Hi, i am analyzing an industrial building, 40m tall with large 300mm thick concrete walls all around the envelope. These walls are shear walls and make up SFRS with couple of other internal walls. All columns and beams are simply supported. Modal analysis with dead weight alone gives warning that mass participation is not satisfatory(about 60%) and time period is 0.21 which is very less. When i add machinery load that is roughly about 10 to 15 % of dead weight modal analysis gives me a very high fundamental period (88 sec) with 95% mass participation. Any clues what is going on?
