Last week a pedestrian bridge opened in Norway. Ordinarily that wouldn’t be of much interest anywhere else, but this bridge drew media attention from all over the world, because of its designer: Leonardo da Vinci.
The artist behind the Mona Lisa and the Last Supper was a true Renaissance man (in fact, the original Renaissance man), whose notebooks are full of designs for everything from parachutes to flying machines. Most of his designs were never built; in many cases it was because, while his ideas were sound, the construction materials, methods and tools available to him at the turn of the 16th century weren’t up to making his dreams reality.
Today we have the means to make Leonardo’s designs work–and as the Leonardo Bridge, which links Oslo, Norway, with the township of Ås, Norway, spanning a major highway, shows, those designs are not only practical, but beautiful.
In 1502, Leonardo learned that Sultan Bayezid II of Turkey wanted to build a bridge across the Golden Horn, an inlet at the mouth of the Bosporus River, in Istanbul. Leonardo proposed a 240-metre long stone arch, complete with a revolutionary system of braces to withstand wind forces. “I will erect it high as an arch,” Leonardo wrote to the Sultan, “so that a ship under full sail could sail underneath it.”
If the bridge had been built, it would have been the longest bridge in the world at that time. But the Sultan did not believe such a bridge could be built, or could stand, and even though Leonardo offered to build it himself, the project was scrapped.
Since Leonardo had little success at bringing any of his ambitious projects to fruition, that decision may have saved Leonardo from an embarrassing failure. Nevertheless, the design itself was sound–although it was 300 years before the engineering principle behind the bridge became generally accepted.
The bridge uses what is called “pressed-bow construction.” It’s based on the principle that the force of an arch can be distributed over a wider span when the foot of the arch is made wider and the arch uses the counterforce provided by the terrain. In practical terms, that means that the Leonardo bridge is a graceful arch that is very thick at both ends and thin in the middle.
Although the bridge was never built, the sketch Leonardo made of it was used to construct a model of the bridge for an exhibition of Leonardo’s engineering genius that toured various museums in the 1990s. In 1996, Norwegian artist Vebjørn Sand saw the model, and was struck by the beauty of its design.
Amazingly, Sand was able to talk the Norwegian Public Roads Administration (which Sand’s website,www.vebjorn-sand.com, notes drily “would not be generally described as a visionary organization”) into approving the building of a full-sized version of the bridge–not, to be sure, the 240-metre stone bridge Leonardo had in mind for the Sultan, but still, a sizeable span of 100 metres, eight metres high at its highest point. There are also tentative plans to build a stone version of the bridge, although a location has yet to be determined (Iowa, of all places, is a strong contender.)
Several years of consultation with various architects and engineers followed, but last Wednesday, the wooden bridge opened, with Queen Sonja on hand to do the honors and helicopters lifting the cloth veils from the structure.
Three arches of laminated wood, two side bows and a center bow, support the walkway. (The special gluing process used on the wood isn’t a Leonardo invention; it was developed by the Moelven Group of structural engineers and used in many of the structures built for the 1994 Lillehammer Winter Olympics.)
Why wood? “Norway has a tradition of picking up impulses from the continent and transforming them into what we have built our country with–and that’s wood,” Sand said. Oslo’s new airport, which encloses Norway’s largest interior space, is also made of laminated wood.
At each end, the builders first dug until they hit rock. Concrete piles were constructed on the rock, then the wooden footings were mounted into concrete. The cedar arches are reinforced with steel only at their bases. The bridge’s railing is made of stainless teal and teak. The wood has been treated with a new, non-toxic preservative, also developed by a Norwegian company, Jotun Paints. The total cost of the project was just over $2 million Canadian.
What’s so amazing about the bridge is how futuristic it looks, considering its designer died almost five centuries ago. “When you work with geniuses, you work with eternal forms that never go out of fashion,” Sand says. “Architecture from the 1970s looks older than Leonardo’s design.”
Now that the bridge has been built once, and has proven to be as beautiful as it is practical, other locations are considering building versions of their own. In fact, Sand hopes to see Leonardo bridges on every continent.
If nothing else, the bridge in Norway has proven, if any proof was still needed, that Leonardo da Vinci was indeed ahead of his time.
It’s also the perfect illustration of that old adage, “Better late than never.”
