Limit State of Steel Frames under Fire Conditions

Abstract

Fire resistance of structures can be predicted either by experiments or analysis. Because small-scale specimen tests cannot simulate actual fire effects and large-scale specimen tests are quite expensive and suffer from technical constraints, theoretical analysis is being widely employed in practical design for the fire resistance of steel structures. This chapter presents a new approach for the analysis of the limit state of steel frames under fire conditions. The material and geometrical nonlinearities and the non-uniform profile of temperature across section of frame members are taken into account. Thermal forces induced by temperature variation are also considered. The elasto-plastic stiffness equation of elements is established by using the generalized Clough model. The analysis of structures subjected to fire is converted to analysis of structure subjected unbalanced forces induced by temperature increment. The chapter proposes a procedure to calculate the nonlinear response and ultimate load of steel frames exposed to fire. The effectiveness of the proposed method is verified by the analysis of a related experiment.