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The Atherton Bridge is a historic iron truss bridge in Lancaster, Massachusetts, spanning the South Branch of the Nashua River. It is a rare example of a hybrid pony truss that is similar to the 19th century truss design of Simeon S. Post. It was built by J.H. Cofrode & Co. of Philadelphia in 1870. It was the first iron bridge to be constructed in the town.〔(Historic American Engineering Record )〕 The bridge was added to the National Register of Historic Places in 1979. The bridge formerly carried Bolton Road, but was closed to vehicular traffic in 1975 and bypassed by a modern highway bridge in the 1980s. It is still open to pedestrian traffic via a loop path from Bolton Road. ==Technical information== The Atherton Bridge has iron compression posts that incline inward towards the center of the span and diagonal tension rods that incline outward towards the abutments. Unusual features include double end posts with adjustable turnbuckles, channeled castings to join the lower chord bars, and patented "Phoenix" columns〔Patented by the Phoenix Iron company of Pennsylvania〕 for all inclined posts. This bridge does not make use of Simeon Post's patented joints. The floor beams support a wood plank deck. The bridge is long and feet wide, and is composed of eight panels. It rests on granite abutments. The bridge was photographed in 1979 by Jet Lowe of the Historic American Engineering Record, and documented in 1990 as part of the Massachusetts Historic Bridge Project.〔 At that time, it was one of only two known examples of the Post type of truss still surviving.〔(【引用サイトリンク】title=NRHP nomination for Atherton Bridge )〕 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「Atherton Bridge」の詳細全文を読む スポンサード リンク
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