AbstractWire arc additive manufacturing (WAAM) is a method of metal three-dimensional (3D) printing that has the potential for a significant impact on the construction industry due to its ability to produce large parts with reasonable printing times and costs. However, there is currently a lack of fundamental data on the performance of structural elements produced using this method of manufacturing. Seeking to bridge this gap, the compressive behavior and resistance of WAAM square hollow sections (SHS) are investigated in this paper. In a previous study by the authors, testing reported of sheet material produced in the same manner as the studied SHS is first summarized. The production, measurement, and testing of a series of stainless steel SHS stub columns are then described. Regular cross-section profiles were chosen to isolate the influence of 3D printing and enable direct comparisons to be made against equivalent sections produced using traditional methods of manufacturing. A range of cross-section sizes and thicknesses were considered to achieve variations in the local cross-sectional slenderness of the tested specimens, allowing the influence of local buckling to be assessed. Repeat tests enabled the variability in response between specimens to be evaluated; a total of 14 SHS stub columns of seven different local slendernesses was tested, covering all cross-section classes of AISC 370 and Eurocode 3. Advanced noncontact measurement techniques were employed to determine the as-built geometric properties, while digital image correlation measurements were used to provide detailed insight into the deformation characteristics of the test specimens. Owing to the higher geometric variability of WAAM relative to conventional forming processes, the tested 3D printed stub columns were found to exhibit more variable capacities between repeat specimens than is generally displayed by stainless steel SHS. Comparisons of the stub column test results with existing structural design rules highlight the need to allow for the weakening effect of the geometric undulations that are inherent to the WAAM process in order to achieve safe-sided strength predictions.