Finite-element assisted design of eaves joint of cold-formed steel portal frames having single channel-sections

A finite element model is described for the eaves joint of a cold-formed steel portal frame that comprises a single channel-section and bracket connected through both screws and bolts. Such a joint detail is commonly used in practice in New Zealand and Australia; as the bolt-holes are detailed for nominal clearance the intended purpose of the screws is to prevent slip of the joint during frame erection. The results of the finite element model are compared against experimental test results. In the experimental tests, the screws failed in shear followed by twisting of the joint bracket. It is shown that at first screw failure, the bolts had not engaged i.e. they still had not fully slipped. It is also shown that the gradient of load-displacement curve can be accurately predicted from the equations of screw stiffness of Zaharia and Dubina (2006). The finite element model is used to determine upper and lower bounds to the experimental failure load, and thus potentially can be used to assist designers when designing and detailing such eaves joints in practice.