Every time I try, it gives me this error "2 eigenvalues below the shift, Ritz analysis requires all eigenvalues to be above the shift". What can be the problem that makes this error exist?
Dear Abdelrahman Abdelaleem, that warning may be indicative of any modeling error. By default, shift is a very low value. If there are modes below this value, it means there are mode shapes with very low stiffness and, likely, some connectivity problem.
There is a discuss forum on this topic here: http://www.sepakistan.com/topic/1748-ritz-analysis-problem/
I would suggest running some easy tests to check the connectivity. You can also try to use merging
options of nodes. There can be nodes that apparently are connected but they are only close in space and no truly connected.
Hope it may be of any help. Best.
Dear Enrique,
I had already read this attached discussion before I asked this question here. I don't think there's a problem with the connections since I did a modal analysis using eigen vectors, and there is no indication of any connectivity issues within the resulting modes. The model file is attached if you have time to have a look on it.
Thanks
You can read these articales:
http://nptel.ac.in/courses/112105054/ADG_Final/lec8.pdf
http://web.cs.ucdavis.edu/~bai/Winter09/krylov.pdf
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