Post-corrosion axial stability of low-slenderness Q500qENH weathering-steel box members

This study investigates the post-corrosion axial compressive behavior of Q500qENH weathering-steel low-slenderness welded box-section members through experiments, numerical modeling and mechanics-informed prediction. Four welded box-section specimens with nominal corrosion levels of 0%, 5%, 10% and 20% were tested under axial compression, and the associated material degradation was quantified by coupon tests. The results show that corrosion progressively reduces stiffness and ultimate capacity, while accelerating local buckling and post-peak localization. Relative to the uncorroded specimen, the specimen with an actual mass-loss ratio of 19.3% exhibited a 37.3% reduction in ultimate capacity. Two finite-element strategies, namely point cloud reverse modeling and a corrosion random field model, were established and validated against the test results. Among the two approaches considered, the corrosion random field model showed better agreement in the post-peak regime and was therefore adopted for the subsequent parametric study. Based on experimentally validated FE cases, the effects of width-to-thickness ratio, slenderness ratio and corrosion distribution were examined. Corrosion mass loss was found to dominate the magnitude of capacity degradation, whereas corrosion distribution mainly affected the location of buckling localization. Finally, a mechanics-informed surrogate predictor was developed from the experimentally validated FE framework and numerical database. Among multiple linear regression, random forest, and XGBoost, XGBoost achieved the best performance and is recommended only for interpolation-based preliminary capacity estimation of low-slenderness welded box-section members within the investigated range of 10≤ λ ≤20.