A numeric computational model is presented in this paper to investigate the behaviour of steel-framed structures under fire conditions. The analysis methodology is divided into two main parts, related to thermo and mechanical evaluations, respectively associated to the determination of nonuniform temperature range and structural response under fire action. The structural limits, related to the ultimate critical resistance time, are evaluated by means of a second-order refined plastic-hinge model, being allowed the consideration of inelastic effects resulting from the material and geometrical changing in configuration, in a computationally efficient way. Numerical results obtained from the implemented model for a 4-story building frame, are presented and critically compared to those from the FEM program SAFIR, determining the applicability of the proposed analysis model.
steel structures; fire design; plastic-hinges
