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Trajan's Bridge ((セルビア語:Трајанов мост, ''Trajanov Most''); (ルーマニア語、モルドバ語():Podul lui Traian) ) or Bridge of Apollodorus over the Danube was a Roman segmental arch bridge, the first to be built over the lower Danube. Though it was only functional for a few decades, for more than 1,000 years it was the longest arch bridge in both total and span length.〔 The bridge seems to have been surpassed in length by another Roman bridge across the Danube, Constantine's Bridge, a little-known structure whose length is given at 2,437 m (; ).〕 The bridge was constructed in 105 AD by instruction of Emperor Trajan by Greek architect Apollodorus of Damascus for the deployment of Roman troops during the conquest of Dacia. == Description == The bridge was situated East of the Iron Gates, near the present-day cities of Drobeta-Turnu Severin in Romania and Kladovo in Serbia. Its construction was ordered by the Emperor Trajan as a supply route for the Roman legions fighting in Dacia. The structure was long (the Danube is now wide in that area), wide, and high, measured from the surface of the river. At each end was a Roman ''castrum'', each built around an entrance, so that crossing the bridge was possible only by walking through the camps. The bridge's engineer, Apollodorus of Damascus, used wooden arches, each spanning , set on twenty masonry pillars made of bricks, mortar, and pozzolana cement.〔The earliest identified Roman caisson construction was at Cosa, a small Roman colony north of Rome, where similar caissons formed a breakwater as early as the 2nd century BC: ''International Handbook of Underwater Archaeology'', 2002.〕〔Troyano, Leonardo Fernández, "Bridge Engineering - A Global Perspective", Thomas Telford Publishing, 2003〕 It was built unusually quickly (between 103 and 105), employing the construction of a wooden caisson for each pier.〔In the first century BC, Roman engineers had employed wooden caissons in constructing the Herodian harbour at Caesarea Maritima: Carol V. Ruppe, Jane F. Barstad, eds. ''International Handbook of Underwater Archaeology'', 2002, "Caesarea" pp505f.〕 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「Trajan's Bridge」の詳細全文を読む スポンサード リンク
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