RC框架结构合理破坏机制的实现
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摘要
为使RC框架结构在强震中有效形成合理的破坏机制,提高其抗震性能,采用OpenSees平台模拟变轴力柱弯曲性能和结构反应下降段的基于柔度法纤维模型,考虑楼板及板筋、结构超强、内力重分布等影响因素,对按现行规范设计的各设防烈度区6层规则框架进行非线性Pushover分析,考察了我国抗震规范中强柱弱梁措施的有效性及控制效果的影响因素,与汶川地震震害现象进行对比,并通过算例分析探讨了实现以梁铰为主的合理破坏机制的有效措施.分析结果表明:大震下6度区框架出铰较少,7度、8度区框架以柱铰为主,并出现了层侧移机构,结构抗震能力不足,与震害现象基本相符9,度区形成了以梁铰为主的梁柱铰机构.现行规范措施除9度区以外均不能实现框架结构预期的破坏机制,提高强柱弱梁系数、减小轴压比和提高小震设计地震力等措施可有效避免柱铰机制.
To improve the seismic performance of RC frame structure under strong earthquake,the effectiveness of the provisions to ensure the "strong-column-weak-beam" failure mechanism in current Chinese seismic design code is examined,and some effective measures to realize rational failure mechanism are studied.Based on the flexibility method on OPENSEE platform,the fiber model can be used to simulate the biaxial bending behavior of columns under variable axial load and the deterioration phase of the structural response.A 6-story regular frame structure located in each fortification intensity region was designed according to the current seismic design code and studied using the nonlinear pushover analysis to investigate the failure mechanism of the structure.The analysis results were compared with the actual structural damage phenomena observed in Wenchuan Earthquake.The minimum requirement of ensuring the plastic hinge formation mostly in beams was discussed.The analysis results indicated that few plastic hinges were developed in the frame structure in the region of seismic fortification intensity 6.In seismic fortification region 7 and 8,plastic hinges were mainly formed in columns and lateral drift mechanism was developed,leading to inadequate seismic resistance of the structure.The plastic hinge formation mostly in beams was only realized in the frame structure located in seismic fortification region 9.It is proposed that increasing the strong column-weak beam coefficient,reducing the axial load ratio and increasing the design seismic force for small earthquake can help realize the expected failure mechanism that plastic hinges are mainly formed in beams.
To improve the seismic performance of RC frame structure under strong earthquake,the effectiveness of the provisions to ensure the "strong-column-weak-beam" failure mechanism in current Chinese seismic design code is examined,and some effective measures to realize rational failure mechanism are studied.Based on the flexibility method on OPENSEE platform,the fiber model can be used to simulate the biaxial bending behavior of columns under variable axial load and the deterioration phase of the structural response.A 6-story regular frame structure located in each fortification intensity region was designed according to the current seismic design code and studied using the nonlinear pushover analysis to investigate the failure mechanism of the structure.The analysis results were compared with the actual structural damage phenomena observed in Wenchuan Earthquake.The minimum requirement of ensuring the plastic hinge formation mostly in beams was discussed.The analysis results indicated that few plastic hinges were developed in the frame structure in the region of seismic fortification intensity 6.In seismic fortification region 7 and 8,plastic hinges were mainly formed in columns and lateral drift mechanism was developed,leading to inadequate seismic resistance of the structure.The plastic hinge formation mostly in beams was only realized in the frame structure located in seismic fortification region 9.It is proposed that increasing the strong column-weak beam coefficient,reducing the axial load ratio and increasing the design seismic force for small earthquake can help realize the expected failure mechanism that plastic hinges are mainly formed in beams.
引文
[1]GB 50011—2001.建筑抗震设计规范[S].北京:中华人民共和国建设部,2001.
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[4]陈滔.基于有限单元柔度法的钢筋混凝土框架三维非弹性地震反应分析[D].重庆:重庆大学,2003.
[5]TAUCER F F,SPACONE E,FILIPPOU F C.A Fiberbeam-column element for seismic response analysis ofreinforced concrete structures[R].Berkeley:UCB/EERC-91/17,1991.
[6]杨溥,李英民,王亚勇,等.结构静力弹塑性分析(Push-over)方法的改进[J].建筑结构学报,2000,21(1):44-50.
[7]ATC-40.Seismic evaluation and retrofit of concretebuildings[S].Redwood City:Applied TechnologyCouncil,1996.
[8]CHOPRA A K,GOEL R K.Capacity-demand-diagrammethods for estimating seismic deformation of inelasticstructures:SDF systems[R].Berkeley:PEER,Univer-sity of California1,999.
[9]杨溥,李英民,赖明.结构时程分析法输入地震波的选择控制指标[J].土木工程学报,20003,3(6):33-37.
[10]白绍良,李刚强,李英民,等.从R-μ-T关系研究成果看我国钢筋混凝土结构的抗震措施[J].地震工程与工程振动,2006,26(5):144-151.
[11]杨红.基于细化杆模型的钢筋混凝土抗震框架非线性动力反应规律研究[D].重庆:重庆建筑大学,2000.
[2]MAZZONI S,MCKENNA F,SCOTT M H,et al.OpenSees users manual[R].Berkeley:PEER,Univer-sity of California at Berkeley,2006.
[3]ZERIS C A.Three-dimensional nonlinear response of re-inforced concrete building[D].Berkeley:Departmentof Civil Engineering University of California at Berkeley,1986.
[4]陈滔.基于有限单元柔度法的钢筋混凝土框架三维非弹性地震反应分析[D].重庆:重庆大学,2003.
[5]TAUCER F F,SPACONE E,FILIPPOU F C.A Fiberbeam-column element for seismic response analysis ofreinforced concrete structures[R].Berkeley:UCB/EERC-91/17,1991.
[6]杨溥,李英民,王亚勇,等.结构静力弹塑性分析(Push-over)方法的改进[J].建筑结构学报,2000,21(1):44-50.
[7]ATC-40.Seismic evaluation and retrofit of concretebuildings[S].Redwood City:Applied TechnologyCouncil,1996.
[8]CHOPRA A K,GOEL R K.Capacity-demand-diagrammethods for estimating seismic deformation of inelasticstructures:SDF systems[R].Berkeley:PEER,Univer-sity of California1,999.
[9]杨溥,李英民,赖明.结构时程分析法输入地震波的选择控制指标[J].土木工程学报,20003,3(6):33-37.
[10]白绍良,李刚强,李英民,等.从R-μ-T关系研究成果看我国钢筋混凝土结构的抗震措施[J].地震工程与工程振动,2006,26(5):144-151.
[11]杨红.基于细化杆模型的钢筋混凝土抗震框架非线性动力反应规律研究[D].重庆:重庆建筑大学,2000.
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