Snow wizard (ASCE 7)

The snow wizard enables you to define the site information required for the creation of the various uniform, balanced, unbalanced and triangular snow loads.

Basic Data

Property

Description

Terrain Category

Options are:

B (urban, suburban, wooded) - Default
C (open terrain scattered obstructions),
D (flat unobstructed areas), Above treeline, Alaska no trees

Exposure

Options are:

Fully exposed
Partially exposed
Sheltered

Exposure factor, C_e

C_e is determined from the following table:


	Exposure
Terrain Category	Fully Exposed	Fully Exposed	Sheltered
B	0.9	1	1.2
C	0.9	1	1.1
D	0.8	0.9	1
Above treeline	0.7	0.8	0
Alaska	0.7	0.8	0

Risk Category

Option are:

I
II
III
IV

Winter Wind Parameter, W₂

This factor which affects snow drifts is only displayed if working to ASCE-7-22.

Snow Importance factor, I_s

This factor has been removed in ASCE-7-22 and hence it is only displayed if working to earlier code years.

I_s is determined from the following table:


Risk Category	I_s
I	0.8
II	1
III	1.1
IV	1.2

Thermal Condition

Option are:

All except below
Structures kept just above freezing
Unheated open air structures
Structures kept below freezing
Continuously heated greenhouses

Roof Heat Transfer Resistance, R_roof

This factor is only displayed if working to ASCE-7-22.

Thermal factor, C_t

C_t is determined from the following table:


Thermal Condition	C_t
All except below	1
Structures kept just above freezing	1.1
Unheated open air structures	1.2
Structures kept below freezing	1.3
Continuously heated greenhouses	0.85

Ground snow load, p_g

You are required to enter the ground snow load.

Flat Roof Snow load, p_f

p_f is determined from the following:

p_f = 0.7 * C_e * C_t * I_s * p_g

Loadcases

Any loadcases requested in the following table are set up accordingly when the wizard is closed.


Property	Description
Minimum Snow Load	If this loadcase is requested, loads would need to be manually applied to it on completion of the snow wizard - the only snow load applicable being Uniform Snow.
Balanced Snow Load	If this loadcase is requested it is automatically populated on completion of the snow wizard
Unbalanced Snow Load	You can select between 1 and 4 cases to generate (Unbalanced Snow Load 1, Unbalanced Snow Load 2 etc.) Loads would need to be manually applied to these loadcases on completion of the snow wizard - both Uniform Snow and Valley Snow loads may be applicable, (depending on the model geometry).
Drift Snow Load	You can select between 1 and 4 cases to generate (Drift Snow Load 1, Drift Snow Load 2 etc.) Loads would need to be manually applied to these loadcases on completion of the snow wizard - the only snow load applicable being Local Drift Snow.
Rain on Snow Surcharge	If this loadcase is requested it is automatically populated on completion of the snow wizard