循环往复加载的地下结构Pushover分析方法及其在地震损伤分析中的应用

Pushover Analysis Method of Underground Structures under Reversal load and Its Application in Seismic Damage Analysis

摘要:

考虑到地震作用下地下结构往往受到双向往复荷载作用,本文提出了循环往复加载的地下结构Pushover分析方法。介绍了该方法的实施步骤、基本功能与特点。该方法考虑了地震作用下地下结构双向受力的特点,利用多点位移控制的推覆分析算法进行地震作用下正向加载—卸载—反向再加载的全过程分析。该方法将一次循环加载过程近似看作一次地震作用过程,提出了基于循环往复加载Pushover分析的损伤模型,避免了对土—结构整体模型进行复杂的动力相互作用分析;通过一次循环往复加载的Pushover分析,根据结构构件刚度的改变对结构损伤进行有效评估。结合实际工程进行算例分析初步验证了循环往复加载Pushover分析及地震损伤模型的有效性。

Abstract:

Although response history analysis is the most rigorous procedure to compute seismic demand,pushover analysis is more common in practice with its advantage of conceptual simplicity and computational attractiveness.A pushover analysis procedure with monotonically increasing effective earthquake forces following an invariant depth-wise distribution is introduced in the paper.Considering the reversal directions of seismic load,which is not included in the traditional pushover analysis with monotonically increasing forces in one direction,a cyclic reversal loading pattern is proposed in this paper.With the algorithm based on multiple point constraints,the implementation procedure,basic functions and special features of pushover analysis with cyclic reversal loading are introduced in detail.In the proposed procedure,the analysis model is imposed with the effective earthquake forces in the positive direction and unloaded when the target displacement is reached.Then the model is imposed with the reversed forces and unloaded when the opposite target displacement is reached.With the proposed procedure,we can estimate the structural capacity during earthquake more reasonably by considering the double direction stress of the underground structures.Subsequently,a damage model based on the pushover analysis with the cyclic reversal loading pattern is proposed by approximately viewing one cycle of reversal load as an earthquake event.With the proposed model,the complicated analysis of dynamic soil-structure system can be avoid and the damage assessment of underground structures can be conducted with the structural stiffness before and after one reversal load pushover analysis.Finally,the validity of the reversal load pushover analysis procedure and seismic damage analysis model are verified by the case study of the Chongwenmen subway station in Beijing.The research in this paper shows that the proposed pushover analysis procedure with cyclic reversal loading pattern can be effectively applied to seismic analysis and damage assessment of underground structures.