研究了近场脉冲主余震地震动的延性系数特性,通过修正随机组合构建方法构造了大量近场脉冲主余震地震动,然后通过标准化周期来降低延性系数的离散性,最后分析了平均延性系数特性和余震的影响。结果 表明:采用标准化周期能显著降低延性系数的离散性,降低幅度最大可达60%,但随着余震强度的增大,标准化周期对延性系数离散性的影响逐渐减弱。在短周期段内,延性系数随着标准化周期的增大急剧减小,直至在标准化周期等于1.0附近达到最小值,采用标准化周期可以观察到近场脉冲主余震地震动的等位移现象。强余震对延性系数的影响可超过20%并达到30%,余震对非退化模型的影响大于退化模型。
Many earthquakes have shown that mainshock-aftershock(MSAS)sequences would include the near-field fault pulse-like records,and pulse-like records would further increase the danger of earthquake sequences.This paper analyzes the ductility factor for near-field fault pulse-like MSAS ground motions.The revised randomization method is used to generate lots of near-fault pulse-like MSAS ground motions,and then normalizing the period to decrease the dispersion of ductility factor.The mean ductility factor and the effects of aftershocks are finally analyzed.The results indicate that period normalization can decrease the dispersion of results with the maximum level of 60%.However,the strong aftershock would decrease the advantage of period normalization.In the short period region,ductility factor decreased sharply with the increase of period,until the minimum value reached around the normalized period of 1.0 s.The equal displacement rule can be observed when the period normalization is used.The effects of strong aftershocks on the ductility factor can exceed 20% and reach 30%,and aftershocks have larger effects on the ductility factor for un-degrading systems than that for degrading systems.
