| Description | This single bridge is 3,465 ft. long with 3 spans. This new Carquinez Strait bridge carries IH80 across the Sacramento River between Crockett and Vallejo and is an important link between Sacramento and the Bay Area. It is the first suspension bridge in the US with concrete towers. The bridge has two batter-leg concrete frame towers with classic draped cables and vertical suspender ropes to support the steel box girder deck. Each tower is supported by 12 drilled shafts that terminate in pile caps below sea level. The high cap position and deep water precluded use of conventional cofferdams, so the contractor provided a prefabricated, float-in cofferdam system. Designed as thin precast concrete shells in the shape of the specified pile caps, the cofferdams had corrugated block-outs in the bottom to allow the drilled shaft to fit up into the cap while remaining water-tight during the float-in. While the drilled shafts were installed, the cofferdams were cast on a barge deck and launched. Crews then cut the drilled shaft casings off underwater and floated the cofferdams into place. After sealing the cofferdams to the shaft casings, crews dewatered the cofferdam to allow extension of the drilled shaft reinforcing cages and then cast the pile caps. Construction completed in late 2003. This project used prefabricated cofferdams that functioned as float-in pile-cap shells. For the California Department of Transportation, use of prefabricated cofferdams expedited construction of the bridge and will increase the service life of the IH80 crossing. For the contractors, FCI Constructors and Cleveland Bridge California, use of prefabricated cofferdams greatly improved constructibility and work-zone safety. |
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