Strength and stiffness of cold-formed steel purlins with sleeved and overlapped bolted connections

• Nine Z-purlin tests where we vary connection type and length, and steel thickness.
• We explain the plastic failure mechanism that develops at the end of the connections.
• Show the difference in strength/stiffness between sleeved and overlapped connections.
• Propose a model for displacement prediction and compare with tests results.
• Discuss assumptions usually adopted in design that may lead to an unsafe design.

This paper aims to analyze the strength and stiffness of semi-continuous cold-formed steel purlins subjected to flexure. A series of nine cold-formed steel Z sections with sleeved and overlapped bolted connections were tested in bending. Results show that strength is often limited by a plastic mechanism failure, which reduces the web rigidity and induces an early development of local buckling in the compressed flange. In addition to the experiments, this paper presents a numerical and analytical study of the strength and stiffness of semi-continuous purlins, as well as, an analytical method to predict vertical displacement.