地震强度指标选择对长周期钢结构余震IDA分析的影响

Influence of ground motion intensity selection on aftershock IDA analysis of long-period steel structure

结构在主震作用下发生损伤,由于刚度和强度退化导致结构周期的延长,再加上高阶周期的影响,在随后的余震对主震损伤结构抗震性能的影响分析中,基于弹性周期的传统谱加速度可能不适用,有必要对地震动强度指标的选择进行进一步研究。本文以9层Benchmark钢框架为研究对象,选取10种地震动强度指标,分别从离散性和相关性两个维度对比分析了其在余震IDA分析中的优劣性。研究结果表明:与最大层间位移角相比,最大残余层间位移角更能够准确地量化主震对结构造成的损伤;对于钢框架结构,基于一段周期的几何平均谱加速度的IM_(Boj&Lev)指标是最优的地震动强度指标,相对于S_(a)(T_(1))离散性降低了30%左右,相关性提高了6%左右。

The structural periods will be elongated due to stiffness and strength degradation when structures are damaged under mainshocks,and higher mode effects could be significant.In seismic performance analysis of main⁃shock⁃damaged structure under aftershocks,traditional intensity index S_(a)(T_(1))(T_(1) is the elastic fundamental period)is not applicable,further investigation of ground motion intensity selection is necessary.In this paper,9⁃story benchmark steel frame model is taken as the research object,suitability of 10 ground motion intensity measures through variability and correlation are studied on aftershock IDA analysis.The results show that,compared with maximum interstory drift,maximum residual interstory drift can accurately reflect damage states of structure due to mainshock.Based on geometric mean spectral acceleration in a certain range of periods,IM_(Boj&Lev) is a relatively good indicator on aftershock IDA analysis,compared with the traditional intensity index S_(a)(T_(1)),the dispersion of IDA results is reduced by above 30%and the correlation is improved by 6%.