The Torridge Bridge near Bideford in North Devon, England, was overall winner in The Concrete Society's 1988 awards competition. The 2,132-foot bridge carries road traffic over the River Torridge and its flood plain, while maintaining a navigation channel in the river for commercial shipping.
DESIGNED FOR BEAUTY WITH ECONOMY
The bridge site is a region of natural beauty. For this reason it was decided to depart from the conventional form of river bridge, with large main span and multiple short approach spans, and choose instead a structure which crossed the valley in eight approximately equal spans. When the bids came in, the concrete option conforming to the final design was several million pounds cheaper than steel.
Several types of foundation support the bridge. Where the sandstone and mudstone are close to the surface at the banks, simple pad foundations have been built. Where the bedrock lies deeper, 6.9-foot-diameter bored piles hold up the piers. And a hefty caisson supports each of the two main piers to resist erosion and withstand ship impacts.
CASTING THE BOX GIRDER SEGMENTS
The eight-span bridge is made up of 251 precast concrete box units. Each one is 9 feet long, and depths range from 10 to 19 feet as required by the bridge's tapering profile.
ERECTION USING LAUNCHING GIRDER
The Torridge Bridge superstructure was pieced together as a series of balanced cantilevers. The contractor used a 377-foot-long steel launching girder to place individual boxes at the rate of four a day. Abutting faces of the deck boxes were coated with epoxy resin before the boxes were pulled together.