结构周期延长对倒塌分析中地震动强度指标选择的影响

当结构在强震作用下接近倒塌状态时，其刚度和承载力的退化会导致结构周期延长，为此，研究了周期延长对地震动强度指标选择的影响，将不同周期调整系数β对应的谱加速度(Sa(βT1)，T1为弹性基本周期）作为地震动强度指标时，研究其倒塌分析结果的离散性。基于等效单自由度结构周期（Teq），提出了等效周期谱加速度（Sa(Teq)）。研究结果表明：当周期调整系数β增大时，结构抗倒塌能力分析结果的离散性呈现先减小后增大的趋势。与传统地震动强度指标Sa(T1)相比，所提出的Sa(Teq)可以考虑结构非线性变形引起的周期延长，能有效降低倒塌分析结果的离散性达30%以上。

Influence of structural period elongation on ground motion intensity index in collapse analysis

The structural periods will be elongated due to strength and stiffness degradation when structures are near collapse state under strong earthquakes. This paper investigated the influence of structural period elongation on the selection of ground motion intensity index. The discreteness of collapse analysis results were studied, when Sa(βT1)(T1 is the elastic fundamental period)corresponding to different period adjustment coefficient β was used as a ground motion intensity index. Based on the equivalent single degree freedom structural period （Teq）, a new ground motion intensity index （Sa(Teq)） was proposed. The results show that when the period adjustment coefficient β increases, the discreteness of collapse analysis decreases initially and then increases. Compared with the traditional intensity index Sa(T1),Sa(Teq) can reflect the influence of structural period elongation due to structural nonlinear deformation and efficiently reduce the dispersion of results in collapse analysis by above 30%.