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Transient analysis with modale superposition

Transient analysis with modale superposition

Transient analysis with modale superposition

(OP)
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

RE: Transient analysis with modale superposition

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

RE: Transient analysis with modale superposition

(OP)
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.

RE: Transient analysis with modale superposition

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

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