Development of Suitable Strengthening Methods for Thin Steel Roof Battens Subject to Pull-Through Failures

Abstract

Failures of the connections of thin-walled steel roof battens to rafters or trusses were increasingly observed in the form of a localized pull-through failure in the batten bottom flanges during recent extreme wind events. Therefore, an extensive research study was conducted to investigate this local connection failure, and suitable test and design methods were developed to accurately determine the design pull-through capacities of roof battens. The study also showed that optimizing the batten geometry is unlikely to increase the pull-through capacity of batten connections to rafters or trusses because they essentially depend on the diameter of the screw fastener head, batten thickness, and steel ultimate tensile strength. Hence, the study was extended to develop suitable strengthening methods to delay or prevent this critical localized connection failure and thus enhance the pull-through capacity. This article first presents the investigations of some current roof construction practices recommended and used by roof batten manufacturers and builders, then proposes the details of suitable strengthening methods. Detailed experimental investigations were undertaken for this purpose, and their results and discussions are presented in this article. In addition, suitable capacity-improvement factors are proposed for the strengthening methods to accurately determine the design pull-through capacities of roof batten connections to rafters or trusses.