Post-corrosion fatigue performance and fatigue life assessment method of Q370qENH weathering bridge steel

Weathering steel is widely used in bridge construction for its excellent corrosion resistance and low maintenance requirements. However, uncoated weathering steel bridges are susceptible to accelerated fatigue damage due to combined effects of corrosion and cyclic loading. Current methods for evaluating corrosion fatigue life remain inadequate, especially for long-term service conditions. This study investigates the corrosion fatigue performance of Q370qENH weathering bridge steel, with Q370qE structural steel as a reference. Specimens underwent wet–dry cyclic salt spray tests for accelerated corrosion, followed by high-cycle fatigue tests. The effects of corrosion on fracture morphology, fatigue strength, and P–S–N curves were analyzed. Results showed that Q370qENH exhibited significantly better corrosion fatigue resistance than Q370qE. After 30 corrosion cycles, the fatigue strength of Q370qENH decreased by 25.97%, compared to 44.29% for Q370qE. A corrosion-dependent P–S–N curve was established by analyzing parameter evolution across corrosion cycles. Furthermore, a fatigue life evaluation method integrating the post-corrosion P–S–N curve with cumulative damage theory was proposed and validated via alternating corrosion–fatigue tests. This study provides a refined framework for predicting the fatigue life of uncoated weathering steel bridges and supports their application in moderate atmospheric corrosion environments.