New test and design methods for steel roof battens subject to fatigue pull-through failures

Thin steel roof claddings and battens are widely used in low rise buildings all around the world. However, they are vulnerable to premature connection failures when subjected to severe wind uplift actions such as those induced by cyclones and storms. Current design methods exclusively depend on full scale prototype roof tests. This paper proposes an alternative design method using a simple equation for thin-walled steel roof battens subjected to fatigue pull-through failures, developed through a series of small scale cyclic wind load tests of roof battens. Since an acceptable small scale connection test method is not available for fatigue pull-through failures of roof battens, various types of small scale connection tests were initially examined to propose the most suitable test method. For this purpose, a series of constant amplitude cyclic tests was conducted using three different small scale test methods (short, cantilever and two-span battens), for a commonly used steel roof batten. Test results showed that the present state of knowledge based on static pull-through studies could lead to the use of a wrong test method in fatigue pull-through studies. This paper has used the cyclic test results from the selected small scale test method to propose a fatigue pull-through design equation. The use of the proposed design equation will lead to conservative outcomes for roof battens and will enable safe roof batten design without the need for full scale cyclic tests of prototype roof assemblies.