Set Dynamic Boundary Conditions

Dynamic boundary conditions can be applied to boundaries, vertices or nodes using the Set Dynamic Boundary conditions option.

1. Select the Dynamic workflow tab.
2. Select the Set Dynamic Boundary Conditions option from the toolbar or the Dynamic menu. You will see the Set Dynamic BCs dialog.
3. Choose the BC Type:
4. • None (i.e. remove boundary condition)
   • Absorb
   • Transmit
   • Damper (enter damper values in the X and Y directions)
   • Nodal Mass (enter a mass value)
   • Tied
   • Hydro Mass

   Description of these type are explained in details below.

5. Choose the Selection mode (if applicable) - Boundary Segments, Boundary Vertices or Boundary Nodes.
6. Apply at this stage only - select this check box if you want to apply the boundary condition at the current stage ONLY.
7. Use the mouse to select boundary segments, vertices or nodes, according to the selection mode. When finished selecting, press Enter, or right-click and select Done Selection, or select the Apply button in the dialog, to apply the boundary conditions.
8. You may repeat steps 3 to 6 as required to apply different boundary conditions or change the selection mode.
9. Select Close in the Set Dynamic BCs dialog.

Edit Dynamic Boundary Conditions

To edit existing dynamic boundary conditions, you can use the Set Dynamic BCs dialog to apply different boundary conditions, or right-click on a boundary condition and select an option from the popup menu.

Delete Dynamic Boundary Conditions

To delete dynamic boundary conditions you can use the right-click shortcut to delete individual boundary conditions, or select Remove All Dynamic BCs from the Dynamic menu to remove ALL existing dynamic boundary conditions, or use the Set Dynamic BCs dialog and apply the None option.

Boundary condition types:

1. Absorb/Damper

• Absorbs the outcoming wave from the domain
• Used for problems where the dynamic source is inside the domain

2. Transmit

• Only apply in the lateral boundaries
• Consists of load history and a absorb boundary
• The load history is calculated from the free field motion
• Used for earthquake simulation
• When joints intersect the same boundary, joint end condition must be closed on the shared boundary

3. Tie

• To restrain the nodes on the left and right to move in the same displacement
• Only applicable to the model that have the same number of nodes on both sides
• Used to model perfect one dimension soil column to analyze site response

4. Nodal mass

• An additional mass can be assign to a node, can be used to simulate the dynamic load from an external source
• Can be directional (x,y)

5. Hydro mass

• Used to model the effect of hydrodynamic of water based on the formulation of Westergaard (1933) for vertical dam. However, in RS2, the formulation was modified to account for the angle of the slope.
• User can input the hydro mass manually. Two required inputs are:
  • Height of the reservoir
  • Base of the reservoir
    This option provides flexibility to account for cases where material is dry and there are water acting on its surrounding (such as a concrete dam).