脉冲型近断层地震动作用单自由度体系响应分析

近断层前方向性效应地震动含有高幅值,短持时的速度脉冲,与远场地震动相比存在显著差异。本文根据所选取的40条近断层地震波记录,用小波分析方法将原始记录分解为脉冲波部分和高频波部分,对弹性和非弹性单自由度体系进行分析,得出了以下结论:对于弹性体系,大约0.484倍的速度脉冲周期可以作为临界周期,脉冲波部分将对固有周期大于临界周期的结构的响应起主导作用,反之,高频波部分将会产生显著影响;对于非弹性体系,仅仅用等效速度脉冲方法模拟近断层地震动的计算精度将会受到延性系数?的影响,随着延性系数的增加,脉冲波部分满足精度要求的结构固有周期范围将明显缩小,并且向较低周期范围偏移;仅用等效速度脉冲模型来模拟近断层地震动具有一定的局限性。

Seismic Analysis of SDOF Systems under Forward-directivity Ground Motions

Directivity effect of near-fault ground motions which have large amplitudes and short duration are significantly different with far-field ground motions. In this paper, wavelet analysis is used to extract pulse-type components and high-frequency components from the original earthquake records. Based on the elastic and inelastic response analysis of single-degree-of-freedom systems to 40 near-fault ground motions records, conclusions are as follows: according to elastic systems, the initial period which equals to 0.484 times of velocity pulse period can be used as threshold period above which the response of structures is dominated by pulse-type component, while high frequency component control the response of structures with period longer than this period; as for the inelastic system, the period range of pulse-type component in which the deviation is below 20% reduces obviously with the increasing of the ductility value and moves toward to the low-period range. The limitation of the models which just use the equivalent velocity pulse to simulate the near-fault ground motion is discussed.