Design of built-up back-to-back CFS channel compression members sheathed with gypsum plasterboards

Built-up back-to-back cold-formed steel channel (BC) members are increasingly used as studs for increasing the compression capacity of light gauge steel framed (LSF) walls, even though the knowledge of their behaviour is limited. In this study, the behaviour and capacities of LSF walls made of slender BC members sheathed with gypsum plasterboards on both sides were investigated using a series of compression tests and detailed finite element studies based on validated models. The numerical and experimental results showed that (1) screw connections of BC members had marginal effects on the compression capacities of the investigated sheathed BC members with non-staggered stud-to-board screw arrangement, and the capacities were mostly equal to twice the capacities of their individual members, (2) the restraints provided by the plasterboards and stud-to-board screw connections effectively prevented sheathed BC members from in-plane flexural buckling and considerably improved their compression capacities, and (3) the Direct Strength Method in the current design standards in combination with the guidelines and recommendations proposed in this study conservatively predicted the compression capacities of these members. Details of this research study, its results and findings are presented in this paper.