A World Leading Wind Standard Released
Posted on August 26, 2021
We are pleased to announce the arrival of the new edition of “Wind Actions on Structures” under the new designation AS/NZS 1170.2:2021. This document supersedes AS/NZS 1170.2:2011. Windtech directors Tony Rofail and Dr Nicholas Truong have been key contributors to the significant updates and new content in this new edition being key members of the wind load sub-committee of Standards Australia/ Standards New Zealand.
The objective of this Standard is to provide wind actions for use in the design of structures subject to wind action. It provides a detailed procedure for the determination of wind actions on structures, varying from those less sensitive to wind action to those for which dynamic response are to be taken into consideration.
The objectives of this revision are to remove ambiguities and to incorporate recent research and experiences from recent severe wind events in Australia and New Zealand.
Windtech Directors Tony Rofail and Dr Nick Truong, based out of our Sydney HQ, played an integral role in the upgrade of the standard, with Tony chairing the committee responsible for the review of Section 6 (dynamic response of tall, slender structures). Below is a non-exhaustive list of changes that were brought about through the efforts of Windtech staff:
- More clearly defined the scope of Section 6 of the standard to avoid miss-use.
- Updated the cross-wind force spectrum coefficients for the cases of towers having a height to width aspect ratio greater than 3.
- Introduce a simple and reliable method of deriving the rotational velocity and torsional acceleration from the resonant dynamic component of the along-wind response (Appendix E). This technique which was developed by Windtech over a decade ago for their preliminary desktop estimates makes the Australian Wind Standard the first standard to provide this guidance. This third component is important when assessing the effect of building motion on occupant comfort.
- Introduce a method of combining all three components including the torsional acceleration to account for the effects of correlation of the peaks (Appendix E). This method was being used by Windtech for almost 20years.
- Introduced a new section to provide guidance on how to determine design load cases in the form of combination factors for the along-wind, cross-wind and torsion components. This is presented in the form of a total of 4 load cases for buildings less than 70m in height and 12 load cases for buildings taller than 70m.
- Updated the section on cross-wind response of cantilevered chimneys, masts and poles of circular cross-sections.
- Contributed towards simplifying the wind speed map for the southern part of Australia.
- In Section 3, have provided input towards the decision to reduce the direction multipliers for Cyclonic regions.
A more complete overview of the changes can be obtained by downloading a preview of AS/NZS 1170.2:2021 at the following link: AS/NZS 1170.2:2021 Preview
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