非一致氯离子侵蚀下近海桥梁时变地震易损性研究

近海桥梁往往处于氯离子空间分布不均匀的复杂环境，在服役过程中往往会遭受非一致氯离子侵蚀，导致材料及结构性能不断退化，降低桥梁抵御地震的能力。为研究非一致氯离子侵蚀下桥梁地震损伤风险变化规律，文章以氯离子扩散规律及钢筋锈蚀机理为基础，基于Duracrete模型及以往试验结果，确定不同环境参数及锈蚀参数的概率分布类型及统计特征，建立钢筋及混凝土材料退化规律。结合地震易损性分析理论，建立非一致氯离子侵蚀环境下桥梁时变地震易损性评估流程。随后，以一座多跨连续梁桥为例，分析退化桥梁抗震能力变化特征，研究不同构件的地震损伤时变规律。研究结果表明，氯离子侵蚀下的桥墩截面抗弯承载力和曲率延性均表现出明显的退化，并且曲率延性退化程度高于抗弯承载力。非一致氯离子侵蚀会导致桥墩损伤分布发生演变，桥墩易损位置可能从墩顶、墩底转移至低水位处。随着服役时间增加，桥墩损伤概率明显增大，而支座、挡块及桥台的损伤概率略有降低。

Time-dependent seismic fragility assessment of offshore bridges subjectto non-uniform chloride-inducedcorrosion

Numerous offshore bridges are located in the complex environment with the non-uniform spatial distribution of chloride ions. During the service life, the non-uniform chloride-induced corrosion often leads to the performance degradation of material and structure as well as the reduction in the seismic resistance of the bridge to earthquake. In order to investigate the variation of seismic damage risk of bridges subject to the non-uniform chloride-induced corrosion, the probability distribution type and statistical characteristics of different environmental parameters and corrosion parameters are determined, and the degradation laws of reinforcement and concrete are established combine the Duracrete model, the previous test results, the diffusion law of chloride ions and the corrosion mechanism of reinforcement. According to the analysis theory of seismic fragility, the evaluation process of the time-dependent seismic fragility of bridges subject to non-uniform chloride-induced corrosion is established. Then, a multi-span girder bridge is taken as an example, the variation characteristics of seismic capability of degenerated bridges are analyzed and the time-dependent seismic damages of various components are investigated. The results show that the flexural capacity and curvature ductility of the cross-section of the piers degrade obviously due to corrosion of the chloride ion, and the degradation of curvatureductility is more significant than that of the flexural capacity. Non-uniform chloride-induced corrosion may change the damage distribution of the pier, and the vulnerable position of the pier may be shifted from the top and the bottom of the piers to the position at low water level. With the increase of service time, the damage probability of the pier maybe increased obviously, and the damage probabilities of the bearing, shear keys and the abutment may be decreased slightly.