Experimental study on the structural performance of cold-rolled steel flexural members exposed to localized fire

Abstract

Cold-formed steel (CFS) sections are gaining popularity due to rapid growth in their application and contribution for framing, partition system, metal buildings, and racks. Due to the varied applications of CFS members, the fire safety of these members becomes crucial. In an event of a fire scenario, the possibility of localized fire on the member cannot be neglected. Past studies on CFS flexural members focused majorly on uniformly elevated thermal profiles of the members, however, the experimental or numerical data are scarce with relevance to localized fire. Thus, to bridge this gap, this paper investigates the effect of localized fire on behaviour of cold-formed lipped channel flexural members. CFS members come in numerous shapes and sizes, but due to ease of manufacturing and wide application range, lipped channel members are one of the most used versatile members, thus in this study, lipped channel beam (LCB) profile was adopted. Fire test was conducted in open space, with a 4-point loading setup (loaded for major axis bending) under simply supported boundary conditions. In order to introduce the worst fire scenario, the fire was imposed on the compression side of the beam. The temperature on the fixed locations of the member is recorded to understand the possible temperature spread profile. To produce rapid controlled fire, the member was heated using the gas-powered burner. It was found that due to the thin profile, these members are very prone to sudden rise and drops in temperature. With the increase in temperature in a limited area, the member lost its mechanical properties in the vicinity of the fire exposed area, ultimately leading to member failure locally. This experimental study demonstrated the possible pattern/mode responsible for the failure of CFS LCBs under the influence of local fire. It was concluded that in an event of a localized fire there is an urgent need for the critical temperature/time prediction model for CFS lipped channel flexural members.