Implementation of advanced analysis method for steel-framed structures under fire conditions

This paper is concerned with the development of an advanced analysis numerical tool capable of estimating the inelastic large-displacement behaviour of plane steel-framed structures under fire conditions. A non-linear transient heat transfer analysis is performed on the basis of the finite element method (FEM), following the main guidelines proposed by the European Code for steel structures under fire conditions. The computational analysis program is used to assess the structural load-bearing functions and to estimate the structural behaviour and the corresponding time-resistance period. The original refined plastic hinge method is extended for fire design analysis considering both tangent modulus model and inelastic stiffness degradation concepts in the developed computational program. A tangent modulus model is developed for the European column buckling-curve for fire condition. A gradual inelastic surface is proposed as a function of the temperature and the loading combination. The results obtained are compared with those from an FEM computational program and those from the Eurocode simplified design recommendations. The benefits of using steel ductility in the current design of fire-unprotected structures are outlined.