An approach for calculating the failure loads of unprotected concrete filled steel columns exposed to fire

This paper deals with the development of an approach for evaluating the squ ash load and rigidity of unprotected concrete filled steel columns at eleva ted temperatures. The current approach of evaluating these properties is re viewed. It is shown that with a non-uniform temperature distribution, over the composite cross-section, the calculations for the squash load and rigid ity are tedious in the current method. A simplified approach is proposed to evaluate the temperature distribution, squash load, and rigidity of compos ite columns. This approach is based on the model in Eurocode 4 and can conv eniently be used to calculate the resistance to axial compression of a conc rete filled steel column for any fire resistance time. The accuracy of the proposed approach is assessed by comparing the predicted strengths against the results of fire tests on concrete filled circular and square steel colu mns. The applicability of the proposed approach to a design situation is il lustrated through a numerical example.