考虑高阶振型影响选波方法对近断层地震动输入适用性研究

摘要

目的 为近断层地震动输入下高层结构的抗震时程分析提供合适的选波方法, 将适用于远断层地震动的考虑高阶振型影响的多频段加权匹配地震波选波方法 (简称多频段加权选波法) 用于近断层地震动, 探讨该方法的适用性.方法 以20条均存在速度脉冲的近断层地震动作为备选波, 并将其均值放大系数谱作为目标谱, 采用多频段加权选波法进行选波.以美国SAC Steel Project设计提出的9层和20层的抗弯钢框架结构为实例建立有限元分析模型, 以20条近断层地震动时程分析所得结构最大层间位移角均值及分布为目标反应, 将多频段加权选波法选出的3条波输入下结构反应均值及美国《建筑荷载规范》 (ASCE 7-05) 选波要求方法输入下所得结构反应与目标反应进行对比分析.结果 对于9层结构, 多频段加权选波法与目标反应更为接近;对于20层结构, 虽然多频段加权选波法出现了薄弱层位置判断不准确的情况, 但最大层间位移角数值的确定基本合适;对于9层和20层结构, 多频段加权选波法和ASCE 7-05方法均未出现低估最大层间位移角的情况.结论 在进行近断层地震动作用下结构的非线性时程分析时, 考虑高阶振型影响的多频段加权匹配选波方法具有较好的适用性.%A ground motions selection method is presented for seismic analysis of high-rise buildings subjected to near-fault ground motionsaiming to investigate the applicability of weighted multi-band matching method (which can consider higher modes effects) for selecting near-fault ground motions. A total of 20 near-fault earthquake records containing velocity pulse are considered as alternative records for selection, and their average response spectrum is viewed as the target spectrum. The 9-and 20-story steel moment resisting frame structures proposed by the United States SAC Steel Project are adopted to establish the finite element analysis models. Firstly, the average maximum inter-story drift ratios of the structures and their distribution along the floors calculated from the 20 near-fault records are considered as the target seismic responses. Then, the average value obtained from 3 records selected by the adopted method and 7 records by America standard "Minimum design loads for buildings and other structures" (ASCE 7-05) are compared with the target seismic response. The results highlight that, for the 9-story structure, the calculated result of the adopted method is more similar to the target seismic response, while for the 20-story structure, the maximum inter-story drift ratio can be accurately calculated by the adopted method though the recognition of the weakest floor is not correct. Moreover, the seismic responses of the 9-story and 20-story structures are not underestimated based on both the adopted method and ASCE 7-05. It can be concluded that the weighted multi-band matching method has preferable applicability for nonlinear time history analysis of high-rise buildings under near-fault ground motions.