结合汶川地震中钢筋混凝土框架结构的塑性铰普遍出现在柱端的震害现象,重点研究了“强柱弱梁”措施和“超烈度”对结构抗震形态的影响。按中国规范分别设计7度0.1g区和0.15g区三级抗震规则空间框架,并采用逐渐增大的“强柱弱梁”措施,对两类7度区框架各形成5个算例结构。在OpenSees平台上,计算框架在双向水平地震作用下的非线性反应。结果表明,抗震规范GB50011-2001给出的三级抗震的“强柱弱梁”措施取值明显偏低,在罕遇地震作用下7度0.1g区框架塑性铰数量少、基本为柱铰,7度0.15g区框架塑性铰数量较多、梁铰少。抗震规范GB50011-2010提高柱端弯矩增大系数取值后,结构的塑性铰分布规律基本没有改善。按抗震规范GB50011-2001设计的7度区空间框架在“超烈度”地震波作用下的塑性铰特征是塑性铰普遍出现在柱端,与汶川地震的震害现象一致,7度区框架的梁端地震组合弯矩小、现浇板钢筋影响幅度大、“强柱弱梁”措施过低、结构遭遇“超烈度”共同导致了该危险的塑性铰分布特征。
Abstract
Based on the damage characteristic of Wenchuan earthquake that plastic hinges of reinforced concrete frame structures developed prevalently at column ends, the influences of “strong column weak beam” measures and super intensity earthquake on seismic performance of structures are analyzed. Regular spatial frames of 7 earthquake intensity 0.1g region and 0.15g region were designed according to the specifications of the 3rd class seismic measure in Chinese code, respectively. By increasing “strong column and weak beam” measures gradually, five examples of each kind of 7 earthquake intensity frames were obtained. Based on the OpenSees framework, nonlinear responses of every frame under bi-directional horizontal earthquake excitations were calculated. The results showed that when the “strong column and weak beam” measures of code GB50011-2001 is adopted, for 7 earthquake intensity 0.1g region frame, the quantity of plastic hinges is few, almost all of the plastic hinges developed at the column end under rare earthquake, while for 0.15g region frame, quantity of plastic hinges is larger, plastic hinges rarely appear at beam ends. When the value of the moment amplification factor of column end of the 3rd class seismic measure is improved according to the seismic code GB50011-2010, almost no improvement of plastic hinges distribution can be found. The characteristic of plastic hinges distribution of 7 earthquake intensity frames designed by the “strong column and weak beam” measures of code GB50011-2001 under super intensity earthquake is plastic hinges developed prevalently at column ends, which is consistent with damage phenomenons of Wenchuan earthquake. For the frames of 7 earthquake intensity, this dangerous plastic hinges distribution characteristic is result from the comprehensive effect of smaller combination moment of beam ends, bigger influence of reinforcement of site casting slab, too weak “strong column and weak beam” measures and super intensity earthquake.
关键词
钢筋混凝土 /
三维框架 /
双向水平地震作用 /
强柱弱梁 /
非线性分析
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Key words
reinforced concrete /
3D frame /
bi-directional horizontal seismic excitation /
strong column weak beam /
nonlinear analysis
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