A Digital Workflow for the Design and Manufacturing of 3D Printed Concrete Bridges in a Circular Economy:A Parametric Approach to Integrated Design and Fabrication

Low productivity, material depletion, waste, and emissions are widespread in the construction industry. On top of this, many bridges reaching the end of their service life need repair or replacement.This design project investigates how digitisation and integrated design and manufacturing processes can aid in addressing sustainability and productivity issues. This project develops a digital workflow for bridge design and manufacturing using 3D printed concrete in combination with circular economy design concepts of disassembly and material reduction.Design CriteriaFor the development of the project, design criteria were established. This process initially looked at two previously printed bridges in the Netherlands. From this, design criteria for both the design tool and the resulting bridge designs were established. These criteria include:• Use concrete 3D printing and work with relevant printing systems.• Use structural analysis to guide user decisions.• Use prestressed tendons and modularise for simple assembly and disassembly.• Implement principles of the circular economy.Design ToolThe project developed a parametric design tool for creating bridges using 3D-printed concrete. Five ‘blocks’ manage distinct design elements in the design tool.1. Alignment allows the user to match the bridge to an existing location or shape a new bridge through length, span and shape.2. Cross-sections along the curve allow the user to shape the bridge. Size and thickness control linked to a structural check enables efficient material distribution.3. 3D Form interpolates the cross-sections into a 3D shape. Here the user can see how the beam will look.4. Segments are created in the beam to engage with material, manufacturing and transport constraints.5. Code Generation block generates code suitable for standard printing systems.The user can make changes and modifications at any stage in the process. The manufacturing constraints are embedded into the design process, helping to ensure that what is designed can be produced.Design ConceptsTwo bridge concepts were created to demonstrate the tool’s flexibility in different scenarios. One design uses a freeform cross-section type to create a pedestrian bridge over a river. The other is a more straightforward highway bridge using a modular cross-section type and reuses existing supports.Public DisseminationOne of the ambitions is to share results and knowledge generated throughout the project. This knowledge dissemination is demonstrated by three public presentations reaching an industry, academic and general public audience.Conclusions and RecommendationsThe tool created helps demonstrate how integrated approaches to design and fabrication can help with the challenges presented in sustainability and productivity but simultaneously with the ambition that what we produce is attractive and appropriate to its location