Overview
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 is one of the vulnerable roof members, and pull-through failure in the vicinity of the batten to rafter/truss connection is one of the common failures during cyclones. Unlike other connection failures, batten to rafter/truss connection failures could result in a catastrophic roof failure as they could disengage the entire roofing assembly from the rafters/trusses.
Research Activities
Preliminary research conducted on fatigue pull-through failures of roof battens indicated that the current design equations in the Australian, American and European standards cannot be used to determine the fatigue pull-through failures of roof battens to rafter/truss connections. Current fatigue design method (Low-High-Low cyclic test) recommended in the National Construction Code of Australia is a complex, expensive and time-consuming design method. This project focuses on simplifying the current LHL cyclic test design method by proposing a simple design equation by means of full-scale air-box tests (Figure 1) and small-scale isolated connection tests (Figure 2). Finite element analysis was also adopted in the project to reduce the number of expensive and time-consuming full and small-scale laboratory tests.
Expected Findings
- Determination of the critical parameters influencing the fatigue pull-through performance of cold-formed steel roof battens
- Development of a suitable test method for the fatigue studies of steel roof battens.
- Knowledge and understanding of the fatigue behaviour and capacity of cold-formed steel roof battens for various combinations of steel grade (both low and high strength steels: G300 and G550) and thickness (0.75 and 1.0 mm), fastener head diameter (11 and 14.5 mm) by using an experimental study based on constant amplitude and multi-level cyclic load tests.
- Development and validation of finite element models for fatigue pull-through behaviour of roof battens under cyclic wind loading
- Determination of suitable fatigue pull-through design equations and guidelines for cold-formed steel roof batten to rafter connections
- Verification of current LHL cyclic test for fatigue pull-through design of cold-formed steel roof battens
Funding / Grants
- Australian Research Council (ARC) Discovery Project (2013 - 2016)
Other Team Members
Video: Finite element simulation of batten fatigue
