Pressure Loads on Face of Shell and Solid Elements
Description: Defines a load on a face of a shell or solid element. Only CQUAD4, CQUADR, CTRIA3, CTRIAR, CHEXA, CPENTA, CPYRA, and CTETRA elements may have a pressure load applied to them via this entry.
Format:
Example:
Alternate Format and Example:
| Field | Definition | Type | Default |
|---|---|---|---|
| SID | Load set identification number. | Integer > 0 | Required |
| EID | Element identification number. | Integer > 0 | Required |
| P1, P2, P3, P4 | Load per unit surface area (pressure) at the corners of the face of the element. | Real or blank | P1 is the default for P2, P3, and P4 |
| G1 | Identification number of a grid point connected to a corner of the face. | Integer > 0 or blank | Required for solid elements |
| G3 | Identification number of a grid point connected to a corner diagonally opposite to G1 on the same face of a CHEXA, CPENTA, or CPYRA element. Required for the quadrilateral faces of CHEXA, CPENTA, and CPYRA elements. Must be omitted for a triangular face on a CPENTA or CPYRA element. | Integer > 0 or blank | Required for CHEXA and CPENTA elements |
| G4 | Identification number of the CTETRA grid point located at the corner; this grid point may not reside on the face being loaded. | Integer > 0 or blank | Required for CTETRA elements |
| CID | Coordinate system identification number. | Integer ≥ 0 or blank | See Remark 2 |
| N1, N2, N3 | Components of vector measured in coordinate system defined by CID. Used to define the direction (but not the magnitude) of the load intensity. | Real | Required if CID is not blank and must have at least one non-zero component |
Remarks:
- Load sets must be selected in the Case Control Section (LOAD = SID).
- The continuation entry is optional. If fields 2, 3, 4, and 5 of the continuation entry are blank, the load is assumed to be a pressure acting normal to the face. If these fields are not blank, the load acts in the direction defined in these fields. Note that if CID is a curvilinear coordinate system, the direction of loading may vary over the surface of the element. The load intensity is the load per unit of surface area, not the load per unit of area normal to the direction of loading.
- For the faces of solid elements, the direction of positive pressure (defaulted continuation) is inward. For triangular (and quadrilateral faces) the load intensity P1 acts at grid point G1 and load intensities P2, P3 (and P4) act at the other corners in a sequence determined by applying the right-hand rule to the outward normal.
- For shell elements, the direction of positive pressure (default continuation) is in the direction of positive normal, determined by applying the right-hand rule to the sequence of connected grid points. The load intensities P1, P2, P3 (and P4) act respectively at corner points G1, G2, G3 (and G4) for triangular (and quadrilateral) elements.
- If P2, P3, and P4 are blank fields, the load intensity is uniform and equal to P1. P4 has no meaning for a triangular face and may be left blank in this case.
- Equivalent grid point loads are computed by numerical integration using isoparametric shape functions. Note that a uniform load intensity will not necessarily result in equal equivalent grid point loads.
- G1 and G3 are ignored for CTRIA3, CTRIAR, CQUAD4, and CQUADR elements.
- The alternate format is available only for CTRIA3, CTRIAR, CQUAD4, and CQUADR elements. The continuation entry may be used in the alternate format.
- For triangular faces of CPENTA elements, G1 is an identification number of a corner grid point that is on the face being loaded and the G3 or G4 field is left blank. For CPYRA elements, G1 must be a grid point on the quadrilateral face. For faces of CTETRA elements, G1 is the identification number of a corner grid point that is on the face being loaded and G4 is an identification number of the corner grid point that is not on the face being loaded. Since a CTETRA element has only four corner points, G4 will be unique and different for each of the four faces of a CTETRA element.