GRAV

Bulk Data Entry Defines the gravity vectors for use in determining gravity loading for the static structural model. It can also be used to define the EXCITEID field (Amplitude "A") of dynamic loads in RLOAD1, RLOAD2, TLOAD1, TLOAD2 and NLOAD1 Bulk Data Entries for dynamic solution sequences.

Attention: Valid for Implicit and Explicit Analysis

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
GRAV SID CID G N1 N2 N3 MB    

Example

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
GRAV 47 3 32.2 0.0 0.0 -1.0      

Definitions

Field Contents SI Unit Example
SID Set identification number.

No default (Integer > 0)

  
CID Coordinate system identification number. A CID of zero references the basic coordinate system.
0 (Default)
References the basic coordinate system.

(Integer ≥ 0)

  
G Gravity vector scale factor.

(Real ≠ 0.0)

  
N1,N2,N3 Gravity vector components.

No default (Real; at least one non-zero component)

  
MB Specifies the Bulk Data section in which CID is defined.
This entry is applicable only for partitioned superelements. 5
-1
The coordinate system is defined in the main Bulk Data section.
0 (Default)
The coordinate system is defined in the Bulk Data section of the partitioned superelement.

(Integer ≥ -1)

  

Comments

  1. The gravity vector is defined by:
    g → = G * ( N → 1 , N → 2 , N → 3 )

    The direction of g → is the direction of free fall. N → 1 , N → 2 , and N → 3 are defined in the coordinate system CID.

  2. CID=0 references the basic coordinate system.
  3. The LOAD Subcase Information Entry can be used to reference the GRAV Bulk Data Entry in Static subcases. The GRAV Bulk Data Entry can also be associated by the LOADADD Bulk Data Entry, which is in turn referenced by a LOAD Subcase Entry. For Dynamic or Transient solution sequences, the TYPE field on RLOAD1, RLOAD2, TLOAD1, TLOAD2, and NLOAD1 Bulk Data Entries should be set to LOAD, if GRAV is referenced on the EXCITEID field.
  4. For mass penalization information when GRAV is used in a Topology optimization, refer to Design Variables in the User Guide.
  5. In the context of partitioned superelements, the coordinate systems in the main Bulk Data section are defined with respect to the assembly basic coordinate system, which is fixed. This feature is useful when loading needs to be defined in a fixed coordinate system, irrespective of the orientation of the superelement, defined by a partitioned Bulk Data section.
  6. This card is represented as a load collector in HyperMesh.