Effect of the web hole size on the axial capacity of back-to-back aluminium alloy channel section columns

Aluminium alloy back-to-back channels are becoming popular in building structures. These back-to-back channels often include web hole for installation of services. No previous research, however, is available in the literature for compressive behaviour of such aluminium alloy back-to-back channels with web hole. This paper presents an experimental and numerical investigation on the behaviour of screw fastened back-to-back built-up aluminium alloy intermediate and slender columns with centred web hole under axial compression. Sixteen tests were conducted in total, the results of all are reported in this paper. A non-linear finite element (FE) model was then developed, and the results were compared against the experiment results showing a reasonable match in terms of both the axial strength and failure modes. Based on 600 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 the structural behaviour of back-to-back built-up aluminium alloy channel columns. Furthermore, the performance of current design guidelines by Australian/New Zealand Standard (AS/NZS) and the American Iron and Steel Institute (AISI) standard was assessed by comparing the axial strengths obtained from the experiments and FEA. It is shown that the AISI & AS/NZS (4600:2018) could predict the axial strength with high degree of precision; being conservative by only 10% on average to 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 were able to predict the reduced axial strength of aluminium alloy back-to-back channels with centred web hole.