Define Dynamic Load

Dynamic (time-dependent) loading on boundaries can be defined in terms of displacement, force, velocity or acceleration versus time. To define dynamic loads on boundaries:

1. Select the Dynamic workflow tab.
2. Select Define Dynamic Loads from the toolbar or the Dynamic menu.
3. You will see the Edit Dynamic Loads dialog. To edit an existing load click on the load name in the list at the left of the dialog. To define a new load select the Add button. You may enter or edit the load name or use the default name (e.g. Dynamic Load 1).
4. Select the load Type. There are five possible dynamic load types:
   • Line Force
   • Distributed Force
   • Displacement
   • Velocity
   • Acceleration
5. Choose the load direction(s):
• X and/or Y directions
• Normal (to boundary)
6. Select the Define button beside the X, Y or Normal option, and you will see another dialog which allows you to enter the time-dependent load information. Enter the Time and Load values in the data columns (at least two points must be defined). The input data will be plotted on the right of the dialog.
7. If the load type is one of displacement, velocity, or acceleration, you can use the data outputted from Dynamic Data Analysis by selecting the checkbox for Use Filtered Data and select from the dropdown list.
   You can perform a dynamic data analysis by clicking the Dynamic Data Analysis button in the dialog too. This option also available from Dynamic > Dynamic Data Analysis.
8. Select [OK] in the load function dialog.
   
9. select [OK] in the Edit Dynamic Loads dialog to save the dynamic load(s).

After defining dynamic loads, they can be applied to the model with the Add Dynamic Load option.

Drift Correction

The Drift Correction option is only applicable for Velocity or Acceleration load types. See the Dynamic Analysis Theory document for details.

Compliant Base

The Compliant Base option is only applicable for Velocity or Acceleration load types. Since a rigid base will null the effects of the absorb boundary conditions, in order to absorb outgoing waves from the model (to avoid the reflection of those waves back to the model), the motion restraint is transferred to stresses and applied to the boundaries.