Analytical predictions of moment curvature relationship of steel beam columns under fire attack

Fire attack is one of the worst scenarios that may cause catastrophic consequences of steel buildings such as progressive collapse and failure. Current design codes and standards have addressed fire as one of the extreme loading conditions to be accounted for in the design of buildings. However, most of the approaches and procedures suggested by these codes and standards still lack accuracy and rationality. The purpose of this paper is to develop an analytical approach to predict the elastic-plastic moment-curvature relationship of steel beam - columns section under elevated temperature. The analytical method was derived based on dividing the steel section to layers and integrating the resistance moment equation of each layer in terms of the section curvature taking into account the effect of elevated temperature on the material properties of the steel by using EC3 reduction factors of the yield stress and modulus of elasticity. The suggested method has been validated against numerical simulation results. Validation results have shown the reliability of the suggested method to predict the resistance moment - curvature relationship of steel beam-column members at different elevated temperatures and under different values of the axial compressive force. The suggested methods may be used to develop more accurate design approaches for steel beam columns under fire condition.