Experimental and numerical investigations of press-braked stainless steel channel sections under minor-axis combined loading

Abstract

This paper presents an in-depth experimental and numerical investigation into the behaviour and resistances of press-braked stainless steel channel sections under combined compression and bending moment about the minor principal axis. The experimental programme adopted two press-braked stainless steel channel sections and included initial local geometric imperfection measurements and ten eccentrically loaded stub column tests. The loading eccentricity was varied to achieve a range of ratios of compression load to minor-axis bending moment. Two types of failure mode, namely ‘C’-orientation failure (indicating that failure specimens bent towards the web) and ‘reverse C’-orientation failure (signifying that failure specimens bent towards the flange tips), were observed upon testing. The experimental programme was followed by a numerical modelling programme; finite element models were developed and validated against the test results and then adopted to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and initial loading eccentricities. The obtained test and numerical data were then adopted to assess the accuracy of the current codified design rules for press-braked stainless steel channel sections under combined compression and minor-axis bending, as given in the European code, American specification and Australian/New Zealand standard. The assessment results revealed that the codified design rules yield excessively conservative and scattered resistance predictions, owing to the neglect of the favourable material strain hardening of stainless steel and the beneficial stress redistribution within channel sections under combined loading. Improved design rules featuring more efficient interaction curves, anchored to more accurate end points (i.e. cross-section resistances under pure compression and pure bending), were then proposed. The new design proposals were shown to yield more accurate and consistent resistance predictions over the existing design rules. Statistical analyses were also conducted to confirm the reliability of the new design proposals.