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.