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

constrained Finite Strip Method (cFSM)

The constrained finite strip method, or cFSM, is now implemented in our software CUFSM. Go download the software and give it a try. Using formal mechanical definitions of the buckling classes: global, distortional, local, and other deformations, the constrained finite strip method can provide both modal decomposition (see second figure below) and modal identification (see third figure below) to a conventional finite strip solution. Modal decomposition allows the conventional finite strip solution to be focused on any buckling class (e.g., global, distortional, or local only), resulting in problems of reduced size and definitive solutions for the buckling modes in isolation, as demonstrated for an example section. Modal identification allows the results of a conventional finite strip solution to be judged with regard to the participation of the buckling classes; and thus provide a measure of buckling mode interaction. The conventional finite strip method combined with the constrained finite strip method provides a powerful tool for understanding cross-section stability in cold-formed steel members.

A recent paper discussing the implementation of cFSM into CUFSM is immediately available for download: Schafer, B.W., Ádány, S. “Buckling analysis of cold-formed steel members using CUFSM: conventional and constrained finite strip methods.” Eighteenth International Specialty Conference on Cold-Formed Steel Structures, Orlando, FL. October 2006. (pdf). See the references below for our current research report and recent publications.

Conventional FSM stability solution

Decomposed cFSM stability solution, note that separate analyses now can exist for local, distortional, or global buckling - solution size for decomposed analysis is smaller and the analyst can focus on one stability mode at a time

modal identification results for the same analysis as above, note that relative contributions of the local, distortional, and global deformation modes depends strongly on half-wavelength.

cFSM References

See the online publications list for the most up to date listing of our publications.

Ádány, S., Schafer, B.W. (2006). “Buckling mode decomposition of single-branched open cross-section members via finite strip method: derivation.” Elsevier, Thin-walled Structures Journal. 44 (5) 563-584.

Ádány, S., Schafer, B.W. (2006). “Buckling mode decomposition of single-branched open cross-section members via finite strip method: application and examples.” Elsevier, Thin-walled Structures Journal. 44 (5) 585-600.

Ádány, S., Joó, A., Schafer, B.W. (2006). “Approximate identification of the buckling modes of thin-walled columns by using the modal base functions of the constrained finite strip method.” International Colloquium on Stability and Ductility of Steel Structures, Lisbon, Portugal, September 6-8, 2006. (Submitted)

Ádány, S., Silvestre, N., Schafer, B.W., Camotim, D. (2006). “Buckling Analysis of Unbranched Thin-Walled Columns using cFSM and GBT: A Comparative Study.” International Colloquium on Stability and Ductility of Steel Structures, Lisbon, Portugal, September 6-8, 2006.

Schafer^†, B.W., Ádány, S. “Modal decomposition for thin-walled member stability using the finite strip method.” SMCD 2006, May 14-17, 2006, University of Waterloo, Waterloo, Ontario, Canada.

Ádány^†, S., Silvestre, N., Schafer, B.W., Camotim, D. “Buckling Analysis of Unbranched Thin-Walled Columns: Generalised Beam Theory and Constrained Finite Strip Method.” Third European Conference on Computational Solid and Structural Mechanics: Solids, Structures and Coupled Problems in Engineering (ECCM-2006), Lisbon, Portugal, June 5-8, 2006.

Schafer, B.W., Ádány, S. (2005). “Understanding and classifying local, distortional and global buckling in open thin-walled members.” Annual Technical Session and Meeting, Structural Stability Research Council, May, 2005. Montreal, Quebec, Canada.(pdf) (ppt of presentation)

Ádány, S., Schafer, B.W. (2005). “Mechanics-based modal identification of thin-walled members with multi-branched cross-sections.” McMat 2005, 2005 Joint ASME/ASCE/SES Conference on Mechanics and Materials, Baton Rouge, Louisiana. (ppt of presentation)

Ádány, S. (2004). “Buckling mode classification of members with open thin-walled cross-sections by using the finite strip method.” Research Report, Department of Civil Engineering, Johns Hopkins University, Baltimore, MD, USA. (pdf)

Ádány, S., Schafer, B.W. (2004). “Buckling mode classification of members with open thin-walled cross-sections.” Fourth International Conference on Coupled Instabilities in Metal Structures, Rome , Italy , 27-29 September, 2004 (pdf )