Evaluating the use of standing seam roof as beam lateral bracing

Abstract

The standing seam roof (SSR) system is the most commonly used roof system for metal buildings in North America, wherein, SSR panels are attached to Z-shaped or C-shaped purlins with clips, which are in turn connected to rafters (i.e. roof beams). For the design of the rafters against lateral torsional buckling, bottom flange braces in conjunction with the purlin provide torsional bracing. Separately, the purlin provides some amount of lateral bracing to the rafter top flange; although, the degree to which the SSR system can restrain the purlin against lateral movement, and thus laterally brace the rafter, has not previously been studied. The objective of this study is to quantify the in-plane strength and stiffness of the SSR system and identify how this translational resistance can be used to provide lateral bracing to the rafter. A total of 11 standing seam roof specimens were tested to investigate the effects of different standing seam roof configurations: SSR panel type, clip type, thermal insulation, and purlin spacing, on the in-plane stiffness and strength of the SSR system. Results showed that the in-plane load-deformation behavior of SSR systems was governed by clip deformations, and that in-plane strength and stiffness is, therefore, particularly sensitive to SSR panel and clip type. A method for using these experimental results in calculations of rafter bracing is described and can lead to reduced size and frequency of bottom flange braces.