将不同场地类别和震源机制上的118条近断层地震记录进行分类,基于基础隔震结构的双自由度体系简化模型,利用状态空间法及四阶龙格.库塔法对结构的弹塑性反应谱进行求解,研究了场地类别和震源机制对反应谱频谱特性的影响。通过分析近断层地震记录的3个强度指标与基础隔震结构最大弹塑性响应的相关性,探讨了基础隔震结构地震反应分析时强度指标的选取问题。结果表明,三种场地类别条件中,速度反应谱规律不明显,但逆断层地震动的平均加速度反应谱和逆斜断层地震动的平均位移反应谱均最大。场地类别和震源机制不同,地震动强度指标与结构响应的相关程度不同。因此在进行近断层脉冲型地震动作用下基础隔震结构地震反应分析时,建议考虑结构所在场地及地震动的震源机制后采用不同地震动强度指标来选择和调整地震动输入。
In this study, 118 near-fault pulse ground motion records are classified according to different soil conditions and focal mechanisms, based on the simplified model of base-isolated structural system of two degrees of freedom, the elastic-plastic response spectra are obtained by using state-space method and fourth-order Runge-Kutta method, and the effects of site conditions and focal mechanism on structural response spectra are analyzed. In order to explore the selection problems of the intensity indices for seismic response analysis of base-isolated structure, the correlation between elastic-plastic structural responses and intensity indices composed of PGA,PGV and PGD are discussed. The results show that the average acceleration response spectra under the reverse fault ground motions and the average displacement response spectra under reverse oblique fault ground motions are largest, but the laws of average velocity response spectra are not obvious in three site conditions. For different site conditions and focal mechanisms, the correlation degrees between intensity indices and structural response are different. Hence, when studying the seismic response of base- isolated structure under near-fauh ground motions, it is recommended to select and adjust ground motion inputs using different intensity indices with different site condition and focal mechanisms considered.