Post‐Fire Mechanics of Corroded Q690 High‐Strength Steel and Influence on H‐Shaped Columns

This study aims to characterize the residual mechanical properties and axial compressive behavior of corroded Q690 steel after fire exposure. Monotonic tensile tests were conducted on specimens subjected to indoor accelerated corrosion followed by high‐temperature exposure. Based on the results, an ABAQUS finite element model of corroded H‐shaped columns was developed for parametric analysis of post‐fire axial compression. Above 600°C, steel exhibits significant mechanical transition: strength degradation accelerates, corrosion effects weaken, and temperature becomes dominant. In contrast, stiffness remains stable, and ductility improves. As slenderness increases, temperature‐induced variation in α N ( D n , T ) diminishes, but corrosion effects persist. Comparisons with current design provisions indicate that existing code curves remain applicable for estimating the post‐fire global stability of corroded Q690 H‐shaped columns when the section properties and residual material parameters are properly updated. These findings support improved post‐fire assessment and repair strategies for corroded steel structures with elastic or limited plastic response.