近断层地震反应谱特性分析研究

Study on response spectrum characteristics of near-fault ground motions

为明确近断层地震反应谱的特征及其与抗震设计规范中标准反应谱的差异,以此指导近断层地区桥梁的抗震设计,通过统计分析与对比,开展近断层地震特性的研究,选取126条具有典型脉冲特征的近断层地震波,并按照断层类型分为3类,分别计算地震反应谱,并求得平均谱值。将结果与我国规范反应谱及39条ATC63远场地震波反应谱进行对比分析。研究结果表明:长周期范围(1.5~9 s)脉冲型地震波的反应谱明显高于我国现行规范的规定和ATC63远场地震波,最大可达3.7倍。我国规范规定的反应谱用于近断层结构设计时偏于不安全;在3类脉冲型地震波中,正逆断层的脉冲反应谱最大,近断层桥梁抗震分析应输入正逆断层脉冲型地震;对长周期结构抗震分析,应考虑近断层因素的影响。

In order to guide the seismic design of bridge structures located in near-fault area, the response spectrum characteristics of near-fault seismic waves and its difference from the standard response spectrum in the code for seismic design are made clear through statistical analysis and comparison.126 near-fault seismic waves with typical pulse-like characteristics are selected and classified into three groups according to the fault types. The average seismic response spectrum values of these waves are evaluated and compared with the standard response spectrum in the code for seismic design and the results calculated based on 39 ATC63 far-field seismic waves. The research shows that： The average response spectrum of near-fault seismic waves in the long-period （1.5~9 s） are larger than the suggested values in the current Chinese code and those of ATC63 far-field seismic waves. The maximum can reach to 3.7 times of the former one. It may be unsafety to make seismic design of the structure located in near-fault area based on the current code. Among the three types of pulse-like seismic waves, the response spectrum of normal/reversed fault is the maximum one. The pulse-like seismic waves of normal/reversed fault should be used in seismic analysis of the bridges located in near-fault areas. The effect of near-fault should be considered in seismic analysis, especially for the structures, which have long natural vibration period.