antype, MODAL, RESTART
mxpand, %tab%,,, yes! Mode selection is based on user input array, and element results are
! requested
solve
finish
! Post-process the modal results or perform a mode superposition analysis3.9.6.2. Mode Selection Based on Modal Effective Mass
The mode selection is performed during a modal analysis restart. It is applicable to real eigensolvers
only.
You can select the modes per direction using one of the following methods:
- Use a significance threshold (SIGNIF on the MXPAND command). The significance level of a mode is
equal to the modal effective mass divided by the total mass. The threshold is the same for all directions,
but the user may define the specific global x, y, z directions used (MODSELOPTION command). - Set a minimum ratio for the total modal effective mass to the total mass (MODSELOPTION command).
This ratio can be input for each direction.
A sample input listing of this procedure using a minimum ratio follows:
! Build the Model
/filnam,...
/title,...
/prep7
...
finish
! Obtain the Modal Solution
/solu
antype, MODAL
modopt, LANB, ...! Block Lanczos
solve
finish
! Perform the modal selection and expansion
/solu
antype, MODAL, RESTART
mxpand,,,, yes,,, MODM! Mode selection is based on the modal effective mass, and element
! results are requested
modseloption, .90, no,no, no,no,no! Only direction X is selected, a minimum of 90% of the total
! mass is requested in this direction
solve
finish
! Post-process the modal results or perform a mode superposition analysisNoteIf the minimum ratio cannot be achieved, you may need to extract more modes and run the
procedure again.If you want to calculate residual vectors, do so during the modal restart analysis. Note that the residual
vectors calculation is always based on all the extracted modes and not the selected modes.
Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationModal Analysis Tools for Subsequent Mode Superposition Analysis