Performance and evaluation theory of axial compression capacity for steel angle and tube members in wildfire

This paper deals with the performance of axial compression capacity for steel angle and tube members subjected to wildfire. An indirect thermo-mechanical coupling model of steel members, of which the accuracy was verified by the experimental results, was established to investigate the mechanical and wildfire resistance performance from different perspectives, such as bearing capacity, temperature distribution and critical temperature. Parametric analysis was conducted to further determine the key parameters including slenderness ratio, crosssectional sizes and wildfire conditions that affect the change rule of axial compression capacity for steel angle and tube members. It reveals that the bearing capacity and critical temperature significantly decreased as the slenderness ratio increased, and the difference in wildfire resistance between steel angle and tube became enlarged with the increase of slenderness ratio. Comparatively, the critical temperature of steel angle was obviously lower than that of steel tube, since the additional bending deformation at mid-span induced by the non-uniform temperature distribution on cross-section was more evident for the angle member. Moreover, a calculation method for the ultimate capacity and critical temperature of steel members under wildfires was proposed, which turned out to be reliable to provide reference for wildfire resistance design of steel angle and tube members.