Using the SkyCiv Load Generator in ASCE 7 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.
Using ASCE 7, you just need to put the address of the location in the USA, regardless if it is ASCE 7-10 or ASCE 7-16.
The ground snow load values are derived from Section 7.2 of ASCE 7 utilizing the ground elevation of the structure taken from Google Maps API.
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.
Terrain Category for Snow Loads
This parameter is used in calculating Exposure Factor, Ce. Options for this factor are the following:
- B, C, or D (from Section 26.7 of ASCE 7)
- Above the treeline in windswept mountainous areas
- In Alaska, in areas where trees do not exist within a 2-mile (3-km) radius of the site
Exposure Condition of Roof
Like the Terrain Category for Snow Loads, this parameter is also used in calculating Exposure Factor, Ce. The option for this selection and their corresponding definition from ASCE 7 are the following:
- Sheltered: “Roofs located tight in among conifers that qualify as obstructions. Obstructions within a distance of 10 x height of the obstruction above the roof level provide shelter.”
- Fully Exposed: “Roofs exposed on all sides with no shelter afforded by terrain, higher structures, or trees. Roofs that contain several large pieces of mechanical equipment, parapets that extend above the height of the balanced snow load (hb), or other obstructions are not in this category. If the only obstructions are a few deciduous trees that are leafless in winter, the “fully exposed” category shall be used.”
- Partially Exposed: “All roofs except as indicated above.”
This parameter is used in getting the Thermal Factor, Ct. The options for this are the following:
- Structures kept just above freezing and others with cold, ventilated roofs in which the thermal resistance (R-value) between the ventilated space and the heated space exceeds 25 °F × h × ft2/Btu (4.4 K × m2/W)
- Unheated and open-air structures
- Structures intentionally kept below freezing
- Continuously heated greenhouses with a roof having a thermal resistance (R-value) less than 2.0 °F × h × ft2/Btu (0.4 K × m2/W)
- All other structures
Sloped Roof Condition
This parameter is used in getting the Roof Slope Factor, Cs. This parameter has two options: “Slippery” and “Other cases.”
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 three options for ASCE 7:
Snow Load Drift on Symmetric Gable Roof
This case is used to calculate the snow load drift on a symmetric gable roof.
Snow Load Drift on Asymmetric Gable Roof
This case is used to calculate the snow load drift on an asymmetric gable roof as shown below.
Snow Load Drift on Lower Roof
This case is used to calculate the snow load drift on the lower roof levels and can also be used in obtaining drift on parapet walls for windward and leeward cases.
The snow load results will show the parameters in calculating the balanced snow load as shown below:
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:
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.
For additional resources, you can use these links for reference: