Researchers at MIT have used 3D printing to create a scale model of a bridge designed by Renaissance artist and inventor Leonardo da Vinci.
The design in question was a rejected proposal from Leonardo da Vinci for a bridge to connect Istanbul with its neighboring city Galata. Karly Bast, a recent MIT graduate student, worked with professor of architecture and of civil and environmental engineering John Ochsendorf, and undergraduate Michelle Xie, in order to test the feasibility of the polymath’s bridge design within its historical context.
Using 3D printing, they created a detailed scale model with a similar structure to da Vinci’s bridge design, and tested its ability to stand and support weight, and even to withstand settlement of its foundations.
“Was this sketch just freehanded, something he did in 50 seconds, or is it something he really sat down and thought deeply about? It’s difficult to know,” Bast questions.
“It was time-consuming, but 3D printing allowed us to accurately recreate this very complex geometry.”
Complex bridge design ahead of its time
The proposed bridge design was created by Leonardo da Vinci in 1502 A.D., for the ruler of the Ottoman empire at the time, Sultan Bayezid II. Bayezid sought a bridge design to connect Istanbul and Galata, and was taking in various proposals from artists. Da Vinci came up with his design that he described in a letter to the Sultan, as well as sketching it in his notebook, however it was rejected.
Fast-forward to 2019, the MIT research team seek to test da Vinci’s bridge concept, now over 500 years old, as the design was notable for several reasons. Had it been built, it would have been the world’s longest bridge span of its time, at about 280 meters long. “It’s incredibly ambitious,” Bast explains. “It was about 10 times longer than typical bridges of that time.” It is also structurally different to masonry bridges in Leonardo’s time, as it is supported by a flattened arch, departing from the commonly used formula of semicircular arches.
Furthermore, Leonardo da Vinci included in the concept abutments at the end of the bride that split into two. This was an unusual design proposed by da Vinci in order to stabilize the span against lateral motions, which has often caused many bridges to collapse throughout history. These unique elements, out of place for its time, intrigued the MIT researchers into questioning if da Vinci’s concept was thought through.
Therefore, using 3D printing, they set about answering the question by building a scale model of the bridge. However, da Vinci did not include any details regarding what materials would be used to construct the bridge, nor the construction method itself. Bast and the team instead had to analyze the possible materials and construction methods available during da Vinci’s epoch.
They concluded that it would have been made out of stone, and that it would stand on its own under the force of gravity, without any fasteners or mortar to hold the stones together, as with classical masonry bridges. However to prove the viability of their hypothesis, the researchers were required to build an accurate model in order to demonstrate its stability. It was therefore necessary that the final model structure was made up of assembled individual blocks, as the full-scale bridge would have been made up of thousands of stone blocks.
Testing the bridge design using 3D printing
To achieve the complex design, the team turned to 3D printing, and were able to produce 126 blocks for the model bride, built at a scale of 1 to 500, which measured at 32 inches long altogether. Each block took approximately six hours to 3D print, however it allowed the researchers to accurately capture da Vinci’s design in order to test it. The 3D printed “stones” were supported by a scaffolding structure to hold it together during assembly, which was removed afterwards once complete, allowing the structure to support itself.
Although previous attempts to reproduce Leonardo’s basic bridge design in physical form have been made, they were constructed using modern materials. They did not provide any indication towards the practicality of da Vinci’s engineering. Despite the 3D printed model being made from a different material, its gravity-supported masonry resembles that of the bridge, and therefore represents a suitable test.
The structure’s resilience was tested by Bast and Xie, who constructed the model bridge on two movable platforms. They then moved each platform away from each other in order to simulate the foundation movements that could occur as a result of weak soil. The 3D printed model bridge demonstrated resilience to the horizontal movement, before being stretched the maximum distance. With the results of the test, Bast concludes that it proves the feasibility of many ambitious construction projects that could have been possible during the early years of the Renaissance.
Bast’s 3D printed study was presented in Barcelona at the conference of the International Association for Shell and Spatial Structures last week. It will also be the subject of a talk at Draper in Cambridge, Massachusetts later in October, and will feature in an episode of the PBS program NOVA, set to air on Nov. 13.
Observing history from a 3D printed perspective
3D printing has proved a useful tool for design projects seeking to explore and reconstruct structures, artifacts and artwork from the past.
For example, Dutch 3D printing service bureau Oceanz helped to reconstruct a real-life rendition of The Night Watch painting by famed 17th century painting Rembrandt Harmenszoon van Rijn. Nachtwacht 360 artists recreated the tableau of the famous painting using real people, and 3D printing was used by partner Oceanz to make realistic props helping to bring the artwork “to life.”
Also, in the garden of Spain’s National Archaeological Museum (MAN), a 2.2 m tall replica of the San Pedro de las Dueñas Arch was 3D printed by ACCIONA, the Spanish conglomerate group responsible for infrastructural management and renewable energy. The monument was made to help to demonstrate the potential of emerging technologies and their role in historic preservation.
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Featured image shows Karly Bast beside the 3D printed model of da Vinci’s bridge design. Photo via MIT.
