脉冲型近场地震波反应谱的阻尼调整系数分析

摘要

The damping modification factor quantifies the effect of damping ratio on seismic response of a structure.It is related to the spectral characteristics of ground motion,and is used to obtain the high damping spectra from the low damping spectra.This work aims to explore the damping effect on structural responses induced by near-fault ground motions,and to propose estimation formulas for damping modification factor.A total of 50 ground motions were selected,and the wavelet-based equivalent pulses were extracted.The response spectra were calculated based on the selected ground motions and the equivalent pulses,with the assumed 13 damping ratios ranging from 0.05 to 0.50.The damping modification factors were obtained based on the reference spectra with a damping ratio of 0.05.The results show that increasing damping ratio reduces the spectral values the most significantly if the period ratio T/Tp(structural period to pulse period) is between 0.5 and 1.2,and in this range the same level of damping modification factors are obtained from the equivalent pulses.Based on the numerical results,the empirical functions were suggested for estimating the damping modification factor for acceleration,velocity and displacement,respectively.The proposed formulas take into account the near-fault effect,and are applicable within the period range of 0.5 ＜ T/Tp ＜ 1.2.%阻尼调整系数定量描述了阻尼比对结构地震响应的影响,与地震波频谱特征等相关,用于从低阻尼比反应谱推算高阻尼比反应谱.本文以近场脉冲型地震波为对象,研究其反应谱阻尼调整系数的规律并建立计算公式.选取50条脉冲型地震波并提取出等效低频脉冲,考虑0.05 ～0.50之间13种阻尼比,计算得到地震波、等效脉冲的反应谱和各自基于5％阻尼比的阻尼调整系数.研究结果表明,结构周期与地震波脉冲周期比T/Tp在0.5 ～1.2内,提高阻尼比对位移、速度和加速度响应都有降低作用且减震效果最明显,等效脉冲与实测地震波的阻尼调整系数接近.对加速度、速度和位移谱分别拟合,得到了0.5 ＜T/Tp ＜1.2范围内考虑脉冲周期Tp影响的阻尼调整系数评价公式.