基于分量分离方法的地震动反应谱

地震动反应谱统计分析中存在的离散性一直是影响设计谱精确估计的重要因素.地震动加速度反应谱离散性偏大的区段主要集中于长周期部分.为了进一步研究地震动反应谱及其长周期段的特征,建立了一个综合强地震动数据库,考虑地震动反应谱的特征将强震记录分为普通型和低频型2类,采用数字滤波方法将低频型地震动中的长周期分量分离,引入了一种2阶段平稳简谐地震动模型用于等效所分离的低频分量.结果表明:滤波后的低频型地震动与普通型地震动反应谱仍有明显差别;低频型地震动与分离后得到的低频分量以及高、中频分量参数间存在一定的相关性;指出普通型地震动与低频型地震动的设计谱须分别单独标定,其中普通型地震动设计谱采用平均谱标定,低频型地震动设计谱可以在普通型地震动设计谱标定方法的基础上对长周期段进行修正得到.该研究为地震动反应谱特征及规律的认识提供了新的方法,为设计谱的精确标定提供了参考和依据.

Ground Motion Response Spectra Through Component Decomposition Method

The large discreteness has been the key factor affecting the accurate estimation of design spectra in the statistical analysis of ground motion response spectrum. Long-period portion in ground motion response spectrum usually exhibit larger discreteness. To further study the response spectrum and its long-period characteristics,a comprehensive strong ground motion database was established. The strong motion records were divided into two categories,ordinary type and low-frequency type,by considering the characteristics of ground motion response spectrum;the digital filtering method was adopted to separate the long-period component from the low frequency type motions;then,a two-stage smooth harmonic model was introduced to simulate the separated component. Results show that response spectral characteristics of the filtered low frequency type motions are still very different from those of the ordinary type;there are some correlations in between low frequency motions,low frequency components and the filtered high and median frequency components. It is stressed that the design spectra of ordinary type ground motion and low frequency ground type motion must be calibrated separately. For ordinary motions,design spectra can be constructed by using the average spectra,while for low frequency motions design spectra can be obtained by modifying the spectra of the long period. The study not only provides a new approach to the analysis of response spectrum,but also is helpful in the precise calibrating of design spectra.