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AS/NZS 1170.2 (2021) Wind Load Calculations (Solar Panels)

Using the SkyCiv Load Generator in AS/NZS 1170.2 (2021) Wind Load Calculations for Solar Panels

To calculate the wind load pressures for a structure using SkyCiv Load Generator, the process is to define first the code reference. From there, the workflow is to define the parameters in Project Tab, Site Tab, and Building Tab, respectively. However, free users can only use the calculation for a gable roof for a maximum of 3 solves per day. With a Professional Account or by purchasing the standalone Load Generator module, you can use all the features of this calculation as long as you want. You can purchase the standalone module thru this link.

Calculating the wind speeds can be a complex process in AS/NZS 1170.2  (2021) 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:

Figure 1. Site parameters.

Site Data

Basic Wind Speed

The software will calculate the basic wind speed, VR, based on AS/NZS 1170.0 and AS/NZS 1170.2.

  • 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, VR. 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):
Figure 2. SLS/ULS input parameters.

Note that the user should double check if the wind region detected for the location is accurate based on Figures 3.1(A) and 3.1(B) of AS/NZS 1170.2 in order to obtain the appropriate wind speed for the structure. The Site Data tab should look like this:

Figure 3. Wind speed results from database.

Terrain Data

The next step is to define both the Wind Direction and Terrain Category parameters. The Wind Direction parameter is used in obtaining the upwind (left side) and downwind (right side) ground elevations to calculate for topographic multiplier, Mt, and the wind directional multiplier, Md, for the 8 cardinal directions. On the other hand, Terrain Category is used in calculating terrain/height multiplier, Mz,cat.

Figure 4. Elevation chart and other terrain parameters.

Structure Tab

The structure data and the wind and snow parameters are separated into different accordions. In order to calculate the design wind force for the solar panel, the wind load should be checked. You need to select “Solar Panels” on the Structure dropdown. Note that there are two types of solar panels – ground mounted and rooftop.

Ground Solar Panel

To calculate wind and/or snow load on ground-mounted solar panels, you need to select “Ground” on the Solar Panel Location dropdown.

Figure 5. Ground solar panel parameters.

For Ground Solar Panels, you need to specify the size of the solar panel, mounting height and its tilt angle. Note that the tilt angle should be less than or equal to 45 degrees.

Rooftop Solar Panel

To calculate wind and/or snow load for rooftop solar panels, you need to select “Rooftop” on the Solar Panel Location dropdown.

Figure 6. Rooftop solar panel parameters.

The building parameter where the rooftop solar panels will be installed are required to calculate wind and/or snow load pressures.

Results

Once all the parameters are defined, clicking the Generate Loads button will give a result as shown below.

Ground Solar Panel

Figure 7. Tabulated design pressures for ground-mounted solar panel.

Rooftop Solar Panel

Figure 8. Tabulated design pressures for rooftop solar panel.

Detailed Calculation

The detailed wind load calculations can be accessed only by Professional account users and those who purchased the standalone load generator module. All the parameters and assumptions used in the calculation are displayed on the report to make it transparent to the user. You can download a sample detailed calculation thru this link.

Ground Solar Panel

Figure 9. Detailed wind load calculation for ground solar panel.

Rooftop Solar Panel

Figure 10. Detailed wind load calculation for ground solar panel.

For additional resources, you can use these links for reference:

 

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