Frequency of Risa Models supporting screens

[eit09]

I currently am designing a structure that is supporting two screens with running speed of 840RPM (Freq 14HZ). I usually set up 4 separate models to show that the models frequencies are about 30% above or below the screen frequency i.e. avoiding resonance. I check X, Y, & Z direction frequencies from RISA3D. The first model is the full structure including foundation. The second model is the elevation supporting the screens and whatever is above. The third model is the screen support members along with the members supporting the screen support members. And the 4th model is only the screen support members. I am curious to see how others approach these frequency checks using Risa3D? I have found numerous texts on machine foundation & vibration but not much on elevated machines in structures. Any one come across a good reference.

 

[JoshPlumSE]

EIT -

I think your method works. You could probably be able to do the same thing using one model. After all, it is a decent amount of additional work creating the 3 models to represent the 3 behaviors that you're looking for.

There's an advantage with your method in that you don't have to spend much time thinking about which mode represents which behavior. But, then you really don't get to seen any effects of modal interaction. So, it's got benefits and draw backs.