[MBDyn-users] Eigenvector / Structural Node DOF correlation

masarati at aero.polimi.it masarati at aero.polimi.it
Tue Aug 18 12:15:01 CEST 2009


> Hi,
>
> is there any chance to find out how the entries in an eigenvector
> correlate to
> the structural node DOFs? This would be helpfull for plotting.

Good point.  As a matter of fact, there's a debate going on as per what's
the best way to deal with this issue.  Suggestions are welcome.

Open points are:

- should we aim at one specific plotting tool?

- should we select one general format (UNF? [1]) that's supported by an
acceptable number of tools?

- should we design our own?

- should we rather output data in matlab/octave/scilab/any math env? (this
is what is done right now with raw data, BTW)

To give you a quick answer, in the .log file you find a record "struct
node dofs:".  It contains the offset of each structural node in the
analysis.

Calling "offset" an array containing those integers, and calling "VR" the
right eigenvectors matrix,

        VR(offset + 1, :)

would contain the displacement in direction 1 of all nodes for all
eigenvectors.

Hope it's clear enough.

p.

[1]
<http://www.sdrl.uc.edu/universal-file-formats-for-modal-analysis-testing-1/file-format-storehouse/univ_files.htm/>




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