Strange Mode shapes in ETABS

[VillegasST]

Colleagues:

I am modeling a 6500 m2 footprint building that has 2 levels and one partial basement. Intermediate level is an interstitial structure for cable tray, HVAC ducts, lighting fixture, and piping support. The second level is the roof. This building is a warehouse with a Datacenter.

After running the model, it shows that fundamental mode shapes are local for beams. Beams shape modes look like the strings of a guitar. "Fundamental translational" mode is #16 and it has the main participation factor.

Do you have any idea of how to avoid those local modes?

Thanks!

 

[slickdeals]

Something's wrong. Have you cheecked the beam properties, that is stiffness for it to span a distance. Are the beam mode shapes cantilever type? Maybe there is some fixity issue. Any chance you can post the model?

 

[VillegasST]

Thank you, I hace checked border conditions and those beams are fixed. I am attaching the model, could you please give me your opinion?.
Thanks!