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Arch bridge

Bridge with arch-shaped supports

  • 10 min read
  • 5 chapters

Related on Lably

Through Bridge, Semicircle and Industrial Revolution

History

Possibly the oldest surviving arch bridge is the Mycenaean Arkadiko Bridge in Greece, dating to about 1300 BC. The local populace still uses the stone corbel arch bridge. 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 realize the potential of arches for bridge construction fully. 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 countries (including former Yugoslavia).

Roman arch bridges were usually semicircular, although a number were segmental arch bridges (such as the Alconétar Bridge), which have curved arches that are less than a semicircle. The advantages of the segmental arch bridge were that it allowed great amounts of flood water to pass under it, which would prevent the bridge from being swept away during floods and the bridge itself could be more lightweight. Generally, Roman bridges featured wedge-shaped primary arch stones (voussoirs) of the same size and shape. The Romans built both single-span and lengthy multiple-arch aqueducts, such as the Pont du Gard and Segovia Aqueduct. Their bridges featured from an early time onwards flood openings in the piers, e.g., in the Pons Fabricius in Rome (62 BC), one of the world's oldest major bridges still standing.

Roman engineers were the first and until the Industrial Revolution the only ones to construct bridges with concrete, which they called Opus caementicium. The outside was usually covered with brick or ashlar, as in the Alcántara Bridge.

The Romans also introduced segmental arch bridges into bridge construction. The 330 m-long (1,080 ft) Limyra Bridge in southwestern Turkey features 26 segmental arches with an average span-to-rise ratio of 5.3:1, giving the bridge an unusually flat profile unsurpassed for more than a millennium. Trajan's Bridge over the Danube featured open-spandrel segmental arches made of wood (standing on 40 m-high (130 ft) concrete piers). This was to be the longest arch bridge for a thousand years, both in terms of overall and individual span length, while the longest extant Roman bridge is the 790 m-long (2,590 ft) long Puente Romano at Mérida. The late Roman Karamagara Bridge in Cappadocia may represent the earliest surviving bridge featuring a pointed arch.

In medieval Europe, bridge builders improved upon Roman structures by using narrower piers, thinner arch barrels, and higher span-to-rise ratios. Gothic pointed arches were also introduced, reducing lateral thrust, and spans increased as with the eccentric Puente del Diablo (1282). With more advanced design and bridge-building techniques, the alternative informal name for Devil's Bridge became more widely used across Europe, as many people could not believe that such structures were manufactured and capable of carrying loads of that size.

The 14th century, in particular, saw bridge building reach new heights. Span lengths of 40 m (130 ft), previously unheard of in the history of masonry arch construction, were now reached in places as diverse as Spain (Puente de San Martín), Italy (Castelvecchio Bridge) and France (Devil's bridge and Pont Grand) and with arch types as different as semi-circular, pointed and segmental arches. The bridge at Trezzo sull'Adda, destroyed in the 15th century, even featured a span length of 72 m (236 ft), not matched until 1796.

Constructions such as the acclaimed Florentine segmental-arch bridge Ponte Vecchio (1345) combined sound engineering (a span-to-rise ratio of over 5.3:1) with aesthetic appeal. The three elegant arches of the Renaissance Ponte Santa Trinita (1569) constitute the oldest elliptic arch bridge worldwide. Such low rising structures required massive abutments, which at the Venetian Rialto Bridge (1591) and the Pegnitz or Fleischbrücke (1598) in Nuremberg (span-to-rise ratio 6.4:1) were founded on thousands of wooden piles, partly rammed obliquely into the grounds to counteract more effectively the lateral thrust.

In China, the oldest extant arch bridge is the Zhaozhou Bridge of 605 CE, which combined a very low span-to-rise ratio of 5.2:1, with the use of spandrel arches (buttressed with iron brackets). The Zhaozhou Bridge, with a length of 51 metres (167 ft) and a span of 37.4 metres (123 ft), is the world's first wholly stone open-spandrel segmental arch bridge, allowing greater passage for floodwaters. Bridges with perforated spandrels can be found worldwide, such as the Bridge of Arta, (17th century) Greece, and Cenarth Bridge, (18th century) in Wales.

With the coming of the Industrial Revolution, in the 18th and 19th centuries, stone and brick arches continued to be built by many prominent British civil engineers, including Thomas Telford, John Rennie, and latterly Isambard Kingdom Brunel. They also started the modern usage of different materials, such as cast iron — Telford designed the first bridge built of metal, completed in 1781, the Iron Bridge with a single arch of sections of cast iron constructed in traditional woodworking techniques — and then steel and concrete, which have been increasingly used in the construction of arch bridges, to almost the exclusion of other materials. A key pioneer was Jean-Rodolphe Perronet, who used much narrower piers, revised calculation methods, and exceptionally low span-to-rise ratios.

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