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The Grand Canyon Skywalk is a horseshoe-shaped cantilever bridge with a glass walkway in Arizona near the Colorado River on the edge of a side canyon in the Grand Canyon West area of the main canyon.〔Yost, Mark. (Close to the Edge ), ''Wall Street Journal''. 2007-04-10.〕 USGS topographic maps show the elevation at the Skywalk's location as and the elevation of the Colorado River in the base of the canyon as , and they show that the height of the precisely vertical drop directly under the skywalk is between and .〔(Acme mapper ): USGS topographic map〕 Commissioned and owned by the Hualapai Indian tribe, it was unveiled March 20, 2007, and opened to the general public on March 28, 2007. It is accessed via the Grand Canyon West Airport terminal or a 120-mile (190 km) drive from Las Vegas. The Skywalk is east of Meadview and north of Peach Springs with Kingman being the closest city of some size. ==Design and construction== David Jin, an entrepreneur who had been involved with tourism and the Hualapai Nation for some time, had the idea of extending a platform out over the edge of the Grand Canyon. With the help of architect Mark Ross Johnson, that idea evolved into a rectangular walkway and eventually the "U"-shaped walkway that has now been constructed. The overall Skywalk width is . The Skywalk length extending out from the post supports closest to the canyon wall is . The outer and inner by bridge box beams are supported by eight box posts having four posts on each side of the visitor’s center, once completed. The eight posts are anchored in pairs into four large concrete footings that are in turn anchored to the bedrock by ninety-six DYWIDAG (acronym pronounced Doo-Wee-Dag) high strength steel threaded rod rock anchors grouted deep into the rock. The deck of the Skywalk has been made with four layers of Saint-Gobain Diamant low iron glass with DuPont SentryGlas interlayer. Deck width is . The Skywalk glass sidings were made with the same glass as the deck, but fewer layers (two) bent to follow the walkway’s curvature. The glass sidings are tall and have been designed for high wind pressures. The Skywalk deck was designed for a 100-pound-per-square-foot (490 kg/m²) live load along with code-required seismic and wind forces. The foundation can withstand an 8.0 magnitude earthquake within . Fine-tuning of the project occurred after a wind loading and pedestrian induced vibration analysis. Two tuned mass dampers were installed inside the outer box beam as well as one inside the inner box beam at the furthest extension of the Skywalk to reduce pedestrian footfall vibration. The walkway could carry 822 people that weigh each without overstress, but maximum occupancy at one time is 120 people. The Skywalk was assembled on top of the canyon wall in line with its final placement and moved into final position by a jack and roll rig. The Skywalk infrastructure itself weighs a little over without counterweights but including the tuned mass dampers, railing hardware, glass rails, glass deck and steel box beams. At the time of roll-out, the Skywalk weighed approximately 1.6 million pounds (730,000 kg). The process was completed in two days. The Skywalk glass itself was manufactured and imported from Saint-Gobain Deutsche Glas (Kinon in Aachen) and Glas Döring in Berlin, Germany. Structural design was provided by Lochsa Engineering out of Las Vegas, Nevada. The contractor was Executive Construction Management also located in Las Vegas, Nevada. Foundation design was aided by John Peck (Geologist), Aaron Hastings, P.E. of Arroyo Engineering Consultants, Inc. (Geotechnical Engineer), DJ Scheffler, Inc., and Crux Subsurface, Inc. of Spokane Valley, Washington. Astronauts Buzz Aldrin and John Herrington attended the opening ceremony on March 20, 2007. A National Geographic documentary film on the construction of the Skywalk has been published.〔(NationalGeographic.com )〕 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「Grand Canyon Skywalk」の詳細全文を読む スポンサード リンク
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