RBE3
Bulk Data Entry
RBE3 – Interpolation Constraint Element
Description
Defines the motion at a "reference" grid point as the weighted average of the motions at a set of other grid points.
Format
(1) 
(2) 
(3) 
(4) 
(5) 
(6) 
(7) 
(8) 
(9) 
(10) 
RBE3 
EID 
blank 
REFGRID 
REFC 
WT1 
C1 
G1,1 
G1,2 


G1,3 
WT2 
C2 
G2,1 
G2,2 
etc. 
WT3 
C3 


G3,1 
G3,2 
etc. 
WT4 
C4 
G4,1 
G4,2 
etc. 


"UM" 
GM1 
CM1 
GM2 
CM2 
GM3 
CM3 
blank 


blank 
GM4 
CM4 
GM5 
CM5 
etc. 

blank 

Example
(1) 
(2) 
(3) 
(4) 
(5) 
(6) 
(7) 
(8) 
(9) 
(10) 
RBE3 
14 

100 
1234 
1.0 
123 
1 
3 


5 
4.7 
1 
2 
4 
6 
5.2 
2 


7 
8 
9 
5.1 
1 
15 
16 



UM 
100 
14 
5 
3 
7 
2 


Field 
Contents 
EID 
Unique element identification number. 
REFGRID 
Reference grid point. This is the dependent GRID. Some, or all, of the dependent degreesoffreedom of this grid can be made independent by redefining all of the dependent degreesoffreedom following the UM flag. (Integer > 0) 
REFC 
Global components of motion whose values will be computed at the reference grid point. Any of the digits 1, 2, ..., 6 with no embedded blanks. (Integer > 0) 
WTi 
Weighting factor for components of motion on the following entry at grid points Gi,j. (Real) 
Ci 
Global components of motion that have weighting factor WT, at grid points Gi,j. Any of the digits 1, 2, ..., 6, with no embedded blanks. (Integer > 0) 
Gi,j 
Grid point whose components Ci have weighting factor WTi in the averaging equations. (Integer > 0) 
UM 
Optional flag indicating that a data set redefining the entire dependent degreeoffreedom set is to follow. The default is that all of the components in REFC at the reference grid point form the dependent degreeoffreedom set. See comments 4, 5 and 6. 
GMi 
Grid points with components in the redefined dependent degreeoffreedom set. (Integer > 0) 
CMi 
Components of motion at GMi in the redefined dependent degreeoffreedom set. Any of the digits 1 through 6, with no embedded blanks. (Integer > 0) 
Comments
1.  It is recommended that for most applications only the translation components 123 be used for Ci. An exception is the case where the Gij are collinear. A rotation component may then be added to one grid point, to stabilize its associated rigid body mode for the element. 
2.  Blank spaces may be left at the end of a Gij sequence. 
3.  The default for the dependent degreeoffreedom set should be used except in cases where you want to redefine some or all REFC components as the dependent degreeoffreedom set. If the default is not used for the dependent degreeoffreedom set: 
•  The total number of components therein (i.e., the total number of dependent degreesoffreedom defined by the element) must be equal to the number of components in REFC (four components in the example). 
•  The components therein must be a subset of the components mentioned in REFC and Gij_Ci. 
•  The coefficient matrix [Rm] in the constraints equation [RM] {um} + [Rn] {un} = 0 must be nonsingular, where um denotes the dependent degreeoffreedom set and un denotes the independent degreeoffreedom set. 
4.  When the AMSES eigenvalue solver is used, the UM data should be used when loaded RBE3 have more than 500 DOF. Large loaded RBE3 will dramatically increase the run times for AMSES because the residual vectors will contain many DOF, unless the UM data is used to make the loaded center GRID independent. 
5.  UM data should not be used on large unloaded RBE3, as this will lead to an increase in the run time. 
6.  Dependent degreesoffreedom assigned by one rigid element may not also be assigned dependent by another rigid element or by a multipoint constraint, and may not be specified on SPC data. 
7.  In version 5.0, the RBE3 element calculation was modified in order to make the results independent of the units used in the model. For this purpose, the weights of the rotational degreesoffreedom have been scaled by the square of the average distance between the independent grid points and the reference point. This change will only affect the results if independent grid points with rotational degreesoffreedom exist in the RBE3 element. The previous RBE3 formulation can be enforced with the debug statement debug,OLDRBE3,1.0. 
8.  Rigid elements are ignored in heat transfer analysis. 
9.  This card is represented as an rbe3 element in HyperMesh. 
Go To
Guidelines for Bulk Data Entries