Moment of inertia for lumped masses

gopal_rathore

Hi,

I am doing a modal analysis on a structure with lumped masses in the system. As I have not assigned any MOI for these masses , in modal results I can see a significant displacement of the lumped masses attached via rbe3 and thus the results seems to be irrelevant. If I do not have the MOI for the masses, can we go for adding high inertia values to restrict those displacements. Is the methodology correct?

Kindle let me know.

Rahul Rajan_21763

Hi,

 

Did you tried applying lumped using CONM2 or Rbe2 element.Any specific reason for checking displacement results in modal analysis?

 

Regards

Rahul Rajan | Hyperworks Specialist

www.altairhyperworks.com|rahul.rajan@altair.com

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gopal_rathore

Hi,

I have applied it using CONM2 element through a RBE3 element. 

Considering a mass at some distance from the structure, in modal results if this is not constrained properly it produces its own modes.

Thus thought providing inertia would restrict the mass element motion.