Structural behaviour of high strength cold-formed steel Z purlins with overlaps

This paper presents an experimental and theoretical investigation for lapped connections between high strength cold-formed steel Z sections, and a total of 26 one point-load tests on lapped connections were performed. It is demonstrated from the experiments that combined bending and shear is always critical in the cross-sections at the ends of lap of the lapped sections. An analysis and design method is thus proposed to evaluate all the internal forces within the lapped connections, and hence, to evaluate the co-existing moments and shear forces at the critical cross-sections. Suitable codified design rules are then adopted to check against combined bending and shear, and improvement to the design rule for shear capacities is proposed after careful calibration against test data. Moreover, simple expressions are also proposed after data analyses for the determination of the effective flexural rigidities of lapped connections. Consequently, the structural behaviour of lapped sections between cold-formed steel Z sections in terms of strength and stiffness is quantified rationally for general design. The research project aims to provide understanding to the structural performance of lapped connections between cold-formed steel Z sections, and hence, to develop a set of rational design rules for multi-span purlin systems with overlaps in modem roof construction.