Thin-Walled Structural Members; A Complete Cold-Forming Computer Simulation
Authors:   , Alizadehhesari Kaveh 
Published: October 2024

Cold-Formed Steel (CFS) sections are widely used in contemporary structural steel applications. However, the use of stainless steel as a structural material has increased in recent years to take advantage of its particular properties like being corrosion and fire resistance. The greatest structural advantage of thin-walled cold-formed members is the thinness of the sections, offering high strength/stiffness to weight rations. However, this advantage may be limited since the thin walls of these types of sections make the member more susceptible to buckling failure modes. Further, perforations are commonly placed in the web of cold-formed steel columns to accommodate plumbing and electrical facilities. The use of cold-formed stainless steel profiles with perforation as a structural building material has limitations due to the lack of knowledge of structural behaviour of these members. Due to limitations and difficulties of experimental measurements, Finite Element modelling is a reasonable alternative. Regarding thin-walled cold-formed steel members, generally geometric and material nonlinear analyses are applied on an imperfect member to assess its ultimate resistance and structural response. A successful simulation is largely dependent on the inputs and sensitive parameters such as material properties and geometric imperfections. During the manufacturing process of cold-formed sections, steel sheets undergo plastic deformations which results in enhanced strength, formation of residual stresses and reduced ductility. These changes in the cross sections could affect the structural behaviour of the sections. On the other hand, all real thin-walled cold-formed steel members have geometric imperfections, which could significantly influence the buckling behaviour. Therefore, the response of a structural member is dependent on the distribution, shape and magnitudes of imperfections. The main aim of this research programme is to investigate the structural behaviour of thin-walled cold-formed stainless steel lipped channel sections subjected to axial compression load while the inherent material characteristics such as work hardening in the corners and initial imperfections are considered in numerical modelling. The research also addresses the lack of experimental data available on thin-walled cold-formed stainless steel with perforations. In this research, tests were conducted on austenitic stainless steel sheets to assess the material properties. Lipped channel columns were tested between pinned end conditions with and without perforations under compression load. The initial imperfections of each specimen were measured prior to loading tests. A numerical study was developed to generate additional data on the buckling of stainless steel columns. An in-depth parametric study focusing on cold-formed lipped channel sections under compression load with pinned end conditions was carried out on a range of specimens with varied section and member slenderness. Non-linear finite element models were created to simulate the column tests conducted in experiments. These models incorporate the material characteristics of stainless steel, including non-linear stress-strain behaviour and work-hardened corners. Imperfections were represented by approximating imperfection measurements into nodal coordinates using modal analyses. Overall, it was shown that numerical investigations can be used to obtain a reliable understanding of structural buckling behaviour with a reasonable degree of confidence. The investigation revealed variations in the buckling strength of the structure under compression due to the presence of perforations.