professor ben schafer's thin-walled structures research group - johns hopkins university

Distortional Buckling of Thin-Walled Beams

AISI project: Distortional Buckling of C and Z Members in Bending, Phase 2


Note: the research reported on this page is based on sponsored research conducted with the American Iron and Steel Institute which completed in January 2005. 



Laterally braced cold-formed steel beams generally fail due to local and/or distortional buckling in combination with yielding. For many cold-formed steel studs, joists, purlins, or girts, distortional buckling may be the predominant buckling mode, unless the compression flange is partially restrained by attachment to sheathing or paneling. Distortional buckling of cold-formed steel C and Z members in bending remains a largely unaddressed problem in the current North American Specification for the Design of Col-Formed Steel Structural Members (NAS 2001). Further, adequate experimental data on unrestricted distortional buckling in bending is unavailable. Therefore, a series of distortional buckling tests on C and Z members in bending has been completed at the structural testing lab of Johns Hopkins University. These tests are essentially the extended research (phase 2) of a recently completed experimental project on local buckling of C and Z beams (phase 1, as summarized in Yu and Schafer 2003). This second phase of four point bending tests use nominally identical specimens to the first phase and a similar testing setup. However, the corrugated panel attached to the compression flange is removed in the constant moment region so that distortional buckling may occur. The experimental data is being used to help develop and validate an efficient and reliable design procedure for C and Z members in bending. Further, the experiments are being combined with detailed non-linear finite element modeling in order to make it possible to extend the findings into a broader range of section dimensions, material properties, restraint, and loading conditions.


Project Materials

Proposed work (pdf file) (June 2003)

Progress Report 1: Presentation at AISI-COS meetings (ppt file) (July 2003)

Progress Report 2: Presentation at AISI-COS meetings (ppt file) (pdf report) (February 2004)

Progress Report 3: Presentation at AISI-COS meetings (ppt file) (pdf report) (August 2004)

Final report. (pdf report) (January 2005)


Selected References

Yu, C., Schafer, B.W. (2004). “Distortional Buckling Tests on Cold-Formed Steel Beams.” 17th International Specialty Conference on Cold-Formed Steel Structures, Orlando , FL (pdf)

Yu, C., Schafer, B.W. (2004). “Stress Gradient Effect on the Buckling of Thin Plates.” 17th International Specialty Conference on Cold-Formed Steel Structures, Orlando , FL (pdf)


Related work

Local buckling of C's and Z's in bending (phase 1 of this project)

Distortional buckling of columns (an earlier project on columns)

Direct Strength Method (includes design checks for distortional buckling)

see the publications list for more related work, including links to articles.


last updated 07/19/05