双向水平地震作用下我国框架的“强柱弱梁”屈服机制  

Strong column-weak beam mechanism for RC frames in China under bi-directional horizontal seismic excitation

作　　者：杨红[1] 王七林[2] 白绍良[1] 

机构地区：[1]重庆大学土木工程学院 [2]重庆大学建筑设计研究院,重庆400045

出　　处：《建筑结构》2010年第8期71-76,共6页Building Structure

基　　金：重庆市科委自然基金资助项目(CSTC;2009BB4217)

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.

关 键 词：钢筋混凝土 三维空间框架 双向水平地震 强柱弱梁 纤维模型 

分 类 号：TU378.4[建筑科学—结构工程]