*MODAL

Data format:

A single line with four values

NBEIGVAL To NBEIGVEC EPSI

Status :

Optional

Purpose :

Eigen-frequencies and -modes calculation request

Restriction :

To must not be an exact eigenperiod of the structure

Details :

Parameter	Description
NBEIGVAL	number of requested eigenvalues
To	period around which NBEIGVAL eigenperiods are sought
NBEIGVEC	number of eigenvector used during the iterative procedure deafult at 3*NBEIGVAL
EPSI	convergence criterion for the iterative procedure (def. 10-9)

Notes :

This keyword triggers an iterative procedure on under-spaces
When To is specified, calculations will find the nearest eigenvalues corresponding to \(\lambda_0 = \frac{2\pi}{T^2_0}\)
If \(\lambda\) is an eigenvalue, \(\vec{X}\) the corresponding eigenvector : \(K\vec{X} = \lambda M\vec{X}\)