Hi friends,

Folk supports are used in the lateral torsional buckling analysis of timber, steel and precast concrete beams.

Whether the supports are folk supports or not has a huge impact on the buckling resistance of the beams.

In this newsletter, you’ll learn what folk supports are, and I show you 5 examples of supports which are and are not folk supports.

What Exactly is a Fork Support?

Short explanation: The term fork support means that, at support, the beam is prevented from twisting around its longitudinal axis.

I think it took me 1-2 years of professional experience to fully understand what a fork bearing is.

And I still discuss it with my colleagues in the office from time to time: Is this a fork support or not?

Even when checking other people’s reports, I often see that this boundary condition is entered incorrectly in the structural design software.

In my opinion, the problem is that the boundary conditions of calculation examples at university are usually given. For example, you have to verify a simply supported IPE steel beeam with fork supports for lateral torsional buckling.

But how must the connection of the IPE beam to the column be designed so that it can be calculated as a fork support?

You’ve finished your bachelor’s or master’s degree, and you’re doing structural analysis for the first time.

Then, in software programs such as MB Statik, Frilo, or Polybeam from PolyStruc, you have to select the support type, such as fork support, horizontally supported at the top or bottom, or unsupported.

I always found it very difficult to determine if a beam at risk of buckling horizontally is supported by a fork or at the top—because you don’t learn that at university.

After a few projects and some professional experience, you’ve seen a few connections, and you slowly begin to understand the bearing types.