Design of cold-formed steel wall studs subject to non-uniform elevated temperature distributions

• Published in: Thin-walled structures Vol. 171; p. 108625
• Main Authors: Rokilan, M., Mahendran, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2022
• Subjects: Cold-formed steel; Direct strength method; Effective width method; Load ratio versus failure time curves; LSF walls; Non-uniform temperature distribution; Non-uniform temperature distribution; Cold-formed steel; Effective width method; LSF walls; Direct strength method; Load ratio versus failure time curves
• ISSN: 0263-8231; 1879-3223
• DOI: 10.1016/j.tws.2021.108625

The current design rules for cold-formed steel studs used in wall systems subject to non-uniform elevated temperature distributions are complicated with iterations and different elevated temperature section properties. This paper first investigates the accuracy of the current effective width method (EWM) and direct strength method (DSM) based design equations, and then simplifies the calculation process without compromising the accuracy in calculating the load ratios (elevated to ambient temperature capacity ratio). It also improves the accuracy of the current DSM based design equations. It then investigates the possibilities of using uniform temperature based DSM design equations for non-uniform temperature distributions and identifies the possibilities of using hot flange mechanical properties and uniform temperature based DSM design equations. Hence, it proposes a simplified uniform temperature based DSM design method with hot flange mechanical properties and a correction factor based on hot and cold flange temperatures, yield strength, length and depth of studs. •Describes a detailed numerical study of LSF walls subject to non-uniform elevated temperature distributions in fire.•Derived load ratio-failure time curves of 140 LSF wall systems from sequentially coupled thermal-mechanical analyses.•Showed the accuracy of EWM and DSM based fire design methods in AS/NZS 4600 in deriving load ratio–failure time/FRL curves.•Simplified the calculation processes in the current fire design methods and made improvements to the DSM design method.•Proposed a simplified DSM method based on a uniform temperature approach with hot flange mechanical properties.