基于增量动力分析方法的空间掉层框架结构的抗地震倒塌能力研究

IDA-BASED SEISMIC COLLAPSE-RESISTANT CAPACITY OF SPATIAL MOMENT FRAMES SUPPORTED BY STEPPED FOUNDATION

参照GB 50011—2010《建筑抗震设计规范》和GB 50010—2010《混凝土结构设计规范》设计了7度(0.10 g)区非掉层框架以及掉层框架原型结构,并采用PERFORM-3D软件对相应的平面和空间模型10个算例进行对比分析。基于增量动力分析方法对非掉层框架和掉层框架结构进行了抗地震倒塌能力研究。按照FEMA 350倒塌判定准则对比了两种模型的倒塌易损性曲线规律,同时考察了各算例的抗倒塌安全储备系数,统计了结构的各层间峰值位移角、倒塌模式及倒塌概率。分析结果表明:1)对于第一种倒塌极限状态,在平面模型中,非掉层框架结构安全储备系数值小于掉层框架结构,而在空间模型中则相反;2)在第二种倒塌极限状态下,非掉层框架结构的抗地震倒塌能力远远弱于掉层框架结构,而且在此极限状态下结构的抗地震倒塌能力、倒塌概率以及倒塌模式都与地震动的输入方向有关;3)地震动方向对掉层框架结构的抗地震倒塌能力及相应的安全储备影响较大,双向地震作用下,结构可能出现不同于平面模型和单向地震作用下的新倒塌模式,抗地震倒塌安全储备更小。

Ten plane and spatial moment frame models with or without stepped foundations located in areas with seismic fortification intensity of 7(0.10 g)were designed in accordance with Code for seismic Design of Buildings(GB 50011—2010)and Code for Design of Concrete Structures(GB 50010—2010).Numerical models using PERFORM-3D were established for the comparative studies on seismic collapse-resistant capacity of the ten models through the incremental dynamic analysis(IDA)method.The seismic fragility curves were obtained corresponding to different collapse limit states defined in FEMA 350.And the collapse margin ratio(CMR)of the ten model frames was calculated.According to the IDA results,the peak inter-story drift angles,collapse pattern and collapse probability were calculated.The research results indicated that the CMR value of plane moment frames with stepped foundation was greater than that of normal moment frames under the collapse limit stateⅠ,while the spatial models were the opposite;the CMR value of moment frames with stepped foundation was much larger than normal moment frames under the collapse limit stateⅡ;the seismic collapse-resistant capacity and CMR value of moment frames with stepped foundation were different with the earthquake input direction;the collapse pattern and its occurrence probability were also different between plane and spatial models under the collapse limit stateⅡ.The direction of ground motion had agreat influence on the scismic collapse-resisment capacity and corresponding sofety margin of the frame with stepped foundation.Under the two-way earthquake input,the collapse pattern of spatial structure might vary from the cases under uni-directional earthquake input.The resulting collapse margin ratio was also decreased.