Roman bridge

Following the conquests of Tarquinius Priscus, Etruscan engineers migrated to Rome, bringing with them their knowledge of bridge-building techniques.

[8] By the 2nd century BC, the Romans had further refined their bridge-building techniques, using stronger materials such as volcanic ash, lime and gypsum.

Also, they began to use iron clamps to hold together bridges, constructing midstream arches, and pentagonal stones to allow for wider vaults.

[9] According to Canadian classicist John Peter Oleson, no known stone bridges existed in Italy before the 2nd century BC.

[7][10] This view is not supported unanimously: Spanish engineer Leonardo Fernández Troyano suggested that stone bridges have existed since Pre-Roman Italy.

[2][13] Engineers began to use stone instead of wood to exemplify the Pax Romana and to construct longer-lasting bridges.

[9] Bridges were constructed by the Roman government to serve the needs of the military and the empire's administration.

Sometimes roads and bridges were used for commercial purposes, but this was rare as boats better served the needs of the Roman economy.

[11] Trajan's Bridge over the Danube featured open-spandrel segmental arches made of wood (standing on 40 metres (130 ft) high concrete piers).

This was to be the longest arch bridge for a thousand years both in terms of overall and individual span length.

[18] Roman engineers would begin by laying a foundation for building bridges across moving bodies of water.

At first, they used heavy timbers as pilings in the riverbed, but a later technique involved using watertight walls to redirect the water and then laying a stone foundation in the area.

[15] Marcus Vipsanius Agrippa used ashlar and bricks to cover the outside of bridges and concrete for footings and water channels.

[26] Travertine limestone and tuff were used to build Roman bridges,[7] or they could be made of dry rubble or concrete.

[25] In the first half of the 2nd century BC, blocks of stone held together with iron clamps were used to aid in the construction of bridges.

[14] Examples are bridges in Carmona, Palomas, Extremadura, and the Ponte della Chianche in Italy.

[8] Early Roman bridges were wooden, including one constructed by Apollodorus and the Pons Sublicius, the oldest bridge in ancient Rome, and they were probably common across northern Europe and the Tyrrhenian coast;[15] however, because of their lack of durability few have survived to the modern day.

[28] These bridges were supported by wooden trestles spanned by horizontal timbers and reinforced with struts, and they were possibly cantilevered.

[7][31] For example, according to Livy, during a battle against the Sabines the Romans set one of their wooden bridges on fire, driving the enemy back.

[29][5] During Julius Caesar's campaign in Germany, he built bridges by driving wooden piles into the stream bed from floating platforms and fixing beams at right angles across them to create trestles.

[23] 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; see right table).

Throughout the rest of the Roman world, except for northern Europe, arched bridges made of stone were common.

Their shared costs prove Roman bridges belonged to the region overall, and not to any one town (or two, if on a border).

The Alcántara Bridge in Lusitania, for example, was built at the expense of 12 local municipalities, whose names were added on an inscription.

[39] The Pons Fabricius, built in 62 BC during the late Republic, is the oldest Roman bridge that is still intact and in use.

[41] Roman engineers built stone arch or stone pillar bridges over all major rivers of the Empire save two: the Euphrates, which lay at the frontier in the Roman–Persian Wars, and the Nile, the longest river in the world, which was bridged as late as 1902 by the British Old Aswan Dam.

For rivers with strong currents and to allow swift army movements, pontoon bridges were also routinely employed.

[43] Judging by the distinct lack of records of pre-modern solid bridges spanning larger rivers,[11] the Roman feat appears to be unsurpassed anywhere in the world until into the 19th century.