Citation:
Abstract:
This study set out to examine the thermo-mechanical behavior of gypsum-protected steel columns (GPSC) exposed to fire, including the cooling phase, through numerical analyses with the aim of better understanding the effect of protection materials and identifying the possibility of delayed failure of GPSC during this critical period. A parametric study has been performed with the SAFIR program using a sequentially decoupled thermal structural analysis. The examined factors are the shape of the columns, the fire intensity, and the thickness of the protection. Gypsum serves as insulation, providing passive protection to prevent the degradation of steel mechanical properties and to mitigate and delay the collapse of steel columns during fire exposure. Different thicknesses of gypsum were considered (1 mm, 3 mm, and 5 mm) in order to analyze the effect of the rate of heat storage on the delayed collapse during and after fire exposure. The simulations were performed considering ISO fire and parametric temperature–time curves, which include a cooling regime that is linear. The findings show that the failure of the GPSC over the period of cooling is a possible event where the protection acts as a cooling retarder, which leads to a delayed collapse. Columns with massive sections and thick layers of protection are the most susceptible to delayed failure. Overall, this paper provides a real assessment of the load capacity in a natural fire situation, and the results highlight the possibility of delayed collapse of GPSC.