地震动持时对RC框架结构易损性与抗震性能影响

Effect of ground motion duration on fragility and seismic performance of RC frame structures

作为地震动三要素之一,地震动持时对结构地震易损性的影响有待深入研究。为此,选择分别具有长、短持时特性的两组地震动记录作为输入,以按我国现行规范设计的3个不同高度钢筋混凝土框架结构作为研究对象,采用OpenSees软件,对比分析了不同持时特性地震动作用下钢筋混凝土框架结构的地震易损性,并进一步从失效概率、易损性指数和性能裕度比等3个方面讨论了持时对结构抗震性能的影响。分析结果表明:地震动持时特性对结构地震易损性的影响不容忽视;随着地震动强度和结构损伤水平的增加,地震动持时对地震易损性的影响越发显著;相较于短持时地震动,长持时地震动会使易损性中位值下降超过10%;地震动持时越长,其对结构抗震性能的不利影响也越明显;长持时地震动使结构失效概率增加50%以上,同时提高易损性指数,降低性能裕度比。

As one of the three important characteristics of ground motion, the effect of ground motion duration on seismic fragility of structures has not attracted wide attention. To solve this problem, two sets of ground motion records with long-duration and short-duration, respectively, were selected as earthquake inputs. Three reinforced concrete frame structures of varying heights were taken as the study cases. The structures were designed according to the current Chinese codes. The OpenSees software was used to conduct response analysis, and seismic fragility of these structures subjected to ground motion records with different duration characteristics was further assessed. The effects of duration on structural performance were also discussed from the perspectives of failure probability, fragility index and performance margin ratio. The results show that the influence of ground motion duration on seismic fragility of structures is not negligible. With the increase of the ground motion intensity and structural damage, the effect of ground motion duration is increasingly significant. Compared to short-duration ground motions, long-duration ground motions can reduce the fragility medians by over 10%. The longer the ground motion duration is, the larger the unfavorable effect of ground motion duration on seismic performance of the structures is. The long-duration ground motion can increase the structural failure probabilities by 50%, and it can also increase the fragility indices and decrease the performance margin ratios.