Development of Suitable Test Methods for the Screw Connections in Cold-Formed Steel Roof Battens

Abstract

The roofing systems of low-rise buildings are commonly made of thin, 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, roof batten–to–rafter or truss connection failures have been identified as a major cause of severe roof failures during high-wind events. Most of these connection failures are in the form of localized 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 pull-through failures of light-gauge steel roof battens using both full-scale and small-scale tests. The investigation showed that the design capacity equations and test methods given in current cold-formed steel design standards for single-screw connections cannot be used for roof batten pull-through failures. This paper recommends suitable small-scale test methods and associated calculation methods to determine the pull-through capacities of roof battens.