WS Graphical [SIG]

General

Utilizing GPU for Wind Load Calculation

To accelerate wind load calculations, we leverage the power of GPU by rendering a 3D image of an object and dividing it into sections. Each section is further divided into pixels, and each pixel is assigned a volume unit based on the object's representation in the image. By counting the pixels, we can compute wind load magnitudes. Then we rotate the 3D model of the bridge and perform the same procedure for various attack angles. The projected area will vary for varying angles of attack.

Attack Angle Start: The range of attack angles is typically from 0 to 360 degrees. This parameter is used to specify the starting angle of the wind load.

Attack Angle End: The range of attack angles is typically from 0 to 360 degrees. This parameter defines the ending angle of the wind load.

# of Directions: Typically, the angle range is partitioned into either 12 directions (at 30-degree intervals) or 24 directions (at 15-degree intervals), from the starting point to the endpoint.

Stage: Choose the stage at which to apply the wind load. The wind load analysis results cannot be visualized within this stage after the analysis. OpenBrIM generates sub-stages automatically and assign selected stage as a prior stage. Therefore, the wind load analysis results will be presented in sub-stages, as shown in the screenshot below.

Open

WS Stage (0 deg)

Open

WS Stage (120 deg)

Wind Data:

• Wind Pressure: Typically, the wind pressure values for substructure and superstructure elements are different.

• Applied Elements: Typically, exterior girders, barriers, deck, pier caps and end bents are chosen as the elements to which the wind load is applied.

Coordinate System[Alignment/Global]: If the "Alignment" option is selected, the wind load direction will be perpendicular to the alignment, fulfilling the specifications stated in AASHTO 3.8.1.2.3a: "The skew angle should be measured from the perpendicular to the longitudinal axis of the bridge in plan." If the "Global" option is selected, the wind load rotates in the global direction. Furthermore, for each element, the wind force direction may differ depending on its location as seen in the figure below. In both scenarios, the applied load is calculated based on the projected area of the 3D component. Therefore, the only difference between them is the direction of the loads, not the magnitudes.

Is Active[Yes/No]: Wind load computation can be time-consuming, and it can increase the wait time after each compile. To mitigate this issue, the user can deactivate the wind load computation from this parameter.