林保均 / Pao-Chun Lin. National Center for Research on Earthquake Engineering M.S. / Civil Engineering Department, National Taiwan University

Transcription

1 Seismic Design of WES-BRB and Gusset Connections 林保均 / Pao-Chun Lin Assistant Researcher National Center for Research on Earthquake Engineering M.S. / Civil Engineering Department, National Taiwan University Using WES-BRBs for An Improved Seismic Resisting Performance of Buildings Auckland, Wellington and Christchurch, New Zealand Nov , 14, 2013

2 Seismic design of BRBF Design base shear force V design BRB axial force = 09Py 0.9Py 0.9P y 0.9P y Base shear 0.9P y V design Story drift V design

3 Seismic design of BRBF Design base shear force V design BRB axial force = 09Py 0.9Py Max. base shear force V max BRB axial force = P max The gusset plates are required to sustain the BRB max. axial force P max Base shear V max P max P max P max V design Story drift V max

4 Brace On Demand browser Design requirement space strength stiffness Design results 1WES-BRB 1.WES-BRB 2.Gusset 3Welding 3.Welding 4.DCR checks

5 emandaatuser guide for BOD users 7 categories of limit state Load and Resistance Factor Design Specification for Structural Steel Buildings (AISC ) Seismic Provision for Structural Steel Buildings (AISC ) P.C. Lin, K.C. Tsai, K.J. Wang, Y.J. Yu, C.Y. Wei, A.C. Wu, C.Y. Tsai, C.H. Lin, J.C. Chen, A.H. Shellenberg, S.A. Mahin, C.W. Roeder, Seismic design and hybrid tests of a full-scale three-story buckling-restrained frame using welded end connections and thin profile, Earthquake and Structural Dynamics, 2012, 41: P.C. Lin, K.C. Tsai, A.C. Wu and M.C. Chuang, Seismic design and test of gusset connections for bucklingrestrained braced frames, Earthquake Engineering and Structural Dynamics, 2013, eqe. 2360

6 Outline Introduction Seismic i design of BRBF Design of BRB and gusset connection WES-BRB component design Uniform force method (UFM) Generalized uniform force method (GUFM) Frame action effects Test and analysis on BRBF Large-scale Test and FEM analysis Conclusions

7 DCR-1 / Steel casing buckling The steel casing must prevent the BRB from flexural buckling. I sc : moment of inertia provided by steel casing L sc R P y h y Demand: P max P L Capacity: e 2 2 EI sc sc Axial Force (kn N) R R y P y P y h y Axial Displacement (mm)

8 DCR-2 / Joint region yielding A : joint section cross- j sectional area P max / The BRB joint section must sustain the maximum brace tensile force and remain elastic. Demand: P max / FRA Capacity: y y j 0.90 (AISC , D2)

9 DCR-3 / Joint region buckling The BRB joint section of unrestrained length from W.P. to the steel casing end must sustain the maximum brace force and remain elastic. P max Demand: P max L b work point (W.P.) 0.02L c Capacity: EIy min, FRA 2 4 L b y y j (AISC , E1)

10 BRB end-to-gusset space requirements BRB end-to to-gusset fillet weld length L w 0.707T 0.6F 4L D P L v L w D j max w exx w j L h T w 0.8 t Slab tick. t s (150mm) BRB end clearance requirements: to slab: 50mm to beam face: 75mm to column face: 75mm c mm clearances at the gusset plate edges Configure the gusset plate length L h and height L v

11 DCR-4 / Gusset plate block shear failure Select appropriate gusset plate thickness t g and L w so the gusset must sustain the maximum brace tensile force and avoid the block shear failure. Demand: P max / L w Capacity: P 0.6F A F A Capacity: 0.75 n u, g nv u, g nt F y, g A gv F u, g A nt D j (AISC , J4) t : gusset thickness g shear area tensile area A A 2L t gv nv w g A A Dt gt nt j g

12 DCR-5 / Gusset plate yielding The gusset plate must sustain the maximum brace tensile force and remain elastic. P max / Demand: P max / o The yielding capacity of the Whitmore section region on the gusset plate is adopted as the capacity. (Whitmore RE, 1952) B e Capacity: F B t y, g e g (AISC , D2) F y,g : gusset plate material yield strength

13 DCR-6 / Gusset plate buckling The gusset plate must sustain the maximum brace force and avoid gusset plate flexural buckling. L r L L L Gusset buckling length L 3 o P max L 1 L cr, g 2 Demand: P max The buckling strength th of the Whitmore section region and the average of critical length on the gusset plate is adopted as the capacity. (Thornton WA, 1984) Capacity: 0.90 F B t e g L 2 2 Whitmore section region Bt e g F cr, g c Fyg,, c Fyg,, c 1.5 c (AISC , E1)

14 BRB axial force - Uniform Force Method (UFM) c g c gc gc g gb φ (Thornton, 1991) Adopted by AISC Simple and straightforward Irregular or undesirable gusset shape βg V gc P max gb r b b e Hgc Pmax r 2 2 e β b Vgb Pmax r eb βg α Hgb Pmax c g r r e β e α b g c g tanφ e α c g

15 BRB axial force - Generalized Uniform Force Method c φ max H uc (Muir, 2008) Designers g can configure the gusset in any shape (UFM) Compute p the gusset interface forces according to the gusset shape P max e c e b sinφ β c V uc cos Vub Pmax 2β α e β H uc V ub H ub b b H P φ H ub eb eb β φec sinφ max cos 2α V P φ V uc max sin ub uc b

16 Frame action effects L v L v L h L h L/2 inflection point

17 Frame action effects Joint closes L/2 V beam beam inflection point

18 Frame action effects Joint opens V beam beam L/2 inflection point

19 Frame action effect - equivalent strut model S L g L h N L h p,beam V beam inflection point (Lee, 2002) The equivalent strut axial force represents the frame action force Compute the V beam by assuming the beam plastic hinges form at gusset tips L/2 R M (Kasai, et. al, 2008) (Chou, et. al, 2011) V beam 2 yb, pbeam, L L h V L v dlv b h b L Lh L g N S 4Ib L v dl0.3d 0.18L S t p, beam b h b v L h L h p,beam V b eam dlv0.3l 0.18L L/2 inflection point N g 4 I t g b b v b h dl 0.3d 0.18L b h b v

20 Frame action effects - FEM analysis BRB in tension Beam-to-column joint closes Gusset plate is compressed M p,beam M p,beam M p,beam M p,beam M p,beam von Mises stress (GPa) Gusset plate is tensioned BRB in compression Beam-to to-column joint opens The beam plastic hinges form at inter-story drift of rad.

21 Combined effects: BRB + frame action effects uc uc c c Joint opens ub ub b b uc c Joint closes frame action forces + BRB axial force uc ub ub equivalent strut model + UFM / GUFM Gusset interface force demands V=V c uc+n H=S c - Huc V =N - V H =H +S b ub b ub c b b

22 DCR-7-1, DCR-7-4 / Gusset interface strength The gusset strength th must sustain the combined von Mises stress resulting from brace maximum axial force and frame action. L v H c Pmax Demand: (beam) Demand: (column) V c V b H b 3 Lt h g Lt h g DCR-7-1 H c V c 3 Lt v g Lt v g DCR-7-4 V b Lh h H b Capacity: 1.00 F y, g

23 DCR-7-2, DCR-7-5 / Gusset interface strength The gusset strength th must sustain the maximum normal stress resulting from brace maximum axial force and frame action, and avoid the tensile rupture failure. L v H c P max Demand: Demand: (beam) (column) Vb Lt h g DCR-7-2 H c Lt v g DCR-7-5 V b Lh L h, Capacity: 0.75 F ug F ug, : gusset material tensile rupture strength (AISC , J4)

24 DCR-7-3, DCR-7-6 / Gusset interface strength The gusset strength th must sustain the maximum shear stress resulting from brace maximum axial force and frame action, and avoid the shear rupture failure. L v V c P max Demand: Demand: (beam) (column) Hb Lt h g DCR-7-3 V c Lt v g DCR-7-6 L h H b, Capacity: F ug (AISC , J4)

25 BRBF beam design The beam must be designed to sustain the axial force resulting from the BRB. The beam with suitable flexural capacity (M p,beam ) can reduce the force demands from frame action effect. L v L g N 2 Ry, beamm, L v S Vbeam L L L h L h p,beam V beam V b h p beam V p, beam L/2 inflection point

26 Large-scale BRBF tests roof 3F disp. displacement history Test 1, hybrid test, PGA = 530 gal roof 3F displacement disp. history Test 2, hybrid test, PGA = 530 gal Test 3, Cyclic loading test roof 3F displacement disp. history earthquake time (sec)

27 Large-scale BRBF hybrid tests groun nd accelerati ion (g) LA03 PGA = 0.53g time (time) (sec) Story Sh hear (kn) 3000 LA03 (phase1) gal LA03 (phase2) 530gal nd Story 2 nd Story 3000 LA03 (phase1) LA03 (phase2) gal 530gal Experiment PISA3D 1st Story 1 st Story OpenSEES Inter-Story Drift (% rad.)

28 Gusset interface welding failures Fractured at Hybrid Test 2 inter--story drift: rad. inter Fractured at Cyclic loading test inter--story drift: rad. inter

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30 Gusset plate edge stiffener - increase the out-of-plane stability inter-story drift Reduce the stress concentration at gusset tips (GPa)

31 FEM analytical results (von Mises stress) (GPa) 360 mm gusset thick. (t g ) = 15 mm mm 250 Stiffener thick. t sf = 15mm without stiffener 1.5t 1 g 2.5t g 3.5t g 4.5t g (22.5 mm) (37.5 mm) (52.5 mm) (67.5 mm) Stiffener width w sf 1.5t g 2.5t g 3.5t g 4.5t g Minimum required stiffener cross-sectional area 2.5t g x t g

32 DCR and design checks 1. BRB component DCR-1 / steel casing buckling DCR-2 / joint region yielding DCR-3 / joint region buckling 2. BRB end-to-gusset connection DCR-4 / gusset plate block shear failure DCR-5 / gusset plate yielding DCR-6 / gusset plate buckling 3. Gusset-to-beam and column interfaces DCR-7-1 / gusset-to-beam von Mises yield criterion DCR-7-2 / gusset-to to-beam tensile fracture DCR-7-3 / gusset-to-beam shear fracture DCR-7-4 / gusset-to to-column von Mises yield criterion DCR-7-5 / gusset-to-column tensile fracture DCR-7-6 / gusset-to-column shear fracture

33 Design checks of diagonal BRBF 7 Categories of limit state DCR-6 upper Gusset plate buckling DCR-7-1 upper DCR-7-2 upper Gusset to beam, tensile rupture DCR-7-3 upper Gusset to beam, von Mises yield criterion Gusset to beam, shear rupture DCR-2 Joint region yielding Steel casing buckling DCR-7-1 lower DCR-7-2 lower Gusset to beam, tensile rupture DCR-7-3 lower Gusset to beam, von Mises yield criterion Gusset to beam, shear rupture DCR-6 lower Gusset plate buckling Diagonal configuration - 21 DCRs

34 Design checks of chevron BRBF 7 Categories of limit state DCR-3 left upper Joint region buckling DCR-5 left upper Gusset plate yielding DCR-4 left Gusset plate block shear failure DCR-3 right upper Joint region buckling DCR-5 right upper Gusset plate yielding DCR-4 right Gusset plate block shear failure Steel casing buckling DCR-5 left lower Gusset plate yielding Steel casi sing buckling DCR-5 right lower Gusset plate yielding DCR-3 left lower Joint region buckling DCR-3 right lower Joint region buckling Chevron configuration - 33 DCRs

35 Brace On Demand browser Design requirement space strength stiffness Design results 1WES-BRB 1.WES-BRB 2.Gusset 3Welding 3.Welding 4.DCR checks

36 emandaatuser guide for BOD users 7 categories of limit state Load and Resistance Factor Design Specification for Structural Steel Buildings (AISC ) Seismic Provision for Structural Steel Buildings (AISC ) P.C. Lin, K.C. Tsai, K.J. Wang, Y.J. Yu, C.Y. Wei, A.C. Wu, C.Y. Tsai, C.H. Lin, J.C. Chen, A.H. Shellenberg, S.A. Mahin, C.W. Roeder, Seismic design and hybrid tests of a full-scale three-story buckling-restrained frame using welded end connections and thin profile, Earthquake and Structural Dynamics, 2012, 41: P.C. Lin, K.C. Tsai, A.C. Wu and M.C. Chuang, Seismic design and test of gusset connections for bucklingrestrained braced frames, Earthquake Engineering and Structural Dynamics, 2013, eqe. 2360

37 Conclusions 1. The effects of BRB axial force and frame action must be considered to compute the demands for BRB component and gusset plate design. 2. The GUFM and the equivalent strut model are adopted for BRB axial force and the frame action effects. 3. The BRBF tests and FEM analysis showed the proposed method can be used to evaluate the gusset interface forces. 4. The beam with suitable flexural capacity is suggested since it lowers the frame action force demands on gusset plate design.

38 Thanks for your attention