length Flexural-torsional buckling of pin-ended press-braked S690 high strength steel angle section columns: Testing, modelling and design

This paper presents an experimental and numerical investigation into the flexural-torsional buckling behaviour and resistance of pin-ended press-braked S690 high strength steel angle section columns. An experimental programme was firstly conducted and included initial geometric imperfection measurements and twelve pin-ended column tests. The column test results, including the failure loads and deformations at the failure loads, load-mid-height torsional rotation curves and failure modes, were fully reported and discussed. The experimental programme was accompanied by a numerical modelling programme, where finite element models were developed and validated against the test results and then employed to perform parametric studies to expand the test data pool over a wider range of cross-section dimensions and member lengths. The obtained test and numerical data were then used to assess the relevant codified design rules, as provided in the European code, North American specification and Australian/New Zealand standard, and a DSM-based design approach. The assessment results revealed that all the codified design rules lead to excessively conservative and scattered resistance predictions for pin-ended press-braked S690 high strength steel angle section columns susceptible to flexural-torsional buckling, while the DSM-based design approach yields substantially improved resistance predictions, owing to the rational consideration of the length-dependent characteristic of flexural-torsional buckling and the interaction of flexural-torsional buckling with minor-axis flexural buckling.