Development of suitable test methods for the screw connections in cold-formed steel roof battens

The roofing systems of low-rise buildings are commonly made of thin and high strength steel roof sheeting and battens. These light gauge steel roofing systems are subjected to high wind uplift loads during tropical cyclones and thunderstorms. In recent times, the roof batten to rafter or truss connection failures have been identified as a major cause for severe roof failures during high wind events. Most of these connection failures were in the form of localised pull-through failures of the bottom flanges of steel roof battens at their screw connections. The design practice at present is based on expensive and time consuming full scale tests or inappropriate small scale tests. Hence there is an urgent need to develop suitable test methods to determine the pull-through capacity of roof battens. This paper presents the details of an experimental study undertaken to investigate the pull-through failures of light gauge steel roof battens using both full scale and small scale tests, and the results. It has shown that the design capacity equations and the test methods given in the current cold-formed steel design standards for single screw connections cannot be used for roof batten pull-through failures. It recommends suitable small scale test methods and associated calculation methods to determine the pull-through capacities of roof battens