基于时-频包线的非平稳地震动合成及其对结构非线性响应的影响

摘要

地震动频率非平稳特性对结构的非线性响应有重要影响.引入具有统计参数的时频包线函数来近似模拟地震动频率非平稳特性,建立了以反应谱为目标的非平稳地震动拟合方法.以天然地震动为种子,设计了4种时程拟合方案,得到了满足相同目标谱的4组加速度时程,结果分析表明,(1)本文建立的地震动拟合方法,能够很好地保留原始地震动的非平稳特性和持续时间,且拟合精度较高;(2)基于实际地震动提取的时-频包线函数,能够较好地模拟地震动频率的非平稳特性;(3)基于统计参数定义的时-频包线函数能够近似模拟地震动频率非平稳特性,与真实地震动频率随时间的变化规律符合较好.以这4组地震加速度时程作为输入,分别对层数为7层和1 5层的规则钢筋混凝土框架结构进行三维非线性时程分析,结果表明,采用仅考虑强度非平稳特性的地震输入,存在低估规则钢筋混凝土结构非线性响应的风险,因此在人工合成地震动中应该考虑其频率的非平稳特性,合理估计结构的非线性响应,保证结构设计的安全性.%The non stationarity of frequencies in the earthquake ground motion has an important effect on structural nonlinear responses.By introducing a frequency-dependent amplitude envelope function with statistical parameters to simulate the nonstationarity of frequencies in the earthquake ground motion,a method is developed for the non-stationary earthquake ground motion,which takes the response spectrum as the target.Taking the natural ground motion as the seed,four acceleration time histories for the same target spectrum are obtained by using four different methods.The results suggest that:(1) The fitting method developed could preserve the non stationarity and duration of the original time history with higher fitting precision;(2) Based on the frequency-dependent amplitude envelope function of the natural ground motion,the earthquake ground motion can be used to simulate the non-stationarity of frequency better;(3) The one based on the frequency-dependent amplitude envelope function with statistical significance is able to simulate the non-stationarity of frequencies approximately,which agrees with the frequency time-variation of the natural ground motion.Taking the four time histories as input,the nonlinear time-history analysis of the reinforced concrete frame structure with 7 and 15 layers are presented.The results show that there exists the risk of underestimating the reinforced concrete structural nonlinear response under the earthquake ground motion only considering the non stationarity of the intensity.Therefore,the non-stationarity of frequencies in the earthquake ground motion should be considered in the simulation of the artificial ground motion.In this way,the structural nonlinear responses could be estimated reasonably and the safety of the structure design can be guaranteed.