Strange Architecture: Bridge Design in the Netherlands ~ Civil engineering

Strange Architecture: Bridge Design in the Netherlands

Because of prevalent rivers and high boat traffic, a bridge in the Netherlands needs to be able to quickly raise and lower over relatively small waterways. Dutch architects answer this conundrum with an unusual design known as the tail bridge.

The Dutch have a tendency to do things differently. Take their levees, which are giant storm-surge barriers specially made with synthetic textiles to keep the earth from eroding. Their bike paths are placed on equal footing as automotive roads. And their town planning, which merges private and public life by combining terraced houses with amenities like shops and sports facilities, is a far cry from the way American suburbs are planned.

Then there are Netherlands' bridges. Because of prevalent rivers throughout the country and boat traffic as high as the volume of vehicles on the road, a bridge in the Netherlands needs to be able to quickly raise and lower over relatively small waterways. Your average hinged drawbridge would be too big for most Dutch waterways, and a long, steep bridge would eat up precious resources. Dutch architects answer this conundrum with the tail bridge. A tail bridge can quickly and efficiently be raised and lowered from one pylon (instead of hinges). This quickly allows water traffic to pass while only briefly stalling road traffic.

The Slauerhoffbrug is one tail bridge that stands out, even in the bridge-happy Netherlands. The bridge, located in Leeuwarden, was designed by Van Driel Mechatronica to be a fully automatic bridge with an ability to sense and adapt to its surroundings. While this technology is not for just any bridge—more traffic requires a more intelligent controller—the bridge is sensibly high-tech for its area, says Bart Ney, a Public Information Officer for the San Francisco–Oakland Bay Bridge, which is scheduled to be completed in 2013. "The Slauerhoffbrug is immediately both iconic and utilitarian and allows optimum flow of maritime and automobile traffic," he says.

The Slauerhoffbrug crosses over the Harlinger Vaart River. "A movable bridge was necessary because a new beltway crossed this canal," van Driel says. Constructed in 2000 from iron and steel, the bridge is raised and lowered 10 times a day by two hydraulic cylinders located in a single pylon next to the bridge. The lift bearing, complete with asphalt and road markings, seamlessly disappears into the road when lowered. The base model of the bridge is a limited turntable bascule bridge, in which the rising section is counterbalanced by a weight, like the Pegasusbrug near Ouistreham in France. Such bridges were built all over the world in the 18th, 19th and 20th centuries, van Driel says.

These original tail bridges were composed around the idea of having a fixed center point with rolling units on either side. Van Driel Mechatronica BV created the William Pont Bridge in Zaanstad using more simple measures. Pylons under the center point replaced the left and right rolling elements of the bridge. This small bridge could rest on only one pylon, which is advantageous because it consumes less materials and energy. The Leeuwarden Town Council decided to base the Slauerhoffbrug off these principles.

The Slauerhoffbrug is built in an L-shape, bending the bearing bars that lead to the deck, with the foundation built beside the bridge. The principal beams and cross girders are absent. This allows a low construction height that increases the lifting height. And in true Dutch fashion, this tail bridge isn't just an engineering feat, but a work of art. It is painted in yellow and blue, representative of Leewaurden's flag and seal. The asymmetrical shape can be seen for miles when the deck is completely raised and locked upright in midair.

The Slauerhoffbrug, located in Leeuwarden, was designed by Van Driel Mechatronica to be a fully automatic bridge with an ability to sense and adapt to its surroundings.