雙向水平地震作用下我國(guó)框架的“強(qiáng)柱弱梁”屈服機(jī)制
楊紅1，王七林2，白紹良1
- 摘 要
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(1 重慶大學(xué)土木工程學(xué)院，2 重慶大學(xué)建筑設(shè)計(jì)研究院，重慶 400045)［摘要］汶川地震普遍出現(xiàn)的柱鉸機(jī)制震害現(xiàn)象表明，我國(guó)的“強(qiáng)柱弱梁”彎矩調(diào)整措施有待改進(jìn)。雙向水平地震作用是影響框架“強(qiáng)柱弱梁”屈服機(jī)制的重要因素之一，但在以往的柱端彎矩增大系數(shù)研究中沒(méi)有對(duì)其給予重視。以8度區(qū)二級(jí)抗震等級(jí)框架為例，基于平面模型的研究結(jié)果表明，上部柱采用∑Mc=15∑Mb或∑Mc=∑Mbua的柱端彎矩增大措施，同時(shí)底層柱下端的彎矩增大系數(shù)取15是較優(yōu)化的“強(qiáng)柱弱梁”調(diào)整方案。在OpenSees平臺(tái)上，采用基于柔度法的纖維模型從而更真實(shí)地模擬柱在雙向彎矩和變化軸力作用下的非線性地震反應(yīng)，分析了兩個(gè)鋼筋混凝土六層三維空間框架在罕遇地震下的塑性鉸分布規(guī)律。研究結(jié)果表明，雙向地震下兩空間框架的塑性鉸分布均較對(duì)應(yīng)的平面模型分析結(jié)果更不利；按規(guī)范要求的∑Mc=12∑Mb（底層柱底彎矩增大系數(shù)取125）設(shè)計(jì)的空間框架，在罕遇地震下是典型的柱鉸機(jī)制；按優(yōu)化的∑Mc=15∑Mb（柱底取15）設(shè)計(jì)的空間框架，在罕遇地震下是以柱鉸為主的梁柱鉸混合耗能機(jī)制。［關(guān)鍵詞］鋼筋混凝土；三維空間框架；雙向水平地震；強(qiáng)柱弱梁；纖維模型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重慶市科委自然基金資助項(xiàng)目(CSTC，2009BB4217)。作者簡(jiǎn)介：楊紅(1969)，男，平湖人，博士，教授，Email:yangh@cqu.edu.cn。參考文獻(xiàn)［1］王亞勇.汶川地震建筑震害啟示——抗震概念設(shè)計(jì)［J］.建筑結(jié)構(gòu)學(xué)報(bào)，2008，29(4)：20-25.
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