Buckling of Tank Roof Columns

[EloyRD]

Hello, comunity:

I'm in the middle of the calculations of the columns that support a Cone Roof.

I'm having problems deciding for the k factor to compute the slenderness ratio:
- I visualize the contact area of the roof as a FREE boundary condition.
- I can't decide if the connection with the bottom as per API 650 are a HINGED or CLAMPED boundary condition.

Any help in visualizing this would be extremely helpful. Does anyone has seen a buckling failure of a roof column? How does it deforms at the bottom end?

Thanks for any commentary.

Kind regards.
Eloy Ruiz

 

[JStephen]

I assumed pinned at each end. There's some restraint at the bottom, but it's an undetermined amount, so it's neglected. The details at the top are usually sufficient to keep the top end where it's supposed to be.

 

[EloyRD]

Dear JStephen,

Thanks for the information.

According to your suggestion, the roof support columns could be calculated with an engineering k factor of 1.2 for slenderness calculations.
Would you say that it's safe to assume pinned ends even if the slenderness of the columns is low because of a short tank?

Kind regards.
Eloy Ruiz