/RBE2
Block Format Keyword Defines a rigid body whose independent degrees of freedom are specified at a single independent node and whose dependent degrees of freedom are specified at an arbitrary number of dependent nodes.
Format
(1)  (2)  (3)  (4)  (5)  (6)  (7)  (8)  (9)  (10) 

/RBE2/rbe2_ID  
rbe2_title  
node_ID  Trarot_{ref}  Skew_ID  grnd_ID  I_{flag} 
Definitions
Field  Contents  SI Unit Example 

rbe2_ID  Rigid element
identifier (Integer, maximum 10 digits) 

rbe2_title  Rigid element
title (Character, maximum 100 characters) 

node_ID  Independent node
identifier (Integer) 

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

Skew_ID  Local skew identifier of
element. (Integer) 

grnd_ID  Dependent nodes group
identifier. (Integer) 

I_{flag}  Dependent relation
formulation flag. 1
(Integer) 
Codes for Translation and Rotation: Trarot
(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}  ${\omega}_{X}$  ${\omega}_{Y}$  ${\omega}_{Z}$ 
Definitions
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
 Two formulations of dependent motion are available in
I_{flag}:If Iflag=0
(1) $${\dot{u}}_{s}\left(\text{dependenttranslation}\right)=\left[Tra\right]\left({\dot{u}}_{m}+{\dot{D}}_{sm}\otimes {\dot{\theta}}_{m}\right)$$(2) $${\dot{\theta}}_{s}\left(rotation\right)=\left[Rot\right]{\dot{\theta}}_{m}$$If Iflag=1(3) $${\dot{u}}_{s}\left(translation\right)=\left[Tra\right]{\dot{u}}_{m}+{\dot{D}}_{sm}\otimes \left[Rot\right]{\dot{\theta}}_{m}$$(4) $${\overline{\theta}}_{s}\left(rotation\right)=\left[Rot\right]{\overline{\theta}}_{m}$$(5) $$\left[Tra\right],\left[Rot\right]=\left[\begin{array}{ccc}i& 0& 0\\ 0& j& 0\\ 0& 0& k\end{array}\right]$$With $i$ , $j$ , $k$ =0,1
The default formulation I_{flag} =0 corresponds to OptiStruct's RBE2, in which the motion of a group of dependent nodes depends on the motion of one independent node which always has 6 DOF. The input Trarot_{ref} is applied on the dependent nodes and the element behaves like a rigid body.
The second formulation is similar to /RLINK; but takes into account the equilibrium between translations and rotations. The input Trarot_{ref} is applied on independent node, this formulation is used prior to version 10.0.5.
 A independent node can be attached to a finite element. The independent node can also be defined in a different RBE2 as independent node and/or dependent node, but the dependent node cannot have the incompatible kinematic conditions.
 It is not recommended for dependent or independent nodes of an /RBE2 to also be dependent or independent nodes in another constraint equation (kinematic conditions). However, this is permitted if the hierarchy rule has been respected: RBE2 should have a higher level than Interface TYPE2 (independent nodes of Interface TYPE2 can be dependent node of RBE2); but a lower level than RBE3 and RBODY. The hierarchy between different RBE2s is allowed, reordering will be done automatically to determine the hierarchy by Radioss Starter, if hierarchy levels between RBE2 are too high, error will be printed out.
 Hierarchy rule involving
/INTER/TYPE2, /RBE2,
/RBE3 and /RBODY
is:
RBODY > RBE3 > RBE2 > INTERFACE TYPE2
 More output messages could be obtained using Ipri of /IOFLAG: Ipri > 3 will printout new mass and inertia of the independent nodes; Ipri > 5 will printout the new RBE2 identifier and hierarchy level after reordering.
 The RBE2 uses a scalar inertia calculation similar to using /RBODY with I_{spher}=1.