基于改进条件边缘乘积法的桥梁系统地震易损性分析方法

A Seismic Vulnerability Analysis Method for Bridge System Based on Improved Product of Conditional Marginal Method

桥梁结构是由多种不同类型的构件按照一定的逻辑关系构成的结构系统。既有桥梁易损性分析中,通常基于构件的易损性曲线来评价整个桥梁系统的抗震性能。实际运营中的桥梁,在地震作用下,不同构件间相互影响,发生组合破坏将会增加桥梁系统整体失效概率。因此,将桥梁结构作为整体进行易损性分析能够更好地评估实际工程的抗震性能,弥补了既有分析方法的不足。以一座三跨预应力混凝土连续T梁桥为易损性分析对象,结合桥墩和支座两类构件的地震破坏,分别采用界限估计法、改进的条件边缘乘积法建立了算例桥梁系统易损性曲线。结果表明:界限估计法易受各失效模式排列顺序和相关性的影响,稳定性较差;改进的条件边缘乘积法,作为结构系统失效概率的一种近似求解法,解决了在多个失效模式并存下,结构系统可靠度问题中多维标准正态累计分布函数近似求解问题。后者计算精度较高,易于实现,适用于失效模式较多的复杂桥梁系统,具有一定的工程使用价值,为桥梁系统地震易损分析提供了借鉴参考。

Bridge structure is a structural system composed of many different components according to certain logical relations.The seismic performance of the whole bridge system is usually evaluated based on the vulnerability curves of components in the existing bridge vulnerability analysis.Different components are mutual affected under the action of earthquake for operation bridges,the overall failure probability of bridge system will increase when combined failure occurs.Therefore,analyzing the vulnerability of bridge structure as a whole could better evaluate the anti-seismic property in the practical engineering.Taking a 3-span PC continuous T-beam as the vulnerability analysis subject,considering the seismic damage of piers and bearings,the vulnerability curves of the bridge system are worked out by boundary estimation method and improved product of conditional marginal(I-PCM)method respectively.The result shows that(1)the boundary estimation method subjects to the marshalling sequence and the relevance of each failure mode,leading to less stability;(2)the I-PCM method,as an approximate solution to the failure probability of structural system,solves the approximate solution to the multi-dimensional standard normal cumulative distribution function in the structural system reliability problem under the coexistence of multiple failure modes.Because of the latter method has high calculation accuracy and is easy to implement,it is suitable for the complex bridge system with many failure modes,and has certain engineering value,which provides a reference for the seismic vulnerability analysis of bridge systems.