王益逊 叶枝 冉云军

摘 要：为研究正交异性钢桥面板U肋对接焊缝疲劳裂纹扩展寿命规律，建立正交异性钢桥面板U肋对接焊缝开裂模型，针对U肋对接焊缝开裂后沿表面、沿板厚两种情况分别进行裂纹扩展分析。通过计算裂纹尖端Ⅰ、Ⅱ型应力强度因子，分别获得裂纹尖端应力、扩展角度的变化规律，然后结合Paris定律，基于断裂力学理论对两种情况下的裂纹扩展疲劳寿命进行评估。研究结果表明：表面疲劳裂纹两种裂纹尖端的扩展角度大致相同，呈对称扩展；当裂纹长度小于2.75mm时，板厚疲劳裂纹处于稳定扩展阶段，疲劳裂纹修复应尽量选择该稳定扩展阶段；通过对比可知，表面疲劳裂纹的扩展寿命是板厚疲劳裂纹扩展寿命的16.7倍，应对板厚疲劳裂纹扩展予以重点关注。

关键词：钢桥面板；U肋对接焊缝；裂纹扩展；应力强度因子；疲劳寿命

中图分类号： TG405 文献标志码：A [WT]文章编号：1672-1098（2017）03-0066-06

Abstract：To study the rule of fatigue crack growth life of the U-rib butt weld on orthotropic steel bridge deck， a U-rib butt weld model of orthotropic steel bridge deck was established to analyze the crack growth of U-rib butt weld along the surface and plate thickness respectively. By calculating the stress intensity factor （SIF） of the crack tip of typeⅠand typeⅡ， the change rule of stress and angle growth on the crack tip were obtained. Then combined with the Paris law， the fatigue life of crack growth was evaluated based on fracture mechanics of these two conditions. The result shows that growth angles of the two crack tips of the surface crack are approximately the same and grow- symmetrically； the crack along the thickness grows stably when the crack length is less than 2.75mm， indicating the most appropriate repairing length.The contrast shows that the fatigue life of crack along the surface is 16.7 times that along the plate thickness， thus more attention should be paid to the crack along the plate thickness.

Key words：steel bridge deck； U-rib butt weld； crack growth； stress intensity factor； fatigue life

正交异性钢桥面板以其结构自重小、受力性能好、施工速度快等优点得到广泛应用[1-3]，面板、纵肋、横肋是其基本的组成部分。在纵、横两个方向上，正交异性钢桥面板的刚度不同，加之其承受频繁的车流荷载，受力情况复杂，导致多处构造细节易发生疲劳开裂[4-5]。在钢桥面板出现的各种疲劳病害中，U肋受到循环荷载作用，加之施工焊接时不可避免地存在焊接质量问题，使其在对接焊缝处易产生疲劳损伤。鉴于U肋在桥面体系中起着提高刚度的作用，一旦发生疲劳失效，必然会影响结构的整体安全，因此开展U肋对接焊缝疲劳性能研究尤为重要[6]。……