07.05: Fatigue life assessment of cold‐formed steel roof battens: Fid-Bau Portal

07.05: Fatigue life assessment of cold‐formed steel roof battens

Kathekeyan, Myuran / Mahendran, Mahen

Metal roofs of low‐rise buildings are exposed to highly fluctuating and prolonged suction wind uplift pressures during cyclones. The high suction pressures on roofs lead to premature, low cycle fatigue failures of roof members. Steel roof batten made of thin, high strength cold‐formed steel (CFS) is one of the vulnerable roof members that fails prematurely during cyclones. Pull‐through failure in the vicinity of batten to rafter connection is one of its common failure modes. A preliminary study on this topic revealed that the fatigue pull‐through capacity of a commonly used industrial roof batten is 45% of its static pull‐through capacity. Therefore, in order to assess the fatigue capacity and performance of all available CFS roof battens, a series of constant amplitude cyclic tests was conducted on thin‐walled steel roof battens. Critical parameters which influence the pull‐through failure, such as the steel batten grade, thickness and screw fastener diameter, were considered in the test series. S‐N curves were developed for each combination of the selected critical parameters, and the respective fatigue limits were obtained. Test results led to a simple modification to the recently developed static pull‐through capacity equations in order to include the effects of fatigue. They also improved the understanding of the fatigue behaviour of roof battens. In addition, a series of multi‐level cyclic tests was included in this study to investigate the suitability of the currently available Low‐High‐Low (LHL) cyclic test method. This paper presents the details of this study, and the results.