Simplified elastoplastic analysis of general frames on fire

This paper presents an alternative simplified procedure for the analysis of three-dimensional frames under elevated temperatures. The generalized plastic hinges concept, where normal force and bending moments are considered in the plastification process, is extended to include temperature effects. Additional refinements to allow for the gradual spread of yielding on the member are included, by means of stiffness reduction factors. The determination of the internal forces vector, including nonlinear thermal effects, is detailed. The model is compared with experimental results and more refined models, using examples that cover different situations. The results show that the proposed procedure can be used as an alternative means to analyse 2D and 3D frames on fire, with reasonable accuracy and low computational cost.