Etabs multiple towers

[Abhinai]

may i know if there is any way in etabs to find out the model time periods of the two buildings separately in a multiple tower file.
The two buildings are modeled in separate grids in multiple tower option

 

[vhengr]

I doubt,if Etab/any software (based on stiffness matrix) could distribute the auto lateral seismic force accurately between floors; though it can handle multiple towers in one file.


Nonethelessly; you can ve some useful information regarding the topic at below site.

https://wiki.csiamerica.com/display/etabs/ETABS+Modeling+FAQ

What should be considered when modeling multiple towers in the same file?

Answer: A few notes which concern the modeling of multiple towers in a single file include:
Diaphragms – Different diaphragms should be defined and used for each tower.
Loading – For seismic loading ,do not use a Seismic Auto Lateral Load type , use User defined seismic loads , perform a Response Spectrum or Time History analysis instead.

Vertical systems – In terms of height, unbraced length, response, and all other factors, design of columns and shear walls should proceed as normal.


Cheers! -VH

 

[Abhinai]

Thank you

 

[JoshPlumSE]

Dumb question, but why not just look at the mode shapes. That will tell you which mode is which, right?

Theoretically, you could create a different load combination for the mass of each tower. That way, you run the eigensolution with just mass of the one tower and you get only the modes for that tower.

 

[Agent666]

The separate loads would only be accurate if there is little or no interaction between the two towers. If you have a common podium type structure this will mean some interaction is possible, i.e. one towers dynamic response affects the other to some degree.

Looking at the mode shapes and mass participation should give you a good idea of the periods associated with each superstructure.