Nonlinear behaviour of built-up cold-formed steel section battened columns

• Behaviour and design of built-up cold-formed steel columns was highlighted.
• Nonlinear 3-D finite element models were developed and reported.
• The finite element models were developed against tests conducted by the authors.
• An extensive parametric study was performed comprising 60 built-up columns.
• The finite element analysis strengths were compared against design strengths.

This paper discusses nonlinear behaviour and design of built-up cold-formed steel section battened columns. The built-up columns were pin-ended and consisted of two cold-formed steel channels placed back-to-back and were connected using batten plates. Nonlinear 3-D finite element models were developed to simulate the structural performance of the axially loaded columns. The nonlinear material properties of flat and corner portions of the channels, initial geometric imperfections, actual geometries and boundary conditions were carefully considered in the models. The finite element models were verified against tests, recently conducted and reported by the authors, on the same form of construction. The column strengths, failure modes, deformed shapes at failure, load-lateral displacement and load-axial strain relationships were predicted from the finite element analyses and compared well against the test results. In addition, the validated finite element models were used to perform an extensive parametric study investigating different parameters affecting the behaviour of the columns comprising different slenderness, column lengths, cross-section geometries, steel strengths, spacing between channels and different batten plates spacing. Furthermore, the column strengths predicted in the parametric study were compared with design strengths calculated using the North American Specification, Australian/New Zealand Standard and European Code for cold-formed steel columns.