Eigen Command

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This command is used to perform the analysis.

eigen <$solver> $numEigenvalues

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$numEigenvalues	number of eigenvalues required
$solver	optional string detailing type of solver: -genBandArpack, -fullGenLapack (default: -genBandArpack)

RETURNS:

a tcl string containg eigenvalues.

NOTES:

1. The eigenvectors are stored at the nodes and can be printed out using a Node Recorder, the nodeEigenvector command, or the Print command.
2. The default eigensolver is able to solve only for N-1 eigenvalues, where N is the number of inertial DOFs. When running into this limitation the -fullGenLapack solver can be used instead of the default Arpack solver.
3. The -fullGenLapack option is VERY SLOW for moderate to large models

THEORY:

<math> \left (K - \lambda M \right ) \Phi = 0 </math>

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EXAMPLE:

set eigenvalues [eigen 10];

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Code Developed by: fmk