Numerical modelling of rectangular cold-formed steel and composite columns

Cold-formed hollow sections have a lower resistance capacity than hot-rolled profiles due to their welded seams. However, using design codes for such sections usually leads to an uneconomical and conservative structural design for compressive members. A series of numerical analyses was carried out to understand and evaluate the performance of standard and concrete-filled cold-formed columns. A numerical model was developed and calibrated against experiments, considering residual stresses, initial geometric imperfections and material properties. The developed numerical model was able to represent the experimental results accurately in terms of failure mode, deformed shape and compressive resistance. Based on the results, an alternative buckling curve is proposed for plain steel and steel-concrete composite columns. This design curve was determined from the results of a parametric study and led to the use of new values of the imperfection factor and initial non-dimensional slenderness for the Eurocode design procedure. A reliability index was also evaluated to estimate the scope and validity of the proposed proposed curve.