Behaviour of multi-span cold-formed Z-purlins with bolted lapped connections

In traditional design, multi-span Z-purlins of bolted lapped connections over the internal supports are considered as fully continuous, while the strength and rigidity properties of the lapped zone are obtained as the sum of the two corresponding sections. Starting from experimental evidence, the authors of the present paper assume that purlins are semi-continuous at the junction between the single and lapped sections, and propose to take into account the web crippling action at the edge of the lapped zone in interaction with the bending moment. In author's opinion this type of interaction is a new approach, compared with the traditional interaction bending moment and shear force. Based on this assumption, relevant design formulae are proposed for both strength and stability checking, accounting for different types of overall and local stress interactions. In order to support this proposal, numerical and experimental tests results are used for the comparison with results obtained based on other models.