rotary inertia - how to define the elset?

[pirs]

Hi everyone,

I have got the following problem I require some assistance with: suppose you got a rigid body (for instance,a rigid plate), which is globally restrained using boundary conditions on the reference node - every displacement and rotation is restrained, except for the vertical displacement of said rigid plate.

Now, I want to release one of the rotations, which requires the definition of a rotary inertia. My idea is that I need to define a ROTARYI element, which contains my rigid plate reference node.

*RIGID BODY, REF NODE=SupportPlate.40, ELSET=SupportPlate.SupportPlateElements

*ROTARY INERTIA, ELSET=??
I11, I22, I33, I12, I13, I23

My question is, how do I define the ELSET, which includes the REF NODE, as defined in the *RIGID BODY line?

Thanks in advance for any input on this.