SOLVERS: Modes

Description

The Harmonic Response, Spectral Response and Linear Transient Dynamic (Mode Superposition) solvers are based on the mode superposition method and therefore require the selection of a natural frequency solution file from which the modes to be combined are extracted.

The Modes sub-tab provides the functionality to load the natural frequency result file and to include the required modes for the analysis. If also provides information about the convergence status and the mass participation ratios in the global directions for each mode, if these have been requested for calculation in the Natural Frequency solver (SOLVERS Home: Mode Participation).

Toolbar Functions

Selections

Includes all modes, excludes all modes, or inverts the inclusion status of modes.

Select only converged modes

Selects all modes whose frequency and eigenvector are converged.

Select modes based on mass participation ratio

Selects modes with X, Y or Z translational participation ratios greater than the selected percentage.

Including modes with small mass participation ratios is not detrimental to the solution. In general, all modes should be included in the analysis as long as the mode shapes (eigenvectors) are converged. The option to exclude modes is mainly useful as a way to reduce the calculation time by excluding modes that make a negligible contribution to the results, assuming that the contribution is related to the mass participation ratio.

Retrieve modal damping from NFA file

Retrieves the effective modal damping coefficients calculated by the Natural Frequency solver and copies them to the Damping Ratio column to be used as modal damping ratios in the analysis. See SOLVERS Home: Mode Participation and Special Topics: Damping for information on calculating effective damping coefficients.

Select File

Displays the Open File dialog, enabling the selection of a natural frequency results file for mode superposition.