Response of Steel Members Subject to Temperature Gradient in Localized Fires

Abstract

The current structural fire design approaches are developed for fully developed compartment fires, the gas temperatures of which can be approximated as uniformly distributed in the compartment. In localized fires, the gas temperature distributions are spatially nonuniform. Recent numerical studies on the response of steel members subjected to localized fires are presented. Simple models based on plume theory and sophisticated computational fluid dynamics model were used to predict the heat fluxes from localized fires to exposed steel members. Thermomechanical simulations were conducted to predict the temperature and structural responses of the members. The numerical models were validated against standard fire tests and localized fire tests. The lateral torsional buckling behavior of simply supported steel beams, failure behavior of restrained steel beams, and buckling behavior of steel columns in localized fires were predicted and compared with the behaviors in the standard fire. The main finding of these studies was due to temperature gradient, the behavior of steel members in localized fires may be totally different from that in the standard fire, and the failure or buckling temperature of steel members in localized fires may be much lower than that in the standard fire. Structural fire design for steel members based on the standard fire may not be conservative if the potential real fires are localized fires.