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20-463: The first Bloomfield Bridge was a steel cantilever bridge built in 1914 by the Fort Pitt Bridge Works. The bridge was 2,100 feet (640 m) long with a 400-foot (120 m) main span consisting of two 140-foot (43 m) cantilever arms supporting a 120-foot (37 m) suspended section. It was designed by engineer T. J. Wilkerson and architect Stanley L. Roush and cost about $ 500,000. At

40-453: A bus rapid transit system, also traverses the ravine. Also under the edifice is a community football and baseball field. Originally known as Dean's Field, it is historically significant as the place where Johnny Unitas played semi-pro football before jumpstarting his NFL career. After a shootout that killed three police officers , the area was renamed after a fallen officer who resided nearby. Cantilever bridge A cantilever bridge

60-653: A cantilever bridge. The Forth Bridge is a notable example of an early cantilever bridge. This bridge held the record for longest span in the world for twenty-nine years until it was surpassed by the Quebec Bridge . The engineers responsible for the bridge, Sir Benjamin Baker and Sir John Fowler , demonstrated the structural principles of the suspended span cantilever by sitting in chairs and supporting their colleague, Kaichi Watanabe , in between them, using just their arms and wooden poles. The suspended span, where Watanabe sits,

80-498: A hinge in the girder. Heinrich Gerber was one of the engineers to obtain a patent for a hinged girder (1866) and is recognized as the first to build one. The Hassfurt Bridge over the Main river in Germany with a central span of 124 feet (38 metres) was completed in 1867 and is recognized as the first modern cantilever bridge. The High Bridge of Kentucky by C. Shaler Smith (1877),

100-405: A major engineering breakthrough when first put into practice, as it can span distances of over 1,500 feet (450 m), and can be more easily constructed at difficult crossings by virtue of using little or no falsework . Engineers in the 19th century understood that a bridge that was continuous across multiple supports would distribute the loads among them. This would result in lower stresses in

120-547: A pin, usually after forcing the union point apart, and when jacks are removed and the bridge decking is added the bridge becomes a truss arch bridge . Such unsupported construction is only possible where appropriate rock is available to support the tension in the upper chord of the span during construction, usually limiting this method to the spanning of narrow canyons. World's longest cantilever bridges (by longest span): Niagara Cantilever Bridge The Niagara Cantilever Bridge or Michigan Central Railway Cantilever Bridge

140-678: A successor until 1984. On the Bloomfield side of the bridge, connections are made to Liberty Avenue, the commercial heart of the traditionally Italian (and increasingly Asian) neighborhood. On the Polish Hill side, PA 380 can be accessed, which runs toward Downtown Pittsburgh and Oakland , the home of several major universities. The Bloomfield Bridge spans a large number of railroad tracks, which are portions of lines managed by CSX and Norfolk Southern . The Martin Luther King Jr. East Busway ,

160-413: A wedding. The old Bloomfield Bridge was closed in 1978 and demolished in 1980. The replacement crossing was erected in 1986, after the previous bridge was deemed deficient after years of heavy traffic, including that of popular Pittsburgh Railways streetcar lines until their 1960s conversion to buses. Although the first Bloomfield Bridge was closed in 1978, state funding issues halted work on constructing

180-400: Is a bridge built using structures that project horizontally into space, supported on only one end (called cantilevers ). For small footbridges , the cantilevers may be simple beams ; however, large cantilever bridges designed to handle road or rail traffic use trusses built from structural steel , or box girders built from prestressed concrete . The steel truss cantilever bridge was

200-505: Is formed by two cantilever arms extending from opposite sides of an obstacle to be crossed, meeting at the center. In a common variant, the suspended span , the cantilever arms do not meet in the center; instead, they support a central truss bridge which rests on the ends of the cantilever arms. The suspended span may be built off-site and lifted into place, or constructed in place using special travelling supports. A common way to construct steel truss and prestressed concrete cantilever spans

220-424: Is in the center. The wooden poles resist the compression of the lower chord , while the outstretched arms support the tension of the upper chord. The placement of the brick counterweights demonstrates the action of the outer foundations. Cantilever Bridge.—A structure at least one portion of which acts as an anchorage for sustaining another portion which extends beyond the supporting pier. A simple cantilever span

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240-405: Is to counterbalance each cantilever arm with another cantilever arm projecting the opposite direction, forming a balanced cantilever ; when they attach to a solid foundation, the counterbalancing arms are called anchor arms . Thus, in a bridge built on two foundation piers, there are four cantilever arms: two which span the obstacle, and two anchor arms that extend away from the obstacle. Because of

260-534: The Lower Arch Bridge . Charles Conrad Schneider , the architect, chose a cantilever design due to the geography of the Niagara Gorge . Construction began in 1883. Boston cement was used for the foundation. The bridge was completed within months as a deadline was imposed by the railway: the steel sections gained approximately 3.8 meters each day and the central section was built in a total of five days. When

280-527: The Niagara Cantilever Bridge by Charles Conrad Schneider (1883) and the Poughkeepsie Bridge by John Francis O'Rourke and Pomeroy P. Dickinson (1889) were all important early uses of the cantilever design. The Kentucky River Bridge spanned a gorge that was 275 feet (84 metres) deep and took full advantage of the fact that falsework, or temporary support, is not needed for the main span of

300-399: The bridge was finished, a crowd watched the final tests conducted by engineers and this was reported on by The New York Times . The bridge could handle two trains crossing simultaneously. The Niagara Cantilever Bridge became less useful as locomotives became heavier. Another steel arch was added in 1923 as an intermediate measure, with plans to replace the bridge entirely. When deconstructing

320-410: The girder or truss and meant that longer spans could be built. Several 19th-century engineers patented continuous bridges with hinge points mid-span. The use of a hinge in the multi-span system presented the advantages of a statically determinate system and of a bridge that could handle differential settlement of the foundations. Engineers could more easily calculate the forces and stresses with

340-411: The need for more strength at the balanced cantilever's supports, the bridge superstructure often takes the form of towers above the foundation piers. The Commodore Barry Bridge is an example of this type of cantilever bridge. Steel truss cantilevers support loads by tension of the upper members and compression of the lower ones. Commonly, the structure distributes the tension via the anchor arms to

360-602: The outermost supports, while the compression is carried to the foundations beneath the central towers. Many truss cantilever bridges use pinned joints and are therefore statically determinate with no members carrying mixed loads. Prestressed concrete balanced cantilever bridges are often built using segmental construction . Some steel arch bridges (such as the Navajo Bridge ) are built using pure cantilever spans from each side, with neither falsework below nor temporary supporting towers and cables above. These are then joined with

380-521: The time of construction, it was the longest, highest, and one of the most expensive bridges in Pittsburgh. The bridge was dedicated on November 19, 1914, with what the Pittsburgh Post described as a "monster celebration" which included a wedding for a local couple performed at the midpoint of the span. This tradition was continued with the dedication of the replacement bridge in 1986, which also featured

400-617: Was a cantilever bridge across the Niagara Gorge . An international railway -only bridge between Canada and the United States , it connected Niagara Falls , New York , and Niagara Falls , Ontario . It was replaced by the Michigan Central Railway Steel Arch Bridge in 1925. Michigan Central Railway commissioned the Niagara Cantilever Bridge as a more cost effective alternative to leasing from

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