Coupling the fire simulation and structural analysis through adiabatic surface temperature
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Insinööritieteiden korkeakoulu |
Master's thesis
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Date
2022-10-10
Department
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Mcode
Degree programme
Master's Programme in Building Technology (CIV)
Language
en
Pages
74+6
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Abstract
This study presents the results of one-way coupling between a fire simulation performed in computational fluid dynamics (CFD) and the structural response in finite element (FE) analysis. A built-in tool of adiabatic surface temperature (AST) in Fire Dynamics Simulator (FDS) is utilized for transferring the boundary conditions into SAFIR, a Finite Element package. A validation study is done using the experimental data where an unprotected steel column is subjected to a localized fire. The results from FDS-SAFIR coupling indicate good agreement with the experimental data however, some discrepancies at different time intervals are noticed. The thermal response is checked based on steel temperatures on all faces of the column while the structural response is in terms of horizontal and vertical deflections. A sensitivity analysis highlights that the material properties of steel and convective coefficients are assumed to have an influence on both thermal and structural responses. A comparison between AST surface and AST gas device indicates that a structure in close proximity to fire has an influence on the development of temperature and therefore it should be modelled as an obstruction in fire analysis. The coupling methodology is then used to investigate the forces redistribution and progressive collapse mechanism in a planar steel frame subjected to a localized fire. It is observed that the fire-induced stresses in a member are redistributed to the adjacent members, and this redistribution of forces continues even during the cooling phase. A comparison of different fire locations in the frame has highlighted that a fire on the central ground floor column and first-floor column is more detrimental to the overall stability of the structure. The analysis shows that a progressive collapse occurs due to a variety of phenomena like high load ratio, cantilever beam and pull-in force mechanism. Further investigation highlights that the addition of one bay to the frame does not significantly improve the forces redistribution however, increasing the stiffness of ground floor columns does improve the overall stability and performance.Description
Supervisor
Hostikka, SimoThesis advisor
Lalu, OctavianKeywords
CFD-FEM integration, adiabatic surface temperature, FDS-SAFIR one-way coupling, progressive collapse mechanism