I want to do modal analysis for my model ( Concrete tower 21 floor) using (seismic pseudo model(ritz))
So , my inquiries as following :
01 . Which mass matrix , I have to use to get more accurate results ?
02. Shall I activate (click on ) the ( disregards density ) and ( sturm check ) when I start run to my model ? knows that the structure mass will be (100% dead loads + 25% live loads only for parking area)
Thanks in advance
Most accurate is consistent I believe. But we normally use lumped with rotations.
If you disregard density there will be no mass participating in the modal analysis. Unless you add it back in via load to mass conversion.
I would NOT disregard density, and also add 30% live load (or whatever percentage) to the load to mass conversion. Normally can ignore Z direction. If you add mass to global or dynamic the mass will be added to all dynamic cases. If you specify the modal case only, it will only be added to that case.