professor ben schafer's thinwalled structures research group  johns hopkins university 
Computational Modeling of ColdFormed Steel
Computational modeling of coldformed steel, that is modeling coldformed steel members and systems to and through collapse is a central focus of the thinwalled structures research group. This brief page does not provide a complete summary of the breadth of efforts in this area but does provide a 2008 paper and presentation that present a reasonably up to date summary of current efforts.
Excerpts from "Computational Modeling of ColdFormed Steel" CIMS 2008 (paper) (presentation)
Note, the paper was revised and improved and published as a journal article in Thinwalled Structures currently (In Press) August 2010. (doi:10.1016/j.tws.2010.04.008)
Abstract The objective of this paper is to summarize recent research and experiences with computational modeling of coldformed steel conducted within the author’s research group at Johns Hopkins University. This admittedly biased view of computational modeling focuses primarily on the use of the semianalytical finite strip method and collapse modeling using shell finite elements. Issues addressed include how to fully compare finite strip and finite element solutions, and the importance of
in collapse modeling of coldformed steel. The paper concludes with a discussion of areas worthy of future study that are within the domain of coldformed steel modeling.
1 Introduction Modeling coldformed steel, particularly through collapse, presents a strongly nonlinear problem with both material and geometric nonlinearity. However, meaningful modeling requires more than a good nonlinear solution scheme and a robust element. Successful modeling requires indepth understanding of the model inputs and their sensitivities, as well the limitations and strengths of the modeling tools themselves. This paper presents a brief introduction to the tools and current issues surrounding computational modeling in coldformed steel, an introduction which is strongly biased by the research experiences within the author’s research group. Thus, this paper does not attempt to provide a comprehensive survey of the computational modeling literature – my apologies to the many excellent researchers who contribute to this area and do not find themselves mentioned herein.
2 Elastic buckling analysis 2.1 Tools Computational modeling of the elastic buckling of coldformed steel members is an important step in understanding the behavior (and even designing) coldformed steel members. Three tools are in regular use in the author’s research group for elastic buckling analysis: CUTWP [1], CUFSM [2], and ABAQUS [3]. The former two are freely available, open source programs distributed by the author, while the latter is a well known general purpose commercial finite element package. CUTWP provides global member stability solutions using expressions based on classical beam theory and Vlasov warping torsion [4]. CUTWP sees regular use in our efforts because it: (i) uses the same mechanics employed in codes and standards; (ii) readily allows for different global effective length factors (KxLx, KyLy, KtLt); and (iii) has been modified to read CUFSM input files. CUFSM, which provides an implementation of the semianalytical finite strip method (FSM), appropriate for coldformed steel members with (locally) pinned boundary conditions (see [5] for another example), is the workhorse of the authors research group. Basic understanding begins with interpretation of the CUFSM buckling analysis of a given member. ABAQUS, is a well known general purpose finite element method (FEM) package; for the purposes of this paper only models built from shell elements are considered for discussion.
Links to full paper and conference presentation
Schafer, B.W. (2008). "Computational Modeling of ColdFormed Steel." Proceedings of Coupled Instabilities in Metal Structures, Sydney, Australia (paper) (presentation)
List of references on computational modeling of coldformed steel
The paper concludes with a number of recent references of interest in this area, these references are provided here for those interested:
[1] Sarawit, A., CUTWP: Cornell University Thinwalled Section Properties. p. December 2006. [2] Schafer, B.W. and S. Adany. Buckling analysis of coldformed steel members using CUFSM: Conventional and constrained finite strip methods. in Eighteenth International Specialty Conference on ColdFormed Steel Structures. 2006. Orlando, FL, United States: University of MissouriRolla, Rolla, MO, 654091060, United States. [3] Simulia, ABAQUS. 2008. [4] Timoshenko, S., Theory of elastic stability. 2d ed. Engineering societies monographs;. 1961, New York: McGrawHill. 541 p. illus. 24 cm. [5] Papangelis, J.P. and G.J. Hancock, Computer analysis of thinwalled structural members. Computers and Structures, 1995. 56(1): p. 157176. [6] Silvestre, N. and D. Camotim, Firstorder generalised beam theory for arbitrary orthotropic materials. ThinWalled Structures, 2002. 40(9): p. 755789. [7] Silvestre, N. and D. Camotim, Secondorder generalised beam theory for arbitrary orthotropic materials. ThinWalled Structures, 2002. 40(9): p. 791820. [8] Adany, S. and B.W. Schafer, A full modal decomposition of thinwalled, singlebranched open crosssection members via the constrained finite strip method. Journal of Constructional Steel Research, 2008. 64(1): p. 1229. [9] Ádány, S., et al., GBT and cFSM: Two modal approaches to the buckling analysis of unbranched thinwalled members. International Journal of Advanced Steel Construction, 2008 (Accepted). [10] Bradford, M.A. and M. Azhari, Buckling of plates with different end conditions using the finite strip method. Computers and Structures, 1995. 56(1): p. 7583. [11] Ádány, S., A. Joó, and B.W. Schafer, Approximate identification of the buckling modes of thinwalled columns by using the modal base functions of the constrained finite strip method, in International Colloquium on Stability and Ductility of Steel Structures, D. Camotim, N. Silvestre, and P.B. Dinis, Editors. 2006: Lisbon, Portugal. p. 197204. [12] Ádány, S., Flexural buckling of thinwalled columns: discussion on the definition and calculation, in International Colloquium on Stability and Ductility of Steel Structures, D. Camotim, N. Silvestre, and P.B. Dinis, Editors. 2006, IST Press: Lisbon, Portugal. p. 249258. [13] Schafer, B.W., Coldformed steel behavior and design : analytical and numerical modeling of elements and members with longitudinal stiffeners. 1997, Cornell University. p. xxiv, 454 leaves. [14] Moen, C.D., Schafer, B.W., Direct Strength Design for ColdFormed Steel Members With Perforations, Progress Report No. 1. 2006, American Iron and Steel Institute. [15] Dawson, R.G. and A.C. Walker, Post buckling of geometrically imperfect plates. 1972. 98(ST1): p. 7594. [16] Gardner, L. and D.A. Nethercot, Numerical modeling of stainless steel structural components  A consistent approach. Journal of Structural Engineering, 2004. 130(10): p. 15861601. [17] Ashraf, M., L. Gardner, and D.A. Nethercot, Finite element modelling of structural stainless steel crosssections. ThinWalled Structures, 2007. 44(10): p. 10481062. [18] Borges Dinis, P., D. Camotim, and N. Silvestre, FEMbased analysis of the localplate/distortional mode interaction in coldformed steel lipped channel columns. Computers and Structures, 2007. 85(1920): p. 14611474. [19] Schafer, B.W. and T. Pekoz, Computational modeling of coldformed steel: Characterizing geometric imperfections and residual stresses. Journal of Constructional Steel Research, 1998. 47(3): p. 193210. [20] Moen, C. and B.W. Schafer, A general prediction method for residual stresses and strains in coldformed steel members, in Fifth International Conference on Coupled Instabilities in Metal Structures. 2008: Sydney, Australia. [21] Dinis, P.B. and D. Camotim. On the use of shell finite element analysis to assess the local buckling and postbuckling behaviour of coldformed steel thinwalled members. in Third European Conference on Computational Mechanics Solids, Structures and Coupled Problems in Engineering. 2006. Lisbon, Portugal.
last updated 08/16/10
