主余震序列作用下基于时间维度的连续梁桥易损性分析

Vulnerability analysis of continuous girder bridges based on time dimension under mainshock-aftershock sequences

摘要:

为研究连续梁桥在主余震序列作用下基于时间维度的易损性情况,以一座三跨连续梁桥为研究对象,基于OpenSees有限元软件进行非线性动力分析。选取符合区域场地类型的地震动,通过改进的大森定律和区域主余震统计关系,构建基于时间的主余震序列。以改进的Park-Ang损伤指数作为结构的损伤指标,运用直接回归概率线性拟合的方法建立主震后短期内各时间节点桥墩在不同损伤状态下的地震易损性曲线,研究区域时间范围内主余震序列对连续梁桥抗震性能的影响。结果表明:(1)余震会给桥梁结构带来明显的增量损伤;(2)各种损伤状态的超越概率随着PGA的增大和时间的推移而不断增大,且主震造成的损伤状态等级越高,其超越概率越低,余震作用时超越概率增大越明显。超越概率在震后第1日增幅最大,随着时间的推移逐渐减小,第10日趋于平稳,因此在分析地震给桥梁带来的损伤时,要充分考虑主余震序列的时间效应。

Abstract:

This study examines the vulnerability of continuous girder bridges based on time dimension under the action of mainshock-aftershock sequences. A three-span continuous girder bridge was taken as the research object, and the nonlinear dynamic analysis was performed based on the OpenSees finite element software. By selecting ground motions corresponding to the regional site type, the time-based mainshock-aftershock sequences were constructed through the improved Omori's law and the statistical relationship of regional mainshock-aftershock sequences. The improved Park-Ang damage index was used for the structure. The linear fitting method of direct regression probability was used to establish the seismic vulnerability curves of piers at different time points in a short term after the mainshock, and the influence of mainshock-aftershock sequences on the seismic performance of the continuous girder bridge in regional time domain was studied. The results show that aftershocks will bring obvious incremental damage to the bridge structure. The exceedance probability of each damage state increases with the increase of peak ground acceleration and time. The higher the level of damage caused by the mainshock, the lower the exceedance probability, and the greater the exceedance probability under the action of aftershocks. The exceedance probability shows the largest increase on the first day after the mainshock, and then, it gradually decreases over time and becomes stable on the tenth day. Therefore, the time effect of the mainshock-aftershock sequence should be fully considered when analyzing the damage caused by the earthquake to the bridge.