Static Pressure Load
Description: Defines a uniform static pressure load on a triangular or quadrilateral surface comprised of surface elements and/or the faces of solid elements.
Format:
Example:
| Field | Definition | Type | Default |
|---|---|---|---|
| SID | Load set identification number. | Integer > 0 | Required |
| P | Pressure value. | Real | Required |
| Gi | Grid point identification numbers. | Integer > 0; G4 may be blank | Required |
Remarks:
- Load sets must be selected in the Case Control Section (LOAD = SID).
- The grid points define either a triangular or a quadrilateral surface to which a pressure is applied. If G4 is blank, the surface is triangular.
- In the case of a triangular surface, the assumed direction of the pressure is computed according to the right-hand rule using the sequence of grid points G1, G2, G3 illustrated in Figure 1. The total load on the surface is divided into three equal parts and applied to the grid points as concentrated loads. A minus sign in field 3 reverses the direction of the load.
- In the case of a quadrilateral surface, the grid points G1, G2, G3, and G4 should form a consecutive sequence around the perimeter. The right-hand rule is applied to find the assumed direction of the pressure. Four concentrated loads are applied to the grid points in approximately the same manner as for a triangular surface. The following specific procedures are adopted to accommodate irregular and/or warped surfaces:
- The surface is divided into two sets of overlapping triangular surfaces. Each triangular surface is bounded by two of the sides and one of the diagonals of the quadrilateral.
- One-half of the pressure is applied to each triangle, which is then treated in the manner described in Remark 2.
- The follower force effects due to loads from this entry are not included in the stiffness in all linear solution sequences that calculate a differential stiffness.
Figure 1. Pressure Convention for Triangular Surface
Figure 2. Pressure Convention for Quadrilateral Surface