中文摘要：

基于线弹性断裂理论,建立了正交异性钢桥面板U肋对接焊缝的裂纹扩展数值模拟方法,通过模型试验验证了数值模拟方法的有效性和可行性;采用Monte-Carlo法对随机交通荷载进行模拟,获得了随机交通荷载作用下疲劳易损细节的应力历程和应力幅值谱。在此基础上,建立了基于概率断裂力学的U肋对接焊缝疲劳性能评价方法,以典型的正交异性钢桥面板连续梁桥——港珠澳大桥为研究对象,综合考虑了裂纹扩展模型中各参数的随机性,对U肋对接焊缝的疲劳性能展开研究。研究结果表明：所建立的裂纹扩展数值模拟方法能够较为准确地模拟裂纹扩展过程,可为该部位的疲劳寿命评估提供理论工具;U肋对接焊缝疲劳裂纹扩展呈现两阶段扩展特征;港珠澳大桥U肋对接焊缝疲劳寿命服从Weibull分布。

英文摘要：

Based on the theory of linear elastic fracture mechanics,the fatigue crack propagation numerical simulation method for U-rib butt weld of orthotropic steel bridge deck was established,and then the validity and feasibility of the method were proved by model test;Monte-Carlo method was used to simulate the random traffic loads,and the stress amplitude spectrum and stress history of details vulnerable to fatigue in orthotropic steel bridge deck were obtained under random traffic loads.Based on this,the fatigue life evaluation model was established based on the theory of probabilistic fracture mechanics,which was suitable for the U-rib butt weld of orthotropic steel decks.Taking the typical orthotropic steel deck of continuous girder bridge,Hong Kong-Zhuhai-Macao Bridge,as research object,the random of every parameter in crack propagation model was synthesized,and the fatigue properties of U-rib butt weld were investigated.The results show that by the established numerical simulation method,a relatively accurate crack propagation process can be simulated,which provides a theoretical tool for its fatigue life estimation;the fatigue crack propagation of U-rib butt weld can be classified into twophases;the fatigue life of U-rib butt weld in steel box girder of Hong Kong-Zhuhai-Macao Bridge is fitted to Weibull distribution.