中硬场地两种等效线性地震反应方法的对比

Comparison of two equivalent-linear seismic response methods for medium stiff soil sites

采用传统等效线性化(EERA)和频率一致等效线性(SOILQUAKE)对比分析基岩输入地震动特性对中硬场地地震反应的影响,分析结果表明:弱震时EERA和SOILQUAKE的地表峰值加速度差异基本可忽略;随着基岩地震动强度的增大,二者计算的地表峰值加速度相对差异越显著,EERA给出的地表反应谱在短周期放大效应逐渐减弱,卓越周期处谱值被显著放大;而SOILQUAKE得出的地表反应谱在短周期放大效应并未削弱,反应谱的卓越周期和周期大于0.7s的谱值与EERA法基本一致。0.3s加速度反应谱放大系数随基岩地震动强度增大而减小,但EERA放大系数减小过快,SOILQUAKE的表现则更为合理。故EERA对地震动高频的过分滤波作用存在不合理性,SOILQUAKE在地震动高频段的放大作用较EERA表现好。

One-dimensional(1D)seismic site response analyses are performed by traditional equivalent linear(EERA)and frequency consistent method(SOILQUAKE),to analyze the effects of bedrock motion characteristics on site seismic responses.The results indicate that the difference of the surface peak ground accelerations(PGA)calculated by EERA and SOILQUAKE can be ignored under weak bedrock motion.As the PGA of bedrock motion increases,the relative difference of PGA significantly increases,and surface response spectrum values calculated by EERA attenuate at short periods but markedly magnify at predominant period.However,the surface response spectrum obtained by SOILQUAKE are not significantly reduced at short periods,but the predominant period and the response spectrum values for greater than 0.7s are consistent with EERA.The amplifications of the acceleration response spectrum at 0.3s period decrease with peak accelerations of the bedrock motion increasing,the amplifications calculated by EERA rapidly reduce,while the results of SOILQUAKE are more reasonable.Therefore,it is unreasonable that EERA has the significant filtering effect on the high frequency components of seismic waves,and the amplification of ground motion at high frequency components can be reasonably evaluated by SOILQUAKE rather than EERA.