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The Hadley Parabolic Bridge, often referred to locally as the Hadley Bow Bridge, carries Corinth Road (Saratoga County Route 1) across the Sacandaga River in Hadley, New York, United States. It is an iron bridge dating to the late 19th century. It is the only surviving iron semi-deck lenticular truss bridge in the state, and the only extant of three known to have been built. In 1977 it was listed on the National Register of Historic Places. Shortly afterwards it was closed to vehicular traffic, and at some time later to pedestrians as well. The county had considered demolishing it, but held off after heavy lobbying from local preservation groups. In 2006 it was reconstructed and restored with federal and state grants, and reopened without any load restrictions. ==Structure== The bridge is located just above where the Sacandaga flows into the Hudson River opposite the village of Lake Luzerne, and just south of the central portions of Hadley. It is within the Adirondack Park's Blue Line. The river flows rapidly through a deep gorge here, with its sides sloping steeply from the road grade. An abandoned rail bridge is just upstream, and an interpretive panel is located near the bridge. The bridge is supported by two fieldstone abutments and a pier. Its two spans are identical in construction, with one being much longer than the other. The span at the north end is an end-post three-panel pony truss with both cast and wrought iron elements. Its upper chord is a riveted steel girder supported by lattice-braced members riveted to the flanges of the plate girder. The lower chord consists of two double wrought iron tension bars. The central panel is cross-braced with wrought-iron tie rods. All joints, not just in this span but the main one as well, are secured by threaded iron pins two inches (5 cm) wide capped with hexagonal nuts.〔 The longer span, () uses the same materials but is more intricate. It has nine panels, each wide, creating chords which arch both above and below the deck to the point that they are apart at their most distant from each other, in mid-span. The upper chord is made of flanged plate girders riveted together with top and bottom iron cap plates bolted on; the lower of double wrought iron bars. Both are joined at the span's end with end pins. A lattice-braced system similar to that on the short span supports the lenticular truss, with similar members serving as horizontal braces below the deck. Iron tie rods wide serve as diagonal cross-braces on the panels, and there is a horizontal tension rod at each end of the truss. A set of expansion rollers at the west end, intended to provide additional stability, has since corroded due to road salt and rust.〔 The deck is composed of rough-cut transverse two-by-fours supported by seven iron stringers on eight transverse iron I-beams. It is surfaced with asphalt thick.〔 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「Hadley Parabolic Bridge」の詳細全文を読む スポンサード リンク
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