基于多变量重现期的中国场址危险一致目标谱构建与地震记录选取方法

CONSTRUCTION OF SITE-SPECIFIC HAZARD CONSISTENT TARGET SPECTRUM IN CHINA AND SELECTION OF GROUND MOTION RECORDS BASED ON MULTIVARIATE RETURN PERIOD

  • 摘要: 为了尽可能降低地震动输入中认知不确定性造成的结构响应差异,要求地震动输入反映场址可能遭受的地震危险性水平。传统条件谱理论下的记录选取方案受条件地震动强度指标的选择影响较大。该研究从多变量重现期定义出发,考虑我国概率地震危险性分析三级地震潜源方案与长短轴地震动预测方程的特点,设计了适用于我国的多元概率危险一致目标谱高效记录选取流程。以天津市某场址为算例对比了同现重现期,联合重现期和Kendall多变量重现期定义下的记录选取结果。以多自由度层剪切模型,以及受高阶振型影响显著的高层建筑为算例,比较了多元危险一致目标谱与传统条件目标谱下记录选取结果的结构地震响应差异。结果表明:Kendall多变量重现期定义下的危险一致目标谱均值介于不同条件周期的条件目标谱之间,而基于同现重现期和联合重现期定义下的目标谱谱型过于保守或者过于低估。当目标重现期较高,地震强度较大时,传统条件目标谱记录选取结果输入下的结构响应受条件周期的选择影响较大,而Kendall危险一致目标谱对于条件周期的选择并不敏感,基于其记录选取结果得到的结构响应也基本不受条件周期选择的影响,可以得到稳定的响应中位值估计。采用多变量重现期作为谱形的控制指标,解决了传统条件谱需要事先确定条件地震动强度指标的缺陷,可应用于基于性态的全概率结构地震风险分析。

     

    Abstract: In order to minimize the structural response variation caused by epistemic uncertainty within the ground motion input, it is required that the selected ground motion records should reflect the seismic hazard level of the engineering site. The traditional ground motion selection method based on conditional mean spectrum theory is greatly influenced by the choice of conditional ground motion intensity measures. In this study, multivariate hazard consistent target spectrum is constructed based on the concept of multivariate return period, which is applicable to China considering the characteristics of the three-level seismicity source and the long and short-axis ground motion prediction equation in probabilistic seismic hazard analysis. Taking a site in Tianjin as an example case, the ground motion selection results under the definition of multivariate return period are compared, including joint return period, co-occurrence return period and Kendall return period. Taking the multi-degree-of-freedom shear model and the high-rise building significantly affected by multi-model effect as examples, the differences in the structural seismic response under the selected ground motion records following the multivariate hazard-consistent target spectrum and the traditional conditional target spectrum were compared. The results show that the hazard-consistent target mean spectrum defined by the Kendall return period lies between the conditional target spectra of different conditional periods, while the target spectrum defined by the co-occurrence return period and the joint return period are overly conservative or underestimated. When the return period is long and the ground motion intensity is high, the structural response under the traditional conditional spectrum is greatly influenced by the choice of conditional period. While the Kendall hazard-consistent target spectrum is not sensitive to the choice of conditional period, and the overall spectrum shows good stability. Based on the ground motion selection results, the structural response is not significantly affected by the choice of conditional period, and a stable median value estimate of the response can be obtained. However, the multivariate hazard-consistent target spectra proposed in this study use multivariate return periods as the target to control the spectrum shape, which can well solve the shortcomings that the traditional conditional spectrum requires manual determination of the anchoring conditional ground motion intensity measures, and can be applied to performance-based seismic risk analysis of structures.

     

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