Mega Works

History

For bridges where the deck follows the suspenders, see simple suspension bridge.

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

Drawing of the Chakzam bridge south of Lhasa, constructed in 1430, with cables suspended between towers, and vertical suspender cables carrying the weight of a planked footway below.

Detail of "View of the Chain Bridge invented by James Finley Esq." (1810), wood engraving, William Strickland, delineator. Although not specifically identified, this is likely the Chain Bridge at Falls of Schuylkill (1808).

Early precursor

The Tibetan saint and bridge-builder Thangtong Gyalpo originated the use of iron chains in his version of early suspension bridges. In 1433, Gyalpo built eight bridges in eastern Bhutan. The only surviving chain-linked bridge of Gyalpo's was the Thangtong Gyalpo Bridge in Duksum enroute to Trashi Yangtse, which was finally washed away in 2004. 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.

 First suspension bridges

The first design for a bridge resembling the modern suspension bridge is attributed to Fausto Veranzio, whose 1595 book “Machinae Novae” included drawings both for a timber and rope suspension bridge, and a hybrid suspension and cable-stayed bridge using iron chains (see gallery below).
However, the first suspension bridge actually built was by American engineer and inventor James Finley at Jacob’s Creek, in Westmoreland County, Pennsylvania, in 1801. Finley's bridge was the first to incorporate all of the necessary components of a suspension bridge, including a suspended deck bridge which hung by trusses. In 1808, Finley had patented the suspension bridge and by 1810, he published his design in a New York journal entitled The Port Folio.
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 Suspension Bridge (1826). The Clifton Suspension Bridge shown above (designed in 1831, completed in 1864 with a 214 m central span) is one of the longest of the parabolic arc chain type.

 Wire-cable

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

Wire Bridge at Fairmount (1842, replaced 1874).

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. The first permanent wire cable suspension bridge was Guillaume Henri Dufour’s Saint Antoine Bridge in Geneva of 1823, with two 40 m spans. The first with cables assembled in mid-air in the modern method was Joseph Chaley’s Grand Pont Suspendu in Fribourg, in 1834.
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, and 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.