Area - Springs

Form: Assign Springs to Area Object Face

Use the Assign menu > Area > Area Springs command to access the Assign Springs to Area Object Face form and assign area springs to area objects. SAP2000 distributes the springs associated with the area object to all of the nodes associated with the internal-to-SAP2000 (analysis model) representation of the area object. Note that in some cases, internally SAP2000 may mesh (break up) an area object into several elements with associated joints between each element.

Select the area object to which springs are to be assigned.

Tip: If a nonlinear spring to ground is needed, use a one-joint (grounded) link object. Linear or nonlinear properties can be assigned to the link. If springs to connect between two points in the structure are needed, use a two-joint (connecting) link object. Linear or nonlinear properties can be assigned to the Link.

Click the Assign menu > Area > Area Springs command to access the Assign Springs to Area Object Face form.

- Spring Type.
- - Simple. When this option is selected, use the default value for the stiffness per unit area or enter another value in the Spring Stiffness per Unit Area edit box. Also specify if the spring has both Tension and Compression, or only Tension or only Compression by selecting the appropriate option from the Simple Spring Resists drop-down list.
  - Link Property. When this option is selected, the spring is a based on a link property. The option will be available if link properties have already been defined in the model; in that case, select the property from the drop-down list. If no link property has been defined, clicking the + (plus) symbol beside the drop-down list will access the Link/Support Properties form, which can be used to define the necessary link property. Then select that property in the drop-down list.
  - - Link Local 2-Axis Angle from Default Orientation edit box. This edit box becomes available when the spring is being defined using a link property definition. Use the edit box to specify an orientation angle for the link local axis measured counterclockwise from its default orientation.

- Spring Tension Direction. Specify the direction of the spring tension, or when the Spring Type is Link Property, the direction of the spring, positive local 1-axis:
- - Parallel to Area Object Local Axis option and drop-down list. With this option, use the drop-down list to choose the local axis direction of the area object to which the spring is being assigned. The direction of the spring tension will be parallel to the selected local axis direction.
  - Normal to Specified Area Object Face option and drop-down list. Specify that the spring tension direction be normal to a face of the area object. Use the drop-down list to specify whether tension is inward or outward.
  - User Specified Direction Vector option and Coordinate System drop-down list and Global X, Y and Z Component edit boxes. Use this option to specify the spring tension direction along a specified vector. Select the Coordinate System for the vector from the drop-down list. The possible options include the Global axis, any user-defined coordinate systems, and the local axes of the line object to which the spring is assigned.

- Options: Three area spring assignment options are possible:
- - Add to existing springs: Adds this assignment to the existing spring assigment(s).
  - Replace existing springs: Replaces the existing spring assignment(s) with this new assignment. If no assignment exists, the new assignment is still made. This is the default option.
  - Delete existing springs: Deletes all spring assignments made to the selected area object(s).
- Units drop-down list. Use the units shown in the drop-down list or select other units from the drop-down list for use on this form.

Note: If a slab or mat on an elastic foundation with area springs is being modeled, the Assign menu > Area > Automatic Area Mesh command can be used to specify the area mesh to ensure that a sufficient number of springs is used in the analysis model. SAP2000 will automatically determine the required stiffness for each spring. This feature saves a considerable amount of time.