Finite Element Analysis of the Residual Mechanical Behaviour of Cold-Worked Austenitic Stainless Steel Reinforcing Bars after Exposure to Elevated Temperatures

Austenitic stainless steels, specifically AISI 304 (EN 1.4301), are increasingly utilized in structural and architectural engineering due to their superior corrosion resistance and durability. However, the residual performance of cold-worked stainless-steel reinforcement after exposure to elevated temperatures remains a critical concern for structural safety assessments. This study presents a comprehensive finite element (FE) analysis aimed at predicting the residual mechanical behavior of cold-worked AISI 304 reinforcing bars. The numerical framework incorporates user-defined material parameters within an isotropic elastic model coupled with a multi-linear isotropic hardening model. The predictive capability of these models was evaluated against experimental data across three cooling regimes: Water Quenching (Q), Air Cooling (A), and Slow Furnace Cooling (S). The results demonstrate a robust correlation between the numerical simulations and experimental observations for both virgin and thermally exposed materials. The FE models achieved high precision, with discrepancies in ultimate tensile strength (𝑓ᵤ) generally restricted to less than 1.3%. The deviation in the 0.2% proof strength (𝑓0.2p) was maintained within 6.5% for the majority of cases, with minor exceptions reaching 8.01% for rapid water cooling at 700 °C and 6.53% for slow cooling at 900 °C. the findings indicate that the proposed modeling approach effectively captures the complex stress-strain response and total strain components across diverse thermal histories. This study provides a validated numerical tool for the structural fire engineering community to assess the post-fire capacity of stainless-steel reinforced structures with high confidence.