The Chaban-Delmas Bridge accommodates an exceedingly wide navigation channel—320 ft—and has a lift height of 164 ft. Hardesty & Hanover
Bordeaux, France, recently celebrated the opening of its long, tall, elegant lift bridge, which accommodates both vehicular and light-rail traffic.
May 21, 2013—The French city of Bordeaux, celebrated for its wine and 18th-century architecture, earned another distinction in March, when it became home to what is likely the longest vertical-lift bridge in Europe. Amid fireworks, a three-day festival, and a few glasses of vin rouge, France’s president, Francois Hollande, presided over the opening of the Jacques Chaban-Delmas Bridge, spanning the Garonne River.
The Chaban-Delmas Bridge, named for a former 48-year mayor—is arguably one of the most beautiful moveable bridges anywhere. Moreover, the bridge—a new crossing that is situated between two existing bridges in the city—accommodates an exceedingly wide channel to allow the passage of large cruise ships. A vertical lift bridge, rather than a drawbridge or swing bridge, was required because the navigation channel needed to be 320 ft wide.
The design competition began in 2002 but construction did not commence until 2011. The Vinci Group was chosen as the design/build contractor, working with the design consortium of EGIS/Jean Muller International; Michel Virlogeux; and Lavigne-Cheron Architects. Hardesty & Hanover, LLP, of New York City, provided the conceptual design, detailed final design, and construction support for the lift bridge mechanization and operating systems.
The lift span has a symmetric cross section and carries four lanes of vehicle traffic—two outboard lanes for pedestrians and bicyclists and two tracks for future light-rail use. Four independent pylon towers, one at each corner of the lift span, allow a counterweight (at a quarter of the total lift span weight) to travel vertically inside each pylon. The bridge spans a total of approximately 383 ft, with an out-to-out width of approximately 141 ft, and a design lift height of 164 ft.
The 141 ft wide bridge includes two lanes for pedestrians and
bicyclists and two tracks for future light-rail use. Hardesty
Paul Skelton, P.E., M.ASCE, the H&H principal who oversaw the project and attended the opening ceremony on March 16, said the first challenge was creating a design that was workable for the size of the bridge. “It had to be a very large bridge, meaning a heavy bridge, so the lifting span weighs six million pounds,” Skelton says. “H&H was able to convince the owners to change some of their requirements and we were thus able to put in a smaller and lighter mechanism, which translated into a slimmer tower structure and a lighter and more efficient design. For such a massive structure it’s really quite beautiful, which is unusual.”
Operation of the lift span is achieved via high-strength wire ropes passing over giant pulleys, or sheaves, that connect the lift span to the counterweights. A wire rope winch-drive operating system with an electric motor and flex vector regenerative drives hauls in and pays out the counterweights, thereby raising and lowering the lift span.
From seated position to its full lift height, the rising span consumes a whopping 11 minutes. “It’s a slow lift, but it was mandated by the city, which sees each opening as an event to be witnessed by many residents,” Skelton explains. Openings will probably take place once every two weeks. The bridge is expected to handle 43,000 vehicles a day.
The bridge deck is orthotropic, Skelton says, and resembles an airplane wing. This fact raised alarms that gale-force winds would cause the span to spontaneously rise as the flow of air over a wing creates lift. “There was extensive wind tunnel testing and a lot of work was put into assuring the city that the bridge would be stable in maximum winds,” says Skelton.
The electrical machinery is housed in the base of the concrete piers that support the bridge. In most of the vertical lift bridges in the United States the machinery is mounted at the top of the tower or the span. “This design allowed us to move the machinery into the piers, and we have a robust pumping system in the event of flooding,” Skelton explains. The concrete piers were actually fabricated upstream in a drydock, then floated down the Garonne “like barges” to the bridge site and sunk, he says.
Adding light-rail to the deck posed additional challenges; the bridge had to be built to withstand heavy train loads and the alignment of the rails was crucial. “When a bridge is moveable, the tolerances and the alignment have to be right so that they line up properly when they separate,” says Skelton. “So we had to pay careful attention to the flexion of the structure under the train loads and the alignment of the rails and the span.”