Flexural-torsional buckling behaviour and resistances of fixed-ended press-braked S690 high strength steel angle section columns

Abstract

The flexural-torsional buckling behaviour and resistances of fixed-ended press-braked S690 high strength steel angle section columns have been studied based on testing and numerical modelling, and reported in this paper. A testing programme, employing four different equal-leg angle section sizes, was firstly conducted, and comprised material tensile coupon tests, initial global and torsional geometric imperfection measurements and twelve fixed-ended column tests. The column test setup and procedures were thoroughly presented, and the key obtained test results, including the failure loads and deformations at the failure loads, load–end shortening curves, load–mid-height torsional rotation curves and failure modes, were fully reported and discussed. This was followed by a numerical modelling programme, where finite element models were initially developed to simulate the experimental responses and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member lengths. The obtained test and numerical data were then used to evaluate the accuracy of the relevant codified design rules, given in the European code, North American specification and Australian/New Zealand standard, and a recently proposed DSM-based design approach. The results of the evaluation revealed that all the codified design rules yield excessively conservative and scattered flexural-torsional buckling resistance predictions for fixed-ended press-braked S690 high strength steel angle section columns, while the DSM-based design approach leads to 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.