Local and distortional buckling behaviour of aluminium alloy back-to-back channels with web holes under axial compression

Abstract

Aluminium alloy back-to-back channels are becoming popular in building structures. These back-to-back channels often include web holes for installation of services. No previous research, however, is available in the literature for compressive behaviour of aluminium alloy back-to-back channels with web holes. This paper presents an experimental and numerical investigation on the behaviour of screw fastened back-to-back built-up aluminium alloy stub and short columns with web holes under axial compression. Fourteen tests were conducted in total, the results of all are reported in this paper. Prior to compression tests, tensile tests were conducted to determine the material properties of test specimens and initial geometric imperfections were also measured using a laser scanner. A non-linear finite element (FE) model was then developed, and the results were compared against the experiment results showing a good match in terms of both the axial strength and failure modes. Based on 720 FE models, a comprehensive parametric study was conducted to investigate the effects of hole size, screw spacing, section thickness, column length and modified slenderness on structural behaviour of back-to-back built-up aluminium alloy channel columns. Furthermore, the performance of current design guidelines by Australian/New Zealand Standards (AS/NZS) and the American Iron and Steel Institute (AISI) standards was assessed by comparing the axial strengths obtained from the experiments and FEA. It is shown that the AISI & AS/NZS (4600:2018) are conservative by 10% on average, when compared against the test results. Parametric study results were used to propose the axial strength reduction factor equations for aluminium alloy back-to-back channels, and thereafter a reliability analysis was performed. The results of reliability analysis showed that the proposed equations could closely predict the reduced axial strength of aluminium alloy back-to-back channels with web holes.