This research programme considers both the structural design aspects as well as the construction aspects. The programme is divided into the following essential steps:
Step 1: The conceptual design of modular connections is explored. A comprehensive mapping of steel modular connections was carried out in collaboration with designers, manufacturers and contractors, aiming to understand how the manufacturing processes have affected the design of connections and vice-versa. A plethora of connection systems has been studied and classified based on their unique as well as common characteristics and their performance criteria. Key features are those related to the demountability and reusability of the connections and members connected to them, and the degree of standardisation possible to be achieved.
Step 2: Herein an in-depth study is carried out on the design provisions for flexibility in handling, installation, use, disassembly, and reuse of: (i) flat-pack, (ii) composite and (iii) hybrid modular unit types (for steel and timber modular buildings). Structural topology optimisation tools are also employed to generate novel connection designs with improved performance while reducing material as well as introducing access holes for installation and removal. Optimisation-dedicated software are used to define the objective functions and constraints followed by morphogenesis and mesh-topology editing processes. Organic modelling, digital sculpting, and finite element stress analyses are conducted using parametric modelling (e.g., APDL-Abaqus and Python language) towards the aggregation of the connection components which will result to a number of optimum designs. The project’s industrial partners have contributed offering specific advice on the assembly, handling and disassembly of modular units specific to different companies in order to maximise the benefits in the construction programme.
Step 3: A wide range of metallic structural elements can theoretically be printed, yet limited structural members have been tested at a macro-scale. Therefore, the material selection amongst various metal alloys is critical and is based on the existing knowledge of material performance. The mechanical properties of the components are tested (coupon tests). The structural behaviours of the various optimised connection designs (at least one per modular type, inter-module connection of the volumetric technique – modular unit/box) are examined in different loading conditions including fatigue performance to define their lifespan. Static and fatigue (low & high frequency) tests are carried out in the School’s state-of-the-art Heavy Structures Laboratory at City, University of London and previously at the University of Leeds. Assessing the performance of the optimised connections and their components (pins, bolts, plates, nuts, washers, fuses-like components, etc.) reveals design and manufacturing issues. With regards to the 3D printed components, both printing processes, Direct Metal Laser Sintering – DMLS and Wire Arc Addictive Manufacturing – WAAM, have been employed to examine and evaluate the results qualitatively. In detail, the programme includes: (a) measuring the geometric properties and imperfections, (b) scanning the surface roughness of the printed specimens which affects the stiffness, longevity, and tolerances, and (c) experimental testing under 6 (2-normal, 4-accidental) loading conditions for robustness.
Step 4: Following macro-scale testing, a large testing campaign of full-scale models is conducted at City, University of London and in collaboration with a number of national and international institutions including optimised inter-module and side connections of volumetric modular steel buildings as well as the optimum novel connection system proposed for any panelised timber building.
Step 5: With the support of the core steering group, including key academic partners and the stakeholders (experts from design, manufacturing and construction sectors), design recommendations and systematic approaches will be drafted to showcase and increase confidence in using novel standardised partially 3D printed connections while promoting applications in the UK and international markets.
If you are interested in joining the group, discussing the research programme or in developing a collaboration on this research programme please email Professor Tsavdaridis at Konstantinos.email@example.com