Wind Load Pattern Form

Form: {Code-Specific} Wind Load Pattern
Additional form: Wind Exposure Width Data

Note: The Define Load Patterns form also displays when the Load Cases item is selected and the Define/Show Load Patterns button is clicked on the Bridge Wizard form.

The input required on the form depends on the code, or in the case of a "User Defined" wind load, provide values for Fx, Fy and Mz directly into the spreadsheet cells.

The code-specific forms share the following areas, although the specific parameters in a given area may vary from form to form:

Exposure and Pressure Coefficients. Choose to define these coefficients by checking the appropriate check box:
- Exposure from Extents of Rigid Diaphragms option. If this option is selected, the Wind Exposure Parameters area becomes active. This option allows the same wind load to be applied each time the load pattern is assigned. Diaphragm constraints must be assigned to joint objects in the model for the auto lateral load pattern to apply wind loads using this option.
- - Wind Exposure Parameters. Use the available edit boxes to specify the wind direction angle and the windward and leeward coefficients.
  - Modify/Show Exposure Widths button. Click this button to display the Wind Exposure Width Data form. The Exposure Width spreadsheet is inactive when the Calculate from Diaphragm Extents check box is checked. Check the User Defined check box to edit values in the spreadsheet, including Trib (Tributary) Height and Width. If the form is blank, no diaphragms have been assigned to joints in the model.
- Exposure from Frame and Area Objects option. If this option is selected, the Wind Exposure Parameters area becomes inactive. The windward and leeward coefficients can then be assigned when the wind load is applied to an area object (see Wind Pressure Coefficients). Using this option allows application of wind load coefficients and wind direction on an area-object-by-area-object basis.

If ASCE 7-02 code was selected in the Auto Lateral Load drop-down box on the Define Loads form (the form that precedes use of this form) and the Exposure from Area Objects option is selected, two check boxes will be added in this area of the form: Include Area Objects check box and Include Frame Objects (Open Structure) check box. Choose the appropriate option for your load definition.

Exposure Height options. Choose to have the program calculate the exposure height (i.e., use the Program Calculated option), or specify the Maximum and Minimum Global Z values to define a User-Specified exposure height.
Wind Coefficients options. Specify the wind speed, select the exposure type from the drop-down list, provide an importance factor for the structure, specify a topographical factor, a gust factor, a directionality factor, and when available, a solid/gross area ratio factor.