A THEORETICAL INVESTIGATION OF THE COLUMN BEHAVIOR OF COLD-FORMED SQUARE HOLLOW SECTIONS

An experimental programme investigating the column behaviour of four sizes of square hollow section was undertaken at the University of Sydney using Australian produced cold-formed square hollow sections. Stub and pin-ended column tests were performed and detailed measurements of the yield stress and residual stress taken around the sections. A large deflection elastic-plastic finite strip analysis including the measured distributions. of yield stress and residual stress is used to investigate the behaviour of the stub and pin-ended columns. In particular, the influence of the measured through thickness residual stress components on the ultimate load and behaviour of the square hollow section columns is demonstrated. The analysis accounts for plate geometric imperfections, the variation of yield stress around a section, the stress-strain characteristics of the material forming the section and the highly complex patterns of residual stress produced by the cold-forming process. Comparison of the analytical results with the test results is provided.