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The Huey P. Long Bridge, located in Jefferson Parish, Louisiana, is a cantilevered steel through truss bridge that carries a two-track railroad line over the Mississippi River at mile 106.1 with three lanes of US 90 on each side of the central tracks. Opened in December 1935 to replace the Walnut Street Ferry, the bridge was named for the popular and notorious governor, Huey P. Long, who had just been assassinated on September 8 of that year. The bridge was the first Mississippi River span built in Louisiana and the 29th along the length of the river. It is a few miles upriver from the city of New Orleans. The East Bank entrance is at Elmwood, Louisiana and the West Bank at Bridge City. It was designed by Polish-American engineer Ralph Modjeski. On June 16, 2013, a $1.2 billion widening project by the Louisiana Department of Transportation and Development was completed and opened to motorists. The bridge now consists of three 11-foot lanes in each direction, with inside and outside shoulders. Prior to the expansion, there were two 9-foot lanes in each direction with no shoulders. in 2014, a writer in ''The New Yorker'' described the bridge as "a structure so vaulting and high that it seems to extend from one white, towering Gulf Coast cloud to the next."〔Frazier, Ian, "Streetscape: Do Not Cross," ''The New Yorker,'' June 2, 2014, p. 26.〕 ==Structure== The widest clean span is long and sits above the water. There are three navigation channels below the bridge, the widest being . The distinctive rail structure is long and extends as a rail viaduct well into the city. It has sometimes been described as the longest rail bridge in the US, but the nearby Norfolk Southern Lake Pontchartrain Bridge, at , is considerably longer. The highway structure is long with extremely steep grades on both sides. As originally constructed, each roadway deck was a precarious wide, with two nine-foot lanes; but because of the railroad component, it is unusually flat. Normally, bridges its height have a hump, but this bridge was designed flat to facilitate rail traffic.〔http://www.johnweeks.com/lower_mississippi/pages/lmiss16.html〕 The bridge is a favorite railfan location. It is owned by the New Orleans Public Belt Railroad, which is owned by the City of New Orleans and managed by the Public Belt Railroad Commission. The bridge was hated by many drivers in the New Orleans area due to the narrow wide lanes without shoulders before it was widened. Additionally, where the East Bank approach met the superstructure of the bridge, the two vehicular roadways "jogged" or shifted inwards towards the bridge centerline about since the through-truss portion of the superstructure was wider than the deck truss portion of the east approach. The foundation of the bridge is also unique. The land in and around New Orleans was formed by silt deposits brought down the Mississippi River. The clay topsoil (notorious for its role in the Hurricane Katrina levee failures) is compressible and unsuitable for foundation loads. However, bedrock is around below the surface, making it too deep for normal bridge foundation construction. So, the main piers are seated on a layer of fine sand 160 to below Mean Gulf Level and rely on their massive weight and girth to hold them in place. The bridge dates from an era when the construction of large works presented significant engineering challenges and the needs of rail and auto travel were more matched than they are today. Large bridges mixing rail tracks and highways were common, as typified by the MacArthur Bridge and McKinley Bridge in St. Louis, Missouri and the Harahan Bridge in Memphis, Tennessee. A second Huey P. Long Bridge, which is very similar to the design of this bridge before its renovation, was built further upstream in 1940 in Baton Rouge, Louisiana and was mainly the last of its kind. While both of the Long bridges still carry both types of traffic, most of the others have been converted either to entirely rail use (Harahan since 1949, MacArthur since 1981) or entirely auto use (McKinley since 1978), sometimes with bicycle and/or pedestrian use added (McKinley in 2007, Harahan by mid-2014), and new large bridges are always devoted exclusively to meeting increasing vehicular traffic needs. Current rail demands are well met by existing bridges that are a testament to the care and craftsmanship of early 20th-century bridge builders. 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「Huey P. Long Bridge (Jefferson Parish)」の詳細全文を読む スポンサード リンク
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