Generalized Spring and Damper Connection
Description: Defines a generalized spring and damper structural element that may be nonlinear or frequency dependent.
Format:
Example:
| Field | Definition | Type | Default |
|---|---|---|---|
| EID | Element identification number. | Integer > 0 | Required |
| PID | Property identification number of a PBUSH entry. | Integer > 0 | Required |
| GA, GB | Grid point identification number of connection points. | Integer > 0 | See Remark 6 |
| X1, X2, X3 | Components of vector
 , from GA, in the displacement coordinate system at GA (see Figure 1).
|
Real or blank | |
| G0 | Grid point identification number to optionally supply X1, X2, and X3. Direction of orientation vector is GA to G0. | Integer or blank | |
| CID | Element coordinate system identification. A 0 means the basic coordinate system. If CID is blank, then the element coordinate system is determined from G0 or Xi. See Figure 1 and Remark 3. | Integer ≥ 0 or blank | |
| S | Location of spring damper. See Figure 2. | 0.0 ≤ Real ≤ 1.0 | 0.5 |
| OCID | Coordinate system identification of spring-damper offset. See Remark 8. | Integer ≥ -1 | -1 |
| S1, S2, S3 | Components of spring-damper offset in the OCID coordinate system if OCID ≥ 0. See Figure 2 and Remark 8. | Real |
Remarks:
- Element identification numbers must be unique with respect to all other element identification numbers.
- The bush element geometry is shown in Figure 1 below.
- CID ≥ 0 overrides G0 and (X1, X2, X3). Then the element x-axis is along T1, the element y-axis is along T2, and the element z-axis is along T3 of the CID coordinate system. If the CID refers to a cylindrical coordinate system or a spherical coordinate system, then grid GA is used to locate the system. If for cylindrical or spherical coordinate, GA falls on the z-axis used to define them, it is recommended that another CID be selected to define the element x-axis.
- For noncoincident grids (GA ≠ GB), when G0 or (X1, X2, X3) is given and no CID is specified, then the line GA - GB is the element x-axis and the orientation vector
lies in the x-y plane (similar to the
CBEAM element).
- For noncoincident grids (GA ≠ GB), if neither G nor (X1, X2, X3) is specified and no CID is specified, then the line GA - GB is the element x-axis. This option is valid only when K1 (or B1) or K4 (or B4) or both on the PBUSH entry are specified (but K2, K3, K5, K6, or B2, B3, B5, B6 are not specified). If K2, K3, K5, or K6 (or B2, B3, B5, or B6) are specified, a fatal message will be issued.
- A blank in field 5 may be used to indicate a grounded terminal GB. A grounded terminal is a point whose displacement is constrained to zero.
- If GA and GB are coincident, or if GB is blank, then CID must be specified.
- If OCID = -1 or blank (default) then S is used and S1, S2, S3 are ignored. If OCID ≥ 0, then S is ignored and S1, S2, S3 are used.
Figure 1. CBUSH Element Coordinate System
Figure 2. Definition of Offset S1, S2, S3