Purpose
The purpose of this paper is to propose a simplified representation of the fire load in computational fluid dynamics (CFD) to represent the effect of large-scale travelling fire and to highlight the relevance of such an approach whilst coupling the CFD results with finite element method (FEM) to evaluate related steel temperatures, comparing the numerical outcomes with experimental measurements.
Design/methodology/approach
This paper presents the setup of the CFD simulations (FDS software), its corresponding assumptions and the calibration via two natural fire tests whilst focusing on gas temperatures and on steel temperatures measured on a central column. For the latter, two methods are presented: one based on EN 1993-1-2 and another linking CFD and FEM (SAFIR® software).
Findings
This paper suggests that such an approach can allow for an acceptable representation of the travelling fire both in terms of fire spread and steel temperatures. The inevitable limitations inherent to the simplifications made during the CFD simulations are also discussed. Regarding steel temperatures, the two methods lead to quite similar results, but with the ones obtained via CFD–FEM coupling are closer to those measured.
Originality/value
This work has revealed that the proposed simplified representation of the fire load appears to be appropriate to evaluate the temperature of steel structural elements within reasonable limits on computational time, making it potentially desirable for practical applications. This paper also presents the first comparisons of FDS–SAFIR® coupling with experimental results, highlighting promising outcomes.
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.
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