基于天然橡胶支座老化时变规律下近海隔震桥梁时变易损性分析

对天然橡胶隔震支座开展海洋环境下的耐久性试验,进而得到其随老化时间变化的性能劣化规律,同时参考已有钢筋混凝土材料在氯离子侵蚀作用下的性能劣化规律,通过SAP2000软件建立近海隔震桥梁的非线性动力分析模型。考虑墩柱单独劣化、支座单独劣化及二者共同劣化三种工况,开展全寿命周期不同时间节点的桥梁时变地震易损性分析,对比分析不同工况下不同破坏状态的构件失效概率。结果表明:在相同工况和破坏状态下,支座易损性均大于墩柱易损性,随着服役年份增加,墩柱易损性增加,支座易损性下降;从工况一至工况三,墩柱在不同破坏状态下的易损性都随着劣化时间增长而呈现不同程度的上升,而隔震支座的易损性则随劣化时间增长而呈现下降的趋势,在工况三下,两者易损性的变化最为显著;无论对于墩柱还是对于橡胶隔震支座,和不考虑劣化的初始值相比,三种工况下的易损性曲线均产生了较大变化,以初始值对应的易损性曲线去评估桥梁全寿命期内的抗震安全性会导致低估了墩柱易损性,而高估了支座的耗能能力,无法真实反映隔震桥梁的真实抗震性能变化情况。

Time-Dependent Seismic Fragility Analysis of Offshore Bridges Based on Aging Time-Dependent Law of Rubber Bearings

The natural rubber isolation bearings were tested for durability in the marine environment, and the deterioration of its performance with aging time was obtained. At the same time, the performance degradation law of reinforced concrete under the action of chloride ion erosion was referred to. The SAP2000 software was used to establish nonlinear dynamic analysis model of the offshore bridge. Considering the three conditions of the deterioration of the pier columns, the deterioration of the bearings alone and the common deterioration of the two, the time-dependent seismic fragility analysis of the bridge at different time points in the whole life cycle was carried out, and the failure probability of the components with different failure states under different working conditions was compared and analyzed. The results show that under the same working condition and failure state, the fragility of the bearings is greater than the pier columns. As the service year increases, the fragility of the pier columns increases and the fragility of the bearings decreases. In all conditions, the fragility of the pier columns under different failure states increases with the deterioration time, and the fragility of the bearings decreases with the deterioration time. In the third condition, the change of fragility curves is the most significant. Whether for the pier columns or the bearings, compared with the initial value without considering the deterioration, the fragility curves under the three conditions are changed a lot.Using the fragility curve corresponding to the initial value to evaluate the seismic safety of the bridge during its life cycle will lead to underestimation of the fragility of the pier columns, and overestimate the energy consumption of the bearings, which cannot truly reflect the true seismic performance changes of the bridge.