Reduction of the environmental impact of complex-shaped steel joints through topology optimization and large-scale metal 3D printing

• Topology optimization and metal 3D printing reduce waste in steel joint production. • CNC milling has higher BTF ratio than DED-Arc manufacturing. • DED-Arc manufacturing results in lower GWP than CNC milling. • The use of renewable energy further reduces the overall GWP for DED-Arc manufacturing. • Combining optimization and DED-Arc manufacturing boosts efficiency in steel structures. Metal Additive Manufacturing (or 3D printing) technologies are bringing substantial changes to the entire industrial environment, enabling rapid and cost-effective production of complex components which would be hardly fabricated with conventional technologies. Recent developments in the field of large-scale metal 3D printing increased the potential use for the construction sector, with applications in some pioneering case studies. The present work is intended to assess the potential environmental benefit of the combination of digital technologies such as topology optimization and large-scale metal 3D printing to realize complex-shaped steel joints. The study evaluates the environmental impact of Directed Energy Deposition-Arc (DED-Arc) manufacturing adopted to realize optimized steel joints and compared with the computer-numerically controlled (CNC) milling technique adopted to realize conventional steel joints for gridshell structures. The study is applied to the specific steel joints for the gridshell structure of the British Museum in London. The results demonstrate that topology-optimized joints produced via DED-Arc exhibit superior environmental performances, particularly in terms of reduced carbon footprint and material waste. Additional considerations are made regarding the influence of deposition rate and the use of renewable energy on the environmental impact. The results are also validated through uncertainty analyses. Finally, the combined effect of design optimization and 3D printing technology is investigated in terms of both environmental and economic impact. The study reveals overall a positive impact of the combined use of optimization tools and advanced manufacturing technologies towards greener and more efficient steel structures.