# Wind Load Cases \[FEA]

Wind load cases define the wind pressure loading applied to the structure. The analysis computes wind forces on exposed surfaces of 3D components and FE elements by projecting their areas perpendicular to the wind direction and applying the specified pressure. Multiple wind directions can be analyzed by specifying a range of attack angles.

## Wind

**Wind Pressure:** The base wind pressure applied to the structure (force per unit area). This is typically determined from AASHTO wind speed maps and exposure conditions. The actual force on each element is computed as (Wind Pressure × Projected Area × Pressure Factor).

**Start Attack Angle:** The starting wind direction angle (in degrees). The angle is measured from a reference direction defined by the coordinate system. For analyzing a range of wind directions, this defines the first direction.

**End Attack Angle:** The ending wind direction angle (in degrees). Together with the start angle and number of directions, defines the range of wind directions to be analyzed.

**# of Directions:** The number of equally spaced wind direction angles to analyze between the start and end attack angles. For example, Start=0, End=180, Directions=7 would analyze at 0, 30, 60, 90, 120, 150, and 180 degrees. Each direction produces a separate analysis case.

**Coordinate System:** The coordinate system in which the wind direction angles are defined. This determines the reference axis from which the attack angle is measured.

**Is Active:** Controls whether this wind load case is included in the analysis run. Set to No to temporarily disable it without deleting it.

## Structure

**3D Components:** Selects the 3D component objects whose exposed surfaces will receive wind loading. The wind force is computed from the projected area of these components perpendicular to the wind direction.

**Pressure Per 3D Components:** Custom wind pressure values for individual 3D components, allowing different pressures to be applied to different parts of the structure (e.g., higher pressure on the superstructure, lower on substructure).

**FE Group:** The FE group containing the finite elements that receive wind loading. Elements within this group have their projected areas computed and loaded with wind pressure.