New Australian cyclonic wind induced fatigue loading criteria for roofing

Windstorm damage investigations following cyclones and thunderstorms show that roof failures during windstorms are mainly caused by large external suction pressures at the windward roof edges combined with large positive internal pressures, resulting in large net uplift loads. The Building Code of Australia states that for the cyclonic regions of Australia, roof cladding now needs to comply with a low cycle fatigue test, known as the Low-High-Low (LHL) test. This LHL is a modified version of the one originally proposed by Mahendran, et al. In order to have a repeatable standard test that can be performed by different testing laboratories within a reasonable time frame on different types of test equipment, the modified LHL loading sequence is a simplification of the dynamic wind loading environment. In the formulation of this representative fatigue loading sequence, assumptions such as cycle counts, load range, cyclone duration, wind direction change, building orientation and building geometry have been made. For example, when applying the LHL to cladding in cyclonic regions, the maximum negative external and maximum positive internal pressures are combined and applied across the load cycles. However, when analysing external and net pressure cycles for various windward, side-wall and leeward dominant opening cases, the numbers of cycles change along with the mean and range, reflecting a potentially conservative test criteria. An assessment of the impact of the various conservative and unconservative assumptions within the LHL test regime will be presented.

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Australasian Structural Engineering Conference 2008

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978-1-877040-69-6

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