Experimental and analytical technique for estimating interface thermal conductance in composite structural elements under simulated fire conditions

Composite structural elements in the form of steel tubes filled with concrete are being increasingly used in buildings for their dual advantge of increased load bearing capacity and fire resistance. Models to predict the response of composite structures under fire conditions have been developed with varying degrees of accuracy. One of the major drawbacks for these models is ignoring the effect of thermal contact resistance at the steel-concrete interfacial. The reason for this oversight is due mainly to the absence of data in the literature quantifying this parameter. This paper summarizes an experimental and analytical investigation of the interfacial thermal contact conductance of an unloaded circular steel tube filled with non-reinforced normal concrete and exposed to high heat fluxes. Inverse heat conduction analysis and experimental measurements are used to estimate the thermal contact conductance as a function of steel temperature. Sensitivity analysis of the effect of the magnitude of the contact conductance on the temperature response of the composite element using direct heat conduction modelling is also presented. (C) 2003 Elsevier Inc. All rights reserved.