Buckling vs. Yielding Failure of Columns

Question

As I have been working through examples of construction projects, I've noticed that in nearly every case of a structural column (sample size considers only homogeneous material columns, no composite structures) the materials chosen to construct the beam will yield before the beam design chosen will experience Euler buckling. I may not be considering all use cases but is it easier (or more likely, safer) to design for yield failure modes than for buckling failure modes?

Perhaps manufacturing tolerances on mass produced steel beams are sloppy enough compared to material composition that it requires a larger Factor of Safety?

Answer 1

The basic Euler buckling formula is unrealistic because it implies perfect geometry and perfect alignment of the loads. Therefore a large empirical safety factor is required.

It is also a potentially catastrophic failure mode, in the sense that the buckled column supports no load at all, unlike plastic failure in compression for example.

There are situations where it makes sense to design light weight structures with buckling failure at the limiting loads, but civil engineering is not one of them - there are far too many unknowns.

Answer 2

Yes, it is better to design for yield than buckling because Euler buckling is a result of instability as opposed to overloading force. Gamma f is determined from Eurocodes which are from extensive research and materials testing. This means yield is safer than buckling because buckling is not predictable nor easily counteracted in design. It also would mean the engineer had not applied the correct factor of safety for the structure or that the moments of force were incorrectly accounted for.

Answer 3

The code has prescribed how to design a column, wood, steel alloy, or many common materials, depending on their effective length and slenderness, the radius of gyration, and the eccentricity of axial load and type of connection.

Short columns fail under the crushing, mid-range columns should be considered for both crushing and buckling, long columns have to be checked for buckling. Each code has a set of load combinations and each of these combinations has its own way of handling the ultimate buckling load.