Fatigue behavior of corroded non-load-carrying fillet welded joints exposed to atmosphere in Nanjing for 1-year which were made of bridge weathering steel Q345qNH was explored in this paper. Fatigue tests were conducted on 8 specimens which were under 8 stress ranges, fitted S-N curve and lower bound of 95% survival probability were established. It was found that fatigue strength dropped by 26.2% after 1-year exposure compared to uncorroded specimens, the design S-N curve for non-load-carrying fillet welded joint in Eurocode 3 is still satisfactory for fatigue assessment of this batch of specimens. Fractography analysis revealed that fatigue cracks always originated from multiple corrosion pits, geometries of corrosion pits were quantified by surface morphology analysis. Numerical simulation of mixed-mode fatigue crack propagation was conducted, it is found that taking the geometry of the deepest pit as the equivalent initial crack and orienting the crack in the direction normal to the maximum tensile stress plane could predict fatigue lives safely and satisfactorily. The research provides reference for design and fatigue assessment of uncoated weathering steel bridges.

本文研究了由桥梁耐候钢Q345qNH制成的南京腐蚀暴露于大气中的为期一年的非承重角焊缝的疲劳行为。在8个应力范围内的8个试样上进行了疲劳试验，拟合了SN曲线，并建立了95％生存概率的下限。结果发现，与未腐蚀的试样相比，暴露一年后的疲劳强度下降了26.2％，欧洲规范3中无载荷角焊缝的设计SN曲线对于这批试样的疲劳评估仍然令人满意。断口分析表明，疲劳裂纹总是起源于多个腐蚀坑，通过表面形貌分析量化了腐蚀坑的几何形状。进行了混合模式疲劳裂纹扩展的数值模拟，结果发现，将最深凹坑的几何形状作为等效的初始裂纹，并在垂直于最大拉伸应力平面的方向上定向裂纹，可以安全可靠地预测疲劳寿命。该研究为无涂层耐候钢桥的设计和疲劳评估提供参考。