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in dollars) | open = | traffic = 30,000 vehicles per day | lat = 38.9382 | long = -77.0364 | coordinates_display = inline,title | coordinates_region = US-DC_type:landmark | references = }} The 16th Street Bridge, also known as the Piney Branch Bridge, is an automobile and pedestrian bridge that carries 16th Street NW over Piney Branch and Piney Branch Parkway in Washington, D.C. It was the first parabolic arch bridge in the United States. Construction on the first span began in 1905 as part of the northward extension of 16th Street, and was finished in 1907 but was never opened to traffic. The second span began construction in 1909 and was completed in 1910. The bridge was renovated in 1990, and again beginning in October 2014. The bridge, which spans the Piney Branch addition to Rock Creek Park, sits at the corner of four Washington, D.C., neighborhoods: Sixteenth Street Heights, Crestwood, Columbia Heights, and Mount Pleasant. ==Description== The 16th Street Bridge is long.〔 Its span is in length, and has a rise of .〔 The span is a parabolic arch, the first built in the United States〔 and the longest in the world at the time, according to its designer, W.J. Douglas.〔 The abutments and substructure of the bridge are of reinforced concrete;〔〔〔 the arch itself is not reinforced with steel.〔 The interior of the bridge is hollow. Square vertical interior columns in length on each side support the road deck. A latticework of horizontal square beams, each in size, intersect the columns and are set perpendicular to one another. This system of columns and beams compress the arch and keep it stable as well push outward against the walls.〔 The bridge's abutments are hollow.〔〔 The abutments are stabilized by soil pressing against them from the outside, and the system of beams and columns on the interior of the bridge.〔〔 The walls of the bridge and the abutments are thick.〔 A bluish crushed diorite was added to the concrete used to pour the walls of the abutments and the spandrel walls, which were left unfinished, and reflect the texture of the wooden forms used to create them. However, the archivolt, balustrade, and pilasters, whose concrete includes yellow sand and crushed granite, have a much different texture. These elements were removed from their molds before the concrete was fully hardened, then roughened with stiff brushes, helping to expose the granite particles within and make them glitter in the sun. The bridge superstructure rests on walls and columns.〔 The wide spans〔are of reinforced concrete.〔 Steel beams, their ends resting on the walls of the two bridges, close the gap between the spans.〔 Reinforced concrete slabs lie atop these beams to create a unified deck.〔 Concrete balustrades and newels create a railing on the east and west sides of the bridge.〔 The road is wide, and sidewalks are on either side of the roadway. Granite curbs define the cement sidewalk. The deck is topped by asphalt.〔 At in width (roadway and sidewalks), the deck was the widest in the city when built and could support .〔 The bridge has four ornamental cast iron lampposts.〔 The ends of the bridge are flanked by two bronze reclining tigers on concrete pedestals.〔 The archivolt consists of three arch rings, and is of smoothed concrete. Pilasters flank the arch on the sides of the bridge. Stylistically, the bridge is Neoclassical in design. The bridge cost about $135,000 to build. 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「16th Street Bridge (Washington, D.C.)」の詳細全文を読む スポンサード リンク
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