Hi,
I have model simply supported beam with one end fixed and other end only rest support. At the middle i break one element. When i run dynamic analysis of that system. I received following notification.I have consider lumped mass system.

" Not enough mass DOFs in the model to satisfy the number of eigen pairs requested.Continuing with those that were computed."

When i select consisten mass model above notifiaction won't appear.

Can anyone please clarify why does it so. ?

Thanks
Maulik