Gravity Vector
Description: Used to define gravity vectors for use in determining gravity loading for the structural model.
Format:
Example:
| Field | Definition | Type | Default |
|---|---|---|---|
| SID | Load set identification number. | Integer > 0 | Required |
| CID | Coordinate system identification number. | Integer ≥ -1 or blank | 0 |
| G | Gravity vector scale factor. | Real | Required |
| N1, N2, N3 | Gravity vector components measured in coordinate system defined by CID. | Real | Required; must have at least one nonzero component |
| TID1, TID2, TID3 | TABLEDi set identification numbers that define position dependent scale factors in the x, y, and z directions of the basic coordinate system. See Remark 1. | Integer > 0 or blank |
Remarks:
- The static load applied to grid point G is given by:
where
is the unit vector defined in fields 5, 6, and 7 and
f (x, y, z) is defined as the product of scale factors returned by tables defined in fields 2, 3, and 4 on the continuation entry.
- A CID of zero references the basic coordinate system.
- If CID = -1, the gravity vector components are in the local displacement coordinate system of the grid points.
- Gravity loads may be combined with "simple loads" (e.g., FORCE, MOMENT). The SID on a GRAV entry may be the same as that on a simple load entry.
- Load sets must be selected in the Case Control Section (LOAD = SID).