Modelling the influence of steel structure compartment geometry on travelling fires

Abstract

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.

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

“…Devices on solid surfaces allow prescribing a solid phase quantity, and they can be coupled with a spatial statistics option (in which case the output quantity is not associated with just a single point on the surface). The spatial statistics option MAX was used and caused FDS to write out the maximum value of the surface temperature over the cells that are included in the specified bounded volume (Charlier et al , 2020). If the latter reaches 250°C on at least one face of the cube, then all five burning faces are set to ignite and follow the same prescribed heat release rate per unit area (HRRPUA) curve.…”

“…However, in the FE model, a slab is generally modelled in correspondence to its centreline. Thus, the slab would fall outside the CFD domain, and assumptions have to be made to determine thermal information at the slab centreline (Charlier et al , 2020). In this paper, the slab was not contained in the transfer zone.…”

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

“…These models are consequently complex and imply a high computational cost. The recent years have seen growing interest in investigating travelling fires which underlined the inadequacy of uniform heating in large compartments [7][8][9][10][11][12][13][14]. Further research efforts are needed, especially to extend the experimental data related to such fire scenarios which is scarce, limited, and partial.…”

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

“…Travelling fires have been observed in several structural failures especially from 2000: The World Trade Center Towers (Gann et al, 2013) in New York City in 2001, the Windsor Tower (Fletcher et al, 2005) in Madrid in 2005, and the Faculty of TU Delft Architecture building (Zannoni et al, 2008) in Netherlands in 2008. The recent years have seen growing interest in investigating travelling fires which underlined the inadequacy of uniform heating in large compartments (Rein et al, 2007;Horov a et al, 2013;Hidalgo et al, 2017Hidalgo et al, , 2019Gamba et al, 2020;Degler et al, 2015;Charlier et al, 2018;Rackauskaite et al, 2015). Further research effort is still needed, especially to extend the experimental results of such fire scenarios.…”