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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(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)［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=15∑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15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=12∑Mb（底层柱底弯矩增大系数取125）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=15∑Mb（柱底取15）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。［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Strong column-weak beam mechanism for RC frames in China under bi-directional horizontal seismic excitationYang Hong1, Wang Qilin2, Bai Shaoliang1(1 Civil Engineering College, 2 Architecture Design and Research Institute，Chonqing University, Chongqing 400045, China)Abstract: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 ∑Mc=15∑Mb or ∑Mc=∑Mbua 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 ∑Mc=12∑Mb（125 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 ∑Mc=15∑Mb（15 for the lower column ends of first floor） develops a column hinges dominated columnbeam mixing hinges mechanism under rare earthquake.Keywords:reinforced concrete; 3D spatial frame; bi-directional horizontal seismic; strong column-weak beam; fiber model重庆市科委自然基金资助项目(CSTC，2009BB4217)。作者简介：杨红(1969)，男，平湖人，博士，教授，Email:yangh@cqu.edu.cn。参考文献［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.
