Semi-Rigid Joist–Stud Joints in Cold-Formed Steel Frames: An Experimental Study

Cold-formed steel (CFS) framing systems are widely adopted in low- and mid-rise construction due to their light weight, high strength-to-weight ratio and ease of fabrication. In conventional design practice, floor-to-wall joist–stud joints in CFS frames are idealised as nominally pinned, with overall lateral stability ensured through bracing systems. However, growing experimental evidence indicates that these joints can provide appreciable rotational restraint, resulting in semi-rigid behaviour that is currently typically neglected in design. This study presents a detailed experimental investigation into the rotational behaviour of semi-rigid joist–stud joints in lightweight CFS frames. A comprehensive experimental programme comprising ten full-scale CFS T-frame tests subjected to quasi-static cyclic loading was conducted. Joint stiffness was systematically varied through different screw fastener arrangements and joist–stud geometries. Additional consideration was given to the influence of floor sheathing, with two out of ten specimens tested without floor sheathing, to assess the potential effects of composite action. The test results revealed the extent of the influence of the number and arrangement of the fasteners on the rotational response of the joints. Overall, the study confirms that a broad range of joint stiffness levels can be achieved in CFS joist–stud joints. The findings provide important insights into the realistic modeling of semi-rigid joints and highlight their potential to improve the structural performance, robustness, and economy of cold-formed steel framing systems.