Finite Element Modelling and Parametric Studies of Perforated Thin-Walled Steel Columns (No. R948)

Abstract

This report presents a comprehensive parametric study on the ultimate strength of perforated cold-formed steel columns using the Finite Element package ABAQUS. FE models were first developed for columns predisposed to local (L), distortional (D) and global (G) buckling failures respectively. Modelling issues such as boundary conditions, meshing, initial imperfections, material models, and non-linear solution controls in FEA were addressed. The FE models were validated against documented experiments and also theoretical solutions. The parametric study involved five cross-section types (i.e. C, stiffened C, Z, rack, and hat sections), five widths of holes, four lengths of holes, four spacings of holes, three material properties, and three buckling modes (i.e. L, D, and G) and all the possible interactions between them (i.e. LD, LG, DG, and LDG). Ultimate strengths, as well as failure modes, were obtained from the analyses and are plotted against the current codified DSM in AS/NZS 4600:2005. Significant discrepancies between the numerical results and the DSMpredicted strengths were observed due to the influence of holes, and more severely, the interaction of buckling modes, and occasionally, the inherent limitations of the DSM itself. The effects of column length, material properties, centroid shift due to perforation were also discussed. A data pool including 146207 column ultimate strengths was obtained which was used to formulate new design equations for perforated thin-walled columns based on the Direct Strength Method, as presented in another report (Yao and Rasmussen 2014).