On the plastic moment-shear interaction curves of steel sections under fire

Purpose Different approaches, originally developed for ambient conditions, exist in current codes and standards for incorporating the effect of moment–shear (M–V) interaction on the plastic-carrying capacity of wide-flanged (WF) steel sections. There is a lack of experimental and theoretical studies that address this issue under fire conditions. Design/methodology/approach The current paper presents a numerical study investigating the effect of fire exposure on the plastic M–V capacity curves of doubly symmetrical, WF, hot-rolled steel sections. Validated high-fidelity finite element (FE) models constructed via ANSYS are used to study the effect M–V interaction on the plastic capacity of WF sections. Also, a simplified plastic sectional analysis, intended to be used by engineering practitioners, is proposed for generating the plastic M–V interaction curves. Findings The study shows that the fire-induced non-uniform heating of the section plates affects the shape of the plastic M–V interaction capacity curves. Comparison of different methods against FE results shows that the method specified in the Eurocode is very conservative at room-temperature, but it turns out to be barely sufficiently conservative under fire conditions. Originality/value It is well noted that lack of fire tests on the M–V interaction, including the stability of the plates of steel sections under fire, make it difficult to reach a definite assessment on the effect of M–V interaction on the bearing capacity of steel beams.