New interaction ratios and modification factors for combined web-crippling and bending behaviour of cold-formed steel unlipped channel bearer sections in panelised construction under stud support removal scenarios

• Published in: Thin-walled structures 2025-03, Vol.208, p.112843, Article 112843
• Main Authors: Mishra, Sohini, McCrum, Daniel P.
• Format: Article
• Language: English
• Subjects: Combined web-crippling-bending; Lateral restraint; Stud support removal; Unlipped channel bearer; Web slenderness, interaction ratio; Web-crippling capacity
• ISSN: 0263-8231
• DOI: 10.1016/j.tws.2024.112843

•CFS unlipped channel bearers’ combined web-crippling and bending behaviour.•Real-world single, double, and triple studs or single wall panel removal scenarios.•Lateral restraint from one and two sides, multiple vertical concentrated loads.•Included minor axis bending moment in web-crippling-bending interaction equations.•New interaction ratios and modification factors for the bearers' optimal design. Cold-formed steel (CFS) unlipped channel sections are the most commonly used bearers in panelised buildings, supporting gravity loads from the floor panels. The bearers are typically laterally retrained at floor joist locations and vertically supported on CFS-lipped channel studs. Existing web-crippling and combined web-crippling-bending tests of bearers employ laterally and torsionally stable test setups formed by two identical channel sections connected either toe to toe in a box-beam arrangement or back-to-back and three-point bending static loading applied through the section's shear center (i.e., the loading induces no torsional moment to the sample), without employing any lateral restraint to the sample. No research has been conducted thus far to investigate CFS unlipped channel bearer sections' combined web-crippling and bending behaviour in stud(s) or single panel vertical support removal static loading scenarios. This research experimentally and analytically investigated the combined web-crippling and bending behaviour of CFS unlipped channel bearers with structural arrangements similar to CFS panelised buildings i.e., intermediate lateral restraints (representing floor-joists) and simply supported boundary conditions under stud vertical support removal static loading scenarios. The static loading circumstances consist of one stud (Case I), two studs (Case II), and three studs/single panel (Case III) vertical support removal. Twenty-four industry-standard bearers were tested with lateral restraint under Case I. Ninety-six parametric studies were conducted with finite element analysis models validated by testing under Cases I, II, and III. Results showed the bearers failed predominantly due to web-crippling with the interior one flange (IOF) and end one flange (EOF) mechanism being the most critical under Case I and III, respectively. Five different web-crippling equations in literature and web-crippling-bending interaction equations in Eurocode 3 (EC3) and AISI S100 were evaluated considering the above five different web-crippling capacities (develop