双向水平地震作用下我国框架的“强柱弱梁”屈服机制
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摘要
汶川地震普遍出现的柱铰机制震害现象表明,我国的"强柱弱梁"弯矩调整措施有待改进。双向水平地震作用是影响框架"强柱弱梁"屈服机制的重要因素之一,但在以往的柱端弯矩增大系数研究中没有对其给予重视。以8度区二级抗震等级框架为例,基于平面模型的研究结果表明,上部柱采用∑Mc=1.5∑Mb或∑Mc=∑Mbua的柱端弯矩增大措施,同时底层柱下端的弯矩增大系数取1.5是较优化的"强柱弱梁"调整方案。在OpenSees平台上,采用基于柔度法的纤维模型从而更真实地模拟柱在双向弯矩和变化轴力作用下的非线性地震反应,分析了两个钢筋混凝土六层三维空间框架在罕遇地震下的塑性铰分布规律。研究结果表明,双向地震下两空间框架的塑性铰分布均较对应的平面模型分析结果更不利;按规范要求的∑Mc=1.2∑Mb(底层柱底弯矩增大系数取1.25)设计的空间框架,在罕遇地震下是典型的柱铰机制;按优化的∑Mc=1.5∑Mb(柱底取1.5)设计的空间框架,在罕遇地震下是以柱铰为主的梁柱铰混合耗能机制。
The damage characteristics of RC frames in the Wenchuan earthquake,prevalent column hinges mechanism,imply that further research is necessary for the "strong column-weak beam" moment adjustment measures in China.Bi-directional horizontal seismic is one of the most important factors that affects the "strong column-weak beam" mechanism of RC frames,however,it has not been considered seriously in the known researches of the moment amplification factor of columns.For example,research results based on plane model indicated that ∑M_c=1.5∑M_b or ∑M_c=∑M_(bua) used to amplify the moment of the upper floors columns,while 1.5 used for that of the lower ends of first floor columns are optimized moment amplification measures.Based on the OpenSees framework,flexibility method based fiber model was adopted to simulate the nonlinear responses of columns under biaxial bending and varying axial force effectively,and the plastic hinge distributions of two six-stories 3D spatial reinforced concrete frames under rare earthquake were investigated.The results indicate that the plastic hinge distributions of two spatial frames under bi-directional horizontal seismic action are all worse than that of the corresponding plane frames.Spatial frame designed according to the ∑M_c=1.2∑M_b(1.25 for the moment amplification factor of the lower column ends of first floor) in the Chinese building code develops a typical column hinges mechanism under rare earthquake,while spatial frame designed according to optimized measure ∑M_c=1.5∑M_b(1.5 for the lower column ends of first floor) develops a column hinges dominated column-beam mixing hinges mechanism under rare earthquake.
The damage characteristics of RC frames in the Wenchuan earthquake,prevalent column hinges mechanism,imply that further research is necessary for the "strong column-weak beam" moment adjustment measures in China.Bi-directional horizontal seismic is one of the most important factors that affects the "strong column-weak beam" mechanism of RC frames,however,it has not been considered seriously in the known researches of the moment amplification factor of columns.For example,research results based on plane model indicated that ∑M_c=1.5∑M_b or ∑M_c=∑M_(bua) used to amplify the moment of the upper floors columns,while 1.5 used for that of the lower ends of first floor columns are optimized moment amplification measures.Based on the OpenSees framework,flexibility method based fiber model was adopted to simulate the nonlinear responses of columns under biaxial bending and varying axial force effectively,and the plastic hinge distributions of two six-stories 3D spatial reinforced concrete frames under rare earthquake were investigated.The results indicate that the plastic hinge distributions of two spatial frames under bi-directional horizontal seismic action are all worse than that of the corresponding plane frames.Spatial frame designed according to the ∑M_c=1.2∑M_b(1.25 for the moment amplification factor of the lower column ends of first floor) in the Chinese building code develops a typical column hinges mechanism under rare earthquake,while spatial frame designed according to optimized measure ∑M_c=1.5∑M_b(1.5 for the lower column ends of first floor) develops a column hinges dominated column-beam mixing hinges mechanism under rare earthquake.
引文
[1]王亚勇.汶川地震建筑震害启示——抗震概念设计[J].建筑结构学报,2008,29(4):20-25.
[2]清华大学,西南交通大学,北京交通大学土木工程结构专家组.汶川地震建筑震害分析[J].建筑结构学报,2008,29(4):1-9.
[3]叶列平,曲哲,马千里,等.从汶川地震中框架结构震害谈“强柱弱梁”屈服机制的实现[J].建筑结构,2008,38(11):52-59.
[4]冯远,肖克艰,刘宜丰.汶川地震灾害引发建筑结构设计者的思考[J].建筑结构,2008,38(7):25-27.
[5]Comite Euro-international du Beton(CEB)Task GroupⅢ/2.Seismicdesign of reinforced concrete structures for controlled inelastic response(design concepts)[R].London,UK:Thomas Telford Ltd.,1998.
[6]杨红,韦锋,白绍良,等.柱增强系数取值对钢筋混凝土抗震框架塑性铰机构的控制效果[J].工程力学,2005,22(2):155-161.
[7]韦锋,杨红,白绍良.对我国不同烈度区钢筋混凝土框架现行抗震规定的初步验证[J].重庆建筑大学学报,2001,23(6):1-9.
[8]KELLEY T E.Some seismic design aspects of multistorey concreteframes[D].Christchurch:University of Canterbury,1974.
[9]杨红,王珍,韦锋,等.柱底抗弯能力增强措施对钢筋混凝土框架抗震性能的影响[J].世界地震工程,2002,18(4):66-72.
[10]刘光明,杨红,邹胜斌,等.基于新规范的钢筋混凝土框架抗震性能评价[J].重庆建筑大学学报,2004,26(1):40-50.
[11]韦锋,杨红,傅剑平,等.普通钢筋混凝土规则框架的弹塑性地震反应[J].重庆大学学报,2007,30(7):59-65.
[12]何浩祥,张玉怿,李宏男.建筑结构在双向水平地震作用下的扭转振动效应[J].沈阳建筑工程学院学报,2002,18(4):241-243.
[13]邱法维,李文峰,潘鹏,等.钢筋混凝土柱的双向拟动力静力试验研究[J].建筑结构学报,2001,22(5):26-31.
[14]杨红,高文生,王志军.空间框架简化为平面模型的抗震分析[J].重庆大学学报,2008,31(11):1267-1272.
[15]杨红,王建辉,白绍良.双向地震作用对柱端弯矩增强系数的影响分析[J].土木工程学报,2008,41(9):40-47.
[16]MAZZONI S,MCKENNA F,SCOTT M H,et al.OpenSees usersmanual[R].PEER,University of California at Berkeley,2006.
[17]吴勇,雷汲川,杨红,等.板筋参与梁端负弯矩承载力问题的探讨[J].重庆建筑大学学报,2002,24(3):33-37.
[18]杨红,吴晶晶,王志军.模型化方法对钢筋混凝土框架地震反应的影响分析[J].地震工程与工程振动,2008,28(2):20-28.
[19]傅学怡.汶川、台湾建筑震害启示——改进规范的几点建议[J].建筑结构,2008,38(7):15-16.
[20]韦锋,傅剑平,白绍良.我国混凝土框架结构强柱弱梁措施的实际控制效果[J].建筑结构,2007,37(8):5-9.
[2]清华大学,西南交通大学,北京交通大学土木工程结构专家组.汶川地震建筑震害分析[J].建筑结构学报,2008,29(4):1-9.
[3]叶列平,曲哲,马千里,等.从汶川地震中框架结构震害谈“强柱弱梁”屈服机制的实现[J].建筑结构,2008,38(11):52-59.
[4]冯远,肖克艰,刘宜丰.汶川地震灾害引发建筑结构设计者的思考[J].建筑结构,2008,38(7):25-27.
[5]Comite Euro-international du Beton(CEB)Task GroupⅢ/2.Seismicdesign of reinforced concrete structures for controlled inelastic response(design concepts)[R].London,UK:Thomas Telford Ltd.,1998.
[6]杨红,韦锋,白绍良,等.柱增强系数取值对钢筋混凝土抗震框架塑性铰机构的控制效果[J].工程力学,2005,22(2):155-161.
[7]韦锋,杨红,白绍良.对我国不同烈度区钢筋混凝土框架现行抗震规定的初步验证[J].重庆建筑大学学报,2001,23(6):1-9.
[8]KELLEY T E.Some seismic design aspects of multistorey concreteframes[D].Christchurch:University of Canterbury,1974.
[9]杨红,王珍,韦锋,等.柱底抗弯能力增强措施对钢筋混凝土框架抗震性能的影响[J].世界地震工程,2002,18(4):66-72.
[10]刘光明,杨红,邹胜斌,等.基于新规范的钢筋混凝土框架抗震性能评价[J].重庆建筑大学学报,2004,26(1):40-50.
[11]韦锋,杨红,傅剑平,等.普通钢筋混凝土规则框架的弹塑性地震反应[J].重庆大学学报,2007,30(7):59-65.
[12]何浩祥,张玉怿,李宏男.建筑结构在双向水平地震作用下的扭转振动效应[J].沈阳建筑工程学院学报,2002,18(4):241-243.
[13]邱法维,李文峰,潘鹏,等.钢筋混凝土柱的双向拟动力静力试验研究[J].建筑结构学报,2001,22(5):26-31.
[14]杨红,高文生,王志军.空间框架简化为平面模型的抗震分析[J].重庆大学学报,2008,31(11):1267-1272.
[15]杨红,王建辉,白绍良.双向地震作用对柱端弯矩增强系数的影响分析[J].土木工程学报,2008,41(9):40-47.
[16]MAZZONI S,MCKENNA F,SCOTT M H,et al.OpenSees usersmanual[R].PEER,University of California at Berkeley,2006.
[17]吴勇,雷汲川,杨红,等.板筋参与梁端负弯矩承载力问题的探讨[J].重庆建筑大学学报,2002,24(3):33-37.
[18]杨红,吴晶晶,王志军.模型化方法对钢筋混凝土框架地震反应的影响分析[J].地震工程与工程振动,2008,28(2):20-28.
[19]傅学怡.汶川、台湾建筑震害启示——改进规范的几点建议[J].建筑结构,2008,38(7):15-16.
[20]韦锋,傅剑平,白绍良.我国混凝土框架结构强柱弱梁措施的实际控制效果[J].建筑结构,2007,37(8):5-9.
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