Flexural buckling of high-strength aluminium alloy CHS columns

Abstract

High-strength aluminium alloys are increasingly popular and gaining more prominence in structural engineering. The global buckling behaviour and design of high-strength aluminium alloy circular hollow section (CHS) columns subjected to axial compression are investigated in this study. Ten experiments on CHS specimens with two extruded 7A04-T6 CHS profiles – 165 × 15 and 165 × 7.5 (in mm), were conducted. The material tests and initial geometric imperfection measurements were carried out prior to column tests. The test setup, procedure and results, including failure modes, ultimate resistances and load–displacement curves were comprehensively reported and analysed. Based on the developed and validated finite element (FE) models, an extensive parametric study, over a broad range of member and cross-section slenderness as well as the strain hardening exponents and proof strengths of the high-strength aluminium alloy material, was performed to complement the test data pool. The applicability of current buckling design provisions used for normal-strength aluminium alloy columns in the European, Chinese, American, Australian & New Zealand standards and the proposal of Rasmussen and Rondal to 7A04-T6 high-strength aluminium alloy CHS columns was evaluated through comparisons with the test and FE results. The results show that the European, Chinese and American standards provide conservative buckling resistance predictions, while the Australian & New Zealand standard and Rasmussen’s proposal generally yield unsafe capacity predictions. Finally, two flexural buckling curves within the framework of the EN 1999-1-1:2007 design method, featuring a revised linear imperfection term and a newly developed hybrid linear-nonlinear imperfection term, were proposed accordingly, and were shown to provide more accurate and consistent buckling resistance predictions.