考虑碰撞效应的相邻框架结构地震易损性分析

Seismic fragility analysis of adjacent frame structures considering pounding effects

针对间距不足和高度不等的相邻钢筋混凝土框架结构,设置考虑碰撞刚度和阻尼非线性的碰撞单元,通过对三维非线性有限元模型的时程分析研究地震碰撞效应,并开展增量动力分析,分别以所有层和碰撞层最大层间位移角为工程需求参数,提出考虑碰撞效应的地震易损性分析方法。以6层和4层、6层和5层、6层和3层相邻钢筋混凝土框架结构为例,对比分析不同周期比下考虑与不考虑碰撞效应的相邻结构地震易损性曲线。结果表明:对于6层和4层相邻结构,考虑碰撞效应后,6层结构所有层的最大层间位移角对应的失效概率略有减小,4层结构的反之,而较低结构的碰撞层及较高结构的碰撞层以上层的最大层间位移角对应的失效概率明显增大,即碰撞效应对结构整体响应影响不明显,而对局部响应影响显著;6层和5层、6层和3层相邻结构地震易损性曲线具有类似规律,且相邻结构自振周期越接近,碰撞对结构地震易损性影响越小。

For adjacent reinforced concrete(RC)frame structures with unequal total heights and deficient separation distance,the seismic pounding response is obtained through nonlinear time history analysis using three-dimensional finite element model with pounding elements considering nonlinear behavior of stiffness and damping during pounding,and then incremental dynamic analysis(IDA)was performed.The seismic fragility analysis method considering pounding effects was proposed using two engineering demand parameters:maximum drift ratio among all the floors and the one at the pounding floor.Taking the adjacent RC frame structures of 6-story and 4-story,6-story and 5-story as well as 6-story and 3-story for instance,seismic fragility curves with and without considering pounding effects were compared for different period ratios.The results show that the failure probability in terms of the maximum drift ratio among all the floors for the 6-story structure decreases a little considering pounding,while it increases a little for the 4-story structure.However,the failure probabilities in terms of the maximum drift ratio at the pounding floor for the lower structure and those at the floors above the pounding floor for the higher structure increase significantly considering pounding,which demonstrates that pounding has little effect on the global response but significant effect on the local response of the structures.Moreover,the fragility curves for the adjacent structures of 6-story and 5-story as well as 6-story and 3-story have similar trends to those of the adjacent structures of 6-story and 4-story.Furthermore,effects of pounding on seismic fragility become less obvious for adjacent structures with closer natural periods.