考虑氯离子侵蚀的高墩桥梁时变地震易损性分析

以一高墩大跨连续刚构桥为例,基于OpenSees 程序建立其非线性分析模型。考虑氯离子侵蚀引起的钢筋直径和屈服强度退化,根据截面非线性分析结果探讨了氯离子侵蚀效应对高墩抗震能力的影响。通过单条地震波的非线性时程地震响应,定性地研究了氯离子侵蚀效应对桥梁地震需求的影响。然后输入15 条地震波进行多次增量动力分析,采用对构件能力需求比(Demand/Capacity)进行对数回归分析的方法形成了桥梁的时变地震易损性曲线,对高墩桥梁的时变抗震性能进行评估。分析结果表明:氯离子侵蚀效应会导致高墩屈服弯矩下降,而延性能力略有提高;考虑纵筋锈蚀以后,高墩的位移需求和曲率需求则会显著增加;在桥梁全寿命设计基准期内,结构在不同损伤状态的地震易损性随桥梁服役时间增加而增大。

TIME-DEPENDENT SEISMIC FRAGILITY ANALYSIS OF HIGH PIER BRIDGE BASED ON CHLORIDE ION INDUCED CORROSION

A high-pier and long-span rigid frame bridge is taken as an example, and the nonlinear finite element model of bridges is modeled by using OpenSees program. The deterioration of the diameter and yield capacity induced by chloride corrosion is accounted for longitudinal steel. The sectional nonlinear analyses are applied to investigate the influence of chloride ion induced corrosion (CIIC) on aseismic capacity of high piers. A one-record time history analysis is applied to qualitatively study the influence of CIIC on the aseismic demand of high piers. Moreover, 15 ground motions are selected to conduct multi-records incremental dynamic analyses. The logarithm regression analysis for the ratios of the capacity and demand are adopted to develop the time-dependent fragility curves so as to evaluate the time-variable aseismic performance of the bridge with high piers. It is concluded that: the CIIC reduces the yield bending moment of high piers, whereas the ductility capacity increases slightly; the corrosion of longitudinal steels evidently increases the displacement and curvature demand of high piers; furthermore, the aseismic fragilities of various damage states increase along with the service time of a bridge during its life-cycle design reference period.