Geometric imperfections in CFS structural members: Part I: A review of the basics and some modeling strategies

• Published in: Thin-walled structures Vol. 186; p. 110619
• Main Authors: Farzanian, S., Louhghalam, A., Schafer, B.W., Tootkaboni, M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2023
• Subjects: CFS structural members; Elastic buckling modes; Geometric imperfection models; Modal characterization; Shell FE collapse analysis; Elastic buckling modes; Shell FE collapse analysis; Geometric imperfection models; CFS structural members; Modal characterization
• ISSN: 0263-8231; 1879-3223
• DOI: 10.1016/j.tws.2023.110619

Unavoidable geometric imperfections complicate the load–displacement response of thin-walled cold-formed steel (CFS) structural members. While the inclusion of geometric imperfections in shell finite element (FE) collapse simulations has long been the subject of research, no consensus exits on modeling their full three-dimensional spatial pattern. This paper is the first part in a two-part series and provides a review of the basics and a summary of some efforts geared towards modeling geometric imperfections. We discuss the necessary ingredients for systematic characterization of elastic buckling mode shapes, due to their frequent use in approximating geometric imperfections, and make a conscious effort to express some of the existing geometric imperfection models through three components: imperfection shape, magnitude, and combination coefficient. Different choices and selections of these components, pertaining to either the inherent buckling behavior of the members and/or physical measurements are critically examined. The details required to develop high fidelity nonlinear FE models of CFS members seeded with geometric imperfections are presented. We then perform a comparative study of collapse analysis results obtained from adopting different imperfection modeling strategies. The noticeable variability in the load carrying capacity and the stability behavior highlights an urgent need for reliable probabilistic frameworks for this class of problems. A stochastic framework to generate samples of imperfect shell FE models from limited available data and validate the prescribed or practice-oriented geometric imperfection models is presented in a companion paper (see Part II Farzanian et al., (2023)). •The role of geometric imperfections in nonlinear behavior of CFS members is studied.•The links between buckling modes, geometric imperfections, and nonlinear response of CFS members are established.•A unified view of common geometric imperfection modeling strategies is provided.•The impact of the choice of imperfection model on nonlinear response and collapse behavior is explored.