Travelling fire experiments in steel-framed structure: numerical investigations with CFD and FEM

Abstract

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.

Large scale fire test: The development of a travelling fire in open ventilation conditions and its influence on the surrounding steel structure

“…Several CFD simulations were launched with FDS software to calibrate the model representing the largescale tests. These CFD simulations consider a simplified representation of the continuous fire load consisting of discrete volumes based on a regular arrangement [16]. Simplification was targeted, as modelling the exact wood stick size in CFD requires a very fine mesh and therefore a very significant computational time for real building dimensions.…”

“…The inspection of the temperatures obtained via FDS-SAFIR (see label "SAFIR" on Figure 15 and Figure 16) shows that the global profile versus time is well captured, even though steel temperatures from lower levels are higher than the ones measured. More details are provided in Charlier et al [16]. three tests, only the ventilation was varied to assess its influence on the fire behaviour.…”

Thermal response of steel framing members in open car park fires

“…The fictitious temperature is calculated based on the incident radiative heat flux and the gas temperature near the surface [34]. Then the is applied to the FEM thermal analysis as thermal constraints.…”

Travelling fire in full scale experimental building subjected to open ventilation conditions

“…Several CFD simulations were launched with FDS software to calibrate the model representing the large-scale tests. These CFD simulations consider a simplified representation of the continuous fire load consisting of discrete volumes based on a regular arrangement (Charlier et al, 2021). The proposed approach can allow for both an acceptable representation of the travelling fire in terms of fire spread and steel temperatures while being less computationally demanding than modelling the exact geometry of the fire load, making it more desirable for practical applications.…”