Parameter

Values

Description

EFFMAS

<YES, NO, Integer>

Default = NO

When EFFMAS < 0 or NO, the modal participation factors, modal participation factor ratio, and modal effective mass are not output for normal modes analysis.

When EFFMAS > 0 or YES, the modal participation factors, modal participation factor ratio, and modal effective mass will be computed and output to the .out and .pch files (OUTPUT,PUNCH should be active for .pch file output) for normal modes analysis. They are computed as follows:

Modal Participation Factor =

The Modal Participation Factor is a measure of how close each mode is to a rigid body mode.

The Modal Participation Factor Ratio is the Modal Participation Factor for each rotational and translational direction divided by the maximum Modal Participation Factor of all the modes for that direction. So, each of the six directions will have a value of 1.0 for the mode that has the maximum Modal Participation Factor and the other modes will have a value less than 1.0.

Modal Effective Mass =

The Modal Effective Mass is a measure of how much mass is associated with each mode.

where

is the matrix of eigenvectors.

[m]

is the system mass matrix.

[V]

is the objective function matrix. Six rigid body modes are used as objective function in normal modes analysis to obtain [PF] and [EFFMAS].

[M]

is the diagonal modal mass matrix.