Dual-steel portal frame design to withstand a fire exposure of 45 minutes

Abstract

This paper presents the design of industrial portal frames with plain carbon steel (S275) and micro-alloyed Fire Resistant (FR) steel, coated with intumescent paint as fire protection for the structure. The coating improves the overall heat resistance of the metallic structure. The portal frames with different spans were calculated to observe their fire behavior. The structure was dimensioned by estimating the stresses to which each particular structural section was subjected and by selecting the most economic combination. The process was then repeated with the new dimensions to reach an optimal structural design. The key variables analyzed in this study are: five different spans, seven intumescent paint thicknesses, and eleven price ratios between the FR and the S275 steels, considering a fire exposure time of 45 minutes in all of the scenarios under study. The main conclusion was that the use of FR combined with S275 and the intumescent paint system was the most profitable option. In many cases, the better performance of this combination offered the most technically feasible option for the design of portal frame steel structures.