07.26: Structural analysis of C and I shaped cold‐formed steel columns

Abstract

ABSTRACTThe market share of light steel framing construction using cold‐formed profiles has been increasing significantly in recent years; this solution is now recognized as suitable to be used as primary structural elements, particularly for residential and mid‐rise buildings. One of the main advantages of this construction typology is related to the very low weight of the individual elements which avoids the use of heavy lifting machinery. However, due to the reduced thickness of the individual plates that compose the cold‐formed steel columns (CFS) element cross‐section, CFS are susceptible to local and distortional buckling (or even a combination of both) in addition to the more common global element buckling, which may compromise their load carrying capacity.This paper explores the behaviour of two distinct CFS cross‐sections under compression, namely a single C section (lipped channel) and a built‐up I section composed of two lipped channels fastened back‐to‐back. The study briefly reports the experimental full scale tests undertaken at the University of Coimbra in order to assess the load carrying capacity of these columns, considering pinned boundary conditions, while comparing it to the design predictions according to the EN 1993‐1‐3; however, the main focus is on the development and validation of a finite element model enabling further parametric studies.The finite element model is developed with the commercial software ABAQUS using shell elements, and accounts for local, global and distortional geometric imperfections; material non‐linearity is also included based on material characterization previously conducted, and implemented following the Ramberg‐Osgood model. The model is found to be reliable in establishing the buckling loads and the buckling failure modes. A combination of flexural buckling about the minor axis in interaction with distortional buckling at mid‐height of the columns is found to be the main collapse mode, as observed in the experimental tests. The parametric study considers thickness and element length variation.