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NBCC 2015 Snow Load Calculation

Using the SkyCiv Load Generator in NBCC 2015 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 NBCC 2015, you need to select Recurrence Interval, Limit State, and Importance Category parameters first before putting an address the Project Address input. The module will search for the location based on Table C-2 of Appendix C (NBCC 2015).

NBCC 2015 snow load data
Figure 1. Site tab of SkyCiv Load Generator

You can manually put the ground snow load and the associated rain load whenever needed. Moreover, Area Classification should be defined in order to calculate for Cw.

NBCC 2015 snow load topo parameter
Figure 2. Additional snow load site parameter on SkyCiv Load Generator NBCC 2015 calculations.

Structure 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.

NBCC 2015 snow load parameters
Figure 3. Snow load parameters for building tab in SkyCiv Load Generator module.

Sloped Roof Condition

This parameter is used in calculating Slope Factor, Cs. The options for this parameter are “Unobstructed slippery” and “Other Cases”

Consider Unbalanced/Drifted Snow Load Case?

This parameter is a “Yes” or “No” to calculate for the 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 five options for NBCC 2015:

Multi-level Roofs – Case 1

This case is used in calculating snow load drift on lower roofs where the wind source is coming from the upper roof as shown in the figure below based on Figure 4.1.6.5-A and 4.1.6.5-B Case I of NBCC 2015.

NBCC 2015 drifted snow load case  multi-level roof case 1
Figure 4. Snow load parameters in solving snow drift for Multi-level roof case 1.

Multi-level Roofs – Case 2

Similar to the previous case, this is used in calculating snow load drift on lower roofs where the wind source is coming from the lower roof as shown in figure below based on Figure 4.1.6.5-A and 4.1.6.5-B Case II of NBCC 2015.

NBCC 2015 drifted snow load case  multi-level roof case 2
Figure 5. Snow load parameters in solving snow drift for Multi-level roof case 2.

Multi-level Roofs – Case 3

This case is used in calculating snow load drift on lower roofs where the wind source is coming from the lower roof in a diagonal direction as shown in the figure below based on Figure 4.1.6.5-A and 4.1.6.5-B Case III of NBCC 2015.

NBCC 2015 drifted snow load case  multi-level roof case 3
Figure 6. Snow load parameters in solving snow drift for Multi-level roof case 3.

Areas Adjacent to Roof Projections

This case is used in calculating snow drifts on areas adjacent to roof projections such as parapets, chimneys, etc.

NBCC 2015 drifted snow load case on obstructions or projections
Figure 7. Snow load parameters in solving snow drift on areas adjacent to roof projections.

Gable Roofs

This case is used to calculate the snow load drift on a symmetric gable roof.

NBCC 2015 drifted snow load case on gable roof
Figure 8. Snow load parameters in solving snow drift on gable roofs.

Results

The snow load results will show the parameters in calculating the balanced snow load as shown below:

NBCC 2015 snow load undrifted case and parameters
Figure 9. Snow load parameters used in the calculation and the calculated balanced snow load.

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 (sample below):

Unbalanced cases results
Figure 10. Sample results for unbalanced snow load on multi-level roofs and areas adjacent to roof projections.
Unbalanced cases results
Figure 11. Sample results for unbalanced snow load on gable roofs.

Detailed Calculation

The detailed snow 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.

Detailed snow load calculation report

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

 

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