考虑主余震作用的近海桥墩时变地震易损性分析

Time-Dependent Seismic Fragility Analysis of Offshore Bridge Piers under Mainshock and Aftershocks

基于OpenSEES平台,以某近海刚构桥桥墩为例,选取符合场地类型的地震波,并根据地震记录构造主余震序列。运用“能力需求比”分析方法建立不同服役时间节点桥墩控制截面在不同损伤状态条件下的地震易损性曲线,研究氯离子侵蚀和主余震序列对桥墩抗震性能的影响。结果表明:同一损伤状态的超越概率随着服役时间延长和PGA增大而不断变大,且随着损伤状态等级提高,超越概率逐渐降低。轻微损伤状态下,主余震序列对桥墩易损性影响较小;中等损伤、严重破坏和完全倒塌状态下,同一服役期,考虑主余震序列作用下桥墩的超越概率相比于仅考虑主震作用明显增大。

With the increase of service time,the durability damage caused by environmental corrosion has a greater influence on the seismic performance of offshore bridges.A pier is the main energy-consuming component of a bridge to resist earthquake.In this study,an offshore rigid bridge pier was taken as an example.Based on the OpenSees platform,seismic waves that meet the site conditions were selected to construct the mainshock-aftershock sequence according to the seismic records.Using the capacity demand ratio method,the seismic vulnerability curves of pier control sections in different service time points under different damage states were drawn,and the influences of chloride ion erosion and mainshock-aftershock sequence on the seismic performance of bridge piers were studied.The results show that the exceeding probability increases with the increase of service time and PGA,but decreases with the increase of damage grade.In the state of slight damage,the mainshock-aftershock sequence has a limited influence on the seismic fragility of the bridge pier.However,under moderate damage,serious damage,and complete collapse,in the same service time,the mainshock-aftershock sequence has a greater influence on the seismic fragility of the bridge pier than the mainshock.