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AS/NZS 1170 Snow Load Calculation

Using the SkyCiv Load Generator in AS/NZS 1170.3 Snow Load Calculations

To calculate the snow 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, only users with a Professional Account or who purchased the standalone Load Generator module will be able to use this calculation. You can purchase the standalone module thru this link.

Site Data

Using the AS/NZS 1170 snow load calculation, you need to define the Annual Recurrence Interval or the SLS/ULS parameters. After selecting the options for these parameters, you need to put the address of the structure. The corresponding snow load for the address will be automatically calculated. Take note that this value is based on the following:

  • Section 2 of AS/NZS 1170.3 for classification of snow regions based on Figures 2.1 and 2.2 and based on elevation
  • Table 5.2 for specific locations in Australia

Take note that the snow region classification automatically displayed in the module shall prioritize the classification of the area based on elevation. To display the snow region map based on Figures 2,1 and 2.2, you need to click “View Map Contours” and then select “Snow” – “Australia/New Zealand.” For Australian locations indicated in Table 5.2, the user should select “Terrain Classification for Snow” as given in AS/NZS 1170.3 Supp 1.

Fgure 1. Site tab of SkyCiv Load Generator

Building Data

The structure data and the wind and snow parameters are separated into different accordions. In order to calculate snow loads, the snow load checkbox should be checked.

Figure 2. Snow load parameters on SkyCiv Load Generator

Snow Exposure Category

This parameter is used in getting Exposure Reduction Coefficient Ce. The definition of each option is defined in table below:

Exposure CategoryDefinition
Sub-alpineSites classified as sub-alpine region.
ShelteredSites where roof is protected from the wind by obstructions such as other structures, terrain features or numbers of closely spaced trees higher than the roof.
SemishelteredSites where roof is only partially protected by numbers of scattered obstructions higher than the roof (e.g., scattered trees).
WindsweptSites where the roof is exposed on all sides, with no protection provided by obstructions, trees, or terrain features higher than the roof.

Consider Unbalanced/Drifted Snow Load Case?

This parameter is a “Yes” or “No” to calculate for Unbalanced Snow Load Case. Upon selecting “No,” the balanced snow load case shall only be calculated. On the other hand, upon selecting “Yes,” the unbalanced snow load case table will show. There are four options for AS/NZS 1170.3 alpine region:

Drift on duopitch roof

This case is used to calculate the drifted snow load on duopitch/gable roof as shown below:

Figure 3. Parameters for calculating drifted snow load on duopitch/gable roof.

Drift on monopitch roof

This case is used to calculate the drifted snow load on monopitch/monoslope roof as shown below:

Figure 4. Parameters for calculating drifted snow load on monopitch/monoslope roof.

Drift on lower roof

This case is used to calculate the snow load drift on lower roof level.

Figure 5. Parameters for calculating drifted snow load on lower roof.

Drift on projections and obstruction

This case is used to calculate the snow load drift on obstructions above the roof level such as parapet walls, firewalls, chimneys, etc.

Figure 6. Parameters for calculating drifted snow load on obstructions and projections above roof.

On the other hand, there are additional two options for AS/NZS 1170.3 sub-alpine region:

Drift on obstructed roof with parapet

This case is used to calculate the snow load drift on parapet walls in sub-alpine region.

Figure 7. Parameters for calculating drifted snow load on obstructed roof with parapet in sub-alpine region.

Drift on obstructed roof with abutting

This case is used to calculate the snow load drift on obstructed roof with abutting in sub-alpine region.

Figure 8. Parameters for calculating drifted snow load on obstructed roof with abutting in sub-alpine region.

Results

The snow load results will show the parameters in calculating the undrifted snow load for either alpine or sub-alpine region as shown below:

Figure 9. Snow load parameters used in calculation and the calculated undrifted snow load

Drifted/Unbalanced Snow Load

If Unbalanced/Drifted Snow Load is selected to be considered, the results are tabulated on a table depending on the cases defined:

Figure 10. Sample results for unbalanced/drifted snow load on duopitch and monopitch roof, respectively.
Figure 10. Sample results for unbalanced/drifted snow load on lower roof and on projections and obstructions, respectively.

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