Cold-Formed Steel Channels in Compression under Uniform and Nonuniform Elevated Temperatures

Abstract

Thin-walled cold-formed steel (CFS) members are widely used in gypsum-sheathed assemblies as the load-bearing system in buildings, but their fire behavior is complex and current fire design methods remain prescriptive. Prior studies on the fire response of assemblies, such as standard fire tests on walls, provide limited insight into the behavior of individual members. Meanwhile, existing single-member studies are mostly limited in scope to tests under uniform temperature, with the effects of heating regime and temperature gradients insufficiently examined, which hinders the development of fire design methods for CFS structures. Here, an experimental study was conducted using a custom test rig with electrical heating pads capable of imposing steady-state, transient, uniform, and nonuniform heating on CFS channels in compression. Channels of 457 and 1,219 mm in length were tested to failure under elevated temperatures up to 600°C in uniform steady-state tests, and up to 730°C in transient tests with a 100°C flange-to-flange gradient. The members failed primarily through local and distortional buckling. The results quantify strength reduction with temperature and identify governing buckling modes under realistic gradients. The experimental data and observations provided in this study support the development of analytical and numerical methods to advance performance-based structural fire design for CFS structures.