Self-drilling screw joints for cold-formed channel portal frames

Cold-formed C channel sections have been used in portal frame construction for agricultural and light industrial sheds for many years in Australia. The knee joint designs have been copied from hot-rolled portal frames, regardless of the fact that many designers believe this is not realistic. Earlier testing conducted at the Univ. of South Australia demonstrated that these concerns were justified and that the joint designs widely used in practice do not match the moment capacity of the sections and fail prematurely. An alternative joint design has been developed using self-drilling screws. The joint demonstrates excellent moment capacity and rigidity, and is simple to design. A similar joint has also been examined for the ridge connections, which are at a lower angle than the knee joints. This paper describes the development and testing of the self-drilling screw joints, as well as summarizing testing of the conventional joints.