Uplift Capacity of Z‐Purlins

Abstract

Roof systems constructed using cold‐formed steel components, i.e., Z‐shaped purlins and interconnected roof panels, have become a very popular form of construction. This roof system is used extensively for single‐story commercial and industrial buildings in the United States. The popularity of cold‐formed steel members is due in part to their superior gravity load strength‐to‐weight ratio; however, because of their relatively light weight, a cold‐formed member is very susceptible to wind uplift loading. The design specification in the United States for cold‐formed steel construction does not provide a comprehensive analytical solution to the problem of wind uplift strength of a cold‐formed steel purlin. A general analytical approach, based on the concept of biaxial bending, is presented for evaluating the load capacity of a cold‐formed steel roof system having a Z‐shaped purlin. The analytical approach is applicable only for a through‐fastened roof system, i.e., a roof system for which the roof panel is attached to the purlin by a self‐drilling or self‐tapping screw.