基于汶川地震记录及遗传算法的加速度设计反应谱

Study on the acceleration seismic design response spectrum based on the Wenchuan ground motions and genetic algorithm

现行加速度反应谱的长周期段太短且其取值出现需要抬高和降低两种大相径庭的研究结论;反应谱的特征周期(T_g)与动力放大系数(b)取值也存在争议。该文从中国国家强震动台网中心(CSMNC)数据库中筛选汶川地震主震记录421条,根据地面运动峰值加速度、场地和地震分组对地震记录进行分类,计算常规地震记录与长周期地震动记录的反应谱,与规范反应谱对比。同时,基于遗传算法和a_(max)-T_g四阶段拟合模型,利用得到的地震记录进行设计反应谱拟合,并对设计反应谱拟合模型的各种参数进行标定和校验,对规范设计谱的主要特征参数给出修正建议。研究结果表明:常规地震动计算得到的反应谱长周期段的值比规范设计反应谱要低,而长周期地震动反应谱的长周期段的值比规范设计谱要高,揭示了两种不同研究结论的根源;拟合得到的加速度设计谱与实际反应谱吻合程度要好于规范设计谱;说明了补充长周期地震动设计反应谱的必要性,为规范设计反应谱的修订提供参考。

The long period stage of acceleration design response spectrum(ADRS) in current standards is too short and there are two very different conclusions about raising and reducing its value;Meantime, the values of characteristic period(Tg) and dynamic magnification factor(b) of ADRS are also in dispute. In this paper, 421 Wenchuan earthquake main shock records from China Strong Motion Network Center(CSMNC) database are selected. These seismic records are classified according to the PGA, site and classification of design earthquake.Response spectrum of conventional seismic records and long-period seismic records are computed and compared with ADRS in current standards. Meanwhile, the DRS fitting model is obtained by using these records based on the αmax-Tg four stages model and Genetic Algorithm(GA), the parameters of the response spectrum model are calibrated and verified, The suggested amendments for characteristic parameters of ADRS are brought up. The results show that the spectral value of long-period stage of conventional seismic records are lower than the ADRS in current standards, however, the spectral value of long-period stage of long-period seismic records is higher than the ADRS in current standards. It reveals why there are two different viewpoints on the value of the long period stage of ADRS in current standards. The fitting ADRS coincides with the actual response spectrum which is better than that with standard ADRS;It explains the necessity to supplement the ADRS of long-period ground motions and provides a reference for revision of the specification DRS.