Experiments on load-bearing cold-formed steel sheathed studs at elevated temperatures.

This paper assesses the stability and strength of sheathed cold-formed steel studs at elevated temperatures. Short and intermediate-length studs braced with gypsum, fire-rated gypsum, and oriented strand board were subjected to compressive axial load and temperatures ranging from 20 °C to 600 °C. A total of 40 tests were conducted in the steady-state regime, where the studs were first heated, then a compressive axial load was applied until failure occurred. Results show that the load-carrying capacity of the structural members decreases with increasing temperature, as the mechanical properties of the cold-formed steel reduce, and the bracing provided by the sheathing degrades. Local and distortional cross-section buckling failures are observed in the cold-formed steel member. The stabilizing effect and increase of load-carrying capacity attributed to the sheathing at ambient temperature is eventually lost at elevated temperature and the behavior of the sheathed studs becomes similar to the behavior of unsheathed members. Direct Strength Method design equations provided in the U.S. AISI S100 design specification are used with experimentally determined elevated temperature properties to predict the load-carrying capacity of the studs, then compared to experimental results to explore the feasibility of current design methods for performance-based fire design applications. • Degraded strength of sheathing-braced cold-formed steel studs is measured as temperature is increased. • OSB sheathing provides beneficial bracing for temperatures less than 350 °C while fire-rated and normal gypsum boards provide sheathing bracing for temperatures less than 600 °C. • The Direct Strength Method of AISI S100 can reliably be extended to predict the strength of uniformly heated bare and sheathed studs at elevated temperature. [ABSTRACT FROM AUTHOR]