Grande Ravine Bridge

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Grande Ravine Bridge
Viaduc Grande Ravine
Trois Bassins, Réunion Island, France
532 feet high / 162 meters high
940 foot span / 287 meter span
2009

Grande Ravine Bridge image courtesy of Gregory Viel.


Réunion Island is a French territory located east of Madagascar Island in the Indian Ocean. Just 35 miles (56 kms) across, the region has become a popular tourist getaway as well as a permanent home to more than 800,000 residents.

Travel between the many coastal communities on Réunion Island has always been through a network of older, two lane roads that traverse in and around many deep rifts cut from rain runoff tumbling down the tall volcanic peaks that created the island. To relieve congestion on the west side, it was decided to build a 30 mile (50 km) north-south highway called the Route des Tamarins. Crossing dozens of huge ravines, the new route required the construction of 3 tunnels, 9 interchanges and 4 major bridges including the Saint Paul, the Trois Bassins and the Ravine Fontaine viaducts. The longest and highest crossing of all is the one over Grande Ravine.

Dropping almost vertical for much of its 532 foot (162 mtr) depth, the Grande Ravine site is perfect for a frame bridge. The design chosen by the engineers is a sleek, stealthy looking span with a 940 foot (286.5 mtr) long span box girder resting on two angled struts of just 20 degrees - an incline so shallow they almost look as level as the road deck! The concrete struts are part of a cantilever that is counterweighted on the back sides by two large abutments filled with tons of soil. Like many strut frame bridges that are hard to categorize among bridge types, Grande Ravine is especially complex with an arch effect only occurring under service loads. To construct the main span without using wind prone towers and a high line, the famous French bridge company Freyssinet designed a unique stay cable system to support the two half decks as they were launched out from either side of the canyon.

Less obtrusive than an arch, but just as elegant, the Grande Ravine is a rare type of bridge we can only hope to see more of in the future. The talent behind the Grande Ravine bridge includes designer Setec, architect Alain Spielmann and builders Dodin, VINCI Construction, Eiffel and Freyssinet. A three dimensional computer generated trip along the entire route can be viewed here: http://www.regionreunion.com/fr/spip/spip.php?article1117

If you ever visit Réunion Island, also be sure to check out the equally impressive Bras de la Plaine bridge which opened in 2002. Consisting of a design even less common than the Grande Ravine, the Bras de la Plaine’s 922 foot (281 mtr) main span is essentially two bridges, each composed of a cantilevered warren truss that meet in the middle but are largely supported by the weight of a massive 7,500 ton dead man foundation on either side of the canyon. The transition between these two halves of the bridge was made even more noticeable by a change in grade at the crown from 1 to 5 percent. To construct the bridge, two 131 foot (40 meter) high pylons were erected 1,362 feet (415 mtrs) apart. The slender span is a perfect marriage of our two most basic building materials with two vertical planes of steel tubing sandwiched between two horizontal, thin slabs of concrete.



Grande Ravine Bridge Elevation


Grande Ravine Bridge image courtesy of Gregory Viel.


Grande Ravine Bridge image courtesy of Gregory Viel.


Grande Ravine Bridge image courtesy of Gregory Viel.


Grande Ravine Bridge image courtesy of Gregory Viel.


Grande Ravine Bridge image courtesy of Gregory Viel.


Grande Ravine Bridge image courtesy of Gregory Viel.


Grande Ravine Bridge image courtesy of Gregory Viel.


Grande Ravine Bridge image courtesy of Gregory Viel.


Grande Ravine Bridge satellite image.


Grande Ravine Bridge satellite image.


Grande Ravine Bridge model.



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