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The Carquinez Bridge refers to parallel bridges spanning the Carquinez Strait, forming part of Interstate 80 between Crockett and Vallejo, in the U.S. state of California. The name originally referred to a single cantilever bridge built in 1927, helping to form a direct route between San Francisco and Sacramento. A second parallel cantilever bridge was completed in 1958 to deal with the increased traffic. Later, seismic problems of the 1927 span led to the construction and 2003 opening of a replacement: a suspension bridge officially called the Alfred Zampa Memorial Bridge. Currently, the Alfred Zampa Memorial Bridge carries westbound traffic from Vallejo to Crockett, and the 1958 cantilever span carries eastbound traffic. ==History and description== The original steel cantilever bridge was designed by Robinson & Steinman and dedicated on May 21, 1927. Prior to this, crossing the Carquinez Strait necessitated the use of ferries. The bridge cost $8 million to build. It was the first major crossing of the San Francisco Bay〔''The Barrier Broken'' - Vallejo Evening Chronicle, May 21, 1927〕 and a significant technological achievement in its time. Upon its completion, the span became part of the Lincoln Highway. This historic transcontinental roadway's original alignment, like the Transcontinental Railroad that preceded it nearly sixty years earlier, chose to avoid crossing the Carquinez Strait entirely. The preferred option, given the engineering limitations of the day, was to skirt around the Delta by going south from Sacramento through Stockton, then proceeding west across the San Joaquin River and over the Altamont Pass, and finally reaching Oakland from the south (a route that would later become U.S. Route 50 and ultimately Interstates 5, 205, and 580). This seemingly circuitous route, several miles longer and traversing a rather formidable mountain pass, was nevertheless preferable to the even more formidable prospect of bridging the Carquinez Strait, a deep channel with strong currents and frequent high winds. For decades, building a bridge here was considered prohibitively expensive and technologically risky. Once the bridge was built however, driving from Sacramento to the East Bay became much more direct. The Carquinez Bridge provided a welcome alternative route from the Central Valley to the Bay Area, one that no longer required loading one's vehicle onto and off of a ferry. With the bridge completed, the Lincoln Highway was realigned to cross the Sacramento River, then proceed southwest through Davis and Vallejo, across the Carquinez, and along the shores of the San Pablo and San Francisco bays to Richmond and Oakland (eventually U.S. Route 40 and ultimately Interstate 80). In 1958, at a cost of $38 million a second bridge was built alongside and to the east of the bridge. This new span, nearly identical to the first, was needed to accommodate the ever-increasing levels of traffic. The three-lane 1927 span, originally two-way, now served only westbound drivers while the 1958 span handled eastbound traffic. In 2003, as a resolution to seismic problems of the aging 1927 span brought to light after the Loma Prieta earthquake, a new suspension bridge was opened to replace it, at a cost of $240 million.〔 This new bridge was named the Alfred Zampa Memorial Bridge, after an ironworker who worked on a number of the San Francisco Bay Area bridges, including the Golden Gate Bridge and the original 1927 Carquinez span. This span features a pedestrian and bicycle path, part of a bike trail which it is hoped will eventually circle the entire Bay Area. The span measures . The bridge was dedicated on November 8, 2003 and opened for traffic on November 11. (Originally, the plan was to dedicate the bridge on November 15, but complications involving when just-recalled Governor Gray Davis would have to transfer power to Arnold Schwarzenegger resulted in the date being moved. The coins minted to commemorate the event have the old date on them.〔("Alfred Zampa memorial coins" ) - Official Web Site〕). The 1927 span was dismantled in 2007, after it was temporarily used to hold eastbound traffic while the eastbound span underwent a seismic retrofit, deck and superstructure rehabilitation, and painting to extend its serviceable life.〔(''"Old Carquinez Bridge is disappearing"'' ) - San Francisco Chronicle, April 25, 2006.〕 During demolition, the 3,000-pound bronze bell atop one of the Carquinez Bridge piers was removed and placed into storage. The bell will eventually be displayed in a new museum to be built at the Oakland end of the San Francisco – Oakland Bay Bridge. The new suspension bridge, to the west of the earlier bridges, has spans of 147 m, 728 m, and 181 m. Built by the Joint Venture consisting of Flatiron Structures (Longmont, Co.), FCI Constructors (Benicia, Ca.), and Cleveland Bridge & Engineering Company of Darlington, England, it consists of the south anchorage, a transition pier, two towers (South and North towers), and the north anchorage. The towers are each founded on two footings, which are each supported by six vertical, steel shells infilled with reinforced concrete, followed by drilled shafts in rock (i.e., cast-in-drilled hole, or CIDH, piles). The total length of the CIDH pile at the South Tower is approximately 89 m, with about 43 m of drilled shaft in rock. The total length of the CIDH pile at the North Tower ranges from 49 to 64 m, with about 16 to 26 m of drilled shaft in rock. The design parameters used for the South Tower piles were later confirmed by a pile load test. Additional field investigations during construction revealed significant variations in rock conditions at the North Tower, resulting in the redesign of the length of the piles. Major construction challenges encountered during construction of the South Tower piles, and the revised construction procedure (i.e., under-reaming) used by the constructor to mitigate caving. Materials for the New Bridge came from all over the world: * Steel Caissons for CIDH: XKT Engineering - Mare Island, Ca. * Orthotropic Deck Sections: IHI - Japan * Tower and Splay Saddles: Sheffield Steel (Castings - Sheffield, England) (Finishing and Machining: Kvaerner - England) * Main Cable Wire: Bridon - England * Wire for Cable Wrapping: Canada * Cable Bands - France * Suspenders (Hardware, Casting, Fabrication): WRCA - St. Joseph, Missouri * (3) Maintenance Travelers Under Deck Sections: Jesse Engineering - Tacoma, Washington By September 4, 2007, all of the original 1927 steel structure had been demolished. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Carquinez Bridge」の詳細全文を読む スポンサード リンク
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