Wire arc additive manufacturing (WAAM) is a method of metal 3D printing that can be used to fabricate
large-scale elements of complex form, opening up opportunities to unleash the full potential of
structural optimisation. To demonstrate this potential, optimised steel trusses have been fabricated by
means of WAAM and tested to investigate their structural performance. The tested metal 3D printed specimens, which are considered to be the first optimised WAAM structural systems of this kind and scale, comprised members of tubular cross-section with varying diameters and thicknesses. Three different configurations were considered: cantilever, propped cantilever and simply supported, all 2 m in length. Repeat tests enabled the variability in response between specimens to be evaluated; 6 optimised trusses were tested in total. The geometric features of the tested specimens were determined using 3D laser scanning, while digital image correlation was employed to monitor the displacement and strain fields during testing. Full details of the experimental programme are provided; the obtained
results are analysed and comparisons against equivalent conventional reference designs are made. The results of complementary numerical simulations, undertaken to gain further insight into particular features of the structural response of the examined specimens, are also presented. The structural efficiency of the optimised trusses, as measured by the capacity-to-mass ratio, was found to be up to 95% higher than that of the corresponding reference designs, underlining the benefits in terms of structural efficiency that can be achieved by the combination of WAAM with optimisation methods.