Hybrid wire and arc additive manufactured I-section beams: assessment of material efficiency and carbon footprint

Hybrid wire and arc additive manufacturing (Hybrid WAAM) offers new potentials for local customization of steel structures by adding material precisely where it is required. While the serial production of steel profiles has improved the process efficiency in construction, it is often associated with underutilization of materials, as standard beams are over dimensioned to meet the peak load demands. Hybrid-WAAM I-section beams offer a novel processing solution by combining the benefits of serial production with individualized WAAM strengthening, aiming for efficient material usage. This study evaluates the material efficiency and assesses the carbon footprint of Hybrid-WAAM I-section beams through a cradle-to-gate Life Cycle Assessment (LCA). Results indicate substantial material savings of up to 28% and reductions of CO₂ equivalent up to 27% in the most favorable cases. However, the environmental benefits of Hybrid-WAAM I-section beams depend on structural system, loading conditions and design strategy. In some scenarios, local strengthening may even result in a higher cradle-to-gate CO₂ footprint than conventional profiles. Moreover, the LCA outcomes are highly sensitive to assumptions regarding steel production and regional differences of energy sources, leading to significant variations in CO₂ equivalent estimates. As such, this study highlights that Hybrid-WAAM I-section beams can lead to eco-efficient solutions in steel construction, but the design needs to be supported by a true-to-life LCA.