Simple vs. sophisticated fire models to predict performance of SHS column in localized fire

• Simple and sophisticated fire models are compared.
• Buckling of square hollow steel column in localized fire is studied.
• Thermo-mechanical analyses are conducted.
• Simple fire model is recommends for engineering use.

This paper presents a comparative study on fire models to predict the performance of an axially loaded square hollow steel (SHS) column exposed to a localized fire. A simple fire model based on the classic fire plume theory and a sophisticated computational fluid dynamics (CFD) model named Fire Dynamics Simulator (FDS) were investigated and used to predict the heat fluxes from the localized fire to the column. Thermo-mechanical analyses using finite element software were conducted to obtain the temperature and structural responses of the column exposed to the predicted heat fluxes. A total of 22 cases were considered and the variable parameters included heat release rate, fire source diameter, location of the fire source and load ratio. The steel temperatures predicted using the simple fire model were higher than those predicted using the sophisticated fire model. The buckling temperatures predicted using the simple fire model were generally lower than those predicted using the sophisticated fire model, and the average difference of the predicted buckling temperatures was within 40 °C. Buckling temperature is defined here as the maximum temperature in a steel column on onset of buckling. Comparing with the sophisticated fire model, the simple fire model is computationally efficient and yields conservative results, which may be used in structural fire engineering design.