Hakan, I have the same problem, there is no undefined floor in my construction except the elevator shaft, all floors are created, I entered semi-rigid in my analysis setting inputs, but since there are floors without rigid diaphragm, he talks about the response spectrum?[/quote ] Hello If there is no diaphragm (floor) formation on any of the floors, it is normal that the message "There are floors without rigid diaphragm..." in the Analysis status window. If you are getting this message even though there are floors on all floors, you need to attach the project file.