近断层脉冲型地震动耦合效应特征

指出了近断层脉冲型地震动耦合效应的存在。以典型走滑断层型地震动为数据基础,考虑场地条件的影响,对近断层方向性效应地震动分量(CFN)、滑冲效应地震动分量(CFP)以及相互垂直的两耦合地震动分量(C45°和C-45°)的峰值、反应谱分别做了定性的比较。结果表明,各地震动分量的加速度峰值之间差别不明显,但方向性效应地震动分量的速度和位移峰值明显大于其它分量相应的峰值;不同场地、不同周期段的绝对加速度、相对速度和相对位移反应谱谱比呈现不同的变化特点;岩石场地上方向性效应地震动分量长周期段的加速度反应谱最高,而土层场地上各分量加速度反应谱之间的差别不大;近断层结构抗震设计时,地震动分量和设计谱的选取应适当考虑地震动的方向效应。

Characteristics of Coupling Effect in Near-fault Pulse-like Ground Motions

The existence of near-fault coupling effects in pulse-like ground motions is pointed out. On the basis of typical strike-slip earthquake ground motions,the relations of ground motion amplitudes and response spectra between forward-directivity effect component (CFN),fling-step effect component (CFP) and two orthogonal coupling components (C45°,C-45°) are analyzed by considering the influence of site conditions. The result shows that,the differences of peak ground acceleration between different components are slight,while peak ground velocity and displacement of CFN component are both significantly higher than those of the other components. Absolute acceleration,relative velocity and relative displacement response spectra ratios all exhibit different characteristics with the varieties of site conditions and period ranges; for rock site,acceleration spectrum of CFN component is the highest at long period range than those of the other components,while the differences of acceleration spectra for the components at soil site are negligible. The effects of component direction should be properly considered in the section of ground motion and design spectra for seismic design of structures in the near-fault region.