基于时变耐久性损伤的近海在役RC桥梁地震易损性研究

Considering the durability damages and seismic safety problems at life cycle of offshore existed bridges in our country, according offshore environment simulation, the coupling effect of concrete carbonation and chloride ion erosion are considered in this research subject, object of which is RC bridge. Synthesizes the influence of time-variation durability damages on seismic performance, the order parameter quantitative expressing the seismic performance of offshore existed RC bridge is extracted, and logical relationship between service life, offshore environment and the macro seismic performance is researched, then, the earthquake vulnerability of offshore existed RC bridge is analyzed. The innovation of the study lies in modelling durability damaged reinforced and concrete time-varying mechanical property of offshore bridge, determining the boundary condition of offshore existed RC bridge durability damage analysis, revealing the evolutionary process and time-varying regularity of seismic performance of offshore bridges in full life-cycle, and establishing the time-varying earthquake vulnerability model, which will be applied to research the seismic performance of offshore bridges under main-aftershock and earthquakes in full life-cycle. Based on the service life and durability damage, take a multi-span offshore RC bridge as an example, major aftershock and earthquakes sequence is constructed, and its time-varying seismic fragility and robustness are researched. The project can provide theoretic support to seismic disaster risk assessment of offshore existed bridges in their life cycle.

本课题以我国近海在役桥梁全寿命周期内面临的耐久性损伤及地震安全问题为背景，以RC桥梁为研究对象，通过近海腐蚀环境的模拟，考虑混凝土碳化与氯离子侵蚀的耦合作用，分析桥梁时变耐久性损伤对其抗震性能的影响，提取定量表征近海RC桥梁抗震性能演化的序参量，研究服役年限及近海环境作用与宏观抗震性能的逻辑关联，分析近海在役RC桥梁的时变地震易损性。创新点主要在于建立近海桥梁耐久性损伤RC材料力学性能时变模型；确定近海在役桥梁耐久性损伤分析边界条件，研究近海桥梁全寿命周期内抗震性能演化过程及时变规律；建立全寿命周期内近海RC桥梁在主余震及多次地震作用下的时变地震易损性模型。最后以某在役近海长联RC桥梁为例，根据服役年限及耐久性损伤，构造主余震及多次地震序列，研究不同服役阶段桥梁时变地震易损性及其鲁棒性的强弱，从而为全寿命周期内近海在役桥梁地震风险评估提供理论依据。

随着我国经济快速发展，近海交通运输建设规模不断扩大，近海桥梁数量不断增多。对于近海桥梁，全寿命周期内更为突出的问题是其处于海腐蚀环境的同时又在地震多发带。本课题以我国近海在役桥梁全寿命周期内面临的耐久性损伤及地震安全问题为背景，以钢筋混凝土桥梁为对象，研究了近海耐久性损伤桥梁时变易损性。本项目基于不同荷载模式下锈蚀钢筋力学性能试验，分析了单调拉伸荷载、低周反复荷载作用下锈蚀钢筋的力学性能，对锈蚀钢筋力学性能在不同荷载模式下退化程度进行了对比研究，并给出了锈蚀钢筋力学性能退化计算模型。通过碳化混凝土棱柱体试件单调及反复荷载试验，得到各试件应力应变曲线及骨架曲线，考虑到碳化混凝土构件的截面尺寸效应，从混凝土碳化率的角度对比分析了单调及反复荷载下碳化对试件力学性能的影响，并给出了碳化混凝土力学性能退化计算模型。建立近海桥梁精细化有限元模型，通过的锈蚀钢筋混凝土桥墩试件抗震性能试验验证有限元模型的有效性，分析了不同服役期内桥墩抗震性能的演化过程。考虑混凝土碳化与氯离子侵蚀的耦合作用，通过模拟近海腐蚀环境，进行了近海环境下钢筋混凝土材料力学性能的退化过程的时变性分析。确定近海在役桥梁耐久性损伤分析边界条件，考虑桥梁全寿命周期内地震作用的时变性，采用时变地震易损性分析方法研究了近海桥梁全寿命周期内抗震性能演化过程及时变规律。建立了全寿命周期内近海RC桥梁在主余震及多次地震作用下的时变地震易损性模型，根据服役年限及耐久性损伤，构造主余震及多次地震序列，研究不同服役阶段桥梁时变地震易损性。基于理论易损性、可靠度理论以及构件的概念移除法提出了一种适用于全寿命周期内算例桥型的抗倒塌分析方法, 并进行了基于时变易损性的近海桥梁主余震作用下的鲁棒性分析,从而为全寿命周期内近海在役桥梁地震风险评估提供理论依据。