Blended structural optimization of steel joints for Wire-and-Arc Additive Manufacturing

Metal Additive Manufacturing, and in particular Wire-and-Arc Additive Manufacturing (WAAM) has proved to be a great and efficient alternative to the common subtractive manufacturing processes to realize complex-shape members and connections for construction. With reference to complex spatial structures such as gridshells, the connections play a crucial role both in the design and the construction processes. Novel computational design tools allow designers to conceive optimized joint solutions while minimizing the material use, resulting in difficult geometries to be fabricated with conventional methods. The present work aims at providing an innovative integrated design and fabrication framework to efficiently apply topology optimization algorithms to improve the efficiency of steel joints in complex spatial structures. The framework is based on the so-called “blended” structural optimization approach aimed at incorporating manufacturing constraints, basic principles of conceptual structural design and structural requirements into topology optimization to design ready-to-fabricate complex steel joints. The designs are suitable for fabrication with the WAAM process. The approach is applied to a case study to re-design the joint connections of the world's renowned British Museum gridshell rooftop structure. From a catalogue of various designs for each unique joint, one selected design is optimized and then checked for structural requirements in terms of strengths and stiffness. Then the optimized joint is validated for fabrication with WAAM process.