Steel The Eads Bridge, completed in 1874, was the first large bridge constructed completely of steel, excluding the pier foundations. It was designed by James Buchanan Eads and has three arch spans, the two sides being 151 metres (502 feet) and the centre being 156 metres (520 feet). The total length of the bridge is 810 feet.
It connects St. Louis with East Saint Louis, Illinois, and is one of only four bridges over the Mississippi River between Chicago and St. Louis. The others are the Lewis and Clark Bridge over the Missouri River in Portland, Oregon; the Gerald R. Ford Bridge over the Detroit River in Windsor, Ontario; and the Robert Moses Bridge over the Hudson River in New York City.
Eads originally proposed a wooden bridge, but the cost would have been too high so he designed a steel one instead. The main advantage of a steel bridge is that it lasts longer: despite the fact that wood can be used as a building material, steel frames are now used instead. In addition, a steel bridge is more flexible than a wood one because you can move buildings up or down off the bridge if needed. A third reason is economy: since metal can be recycled, there is no need to replace the materials used in construction every few years like with wood.
The Eads Bridge is also notable for being the first major American structure to be built using the iron-framed skyscraper design.
1874 According to the City of St. Louis, the Eads Bridge in St. Louis, MO, built in 1874, was not only the world's first steel bridge but also one of the first constructions of any sort in the United States to employ steel as a key construction component. The previous year, another steel-frame bridge had been completed over the Ohio River at Louisville, making St. Louis' structure the first true world's-class bridge made entirely from steel.
The St. Louis bridge was an innovative design by John A. Roebling's sons, who had become renowned for their work on other bridges around the country. The elder Roebling had died in 1870, leaving the younger men to run his business alone. They continued to build bridges across America for more than a century after their father's death, using his designs and developing new techniques of their own. The most famous of these structures is probably the Brooklyn Bridge in New York City, which was built between 1869 and 1883.
The Eads Bridge was an improvement upon its predecessor, the Cabell Street Bridge, which had collapsed three years earlier under too much traffic load. The new bridge used heavier materials for its abutments—granite from Massachusetts instead of brick—and employed steel instead of wood for its main span. The design proved so successful that it was repeated across the nation.
Steel, a somewhat scarce resource, was required by Eads to construct the bridge. So, where did you go in the mid-late nineteenth century to get steel? Andrew Carnegie and James Eads got into an argument right away. Eads needed steel of the greatest conceivable grade, substantially more refined than anything else available at the time. So, he decided to make his own!
The process involved taking iron ore and adding carbon to produce steel. The carbon could be in the form of coke, which is burned with the iron ore, or limestone, which can be decarburized with heat from the burning coke. Either way, this produces much higher-quality steel than any previously known. By the time James Eads had finished refining his steel, it was acceptable for use in construction materials. He also designed and built some of the first factories that could successfully produce enough high-quality steel for large structures like bridges.
Andrew Carnegie produced his first shipment of steel in 1872. But he wanted no part in constructing bridges, so he provided only the material needed for hot-rolled stock. That is, he supplied the steel for making other steel products. In 1876, James Eads submitted a proposal to Pittsburgh's Daily Post to build a bridge over the Monongahela River.
Steel and concrete The bridge was the first composite concrete-steel arch bridge built in the United States, and its twin-ribbed arch is the widest in the Western Hemisphere. The two ribs are linked laterally by Vierendeel steel trusses that offer seismic protection, forming a 1,060-foot-long, 277-foot-deep arch. The main span is 865 feet long with 10 vertical lanes for traffic. The deck is 80 feet wide with 12-inch-wide sidewalks on either side.
The original intent was to build the dam first and then come back to build the bridge, but due to cost overruns and changes requested by the Bureau of Reclamation, this did not happen. The project was completed instead in September 1952. The total cost was $750 million ($4.9 billion in 2007 dollars).
The chief architect was James Knox Taylor with assistance from Robert M. Rose who also designed the Lincoln Memorial in Washington, D.C. The chief engineer was William E. Humphreys. Both men were members of the consulting team that designed the Hoover Dam before going their own ways with Humphreys taking charge of the bridge project. He died before it was complete, so his son John L. Humphreys finished what he could and then handed over the job to another contractor (who had no relation). The official opening ceremony was held on July 10, 1952. The first vehicle crossed the new bridge that day. It was a bus full of tourists who had paid $1 each for the privilege.
A steel-spanned bridge Steel bridges are used on roads when big spans, i.e. spans of more than 100–200 meters, are involved. Steel bridges have three main designs: the girder, which is the most popular, the arch, and the suspension. In addition, some special purpose bridges are made of other materials, such as concrete or wood.
Girder bridges have wide beams that carry the load. The space between the beams is filled with girders to form a grid pattern. At each end of the grid, there is a single tower that supports the weight above. These towers can be as high as 80 meters for very large bridges. Girder bridges are the most common type of bridge used across rivers, over railroad tracks, and for highway bridges. They are also used in small towns as stand-alone bridges when no other type of bridge is appropriate. Examples include those crossing creeks or small streams, or where the need is only for pedestrian traffic.
Arch bridges have two parallel beams that form an "S" shape at their top. There may be some vertical posts inside the arch to help support it. At the bottom, there is a single pier that sticks out into the stream or road bed. This type of bridge requires less material per lane mile than other types of bridge because there are no girders under the deck. It is therefore cheaper to build.
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