OptiBridge: a topology optimized 3D-printed concrete bridge

Overview

Ghent University has built a second topology optimized concrete footbridge named OptiBridge. The 5-metre-long bridge girders were based on a 2D topology optimized design by Technion - Israel Institute of Technology (Team led by Prof. Oded Amir) and redesigned at Ghent University by Ticho Ooms and Gieljan Vantyghem into a realistic 3D structure. The bridge was constructed by joining four hollow segments that were printed in less than 1.5 hours. The rapid setting and the increased early-age strength of the 3D-printed concrete mixture were achieved by extensive experimentation in the Magnel-Vandepitte laboratory where Yaxin Tao developed a unique solution. Many improvements compared to the first realization can be observed.

The project is carried out within the Concre3DLab co-operation, aimed at tackling complex 3D printing problems from different angles (Prof. Geert De Schutter: rheology / Prof. Kim Van Tittelboom: durability / Prof. Wouter De Corte: structural aspects and optimization).

Design

The design of this footbridge (measuring 2 x 5 meter) is unique in the sense that its shape was designed using mathematical design tools. In this case, structural topology optimization was applied to a 2D girder problem, including the optimization of the tendon profile for post-tensioning. A 2D topology optimization script was used in order to optimize the stiffness of the two side-girders. The optimized mathematical solutions were then used as an inspiration to develop the 3D shape of the whole bridge. A parametric model was developed to increase the level of flexibility in the pre-design of the 3D geometry. Each of the girders was slightly inclined in order to counteract the horizontal lateral forces introduced by the design loads on the deck. Post-numerical analyses were performed to estimate the internal forces and optimize the actual prestress force and number of reinforcement bars.

Manufacturing

Initially, experiments were performed to 3D-print the bridge in only two pieces. However, due to limitations in transport, the final bridge design was subdivided into four separate segments. The four segments were printed on two consecutive days and took only 40 minutes of printing per day. This time frame only considers the actual printing time and disregards preparation and cleaning. A highly sophisticated printing mixture and system was developed which has a very fast setting time and increased early-age strength, enabling the printing of overhang angles up to 45°. After joining and aligning the four segments, and inserting the rebars and post-tension tendons, the inner void was filled with self-compacting concrete and the whole structure prestressed afterwards. In the final stage, the bridge was flipped upside down to its final orientation and placed in a temporary location (see photo album below).

In the next step of this research project, the bridge will undergo a testing program to analyze its stiffness and bearing capacity. Furthermore, it will be used as a test case to evaluate the sustainability of 3D printed structures.

More information

Ooms, T. et al. (2022). The Production of a Topology-Optimized 3D-Printed Concrete Bridge. In: Buswell, R., Blanco, A., Cavalaro, S., Kinnell, P. (eds) Third RILEM International Conference on Concrete and Digital Fabrication. DC 2022. RILEM Bookseries, vol 37. Springer, Cham. https://doi.org/10.1007/978-3-031-06116-5_6

Press Release

Please contact Gieljan.Vantyghem@UGent.be for Press Release documentation.

Contact

If you are interested in this research or have an idea that you want to discuss, do not hesitate to contact

Gieljan Vantyghem: Gieljan.Vantyghem@UGent.be (Research profile)

Ticho Ooms: Ticho.Ooms@UGent.be (Research profile)

Yaxin Tao: Yaxin.Tao@UGent.be (Research profile)

Concre3DLab: concre3dlab@gmail.com | youtube.com/c/Concre3DLabGhent

Acknowledgements

This research project was supported by Ghent University - Department of Structural Engineering and Building Materials
The following partners were involved:

• 2D topology and shape optimization of the prestressed concrete girder: Technion - Israel Institute of Technology (Oded Amir & Emad Shakour)
• 3D modelling, FE-analysis & robot instructions and machine code: Department of Structural Engineering and Building Materials - Ghent University (Gieljan Vantyghem & Ticho Ooms)
• Rheology mix design and manufacturing technology: Patented Technology IP Ghent University (TechTransfer) and Department of Structural Engineering and Building Materials (Yaxin Tao)
• Assembly and post-tensioning: joint effort by Magnel-Vandepitte Laboratory - Department of Structural Engineering and Building Materials - Ghent University (Dieter Hillewaere, Tom Stulemeijer & Stefan De Bock) & Freyssinet (Herman Wanzeele & Poulus Ardon)
• Resources, supervision & planning (Prof. Geert De Schutter, Prof. Kim Van Tittelboom, Prof. Wouter De Corte & Tommy De Ghein)
• Volunteers: Michiel Bekaert, Sebastiaan Van Heesvelde.