Local stability of press-braked stainless steel angle and channel sections: Testing, numerical modelling and design analysis

Abstract

This paper reports an experimental and numerical investigation into the local stability of press-braked stainless steel angle and channel sections. The experimental programme was performed on two equal-leg angle sections and two plain channel sections, and included material testing, initial local geometric imperfection measurements, eight stub column tests and ten laterally restrained beam tests (about the geometric axes for angle sections and minor principal axes for channel sections). This was supplemented by a numerical simulation programme, where finite element models were firstly established to replicate the test structural responses and then employed to derive further numerical data through parametric studies. The results obtained from the structural testing and numerical modelling were adopted to evaluate the accuracy of the codified local buckling design provisions established in America, Europe and Australia and New Zealand. The evaluation results revealed that all the design codes greatly underestimate the cross-section resistances of press-braked stainless steel equal-leg angle and plain channel section stub columns and laterally restrained beams, mainly attributed to the neglect of the pronounced material strain hardening effect of stainless steel in the design. The continuous strength method (CSM) is an advanced deformation-based design method, allowing for a rational utilisation of material strain hardening in determining cross-section resistances, and its scope of application has been recently extended from doubly-symmetric (I- and tubular) sections to mono-symmetric and asymmetric (angle, channel and T-) sections. Quantitative evaluation of the CSM was conducted through comparing the predicted cross-section resistances against the experimental and numerical results. The CSM was found to yield substantially more accurate and consistent design cross-section resistances for press-braked stainless steel equal-leg angle and plain channel section stub columns and laterally restrained beams than the established design codes.