考虑近断层方向性效应的速度脉冲放大作用预测模型

An empirical approach of accounting for the pulse amplification effects induced by near-fault directivity

近断层速度脉冲型地震动对结构有特殊的破坏作用。所以在近断层概率地震危险性分析以及工程抗震设计时需要考虑速度脉冲的影响。而传统地震动预测模型往往会低估速度脉冲的影响。因此,如何可靠地估计速度脉冲的影响是近年来研究的重要课题之一。该研究以NGA-West2数据库为基础,另外收集近年最新获取的近断层地震动记录,考虑脉冲方向的不确定性,基于小波方法定量进行速度脉冲识别,共获得316条速度脉冲记录。基于该数据,采用最小二乘法拟合得到新的速度脉冲放大作用分段预测模型,并与已有的速度脉冲放大作用预测模型进行比较,验证了其有效性。该模型考虑了近年实际地震动观察结果,在已有的速度脉冲放大作用预测模型基础上,进一步提高了脉冲放大系数的平台高度。基于所提出的脉冲放大作用经验预测模型,通过对传统地震动预测模型进行修正从而对近断层速度脉冲型地震动进行了有效估计。

Near-fault pulse-like ground motions cause severe damage in structures.Hence,for the probabilistic seismic hazard analysis and seismic design in the near-fault region,the pulse effects need to be taken into account.However,traditional ground-motion models may under-predict the velocity pulse-like strong ground motions in the near-fault region.Therefore,how to estimate the near-fault pulse-like strong ground motion is an active research topic in recent years.Here,based on the NGA-West2 database and the near-fault strong ground motions from the recent earthquakes,316 pulse recordings were quantitatively identified by considering the uncertainty of pulse orientation and using the wavelet method.Then,based on the above data,quantitative empirical models of pulse amplification factors were proposed based on piecewise least-squares fitting of the results and compared with the previous pulse amplification model.Furthermore,the efficiency of the proposed model was tested.Compared with the previous pulse amplification model,the constant ordinate of plateau induced by pulse amplification of the proposed model was enhanced through considering the recent pulse ground motions.Finally,it is concluded that through multiplying the proposed model,the traditional ground-motion models can be corrected to reasonably approximate the pulse strong ground motions.