Part 3.10.1 High Wind Areas
AS 4773 Parts 1 and 2.
The Northern Territory Deemed-to-Comply Standards Manual.
Steel framing: AS 4100.
Cold-formed steel structures: AS 4600.
Residential and low-rise steel framing: NASH Standard – Residential and Low-Rise Steel Framing, Part 1 or Part 2.
AS 2047 for the following glazed assemblies in an external wall:
Sliding and swinging doors with a frame, including french and bi-fold doors with a frame.
Window walls with one piece framing.
AS 1288 for all glazed assemblies not covered by (i) and the following glazed assemblies:
All glazed assemblies not in an external wall.
Skylights, roof lights and windows in other than the vertical plane.
Sliding and swinging doors without a frame.
* * * * *
Glazing used in balustrades and sloping overhead glazing.
In cyclonic areas, metal roof assemblies, their connections and immediate supporting members must be capable of remaining in position notwithstanding any permanent distortion, fracture or damage that might occur in the sheet or fastenings under the pressure sequences A to G defined in Table 3.10.1.
Table 3.10.1 Low-High-Low pressure sequence
|Sequence||Number of cycles||Load|
|A||4500||0 to 0.45 Pt|
|B||600||0 to 0.6 Pt|
|C||80||0 to 0.8 Pt|
|D||1||0 to 1.0 Pt|
|E||80||0 to 0.8 Pt|
|F||600||0 to 0.6 Pt|
|G||4500||0 to 0.45 Pt|
The requirements of 22.214.171.124(f) must be read in conjunction with the provisions of AS/NZS 1170.2. The ABCB commissioned research to establish a national consistent testing regime for metal roof cladding assemblies in cyclonic areas. The results of this research are contained in 126.96.36.199(f).
Low cycle fatigue cracking of metal roof cladding elements during tropical cyclones is a complex process where small changes in load, geometry or material properties can significantly affect the fatigue performance of the cladding system (includes immediate supports, fixings and cladding). The consequences of failure of an element can quickly lead to more elements progressively failing. These failed elements become wind driven debris and so pose a threat to people and other structures as potential missiles.
The fatigue loading sequence defined in Table 3.10.1 is to simulate the wind load induced by a cyclonic event. 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 loading sequence is a simplification of the dynamic wind loading environment. In the formulation of the fatigue loading sequence assumptions such as cyclone counts, load range, cyclone duration, wind direction change, building orientation and building geometry have been made.
If a system does not successfully resist the fatigue loading sequence in Table 3.10.1, it does not comply.
The test section consists of cladding elements, fastenings and immediate supporting members assembled together in a manner identical to those parts of the particular roof which the test section is intended to replicate.
STATE AND TERRITORY VARIATIONS
STATE AND TERRITORY VARIATIONS
188.8.131.52(i) is added in the Northern Territory.
Masonry veneer — Masonry veneer construction must be designed so that the structural framing to which the masonry veneer is tied will ensure the stability of the masonry veneer.
|Note:High wind areas exist outside the wind regions indicated on this map.|
The intent of building construction in high wind areas is to ensure the structure has sufficient strength to transfer wind forces to the ground with an adequate safety margin to prevent the collapse of the building and the building being lifted, or slid off its foundations.
To resist these forces it is necessary to have—
- an anchorage system, where the roof is connected by the walls to the footings by a chain of connections; and
- a bracing system to prevent horizontal collapse due to wind forces; and
- continuity of the system where each structural element is interlocked to its adjoining structural element throughout the building.
Anchorage of the system is achieved by using a variety of connectors. Each connector must be capable of carrying the uplift force, because the ability of the building to resist the wind forces is directly related to its weakest link.
Acceptable construction manuals to achieve these requirements are described in this Part.