professor ben schafer's thinwalled structures research group  johns hopkins university 
Distortional Buckling of ThinWalled Columns
Note: The research reported on this page was from a project sponsored by the American Iron and Steel Institute, and concluded in the summer of 2000.
Related paper published in ASCE Journal of Structural Engineering March 2002 issue Schafer, B.W. (2002). "Local, Distortional, and Euler Buckling in Thinwalled Columns." ASCE, Journal of Structural Engineering. 128 (3) 289299. (This paper won the 2003 ASCE Collingwood Prize!) (pdf)
From the introduction of the report on Distortional Buckling of Columns. ...
Distortional buckling, also known as "stiffener buckling" or "localtorsional buckling", is a mode characterized by rotation of the flange at the flange/web junction in members with edge stiffened elements. In members with intermediately stiffened elements distortional buckling is characterized by displacement of the intermediate stiffener normal to the plane of the element. This study focuses on distortional buckling of members with edge stiffened elements.
Distortional buckling may be directly studied by finite strip analysis. Consider the finite strip analysis of a lipped C in pure compression, Figure 1. The analysis proceeds by finding the lowest buckling mode at a variety of different longitudinal half sine waves (halfwavelengths). The minima of the curve reveal different buckling modes that exist for the member. In this case, distortional buckling exists at an intermediate halfwavelength, between local buckling and long halfwavelength flexural or flexuraltorsional buckling. This intermediate length is a defining characteristic of distortional buckling.
As Figure 1 shows, for a typical lipped C member in pure compression local buckling often occurs at a lower buckling stress than distortional buckling. If the local buckling stress is significantly lower than the distortional buckling stress then it is possible that distortional buckling may be safely ignored. However, many situations exist in which distortional buckling must still be considered, even in routine design.
Distortional Buckling of Columns Report (August 2000) Main report and all appendices (zip) Main Report (pdf) Appendix A: Detailed history of distortional buckling of columns (pdf) Appendix B: Example hand calculations of local and distortional buckling (pdf) Appendix C: Detailed elastic buckling results (pdf) Appendix D: Design examples for considered methods (pdf) Appendix E: Ultimate strength results (pdf) Appendix F: Recommended specification changes (pdf)
Reference for above report: Schafer, B.W. (2000). Distortional Buckling of ColdFormed Steel Columns. Final Report to the American Iron and Steel Institute (AISI).
Related references Schafer, B.W. (2001). "ThinWalled Column Design Considering Local, Distortional and Euler Buckling." Structural Stability Research Council Annual Technical Session and Meeting. (Paper) (Presentation)
Schafer, B.W. (2002). "Local, Distortional, and Euler Buckling in Thinwalled Columns." March issue of Journal of Structural Engineering, ASCE.
last updated 07/19/05
