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The original Maroon Creek Bridge is a steel trestle along State Highway 82 at the western boundary of Aspen, Colorado, United States. It was designed by George S. Morison in 1888 for the Colorado Midland Railroad, one of the last viaducts in Colorado built for a standard gauge mountain railroad in the 19th century.〔(【引用サイトリンク】url=http://www.historycolorado.org/oahp/pitkin-county )〕 Of the five steel bridges the Midland built, it is the only one still extant.〔 Due to the later removal of most track and the rail depots, the bridge is the most visible remnant of rail service to Aspen. In 1985 it was listed on the National Register of Historic Places along with other highway bridges in the state, including the Sheely Bridge, also in Aspen. When it was built, the Midland was ahead in its race with the Denver and Rio Grande to make the first rail connection to Aspen, then a booming silver mining center. The Midland had followed the Roaring Fork Valley up from its main line at Glenwood Springs, but was stalled at Maroon Creek by a delay in the bridge steel. The Rio Grande was thus able to make up the difference and bring the first train to Aspen, with the Midland following a few months later. Aspen's boom years ended a few years later, and by the 1920s the bridge was abandoned. It was soon expanded and converted to use as a road bridge. It served as the main entrance to Aspen for many visitors as the city's economy rebounded when the Aspen Mountain ski resort was developed after World War II. As growth spilled over to Aspen's west, it became a traffic choke point for the region. It remained in use until longstanding plans for a newer, wider bridge came to fruition in 2008. At that time the original bridge was the oldest one still in use on Colorado's state highways.〔(【引用サイトリンク】 title=Maroon Creek Bridge Replacement )〕 The award-winning new bridge was designed to be aesthetically similar to its predecessor, which remains in service as a foot bridge. It may be used for a light rail line to further alleviate traffic problems in the valley. ==Structures== Both bridges are located adjacent to each other along Highway 82 approximately one-half mile (1 km) east of the traffic circle where Maroon Creek Road, the access route to the Maroon Bells leaves to the south, just outside the developed portion of the city of Aspen. Due west of that are the remnants of the Holden Mining and Smelting Co. facility, also listed on the National Register as a historic district. The city's corporate limit follows the bridge, with the land to the north within Aspen and the south just Pitkin County. The creek flows through a deep gorge below, roughly 1 mile (1.6 km) upstream of where it drains into the Roaring Fork River to the north. On all corners but the southeast are golf courses; that corner has a small residential neighborhood of modern construction. A steel safety net has been installed since construction of the new bridge in the two-foot (60 cm) gap between the bridges. The original bridge has 20 plate girder spans supported by nine tapered steel piers. Two deep deck girders, iron plate webs with riveted angle flanges and web stiffeners, carry the road. The piers are made up of two bents, their legs made of two back-to-back steel channels with cover plate and double lacing. They are braced by tiers of compression beams and tension eyebars. At the ground they are supported by masonry piers.〔 The new bridge is long, 30 feet (10 m) shorter than its older neighbor. It consists of a main span with two end spans. Its deck is formed from a 73-foot–wide () single-cell box girder at a constant depth of 13½ feet () with ribbed elements supporting the long slab spans. Most segments are long, with a deck rib from the leading edge. The segments are laid out on pier table, with eight in the main cantilever, ten in the side spans and a 5-foot segment closing the two cantilevers.〔 They are supported by A-shaped concrete piers with a capital at the top flared outward at the same angle as the outriggers on the historic bridge. The piers themselves are a constant 10 feet (3 m) in the direction of the bridge but stretch from 6 feet (2 m) at the top to 10 feet (3 m) at the bottom. Their footings are on 12 4-foot–wide () drilled 20 feet (6 m) deep into the bedrock.〔 The abutments on either side of the gorge are supported by 72 micropiles designed to support 150 kips each. 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「Maroon Creek Bridge」の詳細全文を読む スポンサード リンク
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