Lateral Bracing of Beams Provided by Standing Seam Roof System: Concepts and Case Study

The standing seam roof (SSR) system is the most commonly used roof system for metal buildings due to its superior durability, water tightness, and energy efficiency. In this type of system, SSR panels attach to Z-shaped or C-shaped purlins with clips, and the purlins are in turn connected to rafters (i.e. roof beams). In the design of the rafters, it is often assumed that the purlins and SSR system are capable of laterally bracing the rafter against lateral torsional buckling. However, it is unclear whether the SSR system is capable of restraining the purlins from longitudinal movement with adequate strength and stiffness.

In this study, a total of 11 full-scale SSR specimens were tested to investigate the effects of different standing seam roof configurations (SSR panel type, clip type and purlin spacing) on the in-plane stiffness and strength of the SSR system. This data is then used to evaluate the effectiveness of the SSR system for providing restraint to the longitudinal movement of the purlins. Results show that variations in the type of clip and SSR panel have a major impact on the strength and stiffness of the specimens, and that the measured stiffness may not be sufficient to satisfy the requirements in AISC 360-16 for lateral bracing of the rafter.

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