主余震序列型地震下基于延性的强度折减系数

Ductility-based strength reduction factor for main aftershock sequence-type ground motions

基于性态的结构抗震设计理论中的强度折减系数是确定结构非弹性反应谱的重要依据。主要研究了主余震序列型地震作用下单自由度体系的基于延性的强度折减系数谱。首先收集实测的主余震序列型地震记录并按中国《建筑抗震设计规范》(GB 50011—2010)要求进行场地类别划分,对余震峰值加速度进行调幅后,再进行单自由度结构弹塑性动力时程分析,研究了结构周期、延性系数、余震和场地类别等因素对强度折减系数的影响。结果表明,强余震对基于延性的强度折减系数影响显著,尤其是在短周期阶段,余震相对强度系数为1.5时,主余震序列型地震作用下的强度折减系数是仅受主震作用下的0.8倍。最后,经过统计平均和回归分析,建立了强度折减系数谱的简化公式。

The strength reduction factors are the key parameters to derive the inelastic response spectra for performance-based structural seismic design.The ductility-based strength reduction factors of single-degree-of-freedom(SDOF)system subjected to main aftershock sequence-type ground motions were investigated.Firstly,records of main aftershock sequence-type ground motions were collected and the site categories were divided according to the requirements of Code for seismic design of buildings(GB 50011—2010)in China.After amplitude adjustment of the peak acceleration of aftershocks,the elastoplastic dynamic time history analysis of SDOF structure was conducted to study the effects of structural period,ductility coefficient,aftershocks and site types on the strength reduction factor.The results indicate that strong aftershocks have a significant effect on the ductility-based strength reduction factor especially in the short-period stage,the strength reduction factor under main aftershock sequence-type ground motions was 0.80 times that under mainshock ground motions when relative intensity of aftershock ground motion was 1.5.Finally,a simplified formula of strength reduction factor spectrum was established after statistical average and regression analysis.