Suspended–deck suspension bridge

Suspension bridge
The Akashi Kaikyō Bridge in Japan, world's longest mainspan
The Akashi Kaikyō Bridge in Japan, world's longest mainspan
AncestorSimple suspension bridge
RelatedUnderspanned suspension bridge; see also cable-stayed bridge
DescendantSelf-anchored suspension bridge
CarriesPedestrians, bicycles, livestock, automobiles, trucks, light rail
Span rangeMedium to long
MaterialSteel rope, multiple steel wire strand cables or forged or cast chain links
MovableNo
Design effortmedium
Falsework requiredNo
The double-decked George Washington Bridge, connecting New York City to Bergen County, New Jersey, USA, is the world's busiest suspension bridge, carrying 102 million vehicles annually.[1][2]

A suspended–deck suspension bridge (often just suspension bridge) is a type of bridge in which the deck (the load-bearing portion) is hung below suspension cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s.[3][4] Simple suspension bridges, which lack vertical suspenders, have a long history in many mountainous parts of the world.

This type of bridge has cables suspended between towers, plus vertical suspender cables that carry the weight of the deck below, upon which traffic crosses. This arrangement allows the deck to be level or to arc upward for additional clearance. Like other suspension bridge types, this type often is constructed without falsework.

The suspension cables must be anchored at each end of the bridge, since any load applied to the bridge is transformed into a tension in these main cables. The main cables continue beyond the pillars to deck-level supports, and further continue to connections with anchors in the ground. The roadway is supported by vertical suspender cables or rods, called hangers. In some circumstances, the towers may sit on a bluff or canyon edge where the road may proceed directly to the main span, otherwise the bridge will usually have two smaller spans, running between either pair of pillars and the highway, which may be supported by suspender cables or may use a truss bridge to make this connection. In the latter case there will be very little arc in the outboard main cables.

History

The Manhattan Bridge, connecting Manhattan and Brooklyn in New York City, opened in 1909 and is considered to be the forerunner of modern suspension bridges; its design served as the model for many of the long-span suspension bridges around the world.

The earliest suspension bridges were ropes slung across a chasm, with a deck possibly at the same level or hung below the ropes such that the rope had a catenary shape.

Precursor

The Tibetan saint and bridge-builder Thangtong Gyalpo originated the use of iron chains in his version of simple suspension bridges. In 1433, Gyalpo built eight bridges in eastern Bhutan. The last surviving chain-linked bridge of Gyalpo's was the Thangtong Gyalpo Bridge in Duksum en route to Trashi Yangtse, which was finally washed away in 2004.[5] Gyalpo's iron chain bridges did not include a suspended deck bridge which is the standard on all modern suspension bridges today. Instead, both the railing and the walking layer of Gyalpo's bridges used wires. The stress points that carried the screed were reinforced by the iron chains. Before the use of iron chains it is thought that Gyalpo used ropes from twisted willows or yak skins.[6] He may have also used tightly bound cloth.

Chain bridges

The first iron chain suspension bridge in the Western world was the Jacob's Creek Bridge (1801) in Westmoreland County, Pennsylvania, designed by inventor James Finley.[7] Finley's bridge was the first to incorporate all of the necessary components of a modern suspension bridge, including a suspended deck which hung by trusses. Finley patented his design in 1808, and published it in the Philadelphia journal, The Port Folio, in 1810.[8]

An early plan for the chain bridge over the Menai Strait near Bangor, Wales, completed in 1826

Early British chain bridges included the Dryburgh Abbey Bridge (1817) and 137 m Union Bridge (1820), with spans rapidly increasing to 176 m with the Menai Bridge (1826), "the first important modern suspension bridge".[9] The first chain bridge on the German speaking territories was the Chain Bridge in Nuremberg. The Clifton Suspension Bridge (designed in 1831, completed in 1864 with a 214 m central span) is one of the longest of the parabolic arc chain type. The current Marlow suspension bridge was designed by William Tierney Clark and was built between 1829 and 1832, replacing a wooden bridge further downstream which collapsed in 1828. It is the only suspension bridge across the non-tidal Thames. The Széchenyi Chain Bridge, spanning the River Danube in Budapest, was also designed by William Clark and it is a larger scale version of Marlow bridge.[10]

An interesting variation is Thornewill and Warham's Ferry Bridge in Burton-on-Trent, Staffordshire (1889), where the chains are not attached to abutments as is usual, but instead are attached to the main girders, which are thus in compression. Here, the chains are made from flat wrought iron plates, eight inches (203 mm) wide by an inch and a half (38 mm) thick, rivetted together.[11]

Wire-cable

The first wire-cable suspension bridge was the Spider Bridge at Falls of Schuylkill (1816), a modest and temporary footbridge built following the collapse of James Finley's nearby Chain Bridge at Falls of Schuylkill (1808). The footbridge's span was 124 m, although its deck was only 0.45 m wide.

Development of wire-cable suspension bridges dates to the temporary simple suspension bridge at Annonay built by Marc Seguin and his brothers in 1822. It spanned only 18 m.[12] The first permanent wire cable suspension bridge was Guillaume Henri Dufour's Saint Antoine Bridge in Geneva of 1823, with two 40 m spans.[12] The first with cables assembled in mid-air in the modern method was Joseph Chaley's Grand Pont Suspendu in Fribourg, in 1834.[12]

In the United States, the first major wire-cable suspension bridge was the Wire Bridge at Fairmount in Philadelphia, Pennsylvania. Designed by Charles Ellet, Jr. and completed in 1842, it had a span of 109 m. Ellet's Niagara Falls suspension bridge (1847–48) was abandoned before completion. It was used as scaffolding for John A. Roebling's double decker railroad and carriage bridge (1855).

The Otto Beit Bridge (1938–39) was the first modern suspension bridge outside the United States built with parallel wire cables.[13]

Other Languages
Afrikaans: Hangbrug
العربية: جسر معلق
asturianu: Ponte colgante
azərbaycanca: Asma körpü
български: Висящ мост
català: Pont penjant
čeština: Visutý most
Cymraeg: Pont grog
dansk: Hængebro
Deutsch: Hängebrücke
eesti: Rippsild
español: Puente colgante
Esperanto: Pendoponto
euskara: Zubi eseki
فارسی: پل معلق
français: Pont suspendu
Frysk: Hingbrêge
한국어: 현수교
हिन्दी: झूला पुल
Bahasa Indonesia: Jembatan gantung
íslenska: Hengibrú
italiano: Ponte sospeso
עברית: גשר תלוי
қазақша: Аспалы көпір
lietuvių: Kabantis tiltas
magyar: Függőhíd
മലയാളം: തൂക്കുപാലം
Bahasa Melayu: Jambatan gantung
Nederlands: Hangbrug
日本語: 吊り橋
norsk: Hengebro
norsk nynorsk: Hengebru
oʻzbekcha/ўзбекча: Osma koʻprik
português: Ponte pênsil
română: Pod suspendat
русский: Висячий мост
Simple English: Suspension bridge
slovenčina: Visutý most
slovenščina: Viseči most
српски / srpski: Viseći most
srpskohrvatski / српскохрватски: Viseći most
svenska: Hängbro
Türkçe: Asma köprü
українська: Підвісний міст
Tiếng Việt: Cầu dây võng
吴语: 悬索桥
粵語: 懸索橋
中文: 悬索桥