Single Point Constraints

Rigid constraints are defined for structural analyses using the command `PROPERTY BOUNDARY CONSTRAINT'. The user supplies a degree of freedom indicator (eg. 1234) to indicate which degrees of freedom are to be constrained.

The equivalence between FEMGEN degree of Freedom indicator and ANSYS structural degree of freedom label is shown in the table below:

FEMGEN indicator ANSYS label Meaning

1 or X UX x-translation

2 or Y UY y-translation

3 or Z UZ z-translation

4 or RX ROTX x-rotation

5 or RY ROTY y-rotation

6 or RZ ROTZ z-rotation

FEMGEN has also some degree of freedom macros that combine several structural degrees of freedom. They can be used by ANSYS users and are defined in the following table:

Degree of freedom name Meaning

XSYMM x-translation, y,z-rotations

YSYMM y-translation, x,z-rotations

ZSYMM z-translation, x,y-rotations

ALL x,y,z-translations, x,y,z-rotations

XASYMM x-rotation, y,z-translations

YASYMM y-rotation, x,z-translations

ZASYMM z-rotation, x,y-translations

ENCASTRE x,y,z-translations, x,y,z-rotations

PINNED x,y,z-translations

NOROTATE x,y,z-rotations

The interface produces a series of 'D' commands for all constrained nodes in the model for example:

  
D,     1,UX  ,,,,,UY  ,UZ  
D,     2,UY  ,,,,,UZ  
D,     3,UY  ,,,,,UZ  
D,     4,UY  ,,,,,UZ  
D,     5,UY  ,,,,,UZ

Prescribed values for structural and non structural degrees of freedom are defined by using the FEMGEN command PROPERTY BOUNDARY PRESCRIBE specified in Paragraph 5.4.