A structural engineer is designing a cold-formed steel (CFS) stud wall for a commercial building. The studs are 6-inch deep, 16-gauge (0.0596 inches thick) C-sections at 16 inches on center. The wall is 12 feet tall and is braced against lateral displacement at the top and bottom. The design requires checking for stud buckling. Which of the following buckling modes is typically critical for slender compression members like CFS studs before reaching their yield strength?
- ADistortional Buckling
- BLocal Buckling
- CFlexural Buckling
- DTorsional Buckling
Show answer & explanationAnswer & explanation
Correct answer: C. Flexural Buckling
For a slender compression member like a CFS stud, flexural buckling (also known as Euler buckling for ideal columns) is often the critical global buckling mode where the member bends about its weakest axis. Local buckling involves buckling of individual plate elements (flanges, web) before the entire cross-section buckles, while distortional buckling involves rotation of the flange-web junction. Torsional buckling involves twisting of the entire member. Without continuous restraint, flexural buckling of the entire stud is a primary concern.
Why the other options are wrong
- A. Distortional buckling involves the rotation of the flange-web junction and is also a local phenomenon, but distinct from general flexural buckling of the entire member.
- B. Local buckling affects individual plate elements of the cross-section, not the overall member stability in bending.
- D. Torsional buckling involves the twisting of the entire member, which can occur, but flexural buckling is often critical for typical stud sections.
Flexural Buckling (CFS Studs)
A global buckling mode in slender compression members, where the entire member bends or deflects laterally about its weakest axis under axial compressive load.
- Also known as Euler buckling.
- Governed by the member's slenderness ratio and modulus of elasticity.
- Often critical for unbraced lengths of CFS studs.
Memory trick: CFS studs buckle locally, distortionally, or globally.