We have model a underground sump tank, with an internal separation wall and on top of slab, 4 pumps are mounted.
Time history analysis is performed in STAAD, to calculate the allowable velocities, amplitudes, and natural frequency, the mass participation we are getting is 45% only, we are trying to get the mass participation to 90% but we are unable to get it, we need guidance to achieve it 90%.
Thanks Amitava for your response, we have already tried by keeping the CUT OFF MODE SHAPE to 100 also, but we could not get the mass participation to 90%.
The STAAD file is attached for your review. Please check and let us know the problem.
Sump (Dynamic Analysis Model).std
We have done some changes in the input file - mainly enhanced the time-history definition, and also override the default values of Cut Off Mode Shape, Cut Off Frequency. Please refer the attached modified STAAD Input File. This gives around 97% mass participation factor in X- and Z- directions.
Sump-Ray.std