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Roman bridges, built by ancient Romans, were the first large and lasting bridges built. Roman bridges were built with stone and had the arch as the basic structure (see arch bridge). Most utilized concrete as well, which the Romans were the first to use for bridges. == Typology == |- | colspan=2 | |} As with the vault and the dome the Romans were the first to fully realize the potential of arches for bridge construction.〔Robertson, D.S.: Greek and Roman Architecture, 2nd edn., Cambridge 1943, p.231: "The Romans were the first builders in Europe, perhaps the first in the world, fully to appreciate the advantages of the arch, the vault and the dome."〕 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.〔Colin O'Connor: "Roman Bridges", Cambridge University Press 1993, p. 187ff. ISBN 0-521-39326-4〕 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).〔Galliazzo, Vittorio (1994), I ponti romani. Catalogo generale, Vol. 2, Treviso: Edizioni Canova, ISBN 88-85066-66-6, cf. Indice〕 Roman arch bridges were usually semicircular, although a few were segmental (such as Alconétar Bridge). A segmental arch is an arch that is 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 in size and shape. The Romans built both single spans 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 Limyra Bridge in southwestern Turkey features 26 segmental arches with an average span-to-rise ratio of 5.3:1,〔Colin O'Connor: "Roman Bridges", Cambridge University Press 1993, p. 126 ISBN 0-521-39326-4〕 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 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 Puente Romano at Mérida. The late Roman Karamagara Bridge in Cappadocia may represent the earliest surviving bridge featuring a pointed arch. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Roman bridge」の詳細全文を読む スポンサード リンク
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