ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306966
The segmental cantilevers of the west bridge (southbound) extend out over the environmentally sensitive valley where even foot traffic is prohibited. 26 | ASPIRE , Winter 2008 California bridge designers and contrac- tors have not built many segmental bridges, owing to their expertise with other types of construction. But a bridge project now underway along the Pacific Coast Highway in northern California, and another following shortly behind, may open the door to more such projects, particularly in areas with difficult terrain or with requirements for large falsework openings. The project, which consists of two side- by-side curved bridges, is located about 18 miles south of San Francisco between Pacifica and Montara and will connect Highway 1 to the north portal of two tunnels running through San Pedro Mountain. Each three-span bridge is approximately 1000 ft long and 29 ft wide. Two sets of twin piers on each side of the valley support 445-ft-long, cast-in-place concrete box girder main spans. Because of the structures' curved design and the shape of the valley, the end spans for the west structure are significantly longer than the end spans on the east bridge. The west bridge end spans are 281 ft and 251 ft while the east bridge spans are 230 ft and 225 ft. The concrete has a specified compressive strength of 6100 psi. Balanced Cantilever Approach used Caltrans engineers designed the bridges to be constructed by the balanced- cantilever method without falsework under the cantilevers. However, the contractor is using a balanced-cantilever approach that incorporates falsework for the end spans. This method still eliminates the need for falsework in the main span, where it would interfere with the environmental constraints. But it retains falsework for the end spans, which is the method most familiar to contractors in the state. profile D EvIl'S SlIDE BRIDgES / PACIfICA, CAlIfoRnIA E NgiNEER: California Department of transportation, Sacramento, Calif. P RiME CoNTRACToR: Disney Construction Inc., San Mateo, Calif. CoNTRACToR'S ENgiNEER: nutt, Redfield & Valentine (nRV), Sacramento, Calif. CoNCRETE SuPPliER: Central Concrete Supply Co. Inc., South San francisco, Calif. FoRM TRAvElER AND PoST TENSioNiNg SuPPliER: Schwager Davis Inc., San Jose, Calif. TRAvElER FoRMWoRk: DoKA, little ferry, n.J. California engineers and contractors are closely watching this segmental, cast-in-place concrete bridge, which may create new approaches in the state. Devil's sliDe openS poSSiBilitieS by Kevin Harper, California Department of Transportation 10973_ASPIRE_win08.indb 26 12/12/07 3:29:38 PM