No abstract

Metal 3D printing technology can increase the Architecture, Engineering and Construction (AEC) industry's resource‐efficiency by removing a major fabrication constraint: geometrical complexity. Since the large part dimensions are a current limit of metal 3D printers, we propose a ‘hybrid’ manufacturing approach by welding optimized printed nodes to conventional steel elements for tubular constructions. In this work, we identified suitable analytical formulations for metal 3D‐printed parts, and calibrated numerical models for hybrid joints by means of experimental results. Finally, we quantified the structural integrity performance of the hybrid joints. Numerical simulations highlighted the joints' most sensitive regions, where the optimisation reduced the stresses up to 40% under tensile loading. The butt weld between the printed node and the conventional profiles guaranteed a simple state of stress in the weld, providing the hybrid joint a fatigue life of 2 × 106 cycles under 100‐MPa cyclic loading. These results confirm that metal 3D printing combined with topology optimisation can remarkably reduce the quantity of resource‐consuming cutting and welding operations to fabricate a structural joint for static and fatigue loads.

The demand for free-form steel structures having improved performances, reducing labour and resource usage is increasing in the construction sector. Structural nodes are some of the most critical regions for steel structures characterised often by large dimensions. These nodes can exploit the geometrical freedom of metal additive manufacturing (MAM) processes. Laser powder bed fusion (LPBF) is arguably the most developed MAM process, which has limitations regarding the size of the parts to be produced. A way to overcome the size limits of LPBF for producing structural nodes while still exploiting its geometrical capacity is producing hybrid components by welding them to traditionally manufactured beams. Such hybrid joints would constitute a complex system from a mechanical design perspective requiring a systematic analysis in order to be certified for structural use. Accordingly, this work studies the mechanical behaviour of hybrid steel components generated by welding LPBF plates and quarto plates made of AISI 316L stainless steel. The work was guided by a case study based on a large steel node, which helped defining the requirements to fill the gap of the international standards. The mechanical characterisation of LPBF-produced plates and quarto plates, as well as the welded hybrid components revealed a maximum of 10% difference between the properties of the differently manufactured plates. Through the digital image correlation (DIC) analyses, the anisotropic deformation behaviour along the LPBF, weld seam, and quarto plate regions have been identified, and the properties after welding did not show relevant modifications. The tests allowed to define that the failure behaviour is mainly governed by interlayer bounds, and a 0.9 safety reduction parameter for considering the reduction of ductility induced by arc welding to LPBF. Finally, design and production suggestions have been provided for a correct evaluation of gross and effective sections of the designed nodes.