Хьюи П. Лонг Көпірі: Миссисипи өзеніндегі тарих және жаңару

Road and railroad bridge in Louisiana, U. S.

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. It is several kilometers upriver from the city of New Orleans. The East Bank entrance is at Elmwood, Louisiana, and the West Bank at Bridge City. Opened in December 1935, the bridge was named for the late Governor Huey P. Long, who was 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 was designed by Polish American engineer Ralph Modjeski and is designated as a National Historic Civil Engineering Landmark by the American Society of Civil Engineers. 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 feet (3 m) lanes in each direction, with inside and outside shoulders. Prior to the expansion, there were two 9 feet (3 m) lanes in each direction with no shoulders. In both cases, the road lanes flanked the twin railroad tracks contained within the truss. in 2014, a writer at 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."

The widest clear span is 790 feet (241 m) long while each of the three additional spans are 530 feet (162 m) long, making the total river crossing about 2400 feet (732 m) long. There are three navigation channels below the bridge, the widest being 750 feet (229 m). The vertical clearance below the structure is 152.9 feet (47 m). The distinctive rail structure is 22996 feet (7009 m) long and extends as rail viaducts well into the city on both sides of the river from the central spans. It has sometimes been described as the longest rail bridge in the US, but the nearby Norfolk Southern Lake Pontchartrain Bridge, at 5.8 mile (9 km), is considerably longer. The highway structure is 8076 feet (2462 m) long with steep grades on both sides. As originally constructed, each roadway deck was 18 feet (5 m) wide, with two 9 feet (3 m) 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. 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 9 feet (3 m) 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 3 feet (1 m) 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, known colloquially as "gumbo soil," is compressible and unsuitable for foundation loads. As bedrock is around 1000 feet (305 m) below the surface, making it too deep for normal bridge foundation construction, the main piers are seated on a layer of fine sand below Mean Gulf Level and rely on their size and mass to hold them in place. The bridge dates from an era when 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 in New Orleans before its renovation, was built further upstream in 1940 in Baton Rouge, Louisiana. 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 exclusive road use (McKinley since 1978), sometimes with bicycle and/or pedestrian use added (McKinley in 2007, Harahan in 2016).

As early as 1892 the Southern Pacific Railway proposed a high level bridge, but a depression that year prevented further work on a project that would have been an overwhelming challenge for the engineers of the time due to soil conditions and extremely high clearances for river navigation. With the development of the Public Belt Railroad, interest in a river rail crossing grew and led to passage of a constitutional amendment in 1916 granting the city exclusive power to build and operate a crossing. Three general ideas emerged from the planning process: a low level drawbridge, a tunnel, and a high level bridge. The tunnel idea died first, because it would have provided limited capacity, and the War Department (after years of wrangling) ultimately rejected the idea of a drawbridge as too problematic for such a significant concentration of vital transportation infrastructure. Work on the design of the bridge began in earnest in 1925 by the engineering firm of Modjeski and Masters. Some pilings were actually driven that year to prevent expiration of congressional authority and provide further information for the design. As the magnitude of the project became apparent and projected costs ballooned, financing difficulties compounded by the Great Depression delayed the project. Finally, on November 5, 1932, the bonds of the Public Belt Railroad Commission were guaranteed by a complex agreement between the Southern Pacific Railroad, the City of New Orleans and the State of Louisiana. Principal construction contracts were signed on December 30, 1932, and work formally started the following day. Construction of the bridge proceeded smoothly over a three year period with only minor interruptions due to high water and a one month strike in September 1933.

The Huey P. Long Bridge Widening Project is a TIMED (Transportation Infrastructure Model for Economic Development) Program project. The TIMED Program was created by Act 16 of the 1989 Louisiana Legislature, was voted for by the people and is the single largest transportation program in state history. The Program is designed to enhance economic development in Louisiana through an investment in transportation projects. The $1.2 billion widening project started in April 2006 and is the first change to the structure since it opened in 1935. The project expanded the highway on each side of the structure from two 9 feet (3 m) lanes to three 11 feet (3 m) lanes with a 2 feet (1 m) inside shoulder and an 8 feet (2 m) outside shoulder. It also included new signalized intersections to replace the traffic circles at Jefferson Highway and at Bridge City Avenue, both in Jefferson Parish, Louisiana.

On April 27, 2015, a severe storm knocked several double stack train cars off the track as the train crossed the Huey P. Long Bridge, with no injuries reported. The accident was captured by a WGNO News Team dashcam.

Huey P. Long Bridge Widening Project, Louisiana DOTD (June 2007) (archived copy). , HNTB, August 9, 2011. Seven minute animation of erection of trusses widening river spans to enlarge roadway. , May 11, 2012. Seventeen minute long video taken from the westbound Sunset Limited as it climbs the east bank viaduct, crosses the truss spans as construction continues on the new road lanes while old 18 feet (5 m) carriageways are still in use, and then descends the west bank viaduct to its landing. , April 11, 2016. Fifteen minute long video very similar to 2012 video linked immediately above, showing completed highway lanes.