Modelling the influence of steel structure compartment geometry on travelling fires

The response of structures exposed to fire is highly dependent on the type of fire that occurs, which is in turn very dependent on the compartment geometry. In the frame of the European RFCS TRAFIR project, CFD simulations using FDS software were carried out to analyse the influence of compartment geometry and the interaction with representative fuel loads to explore the conditions leading to the development of a travelling fire. The influence observed of ceiling height, crib spacing, and opening geometry in controlling spread rates tend to confirm the possibility to predict the occurrence, or not, of travelling fire. The results of one CFD analysis are then used to perform a nonlinear thermomechanical analysis of a steel structure with SAFIR® software. Indeed, it is possible to use the radiative intensities and gas temperatures obtained with CFD to calculate with FEM the temperatures in structural elements located in the compartment, and to evaluate the structural behaviour of a frame made of these elements. This paper therefore highlights the effect of building design specifications on the temperature development and on the resulting mechanical behaviour of a steel structure that considers comprehensively the travelling nature of the fire.