Post-fire behavior of laser-welded stainless-steel T-section stub columns: Testing, modeling and design

Abstract: This paper presents a systematic experimental and numerical investigation into the post-fire compressive behavior of laser-welded stainless-steel T-sections. An experimental program was initially carried out, covering a heating and cooling scheme with five representative exposure temperatures, namely 25 °C, 300 °C, 500 °C, 700 °C and 900 °C, which were selected to reproduce a wide range of realistic post-fire exposure conditions, from the ambient-temperature reference state to severe thermal exposure. Following the heating and natural cooling process, 15 tensile coupon tests and 20 stub column compression tests were conducted to characterize the residual material properties and the residual load-carrying capacities, respectively. The measured stress–strain responses revealed that the examined austenitic stainless steel retained pronounced strain-hardening behavior, with only minor strength degradation observed after exposure to 900 °C. Numerical models were then established and validated against the test results in terms of ultimate resistances, load–end-shortening responses and local buckling failure modes. Parametric studies were subsequently performed using the validated finite-element models to generate additional post-fire performance data across a broad range of cross-sectional geometries and slendernesses. The test and numerical results were further employed in a design analysis, in which the European and American standards, together with the Continuous Strength Method, were evaluated for their applicability and accuracy in post-fire design. The results indicate that both standards yield relatively scattered predictions (CoV of 0.120 and 0.159), with the AISC provisions being generally unconservative, particularly after exposure to temperatures of 700 °C and above. In contrast, the Continuous Strength Method provides markedly improved consistency (CoV of 0.054) owing to its rational consideration of strain-hardening behavior and cross-sectional deformation capacity.