Performance-based system seismic assessment for long-span suspension bridges under two-level seismic hazard

两水准设防下大跨度悬索桥全桥系统基于性能的抗震评价分析（英文）

Since there are few studies on the performance-based seismic evaluation of the long-span suspension bridge system under two-level earthquake hazard in Chinese code,the developed procedure of this study can be regarded as a general program to assess the seismic performance of the overall system for long-span suspension bridges.In the procedure,the probabilistic seismic demand models of multiple bridge components were developed by nonlinear time-history analyses incorporating the related uncertainties,and the component-level fragility curves were calculated by the reasonable definition of limit states of the corresponding components in combination with seismic hazard analysis.The bridge repair cost ratios used to evaluate the system seismic performance were derived through the performance-based methodology and the damage probability of critical components.Furthermore,the repair cost ratios of the overall bridge system that was retrofitted with fluid viscous dampers for the main bridge and changed restraint systems for the approach bridges were compared.The results show that peak ground velocity and peak ground acceleration can be selected as the optimal intensity measurements of long-span suspension bridges using the TOPSIS(technique for order preference by similarity to an ideal solution).The bridge repair cost ratios can serve as accurate evaluation indicators to provide an efficient evaluation of retrofit measures.The seismic evaluation of long-span bridges is misled when ignoring the interaction of adjacent structures.However,the repair cost ratios of a bridge system that has optimum seismic performance are less sensitive to the relative importance of adjacent structures.

针对规范中关于两水准设防下大跨度悬索桥基于性能的抗震评价研究不充分的问题,建立了可作为评估大跨度悬索桥全桥系统抗震性能的一般程序.首先采用考虑相关不确定性的非线性时程分析建立多个构件的概率地震需求模型,合理定义构件极限状态.其次结合地震危险性分析计算构件级易损性曲线,由关键构件的损伤概率和基于性能的方法推导出全桥系统的修复成本比,评价两水准设防下系统的抗震性能.进一步比较了主桥采用阻尼器加固和改变引桥支承约束体系后全桥系统的修复成本比.结果表明:采用TOPSIS方法可选择PGV和PGA为大跨度悬索桥的最佳地震动强度指标.修复成本比可作为准确评价全桥系统抗震性能的指标,对改造措施进行有效评估.忽略主引桥相互影响及其相对重要性会对桥梁系统的抗震性能评价产生偏差,但在具有良好抗震性能的桥梁系统中,修复成本比对结构相对重要性不敏感.