Hi,
I've currently modelled a 22 story building and period of the structure doesn't look right (I'm getting over 3 s for the first natural period, while I would expect around 1.5 s).
Also, I can't find any mode with mass participation over 90% (all of them are less than 50%).
(file uploaded)
Please advise.
I can't find the uploaded model. Can you please upload it?
If the diaphragms are semi-rigid then the masses are spread over the full diaphragm and it can be harder to get enough mass participation. If the diaphragm is highly flexible, or worse sloped, then long modes representing diaphragm waves can happen. You can usually see this using Process - Results - Mode Shapes. Check out eignevalue and semi-rigid diaphragm posts below for more. communities.bentley.com/.../ramss-eigenvalue-error.aspx communities.bentley.com/.../ram-ss-semirigid-diaphragms.aspx