中文摘要：

为了解决桥梁结构整体承载力设计与优化的难题,基于弹性模量缩减法提出了桥梁结构构件和整体两层面安全性设计及其优化策略。首先研究分析了桥梁结构在构件和整体2个层面上的安全系数取值,然后利用齐次广义屈服函数建立单元承载比,提出了高、低承载构件的动态判别准则。通过有策略地调整构件截面强度,建立了桥梁结构两层面承载力设计方法;进而以结构两层面承载安全性要求为约束条件,以均匀承载为优化准则,提出了桥梁结构优化设计方法。结果表明：所提出的方法能够避免将第2类高承载构件误判为低承载构件,可获得两层面承载安全性能和经济性能均优的桥梁结构设计方案。

英文摘要：

In order to solve the problems in general load carrying capacity design and optimization for bridge structure,the strategies of two-level safety design and optimization were presented for bridge structure components and the overall structure based on the elastic modulus reduction method.Firstly,the values of two-level safety factors were investigated and analyzed for components and overall structure of bridges.The element bearing ratio was established by the homogeneous generalized yield function,and a dynamic criterion was presented to identify highly stressed and lowly stressed components.By adjusting the sectional strength of components with strategies,the design method of two-level load carrying capacity for bridge structures was established.Furthermore,optimization design method for bridge structure under the principle of well distributed was proposed by taking the two-level bearing safety requirement constraint.The results show that the proposed method can avoid misidentifying the second kind of highly stressed components as lowly stressed ones,and gain the design plan both satisfies the requirements of bearing safety and economy for bridge structures.