Suspension bridge types

A suspension bridge is any type of bridge that makes significant use of tension rather than or in addition to compression. A suspension bridge usually has main cables (else ropes or chains), anchored at each end of the bridge. Any load applied to the bridge is transformed into a tension in these main cables. The earliest suspension bridges had the cables anchored in the ground at either end of the bridge, but some modern suspension bridges anchor the cables to the ends of the bridge itself. The earliest suspension bridges had no towers or piers, but these are present in the majority of larger suspension bridges. Although the earlier types of suspension bridges are suitable only for relatively short spans, all of the 14 longest bridges in the world are suspension bridges (see List of longest suspension bridge spans). Ignoring the possibility of pre-Columbian trans-oceanic contact, there were two independent inventions of the suspension bridge, in Eurasia (probably in China) and in Central and South America.

Types of suspension bridge include the following:

A pure suspension bridge is one without additional stay cables and in which the main cables are anchored in the ground. This includes most simple suspension bridges and suspended-deck suspension bridges, and excludes self-anchored suspension bridges.

Some suspension bridges are of unusual hybrid types. Among these are suspension bridges that have an "intermediate deck". These bridges have a portion of deck that resembles an underspanned suspension bridge. Some of the earliest suspended-deck suspension bridges were of this type, and they continue to be constructed. Examples constructed in the 20th century include a viaduct over the river Oberargen near Wangen, Germany. A 258-metre (846 ft) span of the viaduct has a cable support below the deck, with one end of the cable anchored at a pier and the other end tied into a conventional cable stay. The underspanned portion of the span is 172-metre (564 ft) long and has three vertical members.

The Akashi-Kaikyō Bridge, one of the longest suspension bridges in the world, is a suspended-deck suspension bridge with a stiff truss girder deck. Its main span is 1,991 meters long.

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