结构周期延长对倒塌分析中地震动强度指标选择的影响

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 S_a(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 (T_eq), a new ground motion intensity index (S_a(T_eq)) 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 S_a(T₁), S_a(T_eq) 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%.