2010.05.01 1 Eurocode 3 - Design of joints Dr.Eng. Bjørn Aasen 2 Eurocode 3: Design of steel structures Part 1-8: Design of joints 1. Introduction 2. Basis of Design 3. Connections made with bolts, rivets or pins 4. Welded connections 5. Analysis, classification and modelling 6. Structural joints connecting H or I sections 7. Hollow section joints 2010.05.01 2 3 EC3 - Part 1-8: Design of joints 1.4.2 connection Location at which two or more elements meet. … 1.4.4 joint Zone where two or more members are interconnected. … A welded connection A beam-to-column joint 4 EC3 - Part 1 - 8: Design of joints 1.1 Scope This part of EN 1993 gives design methods for the design of joints subject to predominantly static loading using steel grades S235, S275, S355, S420, S450 and S460. The scope should be also include the design of bolted and welded connections, see Part 1-9 Fatigue: EN 1993-1-9 gives methods for the assessment of fatigue resistance of members, connections and joints subjected to fatigue loading. 2010.05.01 3 5 However, be careful when fatigue may govern The requirements given in table 8.7 impose severe restrictions for the use of hollow sections joints when subjected to fatigue: • t 0 and t i ≤ 8mm • d 0 ≤ 300 mm for CHS • b 0 ≤ 200 mm for RHS 6 The new Holmenkollen Ski Jump Hill 2010.05.01 4 7 1 st challenge: transport of steel members! 8 2 nd challenge: the structures are curved! 2010.05.01 5 9 3 rd challenge: the missing link! Fancy output Software Structural analysis the Missing Link Handmade sketches & calculations Paperware Designer Nice drawings CAD Software Drawings 10 The strategy for design of joints Structural analyses (STAAD) Manipulation of results (Excel) Design of joints (Mathcad) Sketches of joints (SmartSketch) 3D Strutural model (Tekla) 2010.05.01 6 11 Fabrication of a joint of the wind screen Design rules for gusset plate connections are not included in Eurocode 3 12 Design of welded a gusset plate connection 2010.05.01 7 13 Strength of welded gusset plate connections 1. Gross section yielding of the hollow section EC3 Part 1-1 2. Tensile strength of the hollow section due to shear lag CIDECT Design Guide No. 3, 2 nd Ed., 2009 3. Tensile strength of the hollow section due to tear-out CIDECT Design Guide No. 3, 2 nd Ed., 2009 4. Yielding and buckling of the gusset plate Design rules proposed by Prof. A. Astaneh-Asl 5. Strength of the welds between gusset plate and chord EC3 Part 1-8 14 CIDECT Design Guide No. 3, 2 nd Ed., 2009 2010.05.01 8 15 Tensile strength of the hollow section Two possible failure modes have been identified for gusset plate-to-slotted RHS joints loaded in tension: • CF: circumferential failure of the RHS and • TO: tear-out or block shear failure of the RHS 16 Circumferential failure (CF) Gusset plate-to-slotted RHS joints: a) longitudinal welds only and b) longitudinal welds plus a weld return p w 7 , 5 4 , 2 w 2 M u n Rd , t t h b w 7 , 0 w L for w L 1 1 1 f A 9 , 0 N − + ≈ ≥ | | | | | | | ¹ | \ | ( ( ¸ ( ¸ | ¹ | \ | + − = γ 2010.05.01 9 17 Tear out failure (TO) Gusset plate-to-slotted RHS joints: a) longitudinal welds only (A nt = 0) b) longitudinal welds plus a weld return 7 , 0 w L for f f 1 3 2 1 A A f 9 , 0 N w 0 M 2 M u y gv nt 2 M u Rd , t < ( ( ¸ ( ¸ ( ¸ ( ¸ + + = γ γ γ 18 Gross yielding of the gusset plate 2010.05.01 10 19 Warning! Failure of truss girder due to gusset plate buckling H. Schmidt et al: An uncommon stability problem causes failure Der Stahlbau 77 (2008) No. 12 20 Erection of the first section of wind screen 2010.05.01 11 21 The bottom supports 22 The transition between welded and bolted connections 2010.05.01 12 23 The upper support 24 Connections made with pins 2010.05.01 13 25 Bolted connections 26 The strength of bolted connections Limits states of fin plate connections • Shear failure of bolts • Bearing failure of beam web or plate • Yielding of gross area of beam web or plate • Fracture of net area of beam web or plate • Buckling of gusset plate • Bending of gusset plate • Fracture of welds 2010.05.01 14 27 Eurocode 3 - Part 1-1: Net section failure t p 4 s nd b A 2 0 net | | ¹ | \ | + − = ∑ 28 Details of a bolted joint 2010.05.01 15 29 EN 14399-6 Washers 8.8 / 8 Property classes EN 14399-3 Bolt/nut assembly EN 14399-2 Suitability test EN 14399-1 General requirements System HR High-strength structural bolting assemblies for preloading 30 Erection of the top section 2010.05.01 16 31 Design of simple joints in steel structures 32 Resistance of fin plate connections Limits states of fin plate connections • Shear failure of the bolts • Bearing failure of the beam web or the plate • Yielding of gross area of beam web or plate • Fracture of the net area of beam web or plate • Buckling of the plate • Bending of the plate • Fracture of the welds 2010.05.01 17 33 Concern about bolt design Some Norwegians question why bolts should be designed for the combined effects of a direct shear and a moment equal to the shear multiplied by the eccentricity of the bolt line from the weld line: 2 1 Rd , b Rd , v Rd p ) 1 n ( z 6 1 ) F , F min( n V ( ¸ ( ¸ + ⋅ + ⋅ = 34 Astaneh: Plate hole deformations after tests The deformations of the plate bolt holes indicate the direction of the movement of the bolts which is expected to be approximately the direction of the applied force due to shear and moment. 2010.05.01 18 35 Astaneh: Recommended design of bolts It is recommended that bolts be designed for combined effects of direct shear and a moment equal to the shear multiplied by the eccentricity of the bolt line from point of inflection given by e b = (n-1)(25,4mm)-a where n = number of bolts used in the connection a = the distance from the bolt line and the weld line 36 Thank you for your attention!