Torsional Mode Shapes

[slickdeals]

Folks,
I am trying to create an idealized model of a tall building using a single column element.

Is there a way to capture torsional mode shapes? Will there be modal correlation between the 3D model and a simplified model?

Has anyone done such an exercise before? Are there any references?

 

[prsconsultant]

Is there a way to capture torsional mode shapes?

No.

Will there be modal correlation between the 3D model and a simplified model?

Probably not.

Has anyone done such an exercise before?

What is the rationale behind your study? Is this for a quick and dirty analysis?

 

[slickdeals]

prs:
I have a model from another engineering company that has a lot of shell elements.

The slab has been meshed very finely in order for it to contribute towards lateral stiffness. I am talking about 50000 individual shell elements. The building is 63 stories.

Is there a way to approximately calculate the lateral stiffness of the slab and then do some magic (i am out of ideas) to account for the slab stiffness in the lateral frame?

The model is in ETABS and can anyone think of finding a way to model the lateral stiffness offered by the slab without exolicitly modeling and meshing it?

Thanks

 

[prsconsultant]

slickdeals:

We do a number of ETABS models for highrise structures. We only do a finer meshing of slabs where we expect the slab to crack significantly. Rest of the slab is modeled with minimal number of elements.

50000 elements sounds way out of range. Just as a quick check you can model the slab as rigid diaphragm and see how much of a difference the slab stiffness makes.