Elastic Support

When the Elastic tab is selected from the Support Definition dialog, the following dialog displays.

At the top of the dialog, the Constant elastic coef. at support node option is available for linear and planar supports. When selected, the values of the elastic coefficients are constant at each node of the linear and planar supports. When cleared, the elastic coefficients are defined per unit of length (linear support) or per unit of surface ( planar support).

The elastic coefficient in a node is calculated as follows:

1. For each node, the Robot calculates the distance between the centers of segments between successive nodes. (See the following image.)
   
2. The calcuated distance, such as, dl, is multiplied by the coefficient per unit of length, defined by the user (for example, for Node 2 KZ*dl2).
3. The calculated value from Step 2 is applied to the node. The values in nodes usually differ.

To define an elastic support:

1. Enter a name for the support label.
2. Select fixed directions (blocked degrees of freedom) in the node:
   • UX
   • UY
   • UZ
   • RX
   • RY
   • RZ

For an elastic support, specify either the blocked degrees of freedom or the coefficients of elasticity in the appropriate directions:

• KX
• KY
• KZ
• HX
• HY
• HZ

Clicking Elastic coefficients opens the Building soils - calculations of K coefficient dialog, which computes the value of the elastic foundation coefficient K for layered soil.

Note: When up-lifting is defined for a support (such as, uplifting based on the orientation of the Z axis, that is, UZ+), you can also determine the elastic base coefficient KZ for each support. Remember that the elastic base coefficient is determined only for the orientation opposite to the one defined for up-lifting (that is, for UZ-).

A diagram of the support being defined is displayed in the lower right of the dialog. Clicking Direction under the digram opens the Support direction dialog, where you can define the direction of the local x axis for the support. The axis is determined by specifying a point, a node, or rotating a support with respect to any axis in the global coordinate system.

Clicking Add, adds the support to the list of active supports.

Clicking Advanced, which is available for nodal and linear supports (it is not available for planar supports), opens a new dialog: Support definition - Advanced.