S. K. Ghosh Associates, Inc.ASCE 7-05 WEB SEMINAR S. K. Ghosh and Susan Dowty S. K. Ghosh Associates Inc. January 30, 2006 www.skghoshassociates.com www.skghoshassociates.com S. K. Ghosh Associates, Inc. SEMINAR TOPICS • Wind • Snow • Seismic • Questions and Answers www.skghoshassociates.com S. K. Ghosh Associates, Inc. CHAPTER 6: WIND LOADS Section 6.4 Simplified Design - • In ASCE 7-02, the restriction on expansion joints and structural separations was included in the list of nine conditions for the applicability of simplified design. • In ASCE 7-05, this requirement was moved and integrated directly into the definition of a simple diaphragm building. CHAPTER 6: WIND LOADS Section 6.4 Simplified Design - • The restriction that the building not be subjected to topographic effects was removed from the list of applicability of simplified design. • Topographic effect factor inserted directly into equation for wind pressure ps= λ KztI ps30 www.skghoshassociates.com skghoshassociates. Additional conditions for applicability: • Building must either be exempted from torsional loading conditions. Ghosh Associates. or • Torsional load cases must not control the design of any main wind-force-resisting system.Exclude torsionally sensitive buildings. K. CHAPTER 6: WIND LOADS Section 6. • Building with flexible roof and floor diaphragms can use Method 1. Fig.4 Simplified Design . 6-10 (Low-Rise Analytical Procedure): delineation of boundary between windward zone pressures and leeward zone pressures www. Inc. S. CHAPTER 6: WIND LOADS Changes in ASCE 7-05 • Modified the pressures for parapets and clarified their application for low-slope roofs • Added a definition for eave height • Clarified Footnote 8.com . 6-1. pitched. or troughed roofs • Clarified exposure categories for main wind- force-resisting systems and components and cladding CHAPTER 6: WIND LOADS Changes in ASCE 7-05 • Provided objective and enforceable criteria for using climatic data to determine the basic wind speed in special wind regions and other non- hurricane-prone regions. Ghosh Associates. • Clarified that the basic wind speed obtained from regional climatic data may be less than that in Fig. K. www.skghoshassociates. CHAPTER 6: WIND LOADS Changes in ASCE 7-05 • Added new design wind loads on free-standing walls and solid signs • Added new design wind loads on open buildings with monoslope.com . S. Inc. clarified requirement when loads are determined using Method 3. Note: W = horizontal distance from eave to ridge www. Ghosh Associates. K. hip and gable roofs with slopes less than the larger of 2. CHAPTER 6: WIND LOADS Changes in ASCE 7-05 • Modified provisions for roof-top equipment • Expanded required protection of glazing in wind- borne debris regions.38 degrees (1/2 on 12) and (70/W)+0.5 with W in ft …. S.skghoshassociates. CHAPTER 7: SNOW LOADS Section 7. and updated referenced standards. Inc.3.4 Minimum Values of pf for Low- Slope Roofs – Minimum values of pf shall apply to ….com . CHAPTER 7: SNOW LOADS Section 7.6.1 Unbalanced Snow Loads for Hip and Gable Roofs – Major revisions have been made in the values as well as the distribution of the unbalanced snow load on hip and gable roofs on which such loads need to be applied.38 degrees. Ghosh Associates.com . Inc. unbalanced snow loads are not required to be applied. S. K.5 with W in ft and 2.1 Unbalanced Snow Loads for Hip and Gable Roofs – For hip and gable roofs with a slope exceeding 70 degrees or with a slope less than the larger of (70/W)+0.6. CHAPTER 7: SNOW LOADS Section 7. www.skghoshassociates. /ft (2. CHAPTER 7: SNOW LOADS Section 7.38 deg.com . Inc. Ghosh Associates. www. sliding.skghoshassociates. all roofs with a slope less than 1/2 in. but not zero.10 Rain-on-Snow Surcharge Load – For locations where pg is 20 psf or less. S.10 Rain-on-Snow Surcharge Load – Moved from Commentary: This rain-on-snow augmented design load applies only to the balanced load case and need not be used in combination with drift.) less than W/50 with W in ft shall have a 5 psf rain-on-snow surcharge. unbalanced or partial loads. CHAPTER 7: SNOW LOADS Section 7. K.) slopes (in deg. • Much improved document that should be easier to use and result in more correct and uniform application of seismic requirements.skghoshassociates. CHAPTERS 11-23: SEISMIC Reformatting and reorganization of seismic provisions – goals: • Create a set of requirements that are more user-friendly. redundancies. Ghosh Associates. • Remove conflicts. K. repetitions. and ambiguities to the extent practicable.com . www. enforceable and understandable. Inc. S. CHAPTERS 11-23: SEISMIC • ASCE 7-02 seismic provisions are completely reformatted and reorganized through a major effort funded by FEMA through BSSC and ASCE. 14.6. seismic provisions were in Section 9.7.2 (6 deep) • Seismic provisions now subdivided into Chapters 11 through 23 and Appendices 11A and 11B. Inc.10.0 and Appendix A-9.3. K.com . Example subsection: 9. CHAPTERS 11-23: SEISMIC • In ASCE 7-02. Resulted in an inordinate number of subsections. S. Ghosh Associates. Subsection numbering less deep.skghoshassociates. ASCE 7-05 Table of Contents for Seismic Requirements Chapter 11 Seismic Design Criteria Chapter 12 Seismic Design Requirements for Building Structures Chapter 13 Seismic Design Requirements for Nonstructural Components Chapter 14 Material Specific Seismic Design and Detailing Requirements Chapter 15 Seismic Design Requirements for Nonbuilding Structures Chapter 16 Seismic Response History Procedures Chapter 17 Seismic Design Requirements for Seismically Isolated Structures Chapter 18 Seismic Design Requirements for Structures with Damping Systems Chapter 19 Soil Structure Interaction for Seismic Design Chapter 20 Site Classification Procedure for Seismic Design Chapter 21 Site-Specific Ground Motion Procedures for Seismic Design Chapter 22 Seismic Ground Motion and Long Period Transition Maps Chapter 23 Seismic Design Reference Documents Appendix 11A Quality Assurance Provisions Appendix 11B Existing Building Provisions www. www. Chapter 23. Inc. • All SDC A requirements located up front in Section 11.7 • Ground motion maps relocated to Chapter 22 CHAPTERS 11-23: SEISMIC • In ASCE 7-02. CHAPTERS 11-23: SEISMIC • Provisions not frequently used relocated to later sections.skghoshassociates. Ghosh Associates. references were listed in different sections and referred to by a reference number within text. K. they are referred to by their common names within text and are listed in one location.com . • In ASCE 7-05. S. and NDS 2005 www.skghoshassociates. CHAPTERS 11-23: SEISMIC • Reference documents in Chapter 23 are either: (1) consensus standards or (2) other reference documents • Any nonconsensus standard falls under “other reference documents” and is identified as such with an asterisk in Chapter 23. Ghosh Associates. K.com . S. Inc. CHAPTERS 11-23: SEISMIC ASCE 7-05 references: ACI 318-05 AISC 360-05 AISC 341-05 MSJC 2005. SEISMIC TECHNICAL CHANGES Most seismic technical changes reflect revisions from 2000 to 2003 NEHRP Provisions www. S.skghoshassociates. K. Inc.com . Ghosh Associates. Inc. Ghosh Associates. FIGURE 11. K.com . S. Chapter 22 Seismic Ground Motion and Long Period Transition Maps The spectral acceleration maps are based on the latest versions of the USGS hazard maps.4-1: DESIGN RESPONSE SPECTRUM www.skghoshassociates. TL. the constant velocity branch terminates at a new long-period transition period. S. where a new branch . Section 12. Inc. DESIGN RESPONSE SPECTRUM • In ASCE 7-05.8 Equivalent Lateral Force Procedure Added Eq.8-4: S D1TL Cs = for T > TL T (R / I E ) 2 www. starts.skghoshassociates. • The period TL is given on new contour maps for all fifty states. Ghosh Associates. • This is the constant displacement part of the design spectrum that governs seismic response of structures with periods beyond TL. K. 12. proportional to 1/T2.com . 75 • Ta < 0. K. Section 11. Ghosh Associates.com .skghoshassociates. or for diaphragms that are flexible.8Ts • T used to calculate story drift < Ts • Upper-bound design base shear is used in design • Diaphragms are rigid.6 Seismic Design Category Can be based on SDS alone. Inc. vertical elements of seismic-force-resisting system spaced at < 40 ft Ground Motion Parameters Ts = SD1/SDS www. provided • S1 < 0. S. C. SDC of ASCE 7-05 vs. Inc. NY C A B B C(B) D(C) www. KY B A B(A) B C(B) D(C) Baltimore.skghoshassociates. K. S. A A A B(A) B C(B) Dover. MI B A A A B(A) B Kansas City.com . IL B A B B C(B) D(C) Indianapolis. IN B A A B(A) C(B) D(B) Lexington. MA C B B B C D(C) Detroit. MO C A A B(A) B(A) C(B) Springfield. KY B A B(A) B C(B) D(C) SDC of ASCE 7-05 vs. Ghosh Associates. SPC of 1999 BOCA / NBC (cont’d) 1999 ASCE 7-05 BOCA/ SITE CLASS LOCATION NBC A B C D E SPC SDC Louisville. CT C A B B C(B) C Washington. MO B A B(A) B(A) C(B) D(C) Albany. SPC of 1999 BOCA / NBC 1999 ASCE 7-05 BOCA/ SITE CLASS LOCATION NBC A B C D E SPC SDC Hartford. DE A A A B(A) B C Chicago. MD A A A B(A) B C(B) Boston. IL A A A B(A) B C(B) Springfield. D. IN 1 A A B(A) C(B) D(B) Wichita. S. AK 4 B B C D(C) D Chico. PA A A A A B(A) C(B) Norfolk.skghoshassociates. AZ 2B B B B C D(C) Little Rock. Seismic Zone of 1997 UBC 1997 UBC ASCE 7-05 LOCATION SITE CLASS Zone A B C D E Tucson. SPC of 1999 BOCA / NBC (cont’d) 1999 ASCE 7-05 BOCA/ SITE CLASS LOCATION NBC A B C D E SPC SDC Syracuse. HI 2A C C D(C) D D Indianapolis. Inc. MO 2A A A B(A) B(A) C(B) www. OH B A A B(A) C(B) D(B) Columbus. OH B A A B(A) B C(B) Pittsburgh. VA B A B B C(B) D(C) Charleston. Ghosh Associates. CA 3 B C(B) D(C) D(C) D Sacramento. NY C A A B(A) B C(B) Cincinnati. CA 3 B C D(C) D D Fresno. CA 4 B C D(C) D D Honolulu. K. WV B A A B(A) C(B) C SDC of ASCE 7-05 vs. VA A A A B(A) B(A) C(B) Roanoke. KS 1 A A A B(A) B Kansas City. SDC of ASCE 7-05 vs.com . NE 1 A A A B(A) B Las Vegas. SDC of ASCE 7-05 vs. NV 2B C C D(C) D D Tulsa. K. SPC of 1999 SBC ASCE 7-05 1999 SITE CLASS LOCATION SBC A B C D E SPC SDC Birmingham. AL B B B B C(B) D(C) Huntsville. S. AK B B B C D(C) D Orlando. GA B A B B C(B) D(C) Macon. MT 1 A A A B(A) B Omaha. OR 3 D(C) D D D D Medford. TX 0 A A A B(A) B Spokane. AL B B(A) B C(B) C(B) D(C) Montgomery. FL A A A A B(A) B Atlanta. GA B A A B C(B) D(C) www.skghoshassociates. Seismic Zone of 1997 UBC (cont’d) 1997 UBC ASCE 7-05 LOCATION SITE CLASS Zone A B C D E Billings. Ghosh Associates. AL A A A B(A) B C(B) Little Rock. WA 2B B B B C(B) D(C) SDC of ASCE 7-05 vs. Inc. OK 1 A A B(A) B C(B) Eugene.com . OR 3 C D(C) D(C) D D Houston. NC B A B(A) B C(B) D(C) Wilmington. NC B A B(A) B C(B) D(C) SDC of ASCE 7-05 vs. LA B A A B(A) B C(B) Jackson. SPC of 1999 SBC (cont’d) ASCE 7-05 1999 SITE CLASS LOCATION SBC A B C D E SPC SDC Savannah. SDC of ASCE 7-05 vs. NC C B B C(B) D(C) D Greensboro. SPC of 1999 SBC (cont’d) ASCE 7-05 1999 SITE CLASS LOCATION SBC A B C D E SPC SDC Raleigh. TX A A A A B(A) C(B) Houston. Inc.skghoshassociates. NC B A B C(B) C(B) D(C) Columbia. SC C B C D(C) D D Nashville. MS B A A B(A) C(B) D(B) Charlotte. K. TX A A A A A B www.com . TN B B B C(B) D(C) D(C) Dallas. S. GA C B B C(B) D(C) D New Orleans. LA A A A A B(A) B Shreveport. Ghosh Associates. ρ. Ghosh Associates. www.com .. ρ. ρ = 1.2 Redundancy Factor. for Seismic Design Categories D through F In ASCE 7-05.4.4.3.0 or 1.skghoshassociates. when failure of a component is failure of entire system. S. depending on whether or not an individual element can be removed from the lateral-force-resisting- system without: • Causing the remaining structure to suffer a reduction of story strength of more than 33%. Section 12.2 Redundancy Factor. • Lack of redundancy is…. Section 12. Inc. • Logical way to determine lack of redundancy is to check whether a component’s failure results in an unacceptable amount of story strength loss or in the development of extreme torsional irregularity.3. for Seismic Design Categories D through F • New redundancy provisions adopted into ASCE 7-05. K.3. or • Creating an extreme torsional irregularity. 4. Design of nonbuilding structures. K. for Seismic Design Categories D through F 2nd condition for which ρ = 1. Drift calculation and P-delta effects.0 for the following: 1.2 Redundancy Factor. ρ. ρ.3. for Seismic Design Categories D through F ρ = 1. Section 12. 2.2 Redundancy Factor. Ghosh Associates.0: If structure is regular in plan and there are at least 2 bays of seismic force-resisting perimeter framing on each side of the structure in each orthogonal direction at each story resisting > 35% of the base shear. www. Structures assigned to SDC B and C. 4. Design of nonstructural components. S.skghoshassociates. Section 12. not similar to buildings.com . Inc.3. 3.4. • Many engineers have been using the vertical earthquake term incorrectly. splices and their connections for which load combinations with overstrength are used. www. S. • New section should eliminate problem.10-1. 6. Design of members or connections where load combinations with overstrength are required for design.0 for the following: 5. Structures with damping systems designed in accordance with Chapter 18.4 added to clarify seismic load combinations. 8. 7.4 Seismic Load Effects & Combinations • New Section 12. Design of collector elements.com . (cont. 12. Diaphragm loads determined using Eq.skghoshassociates.) ρ = 1. K. Inc. Section 12. Ghosh Associates. skghoshassociates.com . • Procedure applies to structures assigned to SDC B.14 is permitted to be used in lieu of the requirements of Sections 12.13 is Foundation Design Section 12. K. www. Ghosh Associates. subject to all of the limitations contained in Section 12.14.14 Simplified Design • Simplified design procedure has been completely revised and placed in a stand- alone Section 12. the simplified design procedure of Section 12. S. Exception to Section 12.1 Structural Design Basis EXCEPTION: As an alternative. Inc. D and E.1 through 12. but is not permitted for structures.12.14. Note: Section 12. C. the design of which is typically drift-controlled. which result in a torsion- resistant regular layout of lateral-force-resisting elements.. K. 3. steel moment frames) • Procedure allowed for bearing wall and building frame systems. Ghosh Associates. Structure shall not exceed 3 stories in height above grade.14 Simplified Design • Approach limited to certain structural systems.skghoshassociates. Inc.com .g. The seismic-force resisting system shall be either a bearing wall system or a building frame system. 4. so as to avoid problems arising from omission of drift check for drift-controlled systems (e. 2. www. S. The site class shall not be E or F. APPLICABILITY OF SIMPLIFIED DESIGN 1. Section 12. provided several prescriptive requirements are met. The structure shall qualify for Occupancy Category I or II. 6. overhangs beyond the outside line of shear walls or braced frames shall satisfy: a ≤ d/5 APPLICABILITY OF SIMPLIFIED DESIGN d = depth of diaphragm parallel to forces being considered at the line of vertical resistance closest to the edge a = distance perpendicular to force being considered from the a extreme edge of the d diaphragm to the line of vertical resistance closest to that edge a ≤ d/5 www. For structures with flexible diaphragms. Ghosh Associates. At least one line of resistance shall be provided on each side of the center of mass in each direction. K. Inc. APPLICABILITY OF SIMPLIFIED DESIGN 5. 7.com . Structure shall have at least two lines of lateral resistance in each of two principal axis directions.skghoshassociates. S. Ghosh Associates. Inc.15b1 CENTER OF MASS b1 d23 d22 d12 = d13 k23 WALL 3 WALL 2 k22 k13 k12 X-AXIS b2 www.14-1 d11 CENTER OF RIGIDITY AXIS-1 e1 e1 ≤ 0. APPLICABILITY OF SIMPLIFIED DESIGN 8. distance between the center of rigidity and center of mass parallel to each principal axis shall not exceed 15% of greatest width of diaphragm parallel to that axis. For buildings with a diaphragm that is not flexible. S.com . 12. APPLICABILITY OF SIMPLIFIED DESIGN Y-AXIS AXIS-2 k11 WALL 1 Fig. K.skghoshassociates. www.skghoshassociates.com . K. S. APPLICABILITY OF SIMPLIFIED DESIGN 8. APPLICABILITY OF SIMPLIFIED DESIGN Equation in Condition 8 need not be checked if: • Arrangement of walls or braced frames is symmetric about each principal axis direction. • Distance between the two most separated lines of walls or braced frames is at least 90% of the dimension of the structure perpendicular to that axis direction. Inc. Ghosh Associates. • Stiffness along each line considered above is at least 33% of total stiffness in that axis direction. skghoshassociates. www. Ghosh Associates. System irregularities caused by in-plane or out-of- plane offsets of lateral-force-resisting elements shall not be permitted. The lateral-load-resistance of any story shall not be less than 80% of that of the story above. Inc. 10. APPLICABILITY OF SIMPLIFIED DESIGN 9. Lines of resistance of the lateral-force-resisting system shall be oriented at angles of no more than 15 degree from alignment with the principal axes. The simplified design procedure shall be used along each principal axis of building. S.com . APPLICABILITY OF SIMPLIFIED DESIGN 11. (Note: Exception for two-story buildings of light- frame construction). K. 12. www. K. SIMPLIFIED DESIGN FSDS V = W R 2 SDS = FaSS 3 SS ≤1.com .skghoshassociates. Inc.5 Fa is permitted to be taken as 1. S.4 for soil sites or determined as for non-simplified design SIMPLIFIED DESIGN • Site may be considered as rock if there is no more than 10 ft of soil between rock surface and bottom of spread footing or mat foundation. Ghosh Associates.0 for rock sites 1. 0 for one-story buildings 1. ρ = 1. Ghosh Associates.0 Ω0=2.skghoshassociates.com .1 for two-story buildings 1.5 www. S. Inc.2 for three-story buildings W = effective seismic weight SIMPLIFIED DESIGN wX FX = V W wX = portion of effective seismic weight of structure at level x. K. SIMPLIFIED DESIGN F = 1. which typically would not conform to special detailing requirements NEW SEISMIC FORCE-RESISTING SYSTEMS Prestressed Masonry Shear Walls • Consistency with ACI 530 / ASCE 5 / TMS 402 • Systems are permitted in SDC A and B only and are assigned an R-value of 1. Inc. Ghosh Associates.skghoshassociates. provided building height ≤ 40 ft • Indirect way of permitting lateral-force-resisting tilt-up walls in SDC D. since behavior is essentially stiffness-dependent linear elastic with little ductility and energy dissipation www. E or F.5. • Intermediate precast walls are permitted as part of the seismic force-resisting system in SDC D.com . E or F. NEW SEISMIC FORCE-RESISTING SYSTEMS (Table 12. S.1-1) Ordinary and Intermediate Precast Shear Walls: • Ordinary precast shear walls are permitted in SDC A or B only. K. S. K.14.1 Seismic Coefficients for Nonbuilding Structures ASCE 7-05 Tables 15. Section 12.1. Inc.4-1 & 15.9 Modal Response Spectrum Analysis • Modal analysis procedure is now referred to as “Modal Response Spectrum Analysis” • Much is deleted because it is considered textbook material and because commercial software is used by engineers to implement procedure. Ghosh Associates.skghoshassociates.com .4-2 Seismic Coefficients for Nonbuilding Structures Similar to Buildings & Seismic Coefficients for Nonbuilding Structures NOT Similar to Buildings www. Chapter 15 NONBUILDING STRUCTURES ASCE 7-02 Table 9.5. S.com . Inc. there is an additional feature which allows the option of less restrictive height limits. Chapter 15 NONBUILDING STRUCTURES Problem in ASCE 7-02: Table 9.14.1 (Seismic Coefficients for Nonbuilding Structures) referred to Table 9. Ghosh Associates.2.1.5. PLUS. www.4-1 sets forth consistent height limits as for building structures.2 for R values. provided a lower R value is used. K. but then set forth more relaxed height limitations than what was specified in Table 9. Chapter 15 NONBUILDING STRUCTURES Solution in ASCE 7-05: Table 15.skghoshassociates.2.5.5.2. 5 1 1.com .5 NL NL NL NL NL Table 15.skghoshassociates.5 1 1.d NPc. Table 15.d NPc.5 2 2.25 2 3.4. Inc.25 NL NL 35b 35b NPb frame With permitted height AISC 341 2.5 NL NL NL NL NL www.5 3 4 NL NL 35c. S.4.5 NL NL 160 160 100 increase With unlimited height AISC 341 1. Ghosh Associates.d frames With permitted height AISC 341 2. K.5 2 2.1 Seismic Coefficients for Nonbuilding Structures Similar to Buildings Structural System and Height Detailing Limits (ft)a Nonbuilding Structure Type R Ω0 Cd Requirements A &B C D E F Moment resisting frame systems: Intermediate steel moment AISC 341 4.1 Seismic Coefficients for Nonbuilding Structures Similar to Buildings Structural System and Nonbuilding Structure Detailing Height Limits (ft)a R Ω0 Cd Type Requirements A &B C D E F Building frame systems: Ordinary steel concentrically braced AISC 341 3.5 NL NL 160 160 100 increase With unlimited height AISC 360 1. 5 3 3 NL NL NPc.5 NL NL 100 100 NPc. Ghosh Associates.8 1 1 NL NL NL NL NL Table 15.d With unlimited height AISC 360 1 1 1 NL NL NL NL NL www.1 Seismic Coefficients for Nonbuilding Structures Similar to Buildings Structural System and Height Detailing Limits (ft)a Nonbuilding Structure Type R Ω0 Cd Requirements A &B C D E F Moment resisting frame systems: Ordinary moment frames AISC 341 3. K. increase Chapter 21 3 2 2. Inc. concrete moment frames Chapter 21 5 3 4.5 NL NL NP NP NP With permitted height ACI 318.d of steel With permitted height increase AISC 341 2. Chapter 21 0. S. Table 15.com .d NPc.4.1 Seismic Coefficients for Nonbuilding Structures Similar to Buildings Structural System and Height Detailing Limits (ft)a Nonbuilding Structure Type R Ω0 Cd Requirements A&B C D E F Moment resisting frame systems: Intermediate reinforced ACI 318.d NPc.4.5 NL NL 50 50 50 With unlimited height ACI 318.skghoshassociates.5 2 2. Visit www. S. the height of the structure shall be taken as the height to the top of the structural frame making up the primary seismic-force resisting system.skghoshassociates.1 Seismic Coefficients for Nonbuilding Structures Similar to Buildings Notes: a NL = no limit and NP = not permitted. c Steel ordinary moment frames and intermediate moment frames are permitted in pipe racks up to a height of 65 feet (20 m) where the moment joints of field connections are constructed of bolted end plates. K. b Steel ordinary braced frames are permitted in pipe racks up to 65 feet (20 m).com .com for ASCE 7-05 Errata www.4.skghoshassociates. Inc. Ghosh Associates. dSteel ordinary moment frames and intermediate moment frames are permitted in pipe racks up to a height of 35 ft (11 m). e For the purpose of height limit determination. Table 15. Height shall be measured from the base.