Prediction to nonlinear behavior of steel frames subjected to fire

A new approach is presented for analysis of nonlinear behavior of steel frames subjected to fire. The material and geometrical nonlinearity as well as 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 strutures subjected to fire is converted to analysis of structures subjected to unbalanced forces induced by temperature increment. Then a procedure to calculate the nonlinear response and ultimate load of steel frames exposed to fire is proposed. For verifying the validity of the approach proposed, tests on two large-scale models of single-story two-bay steel frames are conducted in gas furnace to simulate fire. The temperature elevation and deformation response of the models due to fire are measured. Good agreements between the results measured and calculated are demonstrated on the behavior of the models exposed to fire. (C) 1999 Elsevier Science Ltd. All rights reserved.