 hybrid friction-VE damper -percentage reductions in tip deflection under different earthquake records 227 . 4. The reductions occurred under the other earthquakes were noticeably lower and without any significant results.81 % Deflection Reductions 18 7 9 11 Avg 0 El Centro Hachinohe Kobe Northridge S. the dampers fitted in both placements only slightly reduced intensity of acceleration related to initial strong motions.25 Time (s) 1-2 Time (s) 9-10 9-10 Fig.46 Tip deflection and acceleration responses of the structures with different placement of the hybrid friction-VE dampers under the El Centro earthquake The results of the tip deflection reduction for the structure embedded with the hybrid friction-VE damper are presented in Fig. 6.05 Tip Acceleration (El Centro earthquake) 6 2 0 -2 0 5 10 15 20 -0.17 12 1 Avg.69% was achieved under the El Centro earthquake. respectively.47.2 UN UN -6 1-2 -0. 6. the better results was. also. tip deflection reduction obtained by the dampers placed in the lower storeys was slightly higher. The graph illustrates substantial reduction in tip deflection obtained by the dampers in both placements. displayed for the dampers placed in the lowest storeys.15 -4 -0. 11. 3.15 0. In terms of tip acceleration. 4. 5.81 5 Avg.05 -0. 24 Avg. 6. 6. once again. Adequately high reductions were also experienced under the Kobe earthquake.48 – 12 storey structure embedded with 1 hybrid friction-VE damper -percentage reductions in tip deflection for different placements The percentage reductions in the peak values of the tip deflection experienced by the structures fitted with two hybrid friction-VE dampers are illustrated in Fig.15 12 Avg. The highest overall tip deflection reduction occurred when the damper was embedded in the 3rd storey and the reductions regularly decreased as the damper was moved towards the top or bottom of the structure. the dampers experienced relatively high and very consistent performance. 4. In general. 7. 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects The same results in terms of efficiency of the damper in different placements are presented in Fig.49. the poorest result occurred when the damper was placed in the 5th storey and a regular increase in tip deflection reduction occurred as the damper was moved towards the top or bottom of the structure. 228 . The performance of the dampers under the other earthquakes was noticeably poorer and the lowest average reduction of 6. The best results were. In the case of the Kobe earthquake. 6.48. 5. 6.5% was recorded under the Northridge earthquake excitation. reverse trend was experienced.54 EC Avg. This trend can be observed under the Hachinohe and El Centro earthquakes.35%.00 Avg. 24 Avg.76 % Deflection Reductions 18 KO NO SF Avg 0 1 3 5 7 9 11 -6 Placement of the Dampers Fig. 6.78 Avg.16 6 HA Avg. recorded under the El Centro earthquake with an average tip deflection reduction of 18. 6. while under the Northridge and San Fernando earthquake excitations. 05 10 Avg. 12. 18. the dampers fitted in the lower storeys were slightly more efficient.50 – 12 storey structure embedded with 2 hybrid friction-VE dampers -percentage reductions in tip deflection for different placements 229 .Influence of Damping Systems on Building Structures Subject to Seismic Effects 35 Avg. 12.Fernando -5 Earthquake Records Fig. while.49 – 12 storey structure embedded with 2 hybrid friction-VE dampers -percentage reductions in tip deflection under different earthquake records In terms of efficiency of the dampers in different placements. the results presented in Fig.25 EC Avg.52 % Deflection Reductions 30 HA KO NO SF Avg 5 0 1-2 3-4 5-6 7-8 9-10 11-12 -5 Placement of the Dampers Fig. 7.45 20 1-2 Avg.29 20 Avg. Nevertheless. in the case of the Northridge and San Fernando earthquakes reverse trend was experienced. 10. 9. 12.47 % Deflection Reductions 30 7-8 9-10 11-12 Avg 5 0 El Centro Hachinohe Kobe Northridge S.41 15 3-4 Avg.45 Avg. 6. 9. 6.50 show a consistent performance for the dampers fitted in the all placements. 6.58 25 Avg.55 15 Avg. 9. 11.35 10 5-6 Avg. 6. The tip deflection reductions obtained under the El Centro and Kobe earthquakes increased progressively as the dampers were moved from the top to the bottom of the structures. 35 25 Avg. The tip deflection reductions occurred under the Hachinohe earthquake were relatively constant. 16 20 10 3 Avg. 6. Avg.45 % Acceleration Reductions 30 Hachinohe Kobe Northridge 11 Avg S.22 Avg. 3.77 Avg. Northridge and San Fernando earthquakes were in the vast majority of the cases only miniscule. The best result with the greatest average tip acceleration reduction of 17.51 – 12 storey structure embedded with 1 hybrid friction-VE damper -percentage reductions in tip acceleration under different earthquake records Fig.94 Avg. 17. 3.52 – 12 storey structure embedded with 1 hybrid friction-VE damper -percentage reductions in tip acceleration for different placements 230 . 6.42 1 5 7 9 -10 El Centro Avg.51.Fernando -20 Earthquake Records Fig.37 0 Avg. -6. The poorest results with increase in tip acceleration.16% was obtained under the Hachinohe earthquake. the tip acceleration reductions occurred under the Kobe. 3.27 Avg.66 20 EC HA KO NO SF Avg Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects The results of tip acceleration reduction for the structure embedded with the hybrid friction-VE damper are presented in Fig. -2. was experienced under the El Centro earthquake excitation. 6. 6.01 10 Avg. 6. 0 Avg. 4. -3. 6.52 presents the results of the same structure in terms of tip acceleration reduction in different damper placements. In contrast.66 % Acceleration Reductions 30 -10 1 3 5 7 9 11 -20 Placement of the Dampers Fig. -0. In the case of the El Centro earthquake. In the case of the Northridge earthquake the lowest reduction occurred. the lowest reduction was recorded when the damper was placed in the 1st storey.13 Centro and San Fernando earthquakes. the least effective placement was in the top storeys. Finally. Fig. 19.88 Avg. -1.53 – 12 storey structure embedded with 2 hybrid friction-VE dampers -percentage reductions in tip acceleration under different earthquake records The highest average tip acceleration reductions occurred when the dampers were installed in the storeys 3 and 4. The same trend was experienced under the Hachinohe earthquake and partly under Kobe earthquake. the range of the particular results for different placements was inconsistent and no obvious trends were recognised. In contrast.Fernando Avg.53 presents the percentage reduction in tip acceleration for the same structure fitted with two hybrid dampers. 231 .Influence of Damping Systems on Building Structures Subject to Seismic Effects The highest average reductions occurred when the damper was placed in the 9th storey. yet again. Nevertheless.42 % Acceleration Reductions 24 Avg. The highest average reduction of 19. The reductions under the Northridge and Kobe earthquakes were noticeably lower. the dampers were effective only in the lowest storeys. 6. 10.62 32 Avg. once again.85 8 1-2 3-4 5-6 7-8 9-10 11-12 0 -8 El Centro Hachinohe Kobe Northridge S. while the highest reduction was obtained when the dampers were placed in storeys 9 and 10. 9. Avg -16 Earthquake Records Fig. although still adequately high. for the highest storey placement. 6. The lowest tip acceleration reductions occurred under the El 16 Avg. 1. while.62% occurred. the tip acceleration reductions obtained under the San Fernando earthquake were inconsistent and without any obvious trends. under the Hachinohe earthquake. 9.07 Avg. their efficiency in the lower storeys was slightly higher.87 % Acceleration Reductions 24 Avg. respectively. 10. and 9 and 10. while the structure with two dampers placement obtained the highest tip acceleration reductions when the dampers were placed in storey 3 and 4. 9.54 – 12 storey structure embedded with 2 hybrid friction-VE dampers -percentage reductions in tip acceleration for different Hybrid friction-VE dampers embedded in the 12-storey frame-shear wall structure were investigated in this section.87 16 Avg. while the poorest reductions were experienced under the Northridge earthquake.31 Avg. a number of different features experienced under all earthquake excitations can be observed. 6. the greatest reductions were achieved under the Hachinohe earthquake.61 32 0 KO NO SF Avg -8 -16 1-2 3-4 5-6 7-8 9-10 11-12 Placement of the Dampers Fig. while the reductions experienced under the El Centro and San Fernando earthquakes were relatively poor. nevertheless. 12. 4. In terms of tip acceleration reductions. the structure embedded with one damper experienced the best results when the damper was placed in the 9th or 11th storey. The dampers revealed a consistent performance in all placements. While comparing the performance of the hybrid friction-VE dampers embedded in the 12-storey frame-shear wall structures with the performance of the same dampers embedded in 18-storey frame-shear wall structures.Influence of Damping Systems on Building Structures Subject to Seismic Effects 8 EC HA Avg. In terms of 232 . The dampers experienced consistent and reliable performance under all excitations. The highest tip deflection reductions occurred under the El Centro earthquake. In terms of tip acceleration reduction in different placements. 1.34 Avg. the hybrid dampers experienced tip deflection and tip acceleration reductions. The results for hybrid friction-VE dampers embedded in the 12-storey structure were relatively close to those of the 12-storey structure fitted with the VE diagonal dampers. The dampers embedded in the 18-storey structure obtained clearly the highest tip acceleration reductions when placed in storeys 4 to 6. that whereas. With regards to damper placements both types of the structures experienced similar trends under the Kobe earthquake and partially under the Northridge earthquake. which were close to average under the all earthquake excitations. it can be suggested. while the trends occurred under the Hachinohe earthquake were without any common features. the dampers embedded in the 18-storey structure obtained higher tip acceleration reductions under the San Fernando and El Centro earthquake excitations. Hachinohe and Kobe earthquake excitations In contrast. While comparing the hybrid friction-VE dampers with the other damping systems embedded in the 12-storey structure. rather reverse trends were experienced under the El Centro and San Fernando earthquakes. Based on the presented results. the VE part of the hybrid damper operated appropriately. while the dampers embedded in the 12-storey structure experienced relatively constant reductions in most of the placements. diversity in results experienced by both types of structures was even higher and no common features were observed under any earthquake excitations. In terms of tip acceleration reductions.Influence of Damping Systems on Building Structures Subject to Seismic Effects tip deflection reductions the dampers embedded in the 12-storey structures performed better under the El Centro. On the other hand. In contrast. the dampers embedded in the 18-storey structures performed slightly better under the Northridge and San Fernando earthquakes. the friction part remained less effective. The dampers embedded in the 12-storey structure achieved higher tip acceleration reductions under the Hachinohe and Kobe earthquake excitations. The high efficiency of the diagonal VE part and the low efficiency of the chevron brace friction part of the hybrid damper in the 12-storey structure were in contrast to the results of the hybrid friction-VE damper fitted in 233 . 1 -0.55 – Tip deflection and acceleration responses of the structures with different placement of the lower toggle VE dampers under the El Centro earthquake The graphs illustrate good performance of the dampers in both placements and in both investigated parameters. Tip Deflection (El Centro earthquake) Tip Acceleration (El Centro earthquake) 6 0.25 Time (s) UN -6 1-2 9-10 Time (s) 1-2 9-10 Fig. A contrast in performances makes it obvious that creating a highly effective hybrid friction-VE damper is rather complex and so requires a more comprehensive study.1 Deflection (m) 0 -0. The 234 .2 UN -0.05 2 0 0 5 10 15 20 -2 -4 -0. 6. and 9 and 10. are illustrated in Fig. 6. The tip deflection reductions for the structure embedded with the lower toggle VE damper placed at 6 different locations are presented in Fig. As can be seen in this figure. Time history responses of tip deflection and tip acceleration under the El Centro earthquake in the undamped structure and in the structures with the lower toggle VE dampers placed in storeys 1 and 2. 6.15 0. respectively.05 0 5 10 15 20 -0.2. 6.55. clearly better result occurred for the structure with the dampers placed in the lowest storeys. In terms of peak value of tip deflection.56. while in terms of peak value of tip acceleration slightly better results were experienced by the structure with the dampers placed in the upper storeys.7 Lower toggle VE dampers The results of the tip deflection and tip acceleration experienced by the structures fitted with lower toggle VE dampers are presented in this section.Influence of Damping Systems on Building Structures Subject to Seismic Effects the 18-storey frame-shear wall structures (where only the chevron brace friction dampers operated effectively). the damper revealed very high and consistent performance.15 Acceleration (m/s2) 4 0. 8.93 Avg. similarly narrow range of average tip deflection reductions can be observed for the three upper placements.54 HA Avg. The reductions obtained under the other earthquakes were also adequately high and consistent. 6. 7.19 % Deflection Reductions 25 KO NO SF Avg 5 0 1 3 5 7 9 11 Placement of the Dampers Fig. 8. 6. 10.29 1 3 Avg. 20 Avg. 9.Influence of Damping Systems on Building Structures Subject to Seismic Effects highest average tip deflection reduction of 15. 10.Fernando Earthquake Records Fig.47 10 Avg. In the case of the El Centro. 10.29% occurred under the El Centro earthquake. 7.57 – 12 storey structure embedded with 1 lower toggle VE damper -percentage reductions in tip deflection for different placements The average tip defection reduction for the lower three damper placements were exceptionally close.10 15 Avg.96 20 Avg.71 EC Avg. 7.86 % Deflection Reductions 25 7 9 11 Avg 5 0 El Centro Hachinohe Kobe Northridge S. 6.57 shows the result for tip deflection reduction in terms of different placements. 6. These close ranges were based on two reverse trends. Hachinohe and 235 . Avg.30 15 Avg.56 – 12 storey structure embedded with 1 lower toggle damper -percentage reductions in tip deflection under different earthquake records Fig. 15.21 10 5 Avg. In addition. the dampers performed 236 . in the cases of the Northridge and San Fernando earthquake excitations rather reverse trend was experienced. The tip deflection reductions recorded under the Northridge and San Fernando earthquakes gradually increased when the dampers were moved from the bottom to the top of the structures.83 % Deflection Reductions 30 5-6 7-8 9-10 11-12 Avg 6 0 El Centro Hachinohe Kobe Northridge S.86%. On the other hand. 36 12 Avg. nevertheless.83% was achieved under the El Centro earthquake. 13. represented value of 11. 21.69 24 Avg. In the case of the Kobe earthquake.Influence of Damping Systems on Building Structures Subject to Seismic Effects partially Kobe earthquakes the highest tip deflection reductions occurred for the lowest storey placement and the reductions were decreased as the damper was moved towards the top of the structure. whereas under the El Centro earthquake the reverse trend occurred. when even the lowest average reduction. the reductions obtained by the structure with the dampers fitted in the other placements were also very high. The dampers exhibit a high and consistent performance. occurred under the Northridge earthquake. 11. 6.58 – 12 storey structure embedded with 2 lower toggle dampers -percentage reductions in tip deflection under different earthquake records In terms of efficiency of the dampers in different placements (Fig. the highest average tip deflection reduction occurred for the structure with dampers fitted in storeys 3 and 4. The percentage reduction in tip deflection for structures fitted with two lower toggle VE dampers are presented in Fig.82 Avg.86 18 1-2 Avg.69 3-4 Avg. The high average deflection reductions were also obtained under the other earthquakes.Fernando Earthquake Records Fig. 13.59). The highest average reduction of 21. 6.58. 6. 18. Avg. the reductions occurred under the San Fernando earthquake were rather unfavourable.74 32 3 5 Avg. On the other hand. 6. 7.50 24 Avg. -4. 21.50 Avg.41 18 Avg. 14. 6. 16. 0.36 Avg.26 % Acceleration Reductions 24 Hachinohe Kobe Northridge S Fernando -16 Earthquake Records Fig.91 Avg.65 % Deflection Reductions 30 HA KO NO SF 12 Avg 6 0 1-2 3-4 5-6 7-8 9-10 11-12 Placement of the Dampers Fig. 36 EC Avg.74% was achieved under the Hachinohe earthquake.60 shows the results of tip acceleration reduction for structure embedded with the lower toggle VE damper.Influence of Damping Systems on Building Structures Subject to Seismic Effects significantly better in the lower storeys.60 – 12 storey structure embedded with 1 lower toggle damper -percentage reductions in tip acceleration under different earthquake records The greatest average tip acceleration reductions of 21. 15. 6.59 – 12 storey structure embedded with 2 lower toggle VE dampers -percentage reductions in tip deflection for different placements Fig. 18. the performance was rather consistent for all the placements.06 8 Avg. The tip acceleration reductions obtained under the Kobe and Northridge earthquakes were still relatively high. 15. 14. 237 . while under the Hachinohe earthquake.90 Avg.46 1 16 0 7 9 11 Avg -8 El Centro Avg. 7. 21 % Acceleration Reductions 24 HA KO NO SF 0 Avg 1 3 5 7 9 11 -8 -16 Placement of the Dampers Fig. 3. 6. 11. 2. the poorest results with slight increase in tip acceleration was experienced under the El Centro earthquake excitation.50 Avg. 7.62.Influence of Damping Systems on Building Structures Subject to Seismic Effects Surprisingly. As can be seen from Fig.61 the highest tip acceleration reductions occurred when the damper was fitted in the 9th storey.35 EC Avg. 6.Fernando Avg. 5. -3. 8.79 40 Avg.61 – 12 storey structure embedded with 1 lower toggle VE damper -percentage reductions in tip acceleration for different placements The percentage reductions in tip acceleration for the structures embedded with 20 Avg.41 Avg. 6. whereas the tip acceleration reductions obtained for the other damper placements were clearly less significant. Adequately high reductions were also achieved when the damper was fitted in storey 3 or 5.98 10 1-2 3-4 5-6 0 7-8 -10 El Centro Hachinohe Kobe -20 Northridge S. 32 Avg. 6.62 – 12 storey structure embedded with 2 lower toggle dampers -percentage reductions in tip acceleration under different earthquake records 238 . 17. 21.87 8 Avg.43 % Acceleration Reductions 30 Avg.90 two lower toggle VE dampers are presented in Fig. 13. 9-10 11-12 Avg -30 -40 Earthquake Records Fig.64 16 Avg. 4.34 Avg. With regards to tip acceleration reductions. in the cases of the El Centro 239 . However. However.63 shows the results of structural tip acceleration reduction in terms of different damper placements. 19. The reductions occurred under the Kobe and Northridge earthquakes were also very high.85 % Acceleration Reductions 30 Avg.34 40 0 EC HA KO NO SF -10 1-2 3-4 5-6 7-8 9-10 11-12 Avg -20 -30 -40 Placement of the Dampers Fig. 21. when the dampers were placed in the uppermost storeys. 10 Avg. Based on previous results. 16.13 Avg. the reductions obtained under the other earthquake excitations were also significantly high. The tip acceleration reductions for the structure with the dampers fitted in the lower storeys were also very high.4% increase occurred under the San Fernando earthquake to significant 21.32 20 Avg. The average tip acceleration varied from a 3. Fig. The dampers revealed very high and consistent performance.8% tip acceleration reduction obtained under the Hachinohe earthquake. the highest damper efficiency was achieved under the El Centro earthquake. while. 6. 17. the greatest reductions were achieved under the Hachinohe earthquake.Influence of Damping Systems on Building Structures Subject to Seismic Effects The dampers produced significant overall tip acceleration reduction. In terms of tip deflection reduction. On the other hand. 6.66 Avg. 9. a wide range of results was experienced. a significant increase in average tip acceleration was experienced.03 Avg. in contrast. The highest average reduction occurred when the dampers were fitted in storeys 9 and 10. it is obvious that this acceleration increase was caused by decrease in top storey stiffness due to cut out. -18.63 – 12 storey structure embedded with 2 lower toggle VE dampers -percentage reductions in tip acceleration for different placements The lower toggle VE dampers embedded in the 12-storey structure were investigated in this section. yet again. substantial reductions were 240 . The 12-storey structure experienced the highest tip deflection reduction under the El Centro earthquake. whereas the performances of the 18-storey structures were rather unreliable. Kobe and Northridge earthquake excitations and their performance obtained under the El Centro earthquake was only slightly lower than it was for the diagonal friction and diagonal VE dampers. recorded. In the case of the San Fernando earthquake. high tip deflection reduction was. In terms of reduction in the peak values of tip deflection. the results were inconsistent with a strong increase in tip acceleration for the uppermost storeys placement.2. The result presented in this section confirmed superiority of the lower toggle VE dampers among all investigated damping systems embedded in the 12-storey structure.8 Summary of findings in the 12-storey structure The results from the 12-storey frame-shear wall structure embedded with the six different damping systems installed in twelve different placements were investigated in this chapter. In the case of the 18storey structures reverse results were experienced. whereas its tip acceleration reductions under this earthquake excitation were rather insignificant. In the 18-storey structures tip deflection reductions obtained under the San Fernando earthquake were gradually decreasing when the dampers were moved towards the top of the structure. In the case of the 12-storey structures reverse trends can be observed. while under the El Centro earthquake reverse trend was recorded. While comparing these results with the results obtained by the lower toggle VE dampers fitted in the 18-storey frame-shear wall structures some different features can be observed. The lower toggle VE dampers experienced the highest performance in both investigated parameters under the Hachinohe.Influence of Damping Systems on Building Structures Subject to Seismic Effects and San Fernando earthquakes. 6. which is primary investigated parameter. while in terms of tip acceleration reduction poor results were experienced. The 12-storey structures treated under the Hachinohe earthquake revealed a high and consistent performance in both investigated parameters. 5.Influence of Damping Systems on Building Structures Subject to Seismic Effects obtained.64-6. however. The reductions for the hybrid damping system were comparable to those of the other damping systems.32 16 Avg. the friction part of this damping system was less effective. in few cases this remained rather ineffective. In terms of tip acceleration reduction the range of the results was noticeably wide and some unfavourable results were experienced.84 16 Avg.68 12 Avg. Slightly lower overall deflection reductions for the chevron brace friction dampers and chevron braced VE dampers than those of the diagonal friction dampers were due to their poor performances under the Hachinohe earthquake.9 Avg.58 % Deflection Reductions are shown in Figs.Average percentage tip deflection reductions for all damping systems in all (1 damper) placements 241 . The overall results for the all damping systems embedded in the 12-storey frameshear wall structure in terms of reduction in the peak values of the tip deflection 14 14 8 6 Avg.64 . even this increase in tip acceleration did not represent any decrease in structural safety/performance and these dampers were efficient in reducing tip deflection. 7. The highest tip deflection reductions and the most consistent performances were recorded for the lower toggle VE dampers. whereas the VE part of hybrid damping system operated effectively. The widest range of results was displayed for the diagonal VE dampers. 6. their overall reduction also remained at a satisfactory high level. and in improving overal structural performance. 6. 9. nevertheless. 4.27 10 Avg. The tip deflection reductions for the diagonal friction dampers were generally comparable to those of the lower toggle VE dampers.71. its results suggested that. However. nevertheless. 9. 12 10 8 6 4 4 2 2 0 1 3 5 7 9 11 Avg 0 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle Damping Devices Fig. 9. Fernando -3 Earthquake Records Fig.18 15 15 6 Avg. 9. 7.36 12.66 . 13.91 20 17.5 Avg.84 Avg.67 . 6. 8.Average percentage tip deflection reductions for all damping systems (1 damper placement) under different earthquake excitations 10 8 6 6 4 4 2 2 0 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle Avg 0 1 3 5 7 9 11 Placements of the Dampers Fig.32 18 Avg.80 Avg.27 12 Avg. 4.90 Avg.89 Avg. 8.5 Diag VE 10 Chev FR Chev VE 8 Hybrid 5 Toggle 3 0 Diag FR 13 Avg 0 El Centro Hachinohe Kobe Northridge S. 7. 6. 3. 5.18 12 Avg. 9.67 9 Avg.Average percentage tip deflection reductions for all damping systems in term of damper placements 18 10 7.65 .27 % Deflection Reductions 15 20 Avg. 9.5 -2.58 % Deflection Reductions Influence of Damping Systems on Building Structures Subject to Seismic Effects 12 9 6 3 3 0 EC HA KO NO SF Avg 0 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle -3 -3 Damping Devices 16 14 14 8 12 Avg.52 % Deflection Reductions Fig. 6. 7. 9.27 15 Avg.Average percentage tip deflection reductions of all damping systems under variety of earthquake excitations 242 . 6. 8. 7.5 2.5 5 Avg. 5.13 10 Avg.08 16 Avg.01 Avg. 85 Avg.84 Avg.72 % Deflection Reductions 18 Avg.Average percentage tip deflection reductions for all damping systems (2 dampers placement) under different earthquake excitations 18 15 12 Diag FR Diag VE Chev FR Chev VE 9 9 6 6 3 3 0 Hybrid Toggle Avg 0 1-2 3-4 5-6 7-8 9-10 11-12 Placement of the Dampers Fig. 11.29 21 Avg. 14.12 12 Avg. 15. 6.22 21 Avg.98 Avg.98 30 Avg.77 % Deflection Reductions 18 Avg. 13.Influence of Damping Systems on Building Structures Subject to Seismic Effects 21 Avg. 6.84 30 Avg. 11.70 . 11. 6.72 20 Avg. 13. 13. 12. 13. 10. 13. 15.70 % Deflection Reductions Fig. 11.68 . 14.70 21 18 15 12 1-2 3-4 5-6 7-8 9 9 6 6 3 3 0 9-10 11-12 Avg 0 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle Damping Devices 25 25 Avg.Average percentage tip deflection reductions for all damping systems in all (2 dampers) placements 20 15 10 10 5 5 0 EC HA KO NO SF Avg 0 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle Damping Devices 12 Avg.88 15 Avg. 10.Average percentage tip deflection reductions for all damping systems in terms of damper placements 243 . 9.69 .12 15 Avg.84 15 Avg.21 Fig.85 Avg. 15. However. 22. 244 .54 % Deflection Reductions 25 30 Avg. The tip acceleration reductions of the diagonal friction dampers were uneven and in many cases rather insufficient.79. The reductions for the hybrid friction-VE damper were generally high. the results in terms of the peak values of tip acceleration reduction were considerably poorer. 11. except for the El Centro and San Fernando earthquakes. The poorest results with high increase in tip acceleration were recorded for the chevron brace VE dampers and chevron brace friction dampers. 6.Fernando Earthquake Records Fig.21 Avg. all damping systems performed exceptionally well. 6. which performed effectively only under the Kobe earthquake. 14.Average percentage tip deflection reductions for all damping systems under variety of earthquake excitations While in terms of tip deflection reduction for the 12-storey structures. The highest reductions were recorded for the lower toggle VE dampers.71 . 10. where slight increases in acceleration were recorded. The overall results of all damping systems for the 12-storey frame-shear wall structure in terms of reduction in the peak values of the tip acceleration are illustrated in Figs.72 25 Diag FR 15 10 20 Avg. even these dampers remained unreliable under the San Fernando earthquake.08 30 Diag VE Chev FR 15 Chev VE Hybrid 10 Toggle Avg 5 5 0 0 El Centro Hachinohe Kobe Northridge S. The reductions for the diagonal VE dampers were rather uneven with an increase of tip accelerations under the Northridge earthquake.72-6.64 20 Avg. 6.Influence of Damping Systems on Building Structures Subject to Seismic Effects Avg. 1. 6. -14.47 Avg.79 -30 Avg. 2.96 10 Avg.01 5 Avg.72 .16 0 5 Avg.16 30 Avg.Average percentage tip acceleration reductions for all damping systems in terms of damper placement 245 .54 15 Avg.84 % Acceleration Reductions Fig.48 15 Avg.99 5 Avg. 1. -9.56 % Acceleration Reductions Influence of Damping Systems on Building Structures Subject to Seismic Effects -5 -10 -10 -15 -15 -20 -25 1 3 5 7 9 11 Avg -20 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle -25 Damping Devices 15 15 0 0 Avg. 3. -9. 6.79 Avg. -4. 3.Average percentage tip acceleration reductions for all damping systems (1damper placement) under different earthquake excitations 5 0 -5 -5 -10 -10 -15 -15 -20 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle Avg -20 1 3 5 7 -25 9 11 -25 Placement of the Dampers Fig. -0. 6. 6.00 30 Avg.Average percentage tip acceleration reductions for all damping systems in all (1 damper) placements -15 -30 -45 -60 EC HA KO NO SF Avg -45 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle -60 Damping Devices 0 Avg. 6.28 10 Avg. -1.54 15 Avg. -2.47 -5 0 Avg.15 10 10 Avg.73 .56 % Acceleration Reductions Fig.74 . -14.48 -15 Avg. 3. 2. -3. -0. 8.76 . 5.80 Avg.73 30 Avg.Average percentage tip acceleration reductions for all damping systems in all (2 dampers) placements -30 -45 -60 -15 EC HA KO NO SF Avg -45 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle -60 Damping Devices Fig. 9. -9. 8.01 0 Avg.Average percentage tip acceleration reductions for all damping systems (2 dampers placement) under different earthquake excitations 246 .01 15 Avg. 6.89 -15 15 Avg. 6.Fernando -60 Earthquake Records 20 20 1-2 3-4 Avg.18 0 Avg.75 .95 -10 10 Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects 30 Avg. -16.26 % Acceleration Reductions 15 Chev VE Hybrid Toggle -30 Avg -45 El Centro Hachinohe Kobe Northridge S. 6. 10.73 30 Avg.09 % Acceleration Reductions Fig.Average percentage tip acceleration reductions for all damping systems under variety of earthquake excitations -20 0 7-8 -10 9-10 11-12 -20 -30 5-6 Avg -30 Diag FR Diag VE Chev FR Chev VE Hybrid Toggle -40 -40 Damping Devices 0 -15 -30 Avg.72 15 Avg.18 30 Avg.72 30 Avg. 5. 10. -16.17 10 Avg.09 % Acceleration Reductions Fig. -9. 4.77 . -16.95 0 Avg. 9. -6. 10.43 30 Diag FR 0 Chev FR -30 -45 -60 Diag VE -15 Avg. Fernando -60 Earthquake Records Fig.81 10 Avg. 5. 5.76 Diag FR Avg. 0. similarly as in the case of the 18-storey frame-shear wall structure. With respect to these findings. 3. 247 . 2. 6.78 . which was the more important investigated parameter.92 -15 Avg.Average percentage tip acceleration reductions for all damping systems in term of damper placements -15 Chev VE Hybrid -30 Toggle Avg -45 El Centro Hachinohe Kobe Northridge S.27 Avg. yet again. 1.79 . -16.72 30 10 Diag FR Diag VE 0 0 Chev FR Chev VE -10 -10 -20 -20 Hybrid Toggle -30 Avg -30 1-2 3-4 5-6 7-8 9-10 11-12 -40 -40 Placement of the Dampers 30 30 15 15 0 0 -30 -45 -60 Diag VE Chev FR Avg.Influence of Damping Systems on Building Structures Subject to Seismic Effects 20 Avg. the friction dampers performed more efficiently when placed in the storeys with higher interstorey drift.39 Avg.61 Avg. 7. The hybrid dampers experienced consistent performance in the all placements. the combined damping system.83 % Acceleration Reductions Fig. which consisted of the diagonal friction damper placed in the 11th storey and the diagonal VE damper placed in the 1st storey was also investigated.Average percentage tip acceleration reductions for all damping systems under variety of earthquake excitations The results presented in this chapter.20 Avg.93 % Accelrations Reductions 20 30 Avg. 3. 6. confirmed that in terms of tip deflection reduction. while the VE dampers were more efficient when placed close to source of excitations. 11.47 Avg. -14. 3 -4 -0.15 6 0. 6.2 -0. in terms of tip deflection.05 0 5 10 15 20 -0. 6.25 CO -6 UN Time (s) UN Time (s) VE VE Fig. the structure embedded with combined damping system obtained high and consistent performance in both investigated parameters and under all earthquake excitations.05 6 10 15 20 4 2 5 Acceleration (m/s ) Deflection (m) -0.25 2 0 -2 -0. Northridge and San Fernando earthquakes.1 2 Deflection (m) Acceleration (m/s ) 4 0. 6.15 -0.80 .15 2 0 0 5 10 15 20 -2 -4 -0.2 CO -0. the combined damping system performed stronger under the Hachinohe.80-6.1 -0. Tip deflection (El Centro earthquake) Tip Acceleration (El Centro earthquake) 0.81 .4 VE VE 0 CO UN 8 -8 Time (s) 0 5 10 15 20 Time (s) Fig.Tip deflection and acceleration responses of the undamped structure and the structures fitted with two diagonal VE dampers and the structure fitted with one friction damper and one VE damper respectively under the Hachinohe earthquake 248 .84. at the same time as in terms of tip acceleration reduction under the Kobe. While comparing with the responses for the structure fitted with the diagonal VE dampers.05 0 -0.1 -0. Northridge and San Fernando earthquakes. As can be seen from the graphs.Influence of Damping Systems on Building Structures Subject to Seismic Effects The time history responses of the 12-storey structure fitted with the combined damping system compared with the responses of the undamped structure and also with the responses of the structure with the diagonal VE dampers fitted in the lowest two storeys are illustrated in Figs.Tip deflection and acceleration responses of the undamped structure and the structures fitted with two diagonal VE dampers and the structure fitted with one friction damper and one VE damper respectively under the El Centro earthquake Tip deflection (Hachinohe earthquake) Tip acceleration (Hachinohe earthquake) CO UN 0.35 -6 -0.05 0 -0. Kobe. 15 -3 -4 Time (s) Time (s) Fig.1 Deflection (m) CO UN 4 VE 0 0 5 10 -0.82 .05 VE 4 Acceleration (m/s ) Deflection (m) 0. 6.1 -0.1 CO UN 6 0 5 10 15 20 2 0 0 5 10 15 20 -2 -0.05 15 20 1 0 -1 0 5 10 15 20 -2 -0.15 -0. 6.15 0.05 0 -0.15 VE 2 0.15 -8 Time (s) Time (s) Fig.15 VE 3 2 2 0.Influence of Damping Systems on Building Structures Subject to Seismic Effects CO Tip Deflection (Kobe earthquake) VE VE 6 4 2 0.Tip deflection and acceleration responses of the undamped structure and the structures fitted with two diagonal VE dampers and the structure fitted with one friction damper and one VE damper respectively under the Northridge earthquake Tip Deflection (San Fernando earthquake) CO Tip Acceleration (San Fernando earthquake) UN 0.84 .05 0 -0.1 Acceleration (m/s ) Deflection (m) UN 8 0.2 -6 Time (s) Time (s) Fig. 6.Tip deflection and acceleration responses of the undamped structure and the structures fitted with two diagonal VE dampers and the structure fitted with one friction damper and one VE dampers respectively under the San Fernando earthquake 249 .1 -4 -0.Tip deflection and acceleration responses of the undamped structure and the structures fitted with two diagonal VE dampers and the structure fitted with one friction damper and one VE damper respectively under the Kobe earthquake Tip Deflection (Northridge earthquake) Tip Acceleration (Northridge earthquake) CO UN 0.1 2 0 -2 0 5 10 15 20 -4 -6 -0.83 .05 Acceleration (m/s ) 0.2 0 5 10 15 20 -0.05 CO Tip Acceleration (Kobe earthquake) UN 0. On the other hand.Percentage tip deflection and tip acceleration reduction of the structure fitted with one diagonal friction damper and one diagonal VE damper % Defl. that the combined damping system.47 Northridge 20.73 11.36 Average 20. 250 .30 15. the time history responses of the combined damping system demonstrated a successful involvement of advantages of both damping mechanisms to obtain significant and consistent performance. which include the diagonal friction damper fitted in the storey with maximum interstorey drift and the diagonal VE damper fitted in the storey the closest to the source of excitation can produce better and more reliable result than individual friction or VE dampers. Red.2 . their overall results were slightly lower than those of the other damping systems. Red. it can be suggested. while the advantage of the VE damper was in more gradual decreasing seismic response of the structure.53 Hachinohe 12. El Centro 26. % Accel. While comparing the time history responses for all the damping systems. nevertheless.69 9. it seems more obvious that in the cases of the hybrid friction-VE dampers.02 S.93 19.Fernando 17.13 Kobe 27. Based on this as well as on the results of the 18-storey frame-shear wall structure discussed in the previous chapter. in the vast majority of the cases only one part of the damper was operating efficiently.26 33. The hybrid friction-VE dampers were the most reliable.Influence of Damping Systems on Building Structures Subject to Seismic Effects Table 7.10 As stated previously the friction dampers in the vast majority of cases suppressed the VE dampers in their ability to reduce the intensity of the initial strong strikes.70 26. Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 7 Conclusions and Recommendations 251 . The large amount and variety of information generated in present study can enable effective use of dampers to mitigate seismic response in high and medium-rise building structures. With regards to efficiency of damper configurations: ¾ diagonal dampers experienced highest sensitivity to placement and variations in seismic excitations. This is a novel method of seismic control and the feasibility of this approach has been considered and amply demonstrated for several cases.Influence of Damping Systems on Building Structures Subject to Seismic Effects Chapter 7: Conclusions and Recommendations 7. for all the structures considered in this thesis. These dampers achieved the most significant performances under earthquakes. 252 . which caused high deflection ¾ chevron brace dampers were by 30% more effective in terms of tip deflection reduction. However. ¾ friction dampers are most effective when placed close to regions of maximum interstorey drift ¾ the combined damping system. is clearly more effective than the hybrid friction-VE dampers placed in the same cut outs. Different building structures require different damping systems for the best results. findings of the present study revealed that: ¾ VE dampers are most effective when placed in the lowest storeys. which consists of the diagonal friction damper being placed in the storey with the highest interstorey drift and the diagonal VE damper placed in the lowest storey. which provides an overall assessment of the seismic response of the structure.1 Scientific Contribution from this Research The main contribution of this research was to establish that seismic mitigation of building structures can be achieved by using dampers embedded within cut outs of the shear wall. A strategy for protecting buildings from earthquakes is to limit the tip deflection. under all earthquake excitations. by using appropriate damper types suitably located within the structure. ¾ lower toggle dampers obtained significantly highest seismic mitigation This study has shown that it is possible achieve seismic mitigation. To this end. the present study demonstrated that some trends common for all investigated structures can be observed. passive dampers as energy absorption devices are mostly used. determining the type of damping devices and their optimal placement and size still remains highly an iterative trial and error process. damping coefficient. These damping devices were embedded in a variety of different placements (one at a time). Six different damping systems. location. Even more. Despite the availability of sophisticated computer facilities. there are numerous types of dampers available commercially as well as numerous types of high-rise buildings with varied properties. the basic theories behind these methods are mostly not supporting each other and in many ways are rather contradicting. However. configuration and size were varied and results for tip deflections and accelerations were obtained. In the light of this. VE and hybrid friction-VE damping devices to mitigate the seismic input energy within medium and highrise structures. which optimises the use of energy dissipating dampers in vibration control of buildings under earthquake loads. What makes the problem even more difficult is the uncertainty of seismic inputs as the forces of nature can vary tremendously. This study has investigated the use of friction.Influence of Damping Systems on Building Structures Subject to Seismic Effects including those whose natural frequencies are within the range of the strong motion of the seismic excitation.2 Discussion In order to control the vibration response of the medium and high rise structures during earthquake events. which could be treated under seismic loads. there was a great necessity for further development of methods to determine the effective use of dampers in medium and high rise structures. Finite element techniques were used to 253 . friction and VE chevron brace dampers. hybrid friction-VE dampers and lower toggle VE dampers were placed within cut outs to treat seismic mitigation. 7. namely friction and VE diagonal dampers. The range of the results presented in this study illustrates the complexity of the problem of optimization in the use of damping devices. Damper properties such as stiffness. There have been several studies undertaken to develop a method. Influence of Damping Systems on Building Structures Subject to Seismic Effects model the dampers and the structures to obtain the dynamic responses under five different earthquake excitations. to mitigate the seismic response of shear wall structures were investigated. 15 m wide and 0.2. their results in terms of tip deflection reduction were comparatively high. Hybrid dampers were overall the most efficient and also had the most consistent performance. while friction dampers performed better in the upper parts of the structure and when placed throughout the structure. In this model. At the initial stage 96 m high. located within cut outs of shear walls.7% in the peak values of the tip accelerations were obtained for the shear wall structures. VE dampers performed better than friction dampers in the lower and middle parts of the structures. responses under earthquakes with varying frequency content and strong motion duration yielded a wide range of results. chevron brace friction and VE damper and hybrid friction-VE dampers. However.2 24-storey frame-shear wall structure The second structural model investigated in this study was represented by the 24storey frame-shear wall structure. however. namely diagonal friction and VE dampers. 7. Five types of damping systems. the shear wall was modelled as before and was attached on both sides by frame. The dampers of chevron brace configuration were created to represent only 67% of damping force of diagonal dampers. 7. using time history analyses.4% in the peak values of the tip deflections and up to 71.5 m thick shear wall structure was considered. the best performance was observed when the dampers were placed in the upper level. The structure was fitted with 254 . The results of this investigation confirmed that substantial reductions in tip deflection and acceleration of the structure could be achieved by all five types of dampers in all locations. while greatest reductions in the peak values of tip acceleration were achieved when dampers were placed in the lower level.1 96 m high shear wall structure Five different types of structure were investigated in this study.2. Reductions of up to 45. In terms of reduction in the tip deflection. occurred when the damper was placed in the lower storeys. the range of increasing efficiency was extended up to value of 80 x 106 Ns/m. From the results it is evident. The influence of the properties of the dampers on performance of the 24-storey frame-shear wall structures embedded with diagonal VE dampers under the El Centro earthquake excitation was also investigated. kd. in both investigated parameters.7% and 76. that the damper stiffness. the range of increasing tip deflection reduction with increase in the damping coefficient was extended to the higher values of 70 x 106 Ns/m. the results obtained from 24-storey frame-shear wall structure were slightly better than those of the shear wall structure fitted with 255 . Clearly the better results. however.Influence of Damping Systems on Building Structures Subject to Seismic Effects diagonal VE dampers placed in the cut outs of the shear wall and treated under five earthquake excitations. In the case of the structure with the dampers fitted in the all three parts of the structure. The reductions of up to 45. However. However. has clearly less impact on the response of the structure than the damping coefficient.4% in tip deflections and tip accelerations respectively. The tip deflection and tip acceleration reductions under these earthquake excitations were significantly different. impact of the damping coefficient was similar as in previous cases. the increase in damping coefficient Cd produced strong increase in tip deflection reduction for the lower values (of Cd) to the peak at 30 x 106 Ns/m and than flattened out. When the damper was placed in the upper storeys. Cd. Influence of the damper parameters on seismic response of these 24-storey frameshear wall structures was also calculated in a smaller scale under the Hachinohe and Kobe earthquake excitations. the ranges of the most effective damping parameters were relatively close to those experienced under the El Centro earthquake. Similar results occurred when the damper was placed in the lower storeys. The dampers obtained a high performance over the wide range of damping parameters. While comparing the results of 96 m high shear wall structure and 24-storey frame-shear wall structures. were obtained. namely diagonal friction and VE dampers. which are more common for Australian conditions. lower.Influence of Damping Systems on Building Structures Subject to Seismic Effects diagonal VE dampers. In the case of the frame-shear wall structure higher tip deflection reduction occurred for the lower storey placement. The results of the hybrid friction-VE dampers were close to those of the friction chevron brace dampers. In the 18-storey frame-shear wall structure. The dampers reveal a high level of reliability under all excitations and when fitted in all the placements. in most cases. which indicate that only the friction part of this damping system was working efficiently. reductions of up to 36% in the peak values of tip deflections and 47% in the peak values of the tip accelerations were obtained.3 18-storey frame-shear wall structure Primary objective of this investigation was concentrated on the efficiency of the dampers embedded within cut outs of the medium rise structures. chevron brace friction and VE dampers. The results of the diagonal friction dampers reveal the highest sensitivity to placement and also to variations in seismic excitations. The dampers were embeded into twelve different placements (one at a time) within cut outs of shear walls to mitigate the seismic response of these medium-rise building structures. In terms of tip acceleration reductions the dampers were more efficient in the lower storeys of each structure. as it was expected. for the structure fitted with the lower toggle VE dampers. while in the shear wall structure reverse trend was observed. These dampers achieved the highest performance from all damping systems under the Hachinohe 256 .2. their performance considerably decreased when moved towards the uppermost storeys. however. The highest tip deflection reductions were obtained. The 18-storey and 12-storey frame-shear wall structures embedded with six types of damping devices. The performance of the diagonal VE dampers was even higher for the lower storey placements. while the efficiency of the VE part was. hybrid friction-VE dampers and lower toggle VE dampers were predominantly investigated. The most consistent performances in all placements and under all seismic excitations were revealed for both types of chevron brace dampers. 7. The hybrid friction-VE damper and the friction chevron brace dampers followed similar trends with rather inconsistent acceleration reductions under the El Centro. which caused the highest structural deflections from all excitations. which caused transfer of acceleration to the ambient structural elements as well as decrease in stiffness of the top storeys due to the cut-out in the shear wall. As the results for the diagonal friction damper were inconsistent. a combined damping system consisting of the diagonal friction damper placed in the 16th storey and the diagonal VE damper placed in the 1st storey was also analysed under the same five earthquake excitations. involvement of these dampers under the San Fernando earthquake excitation.Influence of Damping Systems on Building Structures Subject to Seismic Effects earthquake. while the reductions under the Northridge and San Fernando earthquakes were quite small. This tip acceleration increase was mainly due to the operating principle of the friction dampers. The lowest tip acceleration reduction was displayed for the chevron brace VE dampers where satisfactory reductions were recorded only under the El Centro earthquake excitation. The diagonal friction dampers displayed once again the highest sensitivity to variation of the damper placements and seismic excitations. where increase in tip acceleration occurred under each of earthquake excitations. however. The average reductions for lower toggle dampers were close to those of the diagonal VE dampers. their reductions for the lowest storeys placements were noticeably lower. The tip acceleration reductions of these dampers were greatest when placed in the lower storeys. Hachinohe and Kobe earthquakes. Their overall slightly lower tip acceleration reduction was attributed to their poor effectiveness under the San Fernando earthquake excitation as well as their ineffectiveness in the uppermost storey placement. The highest reductions in peak values of the tip acceleration for the same structure were recorded when it was fitted with the diagonal VE dampers. These poor results may be attributed to inadequate compensation for removed stiffness and/or partial resonance of the damped structure and insufficient push on the friction damper to make it fully operational. The combined damping system 257 . On the other hand. was rather unfavourable. which causes the lowest structural deflection. In general. in terms of tip acceleration reduction some unfavourable results were experienced.2. On the other hand.5 12-storey frame-shear wall structure In the 12-storey frame-shear wall structure reductions of up to 43% in the peak values of tip deflections and 50% in the peak values of the tip accelerations were obtained. additional structural models represented by 18-storey frame structures were also treated with embedded diagonal VE dampers.4 18-stoey frame structure In order to further demonstrate feasibility of the procedure used in this study. The results for the 18-storeys frame-shear wall structure embedded with the diagonal VE dampers and for the 18-storey frame (only) structure embedded with the same dampers were compared. however. the dampers placed in the frame-shear wall structure were slightly more consistent in terms of efficiency under different earthquake excitations. The frame structure produced slightly better results in both investigated parameters. the range of the results obtained under different earthquake excitations varied significantly. The highest tip deflection reductions and also the most consistent performances were recorded 258 . the dampers produced relatively consistent results at all placements. 7. In terms of reduction in tip deflection. to emphasize the significance of these results. it should be pointed out that this combined damping system consisted of only two dampers. Furthermore.Influence of Damping Systems on Building Structures Subject to Seismic Effects achieved significant reductions in both investigated parameters under all five earthquake excitations. because the structure did not experience decrease of stiffness due to cut out of shear wall.2. substantial reductions were obtained. The dampers revealed good overall performance. On the other hand. 7. This was expected. The dimensions of the model were kept to be the same as for previously discused 18-storey frame-shear wall structure except for substitution of the shear wall with an interior bay. which is primary investigated parameter. whereas the dampers placed in the frame structure produced more consistent results through all the placements. The tip deflection reductions for the diagonal friction dampers were generally comparable to those of the lower toggle VE dampers. however. which obtained acceleration reductions under the Kobe earthquake only. the friction part of this damping system was clearly less ineffective. nevertheless. In terms of tip acceleration reduction the highest reductions were recorded for the lower toggle VE dampers. The reductions for the hybrid damping system were comparable to those of the other damping systems. The results of the 12-storey frame-shear wall structure confirmed that in terms of tip deflection reduction. The significant tip deflection and acceleration reduction of this combined damping system demonstrated successful involvement 259 . The tip acceleration reductions of the diagonal friction dampers were uneven and in many cases an increase in tip acceleration was experienced. however. The hybrid dampers experienced consistent performance in the all placements. however. the friction dampers performed more efficiently when placed in the storeys with higher interstorey drift. With respect to these findings. their overall reduction also remained at a satisfactory high level. while the VE dampers were more efficient when placed close to source of excitations.Influence of Damping Systems on Building Structures Subject to Seismic Effects for the lower toggle VE dampers. even these dampers remained unreliable under the San Fernando earthquake. its results suggested that whereas the VE part of damping system operated effectively. The reductions for the hybrid friction-VE damper were generally high except for the El Centro and San Fernando earthquakes where slight increases in acceleration were recorded. The widest range of results was displayed for the diagonal VE dampers. in few cases this remained rather ineffective. The reductions for the diagonal VE dampers were rather inconsistent with same acceleration increases under the Northridge earthquake. which consisted of the diagonal friction damper placed in the 11th storey and the diagonal VE damper placed in the 1st storey was also investigated. Slightly lower overall deflection reductions for the chevron brace friction dampers and chevron braced VE dampers than those of the diagonal friction dampers were due to their poor performances under the Hachinohe earthquake. The poorest results were recorded for the chevron brace VE dampers and chevron brace friction dampers. the combined damping system. In contrast. The performance of the diagonal VE dampers was noticeably less sensitive to this aspect. On the other hand. Each of these damping systems performed in a different manner and also their performance varied considerably when treated in different structures. while their performance gradually decreased as the dampers were moved towards the uppermost storeys. while the best performance of VE dampers was achieved when placed in the lowest storeys. The results of these dampers in an 18-storey structure indicated that only the friction part of the hybrid damper was operating properly. 7. The hybrid friction-VE dampers performed in a more stable and reliable manner than the diagonal and chevron brace dampers. However. which caused higher deflections of the structure.6 Conclusion Five high to medium-rise structures embedded with six damping systems were investigated under five different earthquake records. nevertheless their overall reductions were in the majority of cases.2. their overall tip deflection reduction was comparatively high and even more reliable than those of the diagonal dampers. the VE dampers gradually decreased the deflection and acceleration of the structure. both damping systems experienced the best performance in the lowest storeys. Despite the fact. that both types of the chevron brace dampers were created to represent only 66. The friction dampers in the huge majority of cases surpassed the VE dampers in their ability to reduce the intensity of the initial strong strikes. some specific features can be observed. 260 . the diagonal friction dampers performed better under the earthquakes. In contrast. The performance of the friction dampers increased with higher interstorey deflection. In addition.6% of the damping force of the diagonal dampers. both types of chevron brace dampers were clearly the least effective in terms of tip acceleration reduction. slightly lower.Influence of Damping Systems on Building Structures Subject to Seismic Effects of advantages of both damping mechanisms to obtain significant and consistent performance under all earthquake excitations. With regard to the reductions of the tip acceleration. the performance of these dampers under earthquakes that caused a lower structural deflection was less favourable. On the other hand. in the 12-storey structure it was only the VE parts. 2003. These are designed to alter the properties to suit the intensity and frequency content of the earthquake..) study. Kubota et al. ¾ Investigation of performances of the damping systems under synthesized excitations with a wide range of frequencies and peak ground accelerations ¾ Extend the study on use of semi-active damping systems. 2001. etc. 261 . in order to obtained more efficient performance. A number of analyses of the several different structure types fitted with different damping systems and treated under different earthquake excitations were carried out to gain a comprehensive understanding of the effectiveness of the dampers and their placement.3 Recommendations for Further Research The following are suggestions for further research in this area: ¾ The method of optimising the location of the dampers within the structure be further investigated. under all earthquake excitations. 7.Influence of Damping Systems on Building Structures Subject to Seismic Effects The lower toggle VE damper displayed the highest performance and reliability from all damping systems. This study treated the structural response under a range of seismic excitations even when the dominant seismic frequencies matched the natural frequency of the structure.. by using certain damper types appropriately located within the structure. It has been shown that it is possible to have seismic mitigation. ¾ The study be extended by involvig the other toggle configurations proposed by the other authors (Ribakov et al. . March 2005.” Earthquake Engineering and Structural Dynamics. University of California at Berkeley. and Wilson. and Tavassoli. Aiken. Amini. 459-468. S. “Optimal Design of Friction-Based Frames under Seismic Loading. E. Earthquake Engineering Research Center. H. UMCE 87-1. J. vol.” Journal of Structural Engineering. Balendra. (2000). UCB/EERC 93/09. M. pp. National Conf. “Elastic Seismic Response of Buildings with Supplemental Damping. CA.. University of California at Berkeley. and Pister.. (1990). CA. (1985). Palm Springs. Berkeley. 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J. pp. 19. “Seismic Design of Viscoelastic Dampers for Structural Applications. Youssef. Xu. “Seismic Retrofit of Structures with Passive Energy Dissipation Devices. and Li.. P.. 98 8.14 -9.47 9.39 6. Fernando 5.10 -0.87 8.45 14.98 -4.29 12.70 8.15 2.16 4.27 2.55 9.18 8.08 10.89 10.59 7.14 8.45 12.80 7. Fernando 10.11 0.79 13.22 20.21 8.96 3.93 -3.30 7.13 6.75 25.27 12.24 6.61 Hachinohe -3.60 14.50 9.91 1.90 1.86 5.67 7.85 -0.45 .63 8.63 6.71 6.74 9.70 -7.00 -0. Fernando 12.83 8.63 7.49 11.95 7.93 8.68 9.25 7.67 7.86 16.66 12.16 0.32 6.74 7.30 1.52 24.29 -8.58 Kobe 26.55 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with three chevron brace friction dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 1.55 8.50 4.63 6.42 -3.06 2.47 14.70 7.61 S.98 15.95 8.39 0.33 18.46 Kobe 18.36 5.13 3.74 3.40 -0.35 14.39 -1.38 10.23 -0.67 5.20 10.89 0.23 5.02 7.63 4.08 8.80 9.44 1.08 5.60 Northridge -7.56 0.67 10.40 9.15 -0.95 15.63 2.37 Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with three chevron brace friction dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 4.78 0.43 -2.59 12.76 Hachinohe -0.79 1.78 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with three chevron brace VE dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 9.94 Hachinohe 9.12 6.78 S.33 -12.17 13.78 3.39 8.19 Kobe 17.37 S.82 -0.44 10.49 -2.87 2.51 9.Influence of Damping Systems on Building Structures Subject to Seismic Effects Appendix Results of 12-Storey and 18-Storey Structures Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with three chevron brace VE dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 5.73 S.42 3.24 8.63 1.56 5. Fernando 14.50 9.96 Kobe 17.35 278 Northridge -12.14 9.77 17.96 5.59 -1.17 13.96 Hachinohe 12.80 2.70 4.69 8.76 7.34 2.24 8.88 13.87 10.35 13.40 10.49 6.77 0.66 0.61 10.56 6.79 6.30 9.39 9.98 9.45 10.10 2.46 8.02 9.37 2.37 Northridge 6.98 8.61 Northridge 7.34 8.58 8.06 10. 08 4.87 4.01 5.59 11.73 4.91 -2.62 Kobe 13.73 3.88 7.56 7.38 1.65 13.14 S.29 11.05 5.63 5.45 3.82 9.05 5.23 2.08 4.67 5.15 5.37 0.53 3.22 4.87 6.95 5.30 -0.61 Northridge 2. Fernando 7.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with one chevron brace VE damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 0.91 0.17 5.48 2.33 13.73 6.44 -1.63 5.48 5.86 -0.21 5.02 4.02 2.98 4.01 2.79 4.88 2.25 3.45 4.06 7.07 Hachinohe 1.11 7.06 0.80 .69 10.50 4.49 3.25 Kobe -2.25 5.37 11.58 8.92 6.34 3.18 Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with one chevron brace friction damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 1.09 Hachinohe 5.26 5.22 5.28 3.04 9.12 Northridge 2.49 5.70 3.97 6.77 -1.06 4.06 3.63 10.39 -0.70 Kobe 8.92 4.51 8.04 8.77 -2.89 4.69 -1.71 0.21 -3.58 -2.31 7.17 1.79 5.53 3.69 2.67 1.17 5.08 -1.45 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with one chevron brace VE damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 8.27 3.26 2.36 5.04 8.11 5.66 4.89 -1.43 -4.19 8.20 6.63 5.11 5. Fernando 0.63 3.78 1.91 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with one chevron brace friction damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 4. Fernando 10.68 5.28 3.48 5.12 Kobe -8.61 8.24 -5.34 1.98 -0.20 -0.70 4.09 2.04 9.85 2.98 8.82 11.95 10.06 2.30 5.80 4.27 5.77 2. Fernando -4.64 4.09 6.50 S.49 -4.82 5.39 5.58 3.03 279 Northridge -10.18 2.18 -3.35 6.00 Hachinohe -1.58 S.88 4.25 3.74 S.68 4.92 6.39 5.96 -1.85 -1.51 2.53 2.67 5.07 0.34 -5.64 -2.08 5.53 5.22 4.70 5.56 9.07 7.70 Hachinohe -7.79 Northridge 3.43 -1. 36 -6.30 14.05 280 Northridge 37. Fernando 6.22 Kobe 7.22 -34.90 13.62 -21.37 3.61 1.64 19.53 -12.30 -5.87 7.29 18.43 16.50 -7.44 18.40 1.38 0.66 -7.51 4.50 14.19 Hachinohe 31.20 6.16 0.67 5.98 -4.64 Northridge -11.24 25.23 17.89 -17.80 17. Fernando 40.82 -1.23 -1.40 -41.34 3.54 -11.08 25.43 11.16 -28.53 -37.90 -20.68 Kobe 35.95 -35.34 50.51 5.78 19.00 7.13 -4.11 6.51 -54.72 3.70 20.73 8.22 24.47 8.82 20.26 18.15 -25.57 19.39 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with three diagonal VE dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 30.56 13.53 4.31 4.60 12.07 20.89 S.16 5.42 5.65 11.29 1.44 10.58 Northridge 46.94 -35.17 -6.48 40.84 13.16 -2.42 18.37 Kobe 33.33 10.30 26.73 21.84 7.16 10.30 17.58 31.29 15.56 20.97 Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with three diagonal friction dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 14.06 8.50 S.86 7.18 8.27 Hachinohe 15.31 4.27 22.35 -22.38 5.42 -6.43 Hachinohe 14.90 .46 15.57 3.14 35.48 19.74 2.08 23.61 7.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with three diagonal VE dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 33.33 31.97 Hachinohe 13.02 11.66 3.15 28.36 12.97 S.82 3.90 3.56 30.18 18.53 21.38 8.33 36.64 Kobe 13.94 16.73 S.52 12.99 7.56 6.74 10.89 13.55 24.39 7.95 Northridge 11.78 7.67 7.07 -10.53 29.37 26.64 Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with three diagonal friction dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 16.13 2.44 8.67 38.09 22.92 36.22 15.75 -6.54 14. Fernando 33.75 1.32 3.78 -1.30 25.55 13.09 33.25 18.43 23.09 17.96 2.53 -16.71 36.21 22.38 -1.58 28.27 30. Fernando 8.73 6.43 15.36 22.87 5. 28 10.36 6.10 18.20 3.89 11.30 Hachinohe 20.25 Kobe 8.40 7.41 6.92 14.02 7.53 2.86 -1.43 -0.01 4.92 12.81 4.37 7.94 -2.77 6.65 6.91 2.79 -8.48 4.10 1.74 11.91 Northridge 2.91 4.48 8.98 16.90 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with one diagonal VE damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 0.31 Hachinohe 19.50 15.65 7.26 11.07 5.26 Kobe 5.85 22.36 3.90 11.30 .48 281 Northridge -6.06 8.09 12.74 -4.54 2.90 -6.95 9.11 21.59 -1.72 17.72 -4.82 1.27 S.71 -24.23 11.09 4.42 2.42 -0.27 1.59 S.26 3.23 9.10 -10.33 1.18 6.99 1.00 4.08 4. Fernando -20.08 -7.43 1.10 3.45 -2.12 2.94 S.72 7.92 6.14 11.98 16.73 3.84 1.24 -0.69 -4.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with one diagonal VE damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 7.07 1.64 9.53 1.18 3.48 0. Fernando 4.82 4.64 5.44 15.66 9.12 1.11 15.04 Hachinohe 5.04 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with one diagonal friction damper Model H1 H4 H7 H 10 H 13 H 16 El Centro -3.47 7.16 -10.85 19.42 2.61 Hachinohe 3.20 -1.67 1.02 -13.45 2.20 4.99 7.43 -10.58 Northridge 2.35 4.29 Northridge 15.78 12.19 2.88 1. Fernando -4.55 2.59 1.84 2.16 -13.61 8.04 -1.26 21.92 5.91 3.76 18. Fernando 0.61 1.35 14.03 2.53 4.76 3.35 8.70 -2.94 Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with one diagonal friction damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 6.12 10.17 S.09 6.78 11.29 1.76 1.18 2.85 6.04 1.35 1.10 7.51 18.07 2.31 1.15 0.57 -2.39 1.27 2.84 21.65 2.41 6.13 -12.19 -17.95 Kobe 9.16 4.81 -6.21 0.84 1.09 5.49 -0.21 Kobe 12.22 2.23 4.54 -0.59 9.39 1. 67 11.88 8.11 10.81 7.54 7.77 Kobe -6.13 0.83 3.00 .14 5.76 6.33 Kobe 9.84 3.09 2.17 -0.62 7.51 14.00 3. Fernando -1.68 9.08 5.29 4.36 9.28 2.09 12.55 9.73 9.55 17.66 10.53 6.11 15.27 10.04 2.22 24.62 4.92 Northridge 6.57 5.76 7.44 15.68 6.80 5.94 -0.19 0.74 9.98 3.23 1.54 6.02 17.27 2.39 4.56 4.47 Northridge 2.18 7.09 8.43 -3.15 7.04 3.98 3.09 9.18 7.62 45.93 4.55 20.04 Hachinohe -1.87 282 Northridge -4.70 -2.03 -0.94 20.37 1.99 8.98 -3.22 1.56 7.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with three hybrid friction-VE dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 1. Fernando 8.91 2.23 4.00 -0.10 5.38 6.11 4.82 8.92 2.07 3.39 8.43 0.55 3.77 3.67 16.56 S.09 9.52 5.05 15.83 6.37 6.81 7.47 13.13 4.87 7.97 8.09 9.02 26.61 8.61 3.20 16.59 5.79 Kobe 19.67 -0.22 0.62 5. Fernando 16.14 Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with one hybrid friction-VE damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 1.25 9.19 8.74 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with one hybrid friction-VE damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 15.82 -0.83 Hachinohe 2.47 47.29 8.41 S.56 8.36 -0.54 -5.61 9.70 8.54 S.39 1.76 0.25 4.30 Hachinohe 17.24 2.03 -1.38 -2.08 8.75 2.45 9.02 Kobe 24.45 4.22 3.64 8. Fernando -7.59 9.42 2.34 -2.22 6.62 0.47 4.67 21.09 28.78 3.49 3.97 0.68 -0.31 -0.82 S.28 7.11 4.06 2.72 -1.46 -3.62 13.70 14.93 Hachinohe -4.69 10.99 Northridge -9.39 3.96 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with three hybrid friction-VE dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 10.19 6.52 9.41 0.78 0.10 3.24 23. 18 Hachinohe -2.27 S.67 29.91 6.62 7. Fernando 13.84 -0.16 14.57 9.23 Kobe 10.07 21.55 12.19 Hachinohe -0.81 9.72 6.03 -1.82 1.72 2. Fernando 40.22 19.64 4.32 5.93 17.34 8.28 5.89 8.50 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with three lower toggle VE dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 10.87 3.20 9.37 -6.77 8.86 7.64 Kobe 17.89 Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with one lower toggle VE damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 1.69 17.15 6.08 5.42 S.75 Northridge 9.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the18-storey frame-shear wall structure fitted with three lower toggle VE dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 8.67 13.26 7.41 10.52 18.61 -3.17 13.52 22.50 14.73 24.89 9.54 13.18 1.08 3.11 26.35 4.97 8.81 26.81 Hachinohe -0.68 15.34 4.33 21.03 12.22 9.71 Percentage tip acceleration reduction of the18-storey frame-shear wall structure fitted with one lower toggle VE damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 19.27 2.06 17.51 3.31 7.93 Northridge 9.59 Northridge 30.97 .10 4.35 13.10 5.63 3.39 32.27 12.97 18. Fernando 23.66 11.28 13.69 8.56 -2.75 10.67 29.67 10.39 10.96 27.58 8.26 5.20 6.84 6.67 16.56 -1.16 13.37 4.52 8.35 15.19 33.66 4.46 11.80 17.05 7.39 13.67 3.80 10.01 -0.51 6.92 S.33 21.07 3.15 10.74 23.39 14.81 20.62 Kobe 25.91 8.01 11.98 11.78 9.47 5.83 19.41 3.78 8.97 30.78 7.47 21.79 11.90 8.52 13.82 9.62 14.32 11.51 6.05 11.52 13.79 12.40 11.94 18.33 12.84 4.81 6.99 12.06 -13.88 21.05 7.76 12.71 14.25 Hachinohe 7.58 1.66 35.23 -26.94 1.99 17.52 9.94 4.95 8.29 15.01 25.90 Kobe 30.04 24.24 15.75 7.64 25.24 S.80 20.72 6.60 4.22 283 Northridge -4. Fernando 0.92 8.73 6.00 18. 57 14.20 12. Fernando 27.94 31.09 284 Northridge 22.84 16.40 14.49 S. Fernando 3.64 27.85 17.31 S.26 44.57 23.94 13.63 4.72 30.15 13.09 15.68 -0.40 Northridge 38.88 22.93 16. Fernando 8.38 .18 19.57 25.27 11.47 17.34 12.38 Kobe -11.18 Hachinohe 18.25 13.79 17.45 15.02 9.97 2.45 16.26 Hachinohe 5.49 10.04 43.62 4.00 2.90 -12.70 1.74 9.81 16.21 37.23 5.88 2.75 4.46 10.56 7.53 Kobe -4.31 -3.90 3.67 8.89 -1.45 17.99 18.25 1.70 6.65 12.62 2.81 1.47 16.93 14.40 22.63 5.00 31.38 19.83 23.94 Percentage tip acceleration reduction of the18-storey frame structure fitted with one diagonal VE damper Model H1 H3 H5 H7 H9 H 11 El Centro 14.81 8.98 37.81 -1.44 16.24 13.57 4.09 19.69 S.19 Hachinohe 0.92 -9.33 9.64 Kobe 7.91 5.90 33.46 6.71 2.79 50.79 40.48 7.23 -1.90 23.91 4.65 27.33 31.06 37.84 7.19 2.17 3.91 2.70 4.67 11.32 -6.81 6.01 3.79 -3.42 48.41 6.56 4.94 10.93 Northridge 5.98 10.37 18.56 21.09 -7.57 Percentage tip deflection reduction of the18-storey frame structure fitted with one diagonal VE damper Model H1 H4 H7 H 10 H 13 H 16 El Centro 10.48 5.72 28.23 8.36 8.61 7.95 8.75 -10.90 Percentage tip acceleration reduction of the18-storey frame structure fitted with three diagonal VE dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 13.79 36.73 1.48 5.14 18.76 7.26 5.14 11.85 3.42 S.26 36.47 13.23 14.26 6.64 10.60 Hachinohe 13.71 16.69 4.15 26.89 14.59 30.52 10.36 -0.37 12.81 -9.12 Northridge 43.50 -4.79 9.31 19.14 16.57 7.79 4.09 18.77 24.23 24. Fernando 23.32 38.89 -1.69 12.17 15.69 13.01 32.86 13.52 Kobe 13.59 6.14 7.93 13.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the18-storey frame structure fitted with three diagonal VE dampers Model H 1-3 H 4-6 H 7-9 H 10-12 H 13-15 H 16-18 El Centro 19. 13 9.24 13.30 -9.48 16.84 S.88 -14.91 Northridge 6.91 4.90 8.70 16.94 -44.24 -8.12 Hachinohe -9.41 17.68 1.62 20.57 -8.22 -17.48 5.24 17.97 14.27 Kobe -8.53 -20.59 -6.72 -49. Fernando 4.90 11.33 -4.18 Northridge 6.25 0. Fernando -20.48 20.85 -12.97 11.56 11.20 14.84 -89.15 -66.06 -4.50 -27.73 .52 -6.98 6.03 15.41 -12.00 17.83 15.23 -1.75 -54.33 -6.76 8.36 14.79 19.24 -21.50 -2.00 14.34 -16.33 32.79 1.79 2.08 12.17 285 Northridge -23.81 -6.55 -78.72 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with two chevron brace friction dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro -14. Fernando 4.29 6.00 12.44 4.48 15.75 -1.43 22.04 15.17 18.89 2.95 -1.57 -3.92 -10.31 24.31 -32.37 Hachinohe 1.50 Hachinohe 1.61 9.01 S.08 -24.16 S.64 -9.18 18.38 13.17 11.71 11.19 -52.13 -36.18 19.04 14.79 3.57 2.48 10.30 -5.97 Hachinohe -16.29 -17.15 10.26 Kobe 2.88 19.84 9.54 0.37 20.59 -16.65 -42.76 7.85 33.15 -9.59 -43.68 -11.56 13.47 -7.70 20.71 -26.94 18.01 14.84 -22.68 Kobe 18.77 -9.79 2.23 Kobe 18.35 -8. Fernando -13.68 3.57 2.89 13.60 -8.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with two chevron brace VE dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro -0.72 13.17 -49.97 6.57 1.24 14.50 -4.22 27.15 32.05 13.29 10.79 14.13 14.83 S.23 11.54 14.93 17.07 10.25 -16.39 -28.68 3.16 -17.58 16.12 Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with two chevron brace friction dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro 0.85 21.84 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with two chevron brace VE dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro -6.55 Northridge -15.61 18.31 11.58 15.79 0.64 -8.33 11.49 16.45 17.17 12.49 -54.04 3.82 -21.03 25.88 11.68 2. 65 -2.73 14.01 18.02 -1.55 Kobe 16.04 -7.21 9.81 6.50 12.02 -4.16 -0.64 -8.83 Northridge 5.86 -6.66 -14.67 18.71 2.41 7.44 13.41 8.60 Hachinohe -5.95 Northridge 4.75 0.37 S.31 6.27 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with one chevron brace VE damper Model H1 H3 H5 H7 H9 H 11 El Centro -9.91 8.45 6.79 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with one chevron brace friction damper Model H1 H3 H5 H7 H9 H 11 El Centro -12.51 5.00 13.98 6.50 11.67 25.93 -20.11 8.05 9.26 8.16 -0.88 Kobe 13. Fernando -21.24 -0.21 -6.77 -17.63 17.29 18.40 15.69 -48.24 0.58 -39.97 -31.57 -5.56 -11.08 -1.52 7.60 22.48 .61 7.66 10.01 -70.91 9.51 6.25 16.47 -11.97 5.66 9.60 -35.32 -25.39 13.07 -10.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with one chevron brace VE damper Model H1 H3 H5 H7 H9 H 11 El Centro 2.91 -9.65 -34.05 13.24 -2.89 -36.68 -8.61 Hachinohe -0.56 9.78 -3.23 7.91 -58.37 27.72 13.71 -1.01 -74.65 -50.97 11.03 8.60 14.26 9.63 14.89 -5.19 -17.24 Kobe 16.00 17.47 9. Fernando -29.79 10.68 -0.64 11.57 -21.40 14.42 16.46 3.56 -7. Fernando 3.90 S.84 Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with one chevron brace friction damper Model H1 H3 H5 H7 H9 H 11 El Centro 5.18 16.15 -2.24 0.40 16.77 12.82 7.24 -21.36 -6.05 9.05 13.05 13.42 Hachinohe -0.46 2.05 -8.21 8.39 13.07 -26.21 -5.42 -17.21 8.22 -4.96 8.64 8.25 Hachinohe -10.65 2.08 16.97 -14.76 -2.14 -18.35 9.51 7.02 S.24 -0.31 -5.05 13.71 286 Northridge -8.55 11.79 10.60 -40.20 S.14 -6.51 11.94 13.02 8.36 Kobe 20.24 -0.24 -12.89 -31.24 -1.58 -53.58 Northridge 4.68 -0.22 -9.93 23.99 -39.05 14.22 -70.61 6.56 -7.02 -11.45 -6.68 -26. Fernando 5.74 -20. 92 18.21 -2.94 22.14 28.45 2.18 -1.83 18.34 17.68 -3.23 6.97 28.64 9.68 -4. Fernando 8.45 15.03 39.67 15.82 3.60 -3.18 -8.82 27.03 5.30 20.25 19.36 6.76 2.25 8.49 17.76 0.97 21.56 8.33 Northridge -3.55 Hachinohe 5.38 2.98 0.44 5.10 1.17 12.98 Kobe 8.04 -0.13 14.18 5.84 3.44 16.69 3.07 10.06 42. Fernando -9.88 11.51 S.57 3.42 Northridge -5.69 18.52 Northridge -2.89 -10.72 15.80 S.84 -8.40 2. Fernando 0.29 17.14 16.82 6.80 6.70 -10.99 19.64 0.13 22.36 6.64 -1.08 4.99 26.08 287 Northridge 9.14 Hachinohe 23.18 14.46 4.40 1.46 9.72 9.74 S.28 11.46 9.44 1.69 0.98 13.75 7.80 2. Fernando 6.09 .82 -4.13 13.52 8.38 -2.76 10.70 14.83 11.80 10.09 23.24 13.36 35.75 30.86 Hachinohe 4.68 8.26 9.74 20.19 13.72 Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with two diagonal friction dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro 28.82 16.08 7.80 14.53 14.32 14.93 24.82 18.15 7.88 9.34 6.95 8.92 33.70 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with two diagonal VE dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro 42.63 -9.33 21.48 29.05 S.57 4.18 20.61 -1.70 Kobe 12.17 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with two diagonal friction dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro 27.32 15.23 4.35 -1.24 -21.34 18.87 11.61 41.97 18.74 4.27 2.91 10.98 -8.58 12.82 9.44 14.36 5.24 22.18 17.99 19.43 -10.46 6.02 Kobe 25.07 2.93 2.79 14.23 -2.33 -9.58 6.99 Kobe -8.16 14.78 -11.33 0.62 -1.95 15.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with two diagonal VE dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro 39.10 Hachinohe 25.31 -17.65 19.29 13.13 8.88 28.98 18.52 -0.32 18. 85 -18.43 Northridge -1.48 1.71 13.79 13.50 4.91 1.45 23.06 9.87 16.30 5.41 16.10 17.16 2.00 0.85 7.20 4.83 -5.83 S.56 6.92 4.78 2.36 Kobe -22.07 1.14 14.12 4.69 19.57 5.45 7.24 0. Fernando 5.68 0.36 4.70 1.80 17.38 2.38 Hachinohe 6.63 Hachinohe -2.56 .72 2.40 17.85 -4.19 7.60 4.14 6.83 5.13 7.95 3.09 30.68 3.87 3.38 0.58 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with one diagonal VE damper Model H1 H3 H5 H7 H9 H 11 El Centro 14.18 4.46 0.34 16.09 2.12 5. Fernando 1.89 -2.07 Northridge -8.93 0.29 -2. Fernando -2.93 23.69 4.91 -1.76 -7.77 1.37 23.19 -1.76 1.05 Kobe 6.15 -3.98 4.27 4.38 Kobe -17.82 14.26 5.99 Hachinohe 5.15 12.14 -30.45 0.52 9.44 4.28 6.01 8.86 288 Northridge -24.74 20.52 9.04 0.71 15.26 1.18 16.03 16.40 3.11 20.31 11.20 0.47 Hachinohe 2.35 5.92 28.80 13.46 9.25 3.38 S.53 -5.68 2.37 9.65 -16.90 14.22 -3.16 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with one diagonal friction damper Model H1 H3 H5 H7 H9 H 11 El Centro 27.36 0. Fernando -8.47 9.12 -2.73 -3.01 3.75 11.41 16.99 -3.77 4.49 1.47 3.04 6.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with one diagonal VE damper Model H1 H3 H5 H7 H9 H 11 El Centro 26.66 9.15 Northridge 1.21 -36.19 2.18 S.65 6.41 7.68 9.72 1.60 -0.79 3.03 2.41 12.02 20.42 -10.63 2.18 10.16 19.68 Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with one diagonal friction damper Model H1 H3 H5 H7 H9 H 11 El Centro 27.58 4.27 12.91 11.39 1.38 4.27 1.53 -3.10 -9.79 7.21 S.97 10.21 2.45 11.68 2.76 0.51 1.56 5.49 -4.68 2.46 0.60 -1.68 1.29 0.16 6.64 Kobe -6.22 3.64 5. 58 17.21 3.96 5.34 10.78 -2.79 7.44 0.47 Kobe 24.80 3.95 10.66 1.78 3.09 1.43 4. Fernando -4.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with two hybrid friction-VE dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro 30.85 2. Fernando -3.68 0.18 7.03 Northridge 0.77 6.81 Kobe 8.02 5.37 -3.89 9.69 Hachinohe 7.42 3.15 4.96 14.10 19.89 20.29 7.06 5.87 10.07 11.47 -7.14 27.34 -8.20 14.82 -12.61 9.45 S.94 -0.61 9.16 5. Fernando 1.34 8.01 Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with one hybrid friction-VE damper Model H1 H3 H5 H7 H9 H 11 El Centro 20.55 9.83 6.70 9.00 12.61 2.22 3.96 3.03 10.87 10.42 289 Northridge -7.78 29.44 4.64 14.41 -4.47 6.89 -3.86 3.66 4.64 5.13 S.89 9.88 Northridge 8.51 13.81 4.23 0.61 10.99 .41 12.06 18.18 11.85 Hachinohe 20.68 6.87 12.27 2.33 12.57 12.61 1.90 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with one hybrid friction-VE damper Model H1 H3 H5 H7 H9 H 11 El Centro -17.81 6.31 11.04 -2.17 11.58 7.92 17.00 5.66 8.98 21.60 27.84 3.05 -0.16 Kobe 0.61 7.99 4.27 10.66 3.35 Hachinohe 6.44 -1.29 12.17 S.25 9.85 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with two hybrid friction-VE dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro 22.42 9.09 7.22 S.45 10.36 11.21 -2.82 0.84 6.54 5.78 6.64 -4.58 5.95 -1.45 Hachinohe 11.27 5.43 4.38 7.30 -3.27 8.37 3.01 6.06 4.74 14.55 9.75 8.53 -6.19 4.07 4.79 25.03 7.67 3. Fernando -3.06 4.62 Kobe 1.90 2.58 2.90 19.32 9.24 19.95 12.60 0.79 -1.76 7.03 23.17 3.99 -1.89 7.58 Northridge -0.95 6.72 3.05 10.21 12.41 21.31 9.52 11.92 2.87 -2.64 5.59 4.19 9.70 -4.92 3.11 7. 90 26.37 24.50 7.65 14.83 -4.24 13.36 S.12 4.50 13.81 13.04 13.36 33.25 5.91 4.83 6.71 -10.82 Kobe 28.31 9.61 30.37 12.10 10.32 -9.55 31.87 11.30 19.50 21.85 8.85 19.41 15.86 S.97 16.19 18.32 -8.00 10.00 30.41 3.38 14.43 7.98 Hachinohe 19.17 5.88 0.32 11.83 9. Fernando 3.80 6.61 -4.64 7.66 21.50 7.26 Hachinohe 16.34 6.90 15.75 12.03 -18.71 23.08 27.35 5.74 11.40 8.21 Northridge 3. Fernando -6.03 11.32 10.69 6.54 9.30 8.85 5.28 15.11 16.57 6.76 27.39 14.39 9.65 18.63 23.53 26.30 2. Fernando 1.23 18.12 15.77 13.47 33.20 18.97 7.09 7.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with two lower toggle VE dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro 26.83 Hachinohe 9.81 10.47 12.17 11.19 7.51 14.80 8.24 -5.94 7.46 6.95 Percentage tip deflection reduction of the12-storey frame-shear wall structure fitted with one lower toggle VE damper Model H1 H3 H5 H7 H9 H 11 El Centro 23.46 290 Northridge 0.86 Kobe 9.69 Northridge 4.35 9.43 9.53 30.65 19.22 8.72 -0.23 9.92 -2.63 8.28 13.97 9.50 21.68 20.61 7.89 23.04 22.40 7.55 3.17 -37.12 2.81 16. Fernando -0.13 16.19 10.65 3.83 7.30 10.71 8.64 8.47 7.32 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with one lower toggle friction damper Model H1 H3 H5 H7 H9 H 11 El Centro -8.12 2.45 -3.76 21.74 Kobe 3.43 5.80 7.97 7.15 15.79 Kobe 29.91 15.69 14.70 6.29 Hachinohe 12.02 6.93 8.60 21.96 S.53 19.19 17.50 14.06 2.45 -39.48 5.90 -9.36 8.21 7.98 Percentage tip acceleration reduction of the12-storey frame-shear wall structure fitted with two lower toggle VE dampers Model H 1-2 H 3-4 H 5-6 H 7-8 H 9-10 H 11-12 El Centro 4.50 16.44 9.74 12.70 7.43 -6.96 7.90 S.34 17.47 .24 18.68 26.92 12.71 16.50 Northridge 1.50 35. 36 20.69 9.47 291 Northridge 20.92 8.30 15. Fernando 6.18 25.66 Percentage tip deflection and tip acceleration reduction of the12-storey structure fitted with one diagonal friction damper and one diagonal VE damper Model % defl. red % accel.13 Kobe 27. red % accel. red El Centro 26.31 13.82 16.53 Hachinohe 12.28 S.73 11.16 15.36 14.55 Hachinohe 19.10 .70 26.80 Northridge 25.26 33. red El Centro 26.93 19. Fernando 17.85 Kobe 7.Influence of Damping Systems on Building Structures Subject to Seismic Effects Percentage tip deflection and tip acceleration reduction of the 18-storey structure fitted with one diagonal friction damper and one diagonal VE damper Model % defl.99 15.02 S.