Design of sheathed built-up nested CFS channel studs in load-bearing LSF walls

Cold-formed steel built-up nested channel (NC) sections have been increasingly used to replace the commonly used lipped channel sections as the load-bearing studs of light gauge steel framed (LSF) walls with higher compression capacity. However, the related knowledge is limited and no research study has investigated such NC stud walls yet. In this study, an investigation was undertaken on the compression behaviour and capacity of LSF walls made of slender NC studs sheathed with gypsum plasterboards on both sides. Compression tests of sheathed NC studs were conducted first, which were then used in developing and validating suitable finite element models. The results obtained from tests and finite element models showed that plasterboards and stud -to-board screw connections had significant influence on the failure mode and compression capacity of sheathed NC studs, while the end fastener groups recommended in the current cold-formed steel design standards and the stud-to-stud screw connections had only marginal effects. Finally, a simple and conservative design method was proposed based on the Direct Strength Method equations in the current design standards. This paper presents the details of this research study, including the results, discussions and main findings.