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Wind Management Home > Real World Performance > Wind Speed Management
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Wind Speed Management
Roof-Lok®
Corri-Lok®
Square-Lok®
The north west, northern and north eastern coastlines of Australia are frequently battered by high winds and cyclones during the mid to late summer season.

In a high wind situation, the most vulnerable part of any structure to failure is the roof.

The following map of Australia clearly identifies these regions which have been classified by wind region. (For further information refer to AS1170.2 Part2 “Wind Actions”)
A major contributing factor to wind related disasters is the containment of flying debris. In a high wind situation, the most vulnerable part of any structure to failure is the roof. The cause of this is due to the suction forces created on the downwind side of the roof. The roof does not blow off, but is lifted by the suction forces.

These suction forces rise and fall as the wind gusts and then lulls, placing fatigue stresses on the roof connections.

If insufficient retention of the roof exists, fatigue failures occur and the roof will begin to separate and damage will then progress rapidly.

Once the roof has gone there is little chance the building will survive if the high winds prevail.

Wind Regions


The critical factors in roof retention are:

· Strength and spacing of battens and purlins.
· Screw attachment of purlins or batten to frame.
· Screw type used to fix the steel roof.
· Support washers used under the screw heads.
· Frequency of fixing points.




In this photo it can be seen that the wind pressure exceeded both the strength of the timber purlins and the pullover load the fasteners were capable of withstanding under cyclic (fatigue) loading. The greatest influence on the failure of this roof is the lack of effective reinforcing plates under the heads of the screws.

Roof failure


This photo shows the roof ‘Z’ purlins now entwined in the wreckage following the loss of the roof during a 1999 cyclone. The building technology in this example was to current standards.

1999 Cyclone


Once the roof has gone there is little chance the building will survive if the high winds prevail.

Building Collapse



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