地震动永久位移对结构地震反应影响

Influence of permanent displacement of ground motion on seismic response of structures

  • 摘要: 本文推导了基于位移激励计算单自由度体系拟速度谱公式,通过构造的脉冲位移时程对公式精度进行了验证;之后利用小波变换去除强震记录噪声而保留地震动永久位移,再基于去趋势项方法和滤波方法去除永久位移后,计算拟速度谱。算例结果表明:短周期段内,不保留永久位移的位移激励拟速度谱值与保留永久位移的位移激励拟速度谱值相差很小;中长周期段内,不保留永久位移的位移激励拟速度谱值总体上小于保留永久位移的位移激励拟速度谱值,且不保留永久位移时,滤波方法引起的拟速度谱降幅大于去趋势项方法所引起的拟速度谱降幅。因此,基于位移激励计算中长周期结构的地震反应时,应保留地震动永久位移,或基于去趋势项方法去除永久位移。

     

    Abstract: When calculating the seismic response of a structure based on the displacement excitation, the displacement excitation is obtained by integration of the velocity, which is obtained by integration of the acceleration records. At the same time, the acceleration noise must be removed. However, limited by the method for eliminating noise from acceleration records, the permanent displacement of the ground motion in the near-fault earthquake acceleration records is often weakened or even eliminated. This makes it impossible for researchers to judge the effect of permanent displacement of ground motion on the seismic response of structures excited by displacement. In this paper, the authors deduce the pseudo-velocity spectra formula of single degree of freedom system based on displacement excitation, verify the accuracy of the formula with the constructed pulse displacement time history, and then analyze the effect of the permanent displacement of the ground motion on the pseudo-velocity spectra. Firstly, the noise is executed on the acceleration records via wavelet transform, and gound motion with permanent displacement is remained. And then the permanent displacement is wiped out using reducing trend item method or filtering method from those records. Those excitations are used to calculate pseudo-velocity spectra. The results show that in short period, the pseudo-velocity spectra are similar whether ground motions contain the permanent displacement or not; in medium-long period, the pseudo-velocity spectra excited by non-permanent displacement excitation are lower than those by displacement excitation with permanent displacement, and this kind of difference are enlarged when the filtering method is used. Therefore, for seismic design of long-period structures, the ground motion with permanent ground displacement excitation should be used, or reducing trend item method is used to wipe out permanent displacement.

     

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