Eads Bridge
The Eads Bridge is a combined road and railway bridge over the Mississippi River at St. Louis, connecting St. Louis and East St. Louis, Illinois.
The bridge is named for its designer and builder, James B. Eads. When completed in 1874, the Eads Bridge was the longest arch bridge in the world, with an overall length of 6,442 feet (1,964 m). The ribbed steel arch spans were considered daring, as was the use of steel as a primary structural material: it was the first such use of true steel in a major bridge project.[4]
The Eads Bridge was also the first bridge to be built using cantilever support methods exclusively, and one of the first to make use of pneumatic caissons. The Eads Bridge caissons, still among the deepest ever sunk, were responsible for one of the first major outbreaks of "caisson disease" (also known as "the bends" or decompression sickness).[5] Fifteen workers died, two other workers were permanently disabled, and 77 were severely afflicted.[5][6]
On June 14, 1874, John Robinson led a "test elephant" on a stroll across the new Eads Bridge to prove it was safe. A big crowd cheered as the elephant from a traveling circus lumbered towards Illinois. It was believed that elephants had instincts that would keep them from setting foot on unsafe structures. Two weeks later, Eads sent 14 locomotives back and forth across the bridge at one time.[7] The opening day celebration on July 4, 1874 featured a parade that stretched fifteen miles through the streets of St. Louis.[8]
The Eads Bridge, which became an iconic image of the city of St. Louis, from the time of its erection until 1965 when the Gateway Arch was constructed, is still in use. The bridge crosses the St. Louis riverfront between Laclede's Landing, to the north, and the grounds of the Gateway Arch, to the south. Today the road deck has been restored, allowing vehicular and pedestrian traffic to cross the river. The St. Louis MetroLink light rail system has used the rail deck since 1993.
Contents
1 History 2 See also 3 References 4 Further reading 5 External links
History Poster showing the construction of the bridge in different phases, ca. 1874. The Eads Bridge under construction, 1870s Eads Bridge from East Riverfront MetroLink station, Illinois side Eads Bridge showing MetroLink train running on lower deck. Light posts for upper automobile deck can be seen along the upper rails. An 1875 drawing of Eads Bridge by Camille N. Dry. Toll collection
The Eads Bridge was built by the Illinois and St. Louis Bridge Company, with the Keystone Bridge Company serving as subcontractor for superstructure erection.[9]
The domination of the river trade was no longer as important as before the American Civil War, and Chicago was fast gaining as the center of commerce in the West. The bridge was conceived as a solution for St. Louis to regain eminence by connecting transportation across the river.
In an attempt to secure their future, steamboat interests successfully lobbied to place restrictions on bridge construction, requiring spans and heights previously unheard of. Ostensibly this would maintain sufficient operating room for steamboats beneath the bridge’s base for the then foreseeable future. The unproclaimed purpose was to require a bridge so grand and lofty that it would be impossible to erect according to conventional building techniques. The steamboat parties planned to prevent any structure from being built, in order to ensure continued dependence on river traffic to sustain commerce in the region.
Such a bridge required a radical design solution. The ribbed arch had been a known construction technique for centuries. The triple span, tubular metallic arch construction was supported by two shore abutments and two mid-river piers. Four pairs of arches per span (upper and lower) were set eight feet apart, supporting an upper deck for vehicular traffic and a lower deck for rail traffic.
Construction involved varied and confusing design elements and pressures. State and federal charters precluded suspension or draw bridges, or wood construction. There were constraints on span size and the height above the water line. The location dictated reconciling differences in heights from the low Illinois floodplain of the east bank to the high Missouri cliff on the west bank of the river. The bedrock required deep drilling to reach, as it was 38 m below water level on the Illinois side and 26 m below on the Missouri side.[10][11]
These pressures resulted in a bridge noted as innovative for precision and accuracy of construction and quality control. This was the first use of structural alloy steel in a major building construction, through use of cast chromium steel components. The completed bridge also relied on significant—and unknown—amounts of wrought iron.[4] Eads argued that the great compressive strength of steel was ideal for use in the upright arch design. This decision resulted from a curious combination of chance and necessity, due to the insufficient strength of alternative material choices.
The particular physical difficulties of the site stimulated interesting solutions to construction problems. The deep caissons used for pier and abutment construction signaled a new chapter in civil engineering. Unable to construct falsework to erect the arches, because they would obstruct river traffic, Eads's engineers devised a cantilevered rigging system to close the arches.
Although recognized as an innovative and exciting achievement, the Eads Bridge was undercapitalized during construction and burdened with debt. With its focus on the river, St. Louis had a lack of adequate rail terminal facilities, and the bridge was poorly planned to coordinate rail access. An engineering and aesthetic success, the bridge was bankrupt within a year of opening.
Granite for the bridge came from the Iron County, Missouri quarry of Missouri Governor and U.S. Senator B. Gratz Brown who had helped secure federal financing for the bridge.[12]
The Merchants Exchange eventually lost ownership to the Terminal Railroad Association of St. Louis (TRRA). The Exchange, fearing a Terminal Railroad rail monopoly on the bridges, would then build the Merchants Bridge, which in turn would eventually be taken over by the Terminal Railroad. The Terminal Railroad transferred the bridge to the City of St. Louis in 1989 in exchange for the MacArthur Bridge.[13]
Eads Bridge had long hosted only passenger trains on its rail deck. By the 1970s, the TRRA had abandoned its Eads trackage, as the bridge had lost all remaining passenger rail traffic to the MacArthur Bridge during the early years of Amtrak; the dimensions of modern passenger diesels were incompatible with both the bridge and the adjoining tunnel linking the Union Station trackage with Eads.
In 1998, the Naval Facilities Engineering Service Center investigated the effects of the ramming of the bridge by the barge Anne Holly on April 4 of that year. The ramming resulted in the near breakaway of the SS Admiral riverboat casino; several recommended changes reduced the odds of this happening in the future.[14]
