Leonardo's bridge in 1502

MIT engineers prove that Leonardo da Vinci’s 500-year-old bridge design would work.

We know that Leonardo was a genius, that he was far ahead of his time, but even the great man would never have believed that today's engineers would still be amazed by his creations some 500 years later.

Engineers at the Massachusetts Institute of Technology (MIT) have analyzed a bridge designed by Leonardo in 1502. Designed for the Sultan Bayezid II, head of the Ottoman Empire, the huge bridge was intended to connect Istanbul and its neighboring city of Galata.
In the end, Leonardo's design was not realized.
The MIT team carefully modeled the bridge's design and found it to be structurally sound, no small feat considering it would have been the longest bridge in the world at the time.

“It’s incredibly ambitious,” says MIT structural engineer Karly Bast. “It was about 10 times longer than typical bridges at the time.”

Da Vinci sketch (top left) with MIT diagrams (Karly Bast and Michelle Xie)

Using surviving documentation and knowledge of contemporary materials and construction methods, the team found that the 280-meter (919-foot) long bridge would have been able to stand and remain stable.
While the researchers have not yet published a peer-reviewed paper on their work, they have put together a 1:500 scale model to subject it to a rigorous series of tests.
The model is made up of 126 separately created pieces, 3D printed, then joined together like a puzzle: the finished model is approximately 81 centimetres (32 inches) long.

One of the most impressive parts of the bridge design is that it is all held together without any fasteners or mortar to connect the blocks.
“Everything is just held together by compression,” Bast says. “We really wanted to show that all the forces were being transferred into the structure.”

Rather than follow the trend of his time for bridges with semicircular arches, which would have required numerous support points, Leonardo opted for a single, enormous, flattened arch.
It had to be high enough to allow the passage of sailing boats, while maintaining essential rigidity, especially against lateral movements. To counteract these movements, Leonardo imagined widened pillars on each side of the bridge, structures that anchor the bridge in the same way that someone might spread their feet to prevent oscillation.

Da Vinci added additional stabilization features to protect against earthquakes that occurred in the area, and once again scale model tests showed that they would work very well.
The materials and construction methods we have developed since Leonardo's time mean that there are now better designs to use than this, but it is still a phenomenal piece of engineering, underlining the brilliance of Da Vinci's mind.

The scale model was based on a small sketch in one of Da Vinci's notebooks, what we don't know is how long it took to develop. It's possible that this incredibly clever design was the result of just a few minutes of work.

“Was this sketch just freehand, something he did in 50 seconds, or is it something he really sat down and thought about deeply?” Bast says. “It’s hard to know. He knew how the physical world works.”
The research was presented at the International Association for Shell and Spatial Structures conference in Barcelona.