Flexural Buckling of Wire Arc Additively Manufactured Tubular Columns

Wire arc additive manufacturing (WAAM) is a metal three-dimensional (3D) printing method that enables large-scale structural elements with complex geometry to be built in a relatively efficient and cost-effective manner, offering revolutionary potential to the construction industry. However, fundamental experimental data on the structural performance of WAAM elements, especially at the member level, are lacking. Hence, an experimental study into the flexural buckling response of WAAM tubular columns has been conducted and is presented in this paper. A total of 18 stainless steel square and circular hollow section (SHS and CHS) columns were tested under axial compression with pin-ended boundary conditions. Regular SHS and CHS profiles were chosen to enable direct comparisons against equivalent, conventionally manufactured sections and, hence, to isolate the influence of the additive manufacturing process, whereas the cross-section sizes and column lengths were varied to achieve a broad spectrum of member slendernesses. Given the geometric undulations inherent to the WAAM process, 3D laser scanning was used to determine the as-built geometry and global geometric imperfections of the specimens; digital image correlation (DIC) was employed to monitor the surface deformations of the specimens during testing. Full details of the column testing program, together with a detailed discussion of the experimental results, are presented. The applicability of the current column design provisions in EN 1993-1-4 and AISC 370 to WAAM stainless steel members was assessed by comparing the test results with the codified strength predictions. The comparisons emphasized the need to allow for the weakening effect of the inherent geometric variability of WAAM elements to achieve safe-sided strength predictions.