Influence of welded joints modelling on the structural response of stainless steel frames under fire situation

Stainless steel frames with compact cross-section are capable of redistributing internal forces at room temperature in order to form a plastic failure mechanism, which is reflected in the new generation of structural codes for stainless steel by allowing to carry out global plastic analyses on certain types of stainless steel. Nevertheless, the requirements for the fire design of stainless steel structures in current standards is still primarily based on the resistance of individual elements, disregarding strain hardening effects and the redistribution of internal forces in stainless steel structures for fire situation, although preliminary studies have observed considerable redistributions of internal forces also at elevated temperatures. On this basis, this paper presents a numerical study focused on non-sway stainless steel frames with compact rectangular hollow sections, both at room temperature and at elevated temperatures, to assess the plastic redistribution capacity of stainless steel frames, especially under fire situation. The assessment of the plastic redistribution capacity of stainless steel frames confirms the capability of these structures to form full plastic mechanisms, and that formulations accounting for strain hardening effects (such as the Continuous Strength Method) capture the ultimate load of the frames more accurately. Finally, the results have also demonstrated that stainless steel frames are capable of redistributing internal forces and forming plastic collapse mechanisms under fire situations also, suggesting a new procedure to predict the response of these structures under fire situation more accurately. Finally, the paper highlights some remarks on current design standards for stainless steel that need further consideration to guarantee consistency across the different parts of the specifications.Postprint (published version