Transient analysis with modale superposition

[DZ_Ingineer]

hello there, i need to know how to proceed with a transient analysis based on modal superposition with the optimale modal base, i tried to select all the modal base witch contains 60 modes and the response of the system was exactly the response of a full transient analysis, however,when i wanted to select the optimale modal base depending on modes effectives masses (90% of total system mass) i tried with 'modseloption' and 'Mxpand' commands but i can't figure how to expand only the most significant modes PLEASE HELP.
you will finD attached an APDL script for my problem.
THANKS IN ADVANCE

 

[Shu Jiang PEng SE]

Try to add the following two commands in your file.

mxpand,,,, yes,,, MODM !mode selection is based on the modal effective mass
modseloption,0.9 .90, 0.9,no, no,no, !direction X, Y and Z are selected, a minimum of 90% of the total mass is requested in this direction

 

[DZ_Ingineer]

thank you very mush jiang, however i can't figure how to apply this creterion, i tried to apply this commands after the modal analysis is finished but there is an error witch says:''participation factor values are not on the mode.file'', so i tired to apply them before the analysis but there is no mode.file to apply the creterion on.
my regards.

 

[Shu Jiang PEng SE]

Perform modal analysis first to get the *.mode file.