汶川地震中典型RC框架结构的震害仿真与分析
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摘要
四川汶川地震中,一些钢筋混凝土框架结构柱端出现严重的塑性铰,而梁端震害反而较轻,该结果不符合抗震设计的预期目标。基于地震灾区某典型框架结构的震害调查,对该框架结构进行深入的有限元仿真分析。保持该框架结构质量分布基本不变的情况下,建立3种不同的计算模型:①纯框架模型;②带楼板的框架模型;③带楼板-填充墙的框架模型。对3种模型分别进行三维弹塑性时程动力分析,分析中采用本次地震中什邡八角镇的强震记录。分析结果表明,按照规范设计的框架结构无法保证"强柱弱梁"抗震设计目标的实现;填充墙的存在影响结构的破坏机制,填充墙上下设置不均匀容易导致框架软弱层。建议框架结构的设计应充分考虑楼板和填充墙对框架抗震性能的影响,适当提高柱的刚度和承载力,结构弹塑性分析应采用考虑结构楼板和填充墙的计算模型。
Many RC frame structures were severely damaged with plastic hinges formed at column ends rather than beam ends in the Wenchuan Earthquake,significantly different from the expected failure mode in seismic design code. Based on an investigation of a typical RC frame structure damaged in the earthquake area,time history analyses using a sophisticated finite element method were conducted. Three models were considered,i.e. pure frame,frame with floor slab,and frame with both floor slab and infill wall. A ground motion recorded at the town of Bajiao 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 plastic hinges and failure mechanism. Major findings are:① "Strong column and weak beam" cannot be guaranteed for the RC frames designed according to the current Chinese design code. ②Infill walls may significantly alter the failure mechanism of the RC frames. ③Weak story mechanism may easily occur for structures with non-uniform infill walls. These findings suggest that the effects of floor slab and infill wall should be considered in seismic design,the stiffness and strength of columns need be enhanced to achieve "strong column and weak beam" behavior,and structural elasto-plastic analysis model should take slabs and infill walls into account.
Many RC frame structures were severely damaged with plastic hinges formed at column ends rather than beam ends in the Wenchuan Earthquake,significantly different from the expected failure mode in seismic design code. Based on an investigation of a typical RC frame structure damaged in the earthquake area,time history analyses using a sophisticated finite element method were conducted. Three models were considered,i.e. pure frame,frame with floor slab,and frame with both floor slab and infill wall. A ground motion recorded at the town of Bajiao 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 plastic hinges and failure mechanism. Major findings are:① "Strong column and weak beam" cannot be guaranteed for the RC frames designed according to the current Chinese design code. ②Infill walls may significantly alter the failure mechanism of the RC frames. ③Weak story mechanism may easily occur for structures with non-uniform infill walls. These findings suggest that the effects of floor slab and infill wall should be considered in seismic design,the stiffness and strength of columns need be enhanced to achieve "strong column and weak beam" behavior,and structural elasto-plastic analysis model should take slabs and infill walls into account.
引文
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[2]陈立保,陈明祥,高作平,等.主厂房空间框架中考虑楼板作用的有限元分析[J].工业建筑,2005,35(S1):420-422,431(Chen Libao,Chen Mingxiang,Gao Zuoping,et al.FEM analysis for plate effect in spatial frame of main workshop[J].Industrial Construction,2005,35(S1):420-422,431(in Chinese))
[3]Chaker AA,Cherifati A.Influence of masonry infill panels on the vibration and stiffness characteristics of R/C frame buildings[J].Earthquake Engineering and Structural Dynamics,1999,28(9):1061-1065
[4]刘建新.填充墙框架房屋抗震设计新方法[J].四川建筑科学研究,1997,(2):29-33(Liu Jianxin.New seismic design method of Infilled wall-frame structures[J].Building Science Research of Sichuan,1997,(2):29-33(in Chinese))
[5]GB50011—2001建筑抗震设计规范[S].北京:中国建筑工业出版社,2001(GB50011—2001Code for seismic design of buildings[S].Beijing:China Architecture&Building Press,2001(in Chinese))
[6]JGJ3—2002高层建筑混凝土结构技术规程[S].北京:中国建筑工业出版社,2002(JGJ3—2002Technical specification for concrete structures of tall buiding[S].Beijing:China Architecture&Building Press,2002(in Chinese))
[7]黄靓,施楚贤,吕伟荣.对框架填充墙结构抗震设计的思考[J].建筑结构,2005,35(8):27-29(Huang Liang,Shi Chuxian,LWeirong.Some aspects of seismic design method of Infilled wall-frame structures[J].Building Structure,2005,35(8):27-29(in Chinese))
[8]MSC.Software Corporation.MSC.marc volume D:user subroutines and special routines(version2005)[M].2-45～2-49
[9]Lgeron F,Paultre P.Uniaxial confinement model for normal and high-strength concrete columns[J].Journal of Structural Engineering,2003,129(2):241?252
[10]汪训流,陆新征,叶列平.往复荷载下钢筋混凝土柱受力性能的数值模拟[J].工程力学,2007,24(12):76-81(Wang Xunliu,Lu Xinzheng,Ye Lieping.Numerical simulation for the hysteresis behavior of RC columns under cyclic loads[J].Engineering Mechanics,2007,24(12):76-81(in Chinese))
[11]Lgeron F,Paultre P,Mazar J.Damage mechanics modeling of nonlinear seismic behavior of concrete structures[J].Journal of Structural Engineering,2005,131(6):946-954
[12]Zatar W,Mutsuyoshi H.Residual displacements of concrete bridge piers subjected to near field earthquakes[J].ACI Structural Journal,2002,99(6):740-749
[13]李静.矩形截面FS约束混凝土柱抗震性能的试验研究与理论分析[D].北京:清华大学,2003(Li Jing.Experimental investigation and theoretical analysis on seismic behavior of FS confined concrete columns[D].Beijing:Tsinghua University,2003(in Chinese))
[14]Asad U Q.Study on passive control of RC frame with high strength reinforcements in the columns[D].Beijing:Tsinghua University,2007
[15]江见鲸,陆新征,叶列平.混凝土结构有限元分析[M].北京:清华大学出版社,2005
[16]经杰,叶列平,钱稼茹.基于能量概念的剪切型多自由度体系弹塑性地震位移反应分析[J].工程力学,2003,20(3):31-37(Jing Jie,Ye Lieping,Qian Jiaru.Inelasticseismic response of lumped mass MDOF systems based on energy concept[J].Engineering Mechanics,2003,20(3):31-37(in Chinese))
[17]经杰,叶列平,钱稼茹.不均匀剪切型层模型结构基于能量概念的弹塑性地震位移反应分析[J].土木工程学报,2003,36(12):14-19(Jing Jie,Ye Lieping,Qian Jiaru.Inelastic seismic displacement response analysis of non-uniform shearing lumped mass MDOF structure based on energy concept[J].China Civil Engineering Journal,2003,36(12):14-19(in Chinese))
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