焊接构造是钢桥的薄弱部位，在反复车辆荷载作用下，疲劳损伤正逐步成为影响桥梁服役安全的关键问题之一。以Q550E高强钢为研究对象，开展母材和对接焊缝接头的静力拉伸和疲劳裂纹扩展试验，建立母材及焊接连接件的疲劳裂纹增长模型，揭示了应力比对高强钢焊接节点疲劳裂纹扩展速率的影响规律；开展基于FRANC3D和ABAQUS的联合仿真模拟分析，通过敏感性分析明确关键影响参数。结果表明：随着应力比的增大，疲劳裂纹扩展速率参数m增大、lg C减小，应力强度因子门槛值减小；对接焊缝m值约为母材的2倍，对接焊缝裂纹门槛值大于母材，且对应力比更敏感；联合仿真方法可准确预测高强钢焊接接头疲劳寿命，高应力比下试件厚度和初始裂纹深度对疲劳扩展影响显著。

Welded detail is the weak part of steel bridges. The fatigue damage of the welded joint is becoming one of key problems affecting the service safety of bridges under repeated vehicle loads. This study conducted static tensile and fatigue crack growth (FCG) tests of the base metal and weld joint of Q550E high strength steel. The FCG models of base metal and welded joint were established, and the effects of stress ratio on the FCG rate of welded joints of high strength steel were revealed. The coupled simulation method of FRANC3D and ABAQUS was performed, and the key influence parameters were determined by sensitivity analysis. The results show that the FCG rate parameter m increases with the increase of stress ratio. The FCG rate parameter lg C and the threshold stress intensity factor range decreases. The parameter m of butt weld specimen is about twice that of base steel. The threshold stress intensity factor range of weld joint is larger than the base steel and more sensitive to the stress ratio. The developed coupled simulation method can accurately predict the fatigue life of high strength steel welded joints. The specimen thickness and initial crack depth have a significant impact on the fatigue growth under high stress ratio.

U448.36;TG407

国家自然科学基金（52178107）；湖南省自然科学基金创新研究群体项目（2020JJ1006）；湖南省研究生科研创新项目（CX20210776）