Through arch bridge

A through arch bridge, also known as a half-through arch bridge and through-type arch bridge, is a bridge made from materials such as steel or reinforced concrete in which the base of an arch structure is below the deck, but the top rises above it, so the deck passes through the arch. Cables or beams in tension suspend the central part of the deck from the arch.

Function

For a specific construction method, especially for masonry arches, the proportions of the arch remain similar no matter what the size: wider arches are thus required to be taller arches. For a semi-circular arch, the height is half of the span. Bridges across deep, narrow gorges can have their arch placed entirely beneath a flat roadway, but bridges in flatter country rise above their road approaches. A wide bridge may require an arch so tall as to become a significant obstacle and incline for the roadway. Small bridges can be hump-backed, but larger bridges such as the Old Bridge, Pontypridd may become so steep as to require steps, making their use for wheeled traffic difficult. Railways also find arched bridges difficult as they are even less tolerant of inclines. Where simple arched bridges are used for railways on flat terrain the cost of building long approach embankments may be considerable.

Arch bridge

An arch bridge is a bridge with abutments at each end shaped as a curved arch. Arch bridges work by transferring the weight of the bridge and its loads partially into a horizontal thrust restrained by the abutments at either side. A viaduct (a long bridge) may be made from a series of arches, although other more economical structures are typically used today.

History

Possibly the oldest existing arch bridge is the Mycenaean Arkadiko bridge in Greece from about 1300 BC. The stone corbel arch bridge is still used by the local populace. The well-preserved Hellenistic Eleutherna Bridge has a triangular corbel arch. The 4th century BC Rhodes Footbridge rests on an early voussoir arch.

Although true arches were already known by the Etruscans and ancient Greeks, the Romans were - as with the vault and the dome - the first to fully realize the potential of arches for bridge construction. A list of Roman bridges compiled by the engineer Colin O'Connor features 330 Roman stone bridges for traffic, 34 Roman timber bridges and 54 Roman aqueduct bridges, a substantial part still standing and even used to carry vehicles. A more complete survey by the Italian scholar Vittorio Galliazzo found 931 Roman bridges, mostly of stone, in as many as 26 different countries (including former Yugoslavia).

Bridge

A bridge is a structure built to span physical obstacles without closing the way underneath such as a body of water, valley, or road, for the purpose of providing passage over the obstacle. There are many different designs that each serve a particular purpose and apply to different situations. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, the material used to make it, and the funds available to build it.

Etymology

The Oxford English Dictionary traces the origin of the word bridge to an Old English word brycg, of the same meaning. The word can be traced directly back to Proto-Indo-European *bʰrēw-. The word for the card game of the same name has a different origin.

History

The first bridges made by humans were probably spans of cut wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement. Some early Americans used trees or bamboo poles to cross small caverns or wells to get from one place to another. A common form of lashing sticks, logs, and deciduous branches together involved the use of long reeds or other harvested fibers woven together to form a connective rope capable of binding and holding together the materials used in early bridges.

Chaotianmen Bridge

The Chaotianmen Bridge (simplified Chinese: 朝天门长江大桥; traditional Chinese: 朝天門長江大橋; pinyin: Cháotiān mén chángjiāng dàqiáo), is a road-rail bridge over the Yangtze River in the city of Chongqing, China. The bridge which opened on 29 April 2009 is the world's longest arch bridge.

The continuous steel truss arch bridge with tie girders has a height of 142 m (466 ft) from middle supports to arch top, main span of 552 m (1,811 ft) and a total length of 1,741 m (5,712 ft). It carries 6 lanes in two ways and a pedestrian lane on each side on the upper deck, and dual light rails in the middle and 2 traffic lanes on each side on the lower deck.

See also

References

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