Local buckling of cold formed steel sections filled with concrete

This paper investigates the local buckling behaviour of cold formed steel sections which have been constructed with a concrete infill. The beneficial effect of the restraint offered by the rigid concrete medium is modelled using a semi-analytical finite strip method. The finite strip method employs the use of a nonlinear model to represent the stress-strain characteristics of the cold formed steel. The analysis also considers the effect of residual stresses caused through the cold-working process, in addition to the increased longitudinal yield stress which occurs in the vicinity of the bent regions. A thorough parametric study is undertaken in this paper to consider the effects of yield stress and residual stresses for various boundary conditions. The results of the analyses show that after careful consideration of the regions of increased yield stress coupled with the accurate modelling of the residual stresses, that the effects of these issues can be considered to be negligible. This leads to the ability to design for local buckling of cold formed steel sections filled with concrete using elastic local buckling coefficients. The paper concludes with some design suggestions for local buckling and areas of further research which may be necessary.