Fatigue assessment of cope hole details by SHM measurements and multi-level FE models

The fatigue phenomenon is a common issue for steel bridges, affecting their safety and long-term performance. Estimating the fatigue lives of these structures is challenging for bridge managers and owners. This study presents a comprehensive methodology for evaluating fatigue performance of the cope hole detail with two butt weld configurations on the Southern Danube Railway Bridge in Budapest (SDRB). The long-term SHM strain gauge measurement, combined with multi-level finite element models verified and validated through dynamic and static load tests, was utilized for fatigue evaluation. More than 150 FE analyses are performed under various train loads, revealing three critical stress concentration points in the investigated detail. The regression analysis of FE results demonstrates a robust correlation between the measured and the effective stresses experienced at the critical welded detail, allowing for a direct conversion of the stress-time history measured by the SHM strain gauge to the equivalent effective stress-time histories at the relevant critical locations. The nominal stress method and the effective notch stress-based evaluation methods are used for fatigue damage estimation, and the accumulated fatigue damage is assessed to evaluate the fatigue performance over the entire monitoring period. Results indicate that the effective notch stress-based maximum principal stress predicts the shortest lifetime, and the proposed approach is effective for continuous fatigue assessment in steel railway bridges.