Eads Bridge

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Eads Bridge
1983, from Library of Congress HAER project
Carries	4 highway lanes 2 MetroLink tracks
Crosses	Mississippi River
Locale	St. Louis, Missouri and East St. Louis, Illinois
Design	Arch bridge
Longest span	520 feet (158 m)
Total length	6,442 feet (1,964 m)
Width	46 feet (14 m)
Clearance below	88 feet (27 m)
Opening date	1874
Coordinates	38°37′45″N, 90°10′47″W

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, Captain 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.^[1]

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"). Fifteen workers died, two other workers were permanently disabled, and 77 were severely afflicted.^[2]

The bridge was owned and operated by the Terminal Railroad Association of St. Louis from the 1890s until 1989 when it was swapped for the MacArthur Bridge (St. Louis).^[3]

The Eads Bridge is still in use, and stands on the St. Louis riverfront between Laclede's Landing on the north and the grounds of the Gateway Arch to the south. Today the road deck has been restored, allowing vehicle and pedestrian traffic to cross the river. The rail deck has been in use for the St. Louis Metrolink light rail line since 1993.

A panoramic image of Eads Bridge

1 History
2 See also
3 References
4 External links

[edit] History

The Eads Bridge under construction, 1870s

Eads Bridge from East Riverfront MetroLink station, Illinois side

An 1875 drawing of Eads Bridge by Camille N. Dry.

The Eads Bridge was constructed as the first link to Illinois over the Mississippi River at St. Louis. The domination of the river trade was no longer as important as before the War between the States, and Chicago was fast gaining as the center of commerce in the West. The Bridge was conceived as a solution to the futile quest to reverse this new found eminence. The bridge, generated in controversy, was also considered a radical design solution, though 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 also constraints on span size and regarding the height above the water line. The location dictated a change from the low Illinois floodplain of the east bank to the high Missouri cliff on the west bank of the river. The bedrock was exceedingly deep.

These pressures resulted in a bridge noted as innovative for precision and accuracy of construction and quality control. Utilization of cast chromium steel components is arguably the first use of structural alloy steel in a major building construction. (Though the bridge as actually completed contained large - and unknown - amounts of wrought iron.)^[1] 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 falseworks 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 overcapitalized 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.

From material recorded by Kevin Murphy, Historian HAER, April 1984 in the public domain.