Residual capacity of fire exposed light gauge steel frame walls

Abstract

Light gauge Steel Frame (LSF) walls made of cold-formed steel stud and track sections and lined with gypsum plasterboards are commonly used in buildings as load bearing members. During fire events, gypsum plasterboards act as a thermal barrier and delay the temperature rise in the steel studs. Fire usually occurs on one side of LSF walls during which a non-uniform temperature distribution is developed across the steel stud cross-section. This results in thermal bowing deformations and non-uniform distribution of strength and stiffness within the studs. In most situations, fires are extinguished well before excessive or permanent plastic deformations of studs and/or stud failures occur. Hence the LSF wall frames could be re-used provided their residual capacities after fire events are adequate. This paper presents a study aimed at determining the residual compression capacities of LSF wall studs following fire exposure. A full scale standard fire test of LSF wall panel was conducted first, followed by a series of short column tests of lipped channel studs obtained from the tested LSF wall panel. Finite element analyses of the tested studs were undertaken using the measured post-fire mechanical properties of cold-formed steels. The residual compression capacities of these fire exposed short columns were also predicted using the ambient temperature cold-formed steel design rules. A numerical parametric study was then undertaken for 3m long studs in LSF wall panels with varying wall configurations following an exposure to standard fire. This paper presents the details of these experimental and numerical studies of fire exposed LSF wall panels and the results. It demonstrates the potential of re-using LSF wall frames following fire exposures and provides appropriate limits for fire exposure time and stud hot flange temperature for three commonly used LSF wall configurations.