Opening the Snow/Wind Load dialog and clicking the Permeability tab displays the following dialog.
The dialog defines the permeability of the structure wall. Wall permeability has a direct effect on the generation of internal wind pressure coefficients. When you select an option its diagram displays in the upper-right corner of the dialog.
The dialog is divided into the following 3 fields with groups of specific options.
- In Permeability of side walls field specifies the left and right side wall permeability. Permeability is always expressed in %. For a completely open wall, the permeability value is 100%; whereas, for a completely closed wall, it is 0%.
- In Permeability of front and rear walls field specifies the front and rear wall permeability. Permeability is always expressed in %.
For a completely open wall, the permeability value is 100%; whereas, for a completely closed wall, it is 0%.
- The Doors field has the following options:
- Left side - When selected, the door is located on the left-side wall of the building. The permeability value for this wall can be specified in the field on the right.
- Right side - When selected, the door is located on the right-side wall of the building. The permeability value for this wall can be specified in the field on the right.
- Front - When selected, the door is located in the front wall of the building. The permeability value for this side can be specified in the field on the right.
- Rear - When selected, the door is located in the rear wall of the building. The permeability value for this side can be specified in the field on the right.
When the Tight structure option is selected, all the fields on the tab are unavailable and the value of the Cpi parameter is zero.