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AS/NZS 1170 Wind Load Calculations

A guide to calculating wind speed and wind pressures for Australia and New Zealand

Calculating the wind speeds can be a complex process in AS/NZS 1170 for site locations in Australia and New Zealand. That’s why SkyCiv has developed an online wind load tool to help calculate the design wind speed and pressures via our interactive Google Map. Users can also click and drag the marker to move the site location:

Australian wind speed calculator map

Calculating Wind Speeds

Basic Wind Speed

The software will calculate the basic wind speed based (AS1170.0)

basic wind speed calculations as per as 1170 and nz standards

  • Average Recurrence Interval – how often this wind speed is expected to occur. It can also be calculated as the inverse of the annual probability of exceedance. For instance, 1 year is a very high expectancy of recurrence so this wind load will occur a lot. A higher ARI will result in a higher basic wind speed. This is because you are designing for more extreme events.

 

Serviceability and Ultimate Limit State Wind Speeds

Users can also pull the Serviceability Limit State (SLS) and Ultimate Limit State (ULS) wind speeds for both Australia and New Zealand.  It still uses the ARI, however these can be calculated via the following input. Simply click the accordion and enter in the following input:

  • Country – Australia or New Zealand
  • Design Working Life – how long the structure is intended to be used. For instance, is the structure used for construction purposes (e.g. scaffolding) or is the design working life longer term, for say buildings and bridges. The longer the design working life, the higher the basic wind speed (to account for significance). Here, the SLS only increases up to DWL of less than 25 years.
  • Importance Level – The importance level is governed the type of structure and it’s potential impact. Click the (i) for more information about which importance level is correct for your structure
  • Site Location – the address where the site is located

Here is an example of the software calculating the SLS and ULS wind speeds for 11 York Street Sydney (by default the basic wind speed will choose the largest of the two):

serviceability wind speed and ultimate limit state wind speed calculations as per as 1170

Try our Free Wind Load Calculator

 

Wind Pressures

The software goes a step further, calculating the wind pressures to be applied to your structure as per AS/NZS 1170.2. Once you have your basic wind speed, you can enter in some simple building dimensions to calculate the design wind forces to be applied to your building or structure. The following structures are currently supported in SkyCiv:

  • Open Buildings
  • Closed Buildings
  • Gable Roofs
  • Hip Roofs
  • Monoslope Roofs
  • Multiple levels and elevations

Enter in more information such as pitch angle, roof height, building width and building length to get the wind pressures:

wind pressure calculations for as 1170 building

All of our input come with easy references to the design code. Simply click the icon or the to open up clear instructions on what each parameter means. For instance, if we click the Action Combination Case, a popup will display explaining each option and allow you to select which is most applicable: 

Action combination cases as per As1170

 

Output

The software will then product the following wind pressure calculations (in Pa) for main walls and cladding

Wind Pressure values and locations for Windward, Leeward, Side wall and Roof

as1170-wind-pressure-forces-output-1

 

Cladding and Components:

cladding calculations for as 1170 wind pressures

 

Try our Free Wind Load Calculator

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