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Shaw Bridge, also known as Double-Span Whipple Bowstring Truss Bridge, is a historic bridge in Claverack, New York, United States. It carried Van Wyck Lane over Claverack Creek, but is now closed to all traffic, even pedestrians.〔 It is "a structure of outstanding importance to the history of American engineering and transportation technology." Specifically designed by John D. Hutchinson, the bridge employs the basic design of Squire Whipple. It is the only extant double-span Whipple bowstring truss bridge in the U.S.〔 The bridge was listed on the National Register of Historic Places in 1980. Since then its wooden deck has deteriorated to the point where it cannot be used even by pedestrians, and it has been closed. ==Structure== The bridge is located in a quiet residential area where houses, some dating to the early 19th century like the nearby Jacob P. Mesick House, are built on large lots. Many tall trees grow in the area, giving it a wooded feel. The creek, a tributary of the Hudson River to the west, is shallow yet wide here. It is east of NY 23/9H, the main north-south route through the Claverack area.〔 Structurally, the bridge is a bowstring tied arch with two separate yet identical spans supported by end abutments and a center pier of mortared cut limestone blocks. Its lower chord, wrought iron spans between cast iron connecting blocks, is long, wide and above water level. Its upper chords are segmental arches of nine tangential iron castings with their bearing surfaces joined at each panel point. They bear the legend "J. D. Hutchinson, Builder, Troy, N.Y., 1870".〔 Iron floor beams are suspended from the top chord by vertical round threaded iron rods similar to those that form the diagonal crosses and braces of the truss web. Wood stringers bolted to the iron beams run the length of the spans, and more iron rods cross-brace them. The deck itself consists of wooden planks laid across the stringers and braces. Guard rails on either side protect the trusses.〔 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「Shaw Bridge」の詳細全文を読む スポンサード リンク
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