Modeling in ETABS

[meistersd]

Hello,

When analyzing a building in ETABS, deflection can be seen only for the topmost storey as shown in the picture that I have attached along with this thread. Can anybody tell me what might be the reason for this and what is the solution for this??

 

[Trenno]

You've got a modal displacement shown, which suggests there may be something amiss on your top floor. That and your scale may be misleading if something is greatly moving on the top floor relative to the lower floors.

What is the fundamental period? Rules of thumb say that the fundamental period should be roughly Height (m) / 46.

Perhaps try deflection under a lateral load case.

 

[JoshPlumSE]

Is the stiffness of the roof different than the stiffness of other floors?

If the roof were made of plywood and the other floors of concrete then you'd expect to see a much more flexible vertical mode for the roof.