Number of modes for modal analysis

[Anonymous]

I'm having trouble with the number of modes for the model attached. I have already gone to 200 modes and the percentage of mass is around 70%. I don't know if there is an error with the model or if I should keep adding modes. Thanks for the help.

[Rafal.Gaweda · Accepted solution]

Hi @Anonymous

With such model definition we have not bee able to get more than 74% with 500 modes.

I think it is related to locating supports on different levels, especially on Storey 1 and 2 ; these supports block slab masses.

As a test : if you remove supports from Storey 2 level you will reach 90% using 264 modes ; if you replace supports on this level by support with fixed only UZ  - 266 modes.