Structural Eurocodes EN 1993 Design of Steel Structures

1 Structural EurocodesEN 1993 Design of Steel StructuresJohn J Murphy Chartered EngineerDepartment of Civil, Structural & Environmental Engineering Cork Institute of TechnologyDepartment of Civil, Structural & Environmental Engineering Cork Institute of TechnologyDesigners guide to eurocode 3: Design of Steel Structures (L Gardner and D A Nethercot) Thomas TelfordAccess Steel website that provides much information on Design to EC3 Access Steel is a unique electronic resource to ensure that the European Steel construction community takes maximum advantage from the commercial opportunities arising from the input from six leading institutes for Steel construction in Europe, it provides harmonised information for clients, architects and engineers on.

2 Multi storey commercial buildings single storey buildings residential construction fire safety engineering of Civil, Structural & Environmental Engineering Cork Institute of TechnologyPartnersSteel Construction Institute (SCI) (UK)Centre Technique Industriel de la Construction Metallique (CTICM ) (France)Stalbyggnadsinstutet Swedish Institute of Steel Construction (SBI) (Sweden)Rheinish-Westfalische Technische Hochschule Aachen (RWTH) (Germany)Labein Tecnalia (Spain)Profilarbed Research (PARE) (Luxembourg)SponsorsArcelor-Mittal, Corus, Peiner Tr ger, Voest Alpine, Ruuki, Dillinger, SSABD epartment of Civil, Structural & Environmental Engineering Cork Institute of TechnologyEN 1993-1-1: General rules and rules for buildingsEN 1993-1-2: Structural fire designEN 1993-1-3: Cold formed thin gauge members and sheetingEN 1993-1-4: Structures in stainless steelEN 1993-1-5: Strength and stability of planar plated Structures without transverse loadingEN 1993-1-6: Strength and stability of shell structuresEN 1993-1-7.

3 Strength and stability of plate Structures loaded transversallyEN 1993-1-8: Design of jointsEN 1993-1-9: Fatigue strengthEN 1993-1-10: Fracture toughness assessmentEN 1993-1-11: Design of Structures with tension components made of steelEN 1993-1-12: Use of high strength steelsDepartment of Civil, Structural & Environmental Engineering Cork Institute of TechnologyIwItIWplWeliy,zAEC3 HJISZrx,yABS5950tf,twdB,hVMN fy LTfyfyEC3T,tdB,DVMP pcpbpyBS5950 SymbolsDepartment of Civil, Structural & Environmental Engineering Cork Institute of TechnologyTable : fyfuClause = 210000 N/mm2G 81000 N/mm2, = : t < 40 mmfy= 275 N/mm2fu= 430 N/mm240 mm < t < 80 mm fy= 255 N/mm2 fu= 410 N/mm2 Material properties taken from EN 10025-2, which gives additional values for different for S275 16 mm < t < 40 mm fy= 265 N/mm2.

4 Table is a simplification of EN Classification of cross sectionsTable { = (235/fy)}Class 1,2,3,4 Department of Civil, Structural & Environmental Engineering Cork Institute of Technology5 Structural (2) Calculation model and basic assumptions should reflectstructural (2) Depending on joint behaviour simple, continuous, (3) First order analysis when cr= Fcr/FEd 10 elastic analysis15 plastic analysisFcr: Elastic critical buckling loadFEd: Design loadDepartment of Civil, Structural & Environmental Engineering Cork Institute of < EdHEdEdhVH, EdHEdEdhVH, which translates as NEd/Ncr : Design horizontal load at bottom of storeyVEd: Design vertical load at bottom of storeyh: Storey height H,Ed.

5 Horizontal displacement of top of storey relative to bottom of < EdHEdEdhVH, (4) For portal frames and beam-column plane frames, providing axial compression in beams/ rafters is not significant, cr=Department of Civil, Structural & Environmental Engineering Cork Institute of Structural stability of (3) b) Second order effects accounted for partially by global analysis and partially through individual member stability checks according to (5) If cr 3, amplify all horizontal loads by cr 111 Second order effects likely to arise in unbraced Structures and in bracing Design of braced structuresIf cr< 3, second order analysis is necessaryDepartment of Civil, Structural & Environmental Engineering Cork Institute of Technology() + (3) a) Global initial sway imperfection: = 0* h* m 0: Initial value =1/200 h: Reduction factor for column height = 2/ h (2/3 h 1) (h: structure height) m.

6 Reduction factor for number of columns in a row = Recommendation (SCI) - use let h= m= of Civil, Structural & Environmental Engineering Cork Institute of Technologywhich translates as NEd/Ncr equivalent horizontal forces (EHF s) for all load < (3) b) Relative initial local bow imperfection (Table ) (1) ..taken into account using checks in providedDepartment of Civil, Structural & Environmental Engineering Cork Institute of Technology6 Ultimate limit Material factors M M0= (cross-sections) M1= (Buckling) M2= (Fracture) ( in UK) Tension(1) NEd Nt,Rd(2) Npl,Rd= Afy/ M0gross section(3) Nu,Rd= M2bolt holesEN 1993-1-8: (2)For equal angle leg or unequal angle connected (by welding) by its larger leg Aeff= AgrossEN 1993-1-8.

7 (2)Nu,Rd formulae for resistance of angle connected through one leg using 1,2 or 3+ boltsDepartment of Civil, Structural & Environmental Engineering Cork Institute of Compression(1) NEd Nc,Rd(2) Nc,Rd= Afy/ M0(class 1,2,3)Aefffy/ M0(class 4)EN 1993-1-5 Clause :Aeffis determined by excluding ineffective portion of of Civil, Structural & Environmental Engineering Cork Institute of Bending moment(1) MEd Mc,Rd(2) Mc,Rd= Mpl,Rd= Wplfy/ M0(class 1,2)Wel,minfy/ M0(class 3)Weff,minfy/ M0(class 4)(4) Fastener holes in tension flange may be ignored provided.

8 Af, M2 Affy/ M0 Department of Civil, Structural & Environmental Engineering Cork Institute of Shear(1) VEd Vc,Rd(2) Vpl,Rd= Av(fy/ 3)/ M0(3) I sectionAv= A 2btf+ (tw+ 2r)tfbut not less than hwtw(6) Shear buckling if hw/tw> 72 / may be conservatively taken as 1EN1993-1-5 Clause Note 2: = up to and including S460; otherwise Bending and shear(2) VEd1 ,Rd no effect on Mc,Rd(3) Reduced moment resistance: reduced Design yield strength (1- )fy2,12 =RdplEdVV Department of Civil, Structural & Environmental Engineering Cork Institute of Technology1,,,,,, + Bending and axial Class 1 and 2 cross-sections(4) Axial force can be ignored:yy axis: if NEd ,RdandNEd M0zz axis: if NEd hwtwfy/ M0(5) Values of reduced moment capacities.

9 MN,y,Rd, MN,z,Rd(6) Department of Civil, Structural & Environmental Engineering Cork Institute of TechnologyConservative alternative for all sections: (7)1,,,, ++RdzEdzRdyEdyRdEdMMMMNNEq buckling is generally critical and will override Eq. , the more exact equations in need not generally be of Civil, Structural & Environmental Engineering Cork Institute of Buckling resistance of membersElastic buckling theory (Euler)Ncr= 2EI/l2for ideal strutThis value is modified by various imperfections:Geometric imperfections (initial curvature)Eccentricity of loadingResidual stresses ( locked-in due to differential cooling)Non-homogeneity of material propertiesEnd restraintsThese are taken into account in the Perry-Robertson formulaDepartment of Civil, Structural & Environmental Engineering Cork Institute of TechnologyEC3 provides solution for this equation.

10 Effectively cr= fy}{EyEyEycr ++ ++=2)2/))1(((2)1(Department of Civil, Structural & Environmental Engineering Cork Institute of Uniform members in Buckling resistance(1) NEd Nb,Rd(3) Nb,Rd= Afy/ M1 (class 1,2,3) Aefffy/ M1 (class 4)Department of Civil, Structural & Environmental Engineering Cork Institute of 221 +=[]22) (15,0 + +=cryNAf= cryeffNfA= Buckling curves(1) (but 1)(class 1,2,3) : imperfection factor (Table ) (Table )Ncr: Elastic critical buckling load (chi) can also be obtained from Figure (4) If(class 4) () buckling effects can be ignoredDepartment of Civil, Structural & Environmental Engineering Cork Institute of Technology1 = Slenderness for flexural bucklingfcr= Ncr/A = 2EI/Al2= 2 EAi2/Al2= 2E/ 2 Letting fcr= fylimiting slenderness 1= (E/fy) = Lcr/izcryNAf(ratio of actual slenderness to slenderness at boundary between yielding and elastic buckling) = (E/fcr) ( (Efy) ) = (fy/fcr).