The name Leonardo da Vinci has become synonymous with genius across many fields. To add to his unmatched reputation as an artist, inventor, and scientist we can now add bridge designer. Sadly, the description cannot include bridge-builder, since his masterpiece was never constructed, but new research demonstrates it would have worked, and perhaps survived as a wonder of the world.
In 1502 Sultan Bayezid II wished to join Istanbul with Galata by means of a bridge across the Golden Horn inlet. The Golden Horn had been bridged by Justinian the Great in the 6th century, but the Sultan was more ambitious, wishing to span it at a wider point, closer to the two cities’ centers.
Leonard da Vinci submitted a solution to the engineering challenge, producing a design to span the Horn in a single arch, tall enough to allow the ships of the day to sail underneath. Had the Sultan approved the idea it would have been the longest bridge span in the world at the time.
Leonardo’s plans were lost, but since being rediscovered in 1952 they have inspired engineers, and a scaled-down version was built in Oslo using modern materials in 2001. There is even a project to build versions around the world. Hilariously, one proposal was rejected as being “too modern” in design.
However, not everyone has been convinced the ambitious proposal would have been practical with the technology of the day.
Graduate student Karly Bast of Massachusetts Institute of Technology investigated the materials available to Leonardo had he been given the job, construction methods of the era, and even the site’s geology. Even assuming Leonardo didn’t manage to invent some new method for assembling materials, which given his record he very well might have done, Bast concluded the bridge would have done the job if built from stone. Brick or wood, Leonardo’s other options, would not have been strong enough.
Leonardo’s innovation was to replace the semicircular arches used to support the bridges of the day with a single flattened arch 280 meters (924 feet) long. "It's incredibly ambitious," Bast said in a statement. "It was about 10 times longer than typical bridges of that time."
Bast built a 1:500 scale model made from 126 3D-printed blocks and presented her findings at the International Association for Shell and Spatial Structures conference in Barcelona. A program on her work will be aired on PBS NOVA next month. "It's all held together by compression only," she said.
The plan’s other great innovation, adding abutments that splay outward to stabilize the bridge against sideways forces, has already proven its worth in the Olso version, and may have been sufficient to withstand the area’s major earthquakes.