No Buckling

[TonyD71502]

Greetings,

I have a question regarding column buckling. I have a tower with four posts that are tied together with horizontal members. When I put an excessively large, non-eccentric, axial load on the posts, the columns do not buckle. It seems that the columns just keep compressing. Even with a single vertical column loaded at the top, it doesn't ever buckle. The four post example had all pin bases and the single column example had a fixed base. I realize that with a slight bit of eccentricity on the load, the column would buckle.

Basically we are going to be destructive testing a four post scaffold tower using hydraulic jacks to apply the force to the posts. We will apply force until the scaffold fails, and obviously the columns will buckle between the horizontals. Staad does not represent this.

Forgive if this is a newbie question, I'm still figuring out all of the angles with this program.

 

[SethGuthrie]

While STAAD.pro Advanced analysis can do a non-linear buckling analysis, but it's not something you get from general linear-elastic finite element analysis, which is the default for STAAD.pro and most other programs.

 

[JoshPlumSE]

I have to admit that I've never tested this out with STAAD.

But, if STAAD is doing a decent P-Delta analysis and you have any initial lateral displacement, then you should see the structure buckle or diverge. Alternatively, you could get a solution error about the geometric adjustment to the stiffness matrix.

But, capturing of elastic buckling doesn't usually require much more than a decent P-Delta analysis + modeling in some initial displacements.