Transient modale superposition analysis
 

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 it worked, eventhough when i wanted to select the optimale modal base depending on modes effectives masses 90% of total system mass it does not work:confused:, i tried with 'modseloption' and 'Mxpand' commands but i can't figure it out, PLEASE HELP:)