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1 CH INA C IV IL ENG INEER ING JO URNAL Vol. 42 No. 5 May RC (1., ; 2., ) :,,, 3 : ; ; 2 3, ;,,, : RC ; ; ; ; ; ; : TU TU : A : X (2009) Analysis of the damage mechan ism of a typical RC frame in W enchuan Earthquake L in X uchuan 1 Pan Peng 1 Ye L ieping 1 L u X inzheng 1 Zhao Shichun 2 ( 1 Tsinghua University, B eijing , China; 2 Southwest J iaotong University, Chengdu , China) Abstract: Many RC frame structures were severely damaged with p lastic hinges formed at column ends rather than beam ends in the W enchuan Earthquake, significantly different from the expected failure mode in seism ic design code. Based on an investigation of a typ ical RC frame structure damaged in the earthquake area, tim e history analyses using a sophisticated finite element method were conducted. Three models were considered, i. e. pure fram e, fram e w ith floor slab, and frame w ith both floor slab and infill wall. A ground motion recorded at the town of B ajiao in the earthquake zone was used for the analyses, and comparison between the three models were carried out to investigate the effect of floor slab and infill wall on the structural base shear, distribution of p lastic hinges and failure m echanism. M ajor findings are: Strong column and weak beam cannot be guaranteed for the RC frames designed according to the current Chinese design code. Infillwallsmay significantly alter the failure mechanism of the RC frames. W eak story mechanism may easily occur for structures w ith non - uniform infill walls. These findings suggest that the effects of floor slab and infill wall should be considered in seism ic design, the stiffness and strength of columns need be enhanced to achieve " strong colum n and weak beam" behavior, and structural elasto - p lastic analysis model should take slabs and infill walls into account. Keywords: RC frame; seism ic perform ance; floor slab; infill wall; finite element model; tim e history analysis; failure mechanism E2ma il: linxc03@ gmail. com , : (2006BAJ03A02) ( ) :, : ,, ( 1 ),,, ( 2 3 ),, [ 1 ] pushover, [ 2 ],

2 [ 3 ] [ 4 ],,,, ), ( GB ) [ 5 ] :,,,,,,,,,,,, (JGJ ) [ 6 ] :, ,, ( GB ) (JGJ ) :, 0. 15, : M c = c M b (1) 9 : M c = 1. 2 M bua (2) : M c,, ; M b,, ; M bua 1 (, ( ) ; c, 1. 4, 1. 2, 1. 1

3 42 5 RC 15,,,,,,, [ 7 ], (1) (2),,,, (1) M c M b,,, ,, 2,, MSC. MARC [ 8 ], 4, : L geron&paultre [ 9 ] [ 10 ], 2 5,, ; L geron [ 11 ],,, Bauschinger ( 6 ), [ 11 ] [ 10 ] [ ] [ 14 ], F ig. 4 F ibers of the section F ig. 5 Stress2stra in rela tion of concrete F ig. 6 Stress2stra in rela tion of rebar 2. 2 ( 3 ), 6, 7. 2 m m m, 1 m, 9, 6 m, 7 C30, HRB335, 400 mm 500 mm, 250 mm 720 mm, 200 mm 620 mm; 120 mm, 30 GPa, 0. 2 ( a) 1: ( b) 2: ( c) 3: 7 F ig. 7 D ifferen t fram e m odels em ployed in FEM ana lysis

4 ,, 3, : 1 ( 7a) ; 2 ( 7b) ; 3 ( 7c) ;, ; + [ 15 ], 4 MPa, 6. 4 GPa, 0. 5 MPa 3, ,, 2 s, , 1, s,, 1 ( 1),, 3 10 (NS ) F ig. 10 T im e h istory respon se of tota l shear force a t the bottom of the fram e 1 ( NS) Table 1 Param eters of the structure in the tran sverse d irection ( NS) s s s G G G s s : G, G = kn s, s, 3, s,, s 11,,,,

5 42 5 RC 17,,, ;,,, ;,,,,,,,, s, , s 15,,,,,,,, 16,,,,, 17,, s, s, 14 1,,,,,,, 15 3 (18. 0 s ) F ig. 15 D istr ibution of pla stic h inges for Ca se 3 ( a t s)

6 ,, 2,, : (1),,,, (2) ;,,,,,,,, ,, 3,, 3 1 2, 3 1 2,, [ ],,, F ig. 19 Collapse of fram es in W enchuan Earthquake due to soft story m echan ism ,, 1 2,, ;,, 3 3,,,,, ,,,

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8 seism ic response of lumped mass MDOF system s based on energy concep t[ J ]. EngineeringMechanics, 2003, 20 ( 3) : ( in Chinese) ) [ 17 ],,. [ J ]., 2003, 36 (12) : (J ing J ie, Ye L iep ing, Q ian J iaru. Inelastic seism ic disp lacement response analysis of non2 uniform shearing lumped mass MDOF structure based on energy concep t [ J ]. China Civil Engineering Journal, 2003, 36 (12) : ( in Chinese) ) (19842),, (19762),,, (19602),,, FRP (19782),,, (19612),,,