Generative Design for Additive Manufacturing of Rafter‐to‐column Connections in Steel Portal Frames

Abstract Steel portal frames usually employ I‐sections for their columns and rafters, which are jointed utilising haunches, thus accommodating the high bending moments that develop at the eaves and apex and resulting in smaller member sections. I‐sections are susceptible to lateral torsional buckling due to their open nature, thus necessitating the use of stays and increasing the labour required in this type of structures as well as relying on secondary members for their stability and oftentimes dictating their location. Replacing I‐section columns for tubular square hollow sections (SHS) can lead to significantly lighter structures as the latter ones have greater torsional stiffness and therefore are not susceptible to lateral torsional buckling, whilst they also possess higher resistance to minor axis buckling. The present paper reports the weight savings that could be achieved in various portal frame spans and heights by replacing an I‐section column for a SHS column which can be up to around 40%. Employing tubular columns complicates the design and construction of connections. To overcome this problem, this paper proposes the adoption of novel connections utilising additively manufactured components, which can transfer bending moments from the I‐section rafters to the SHS columns for various portal frame sizes. The connections have been developed using generative design, a computer‐based technology that generates optimised 3D models whilst minimizing weights and maximising structural performance. A feasibility study for 3D printing the proposed geometrically complex connections using wire arc additive manufacturing is presented in the present paper, as well as early results and manufactured components.