Coupled CFD-FE analysis of a long-span truss beam exposed to spreading fires. (15th May 2022) - Kallada Janardhan, Rahul
Highlights: Fire simulations show a five-stage fire development in two different spread scenarios. A longer fire path increases the variability of the temperature field in space and time. Computationally efficient coupling enables analyses of large frames in complex fire scenarios. The response of the frame is sensitive to its orientation with respect to fire path. Coverage of elevated temperatures along girders leads to their load-bearing failures. Abstract: This paper presents a unidirectional coupling methodology for combining fire simulation based on computational fluid dynamics (CFD) with finite element (FE) analysis to study the response of long-span steel truss beams exposed to non-uniform temperature distributions. Fire Dynamics Simulator (FDS) was used to simulate the fire scenarios, and Abaqus was used for the FE analyses. Adiabatic surface temperatures from the fire simulations were transferred to the Abaqus model using a coupling tool called FDS2FEM. The coupling methodology was validated using two experimental studies, and it was then used to analyse the response of a long-span steel truss beam inside a warehouse building exposed to two travelling fire scenarios (fire spread perpendicular to or along the truss beams) in the building. The fire simulations showed that the fire load arrangement, ignition location and ignition distance from the ventilation opening determined the severity of the thermal field, temperature heterogeneity and the fire spread behaviour. The computational efficiency of the coupling scheme enabled the structural analysis for a large-scale structure under highly time- and space-dependent thermal exposure. The FE analyses indicated that the direction of fire spread with respect to the truss beam determined if either vertical or lateral displacement at the mid-span of the girder was dominant. The analyses also showed that a long truss beam exposed to highly non-uniform temperature fields exhibits a variety of responses like thermal bowing, lateral oscillations, efficient load redistribution, local deformations, and global failure.