Drag and Inertia Coefficients Form

Use the Drag and Inertia Coefficients form to define drag and inertia coefficients for a specified number of vertical elevations. The data can then be used to calculate the wave forces acting on a structure.

Input the vertical elevation (measured from the datum) and drag and inertia coefficients at each data point in descending vertical elevation order. Clicking the Order Rows button will reorder the data. Note, however, that the program will automatically reorder the data in descending vertical elevation order when you click the OK button to close the form.

The drag and inertia coefficient values used at a particular vertical elevation are linearly interpolated from the specified data.

The drag and inertia coefficients are used in Morison’s equation when calculating the wave forces acting on the structure. By default, a wave load is specified to have API Default drag and inertia coefficients. The values for the API Default drag and inertia coefficients depend on whether the location considered is above or below the specified high tide elevation, as shown in the following table.

Location

Drag Coefficient

Inertia Coefficient

Above High Tide Elevation (Smooth)

0.65

1.6

Below or At High Tide Elevation (Smooth)

1.05

1.2

 

See Also

Wave Load

Current Profile Data

Marine Growth Data

Wave Characteristics

Wave Wind Load

 

Access the Drag and Inertia Coefficients form as follows:

  1. Display the Define Load Patterns form using either of the following methods:

    • Click the  Loads > Load Patterns command.

    • Display the Bridge Wizard; and then select the Loads Cases item and click the Define/Show Load Patterns button.

  2. Specify a Wave Load Type and an Auto Lateral Load other than None and click the Add New Load Pattern button.

  3. Highlight the name of the newly define load and click the Modify Lateral Load Pattern button to display the Wave Load Pattern form.

  4. Click the Drag and Inertia Coefficients Add button or select a previously defined coefficient definition from the drop-down list and click the Modify/Show button to display the Drag and Inertia Coefficients form.