The design and behaviour of a novel WAAM integrated plug & play beam-column connection

Abstract

Beam-to-column joints in steel structures are critical in both the design and execution phase. Bolted beam-to-column joints are widely applied in structures, due to their cost-effectiveness, ease of installation, and well described design guidelines in Eurocode 3. However, bolted connections to hollow section columns are challenging and limited, due to the limited access to the interior of the column. Hollow sections provide several advantages with regard to aesthetics and resistance. Welded beam-to-column joints can be applied to hollow section columns but are costly, require on-site welding and limit the reuse of structural members.
This thesis presents a novel plug-and-play beam-to-column connection, which adheres to modular construction and reuse. Design requirements for the plug-and-play connection were determined based on existing plug-and-play connections to overcome existing limitations and leverage the advantages.

In order to analyse the structural behaviour of the plug-and-play joint, a validated numerical finite element model is developed, using ABAQUS software. First, the plug-and-play joint’s global behaviour is analysed in terms of stiffness and moment resistance. Iteratively the conceptual design is finalised, by analysing the Von Mises stresses in the joint, and reducing material use in the connection. The structural behaviour and material use of the plug-and-play connection were compared to an equivalent single extended end-plate bolted connection, to quantify the improvements.

The plug-and-play joint is then divided into separate active joint components which act together to establish the joint’s behaviour, similar to the component method in Eurocode 3, part 1-8. The identified joint components were analysed in terms of strength and stiffness. Selected data from defined nodes were extracted and processed to determine the isolated behaviour and contribution of each component.

The outputs of the analyses are: i) the plug-and-play joint is significantly stiffer and stronger than its equivalent bolted connection; ii) it uses less material than its equivalent bolted connection; iii) in the considered configuration the joint’s stiffness and moment resistance are dominated by the column web panel in shear; iv) failure in the joint occurs due to the pins in tension and the column web panel in shear.

In order to adapt the plug-and-play connection to hollow section columns, wire arc additive manufac- turing (WAAM) is partially employed to directly print the parts of the connection that are attached to the column. WAAM eliminates the need to access the interior of the hollow section and provides a plug-and-play solution for a beam-to-column connection for hollow section columns. The plug-and-play connection is adapted to a configuration of an open section beam and a circular hollow section (CHS) column. The connection provides an I-beam-to-CHS-column joint which is off-site manufacturable and prevents on-site welding. The adapted plug-and-play joint was compared to the single extended end-plate bolted connection used in the study to assess the structural improvements the CHS column provides. Finally, the adapted plug-and-play joint was compared to its equivalent welded joint. Analysis of the considered configuration showed stiffer and stronger joint characteristics than its equivalent welded joint or comparable bolted joint with HEA column.

The study demonstrates that the novel plug-and-play beam-to-column joint provides significant structural and practical advantages over conventional bolted and welded joints. The proposed connection enhances stiffness and strength while reducing material usage and enabling reusability. Integration of WAAM technology facilitates application to hollow section column, expanding their application in structures. These findings underscore the potential of this plug-and-play connection to enhance construction efficiency and reusability.