基于中国规范的近断层区抗震设计谱研究

Study on near-fault seismic design spectra based on Chinese code for seismic design of buildings

采用211条脉冲型地震动计算得到了保证率分别为50%(平均谱)和84%(平均谱+1倍标准差谱)的近断层地震动反应谱,将得到的反应谱与GB 50011-2010《建筑抗震设计规范》中推荐的近断层区设计谱进行了比较。结果表明,我国抗震规范中针对近断层区给出的设计谱幅值调整方法不能保证近断层区的结构具有足够的安全性,表现为调整后的设计谱值在某些周期段上仍小于实际的近断层地震动反应谱值。根据比较结果,提出了基于我国抗震规范设计谱形式的近断层区抗震设计谱修正方法,通过提高设计谱幅值和限制特征周期最小值来实现修正,将我国抗震规范中的设计谱幅值增大1. 5倍、特征周期下限取0. 75s(多遇地震)和0. 80s(罕遇地震),所提的近断层区抗震设计谱,保证率可达到84%。所提出的抗震设计谱及变形验算的设计建议简单且易于在工程中使用,研究结果可为近断层区的结构抗震设计提供参考。

The 211 pulse-like ground motions are used to develop the actual near-fault response spectra with confidential intervals of 50% (average spectrum) and 84% (average spectrum + 1 standard deviation spectrum).Results given by the comparison of the actual near-fault response spectra and the code-specific near-fault design spectra in China show that the code-specific design spectra can’t fit well with the actual near-fault response spectra in both the spectral amplitude and the shape. A modification method for the code-specific design spectra with consideration of the near-fault effects on spectral amplitude and characteristic period is proposed,the formulas of design spectra are given and design advices for structures in near-fault regions are provided. It seems that the code-specific seismic design spectrum in China can be used as near-fault seismic design spectra with an 84% confidence interval if the spectral amplitude is amplified by 1. 5 times and the characteristic period is restricted to no less than 0. 75s (frequent earthquake) or 0. 80s (rare earthquake). The proposed seismic design spectra are useful to the design of structures in near-fault regions.