/RBE3
Block Format Keyword Defines the motion of a reference dependent node as the weighted average of the motions of sets of independent nodes.
Format
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/RBE3/rbe3_ID  
rbe3_title  
Node_ID_{r}  Trarot_{ref}  N_set  I_modif 
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

WT_{i}  Trarot_M_{i}  skew_ID_{i}  grnd_ID_{i} 
Definition
Field  Contents  SI Unit Example 

rbe3_ID  Interpolation constraint
element identifier. (Integer, maximum 10 digits) 

rbe3_title  Interpolation constraint
element title. (Character, maximum 100 characters) 

Node_ID_{r}  Reference (dependent) node
identifier. (Integer) 

Trarot_{ref}  Code of DOF used for
reference (dependent) node.
(6 Booleans) Default (blank or 6 zeros), set on all DOF 

N_set  Number of different
weighting factor and/or Trarot
sets. (Integer) 

I_modif  Modification of weighting
factor flag. 4
Default (blank or zero), set to 1 (Integer) 

WT_{i}  Weighing factor of set
i. (Real) 

Trarot_M_{i}  Independent nodes' code of
DOF used in interpolation of set i. (6 Booleans) Default (blank or 6 zeros), set on all DOF 

skew_ID_{i}  Local skew identifier of
set i. (Integer) 

grnd_ID_{i}  Node group defining
independent nodes of set
i. (Integer) 
Codes for Translation and Rotation: Trarot_{ref} and Trarot_M_{i}
(1)1  (1)2  (1)3  (1)4  (1)5  (1)6  (1)7  (1)8  (1)9  (1)10 

T_{X}  T_{Y}  T_{Z}  ${\omega}_{X}$  ${\omega}_{Y}$  ${\omega}_{Z}$ 
Definition
Field  Contents  SI Unit Example 

T_{X}  Code for translation
T_{X}.
(Boolean) 

T_{Y}  Code for translation
T_{Y}.
(Boolean) 

T_{Z}  Code for translation
T_{Z}.
(Boolean) 

${\omega}_{X}$  Code for rotation
${\omega}_{X}$
.
(Boolean) 

${\omega}_{Y}$  Code for rotation
${\omega}_{Y}$
.
(Boolean) 

${\omega}_{Z}$  Code for rotation
${\omega}_{Z}$
.
(Boolean) 
Comments
 This is equivalent to OptiStruct's RBE3, in which motion of a dependent node depends on the motion of a group of independent nodes with weighted average. It is similar to but more general than the kinematic condition interface TYPE2 (which is limited by one dependent node to one independent segment (3 nodes or 4 nodes) and for all translations and/or all rotation components), the dependent rotation is computed as a function of translation and rotation of independent nodes, if all DOF are set on in Trarot_M_{i}.
 It is recommended that for most applications only the translation components be used for Trarot_M_{i} (Spot_{flag} =1 in /INTER/TYPE2). An exception is the case where the independent nodes are colinear and some of the dependent rotation components can not be determined. In this case, some rotational component should also be set on.
 The absolute values of the weighting factors are not important; it is the relative values from different sets that are important since these will be normalized.
 All DOF of the dependent node should be
determinable.
If only translation components are used for Trarot_M_{i} and the independent nodes are quasicollinear, numerical instability might occur in explicit analysis to avoid this; Radioss by default, will modify the input weighting factors slightly (I_modif = 1). To prevent this modification, set I_modif =2.
I_modif =3 will give an equivalent behavior as /INTER/TYPE2 with Spot_{flag} =1.
 It is not recommended to define a hierarchy involving RBE3, with other constraint equation (kinematic conditions; however, this is permitted, if the hierarchy rule has been respected.
 Hierarchy rule involving
/INTER/TYPE2, /RBE2,
/RBE3, and /RBODY
is:
RBODY > RBE3 > RBE2 > INTERFACE TYPE2