Difference between revisions of "Tensho Bridge"

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The Kokonoe "Yume" Otsurihashi suspension footbridge is the longest and highest of its type in the world.  Opened in 2006, the main span of 1,280 feet (390 mtrs) surpassed the previous record holder, the Ryujin footbridge - also in Japan - which has a span of 1,230 feet (375 mtrs)Kokonoe was also Japan’s highest bridge at 568 ft. (173 mtrs) - a record it retained for 4 years until 2010 when the Hiroshima Airport arch bridge opened.  Neither bridge however, is as long as the catenary suspension bridge at Sunway Lagoon Theme Park in Selangor, Malaysia with a span of 1,404 feet (428 mtrs).  Switzerland’s Niouc is currently the highest footbridge in the world but is also a catenary suspension bridge with no towers.  Many do not consider catenary bridges to be true suspension bridges since they have uneven, sloping decks that are often unstable.
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The highest and longest concrete arch in Japan, the Tensho bridge soars across a forested river gorge in the mountains of southern Japan’s Miyazaki prefecture. The bridge is located just south of Takachiho Gorge, a region with more high bridges than any other single location in Japan.  These include the highest railway bridge in Japan over the Takachiho gorge as well as the Shintotakachiho and Aoba concrete arches, the Unkai, Ryuten and Seiun steel arches and the Kamiiwato concrete beam bridge.  All 8 bridges are more than 328 feet (100 mtrs) in heightIf you have just one day to visit high bridges in Japan, Takachiho gorge is the place to be!
 
 
Of course the Japanese are no strangers to high and long footbridges.  Prior to Ryujin and Kokonoe, one of the country’s longest suspension footbridges was the 1984-built Teruha bridge in Aya with a tower to tower distance of 820 feet (250 mtrs)At the time Aya also held Japan’s bridge height record at 466 feet (142 mtrs)Other high footbridges in Japan include the Ueno Skybridge some 295 feet (90 mtrs) above a forested valley and the Tanise suspension bridge 177 feet (54 mtrs) high with a length of 974 feet (297 mtrs)Constructed in Totsukawa, Nara prefecture in 1954, Tanise is one of Japan’s oldest suspension footbridges and is unusual for having two separate sets of main support cables.
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The construction of Tensho was somewhat different than similar sized arches whereby a tower is usually erected on either side of the gorge and cables temporarily radiate out from it to support individual sections of the arch until the two halves are joined in the middleWith Tensho, the roadway and support spandrels were built outward at the same time as the archTo prevent the two halves of the arch from falling into the gorge, several cables were attached from an anchor to the road deck and then down to the arch segments.  Once the next vertical spandrel support was built up to deck level and connected to another short span of roadway, then another diagonal cable was connected to the arch rib within the next spandrel and the process repeated itselfWhen the two sides of the arch were closed in the middle, the temporary cable stays were then removed from the inside of the spandrel panels.
 
 
The name "Yume" means dreams - a representation of the people of Kokonoe and their desire to bring the people of the region together in one harmonious exchange of ideals and cultureOr something to that effect.  A more simple reason to have built the bridge is for the outstanding views it offers of the Naruko-gawa gorge and its towering cliffs and waterfalls.  Like any good footbridge of great height, Kokonoe has a narrow 5 foot (1.5 mtr) wide walkway that will induce many with a feeling of vertigo.  Some will find this nerve racking while others will find it euphoric.
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With a span length to rise ratio of just 8 to 1, the Tensho arch is so flat it looks lighter than its size would suggestThis desire to make the bridge an invisible presence is all part of the Japanese ethic to harmonize man and mother nature while maintaining the natural beauty of the environment.      
 
Although it no longer exists, the highest and longest tower supported suspension footbridge ever built was upstream of the massive Glen Canyon Dam over the Colorado River in the U.S. State of Arizona from 1958 to 1964 to aid worker’s during the dam’s construction.  It had a height of 640 feet (195 mtrs) and a span of 1,280 feet.  An accurate conversion puts the 390 meter long Kokonoe bridge span at 1,279.5276 feet - about 6 inches short of the Arizona bridge!     
 
  
  

Revision as of 04:36, 5 November 2009

Tensho Bridge
JapaneseName
Nishiusuki District, Miyazaki, Japan
470 feet high / 143 meters high
853 foot span / 260 meter span
2000

1TenshoBridge.jpg


The highest and longest concrete arch in Japan, the Tensho bridge soars across a forested river gorge in the mountains of southern Japan’s Miyazaki prefecture. The bridge is located just south of Takachiho Gorge, a region with more high bridges than any other single location in Japan. These include the highest railway bridge in Japan over the Takachiho gorge as well as the Shintotakachiho and Aoba concrete arches, the Unkai, Ryuten and Seiun steel arches and the Kamiiwato concrete beam bridge. All 8 bridges are more than 328 feet (100 mtrs) in height. If you have just one day to visit high bridges in Japan, Takachiho gorge is the place to be!

The construction of Tensho was somewhat different than similar sized arches whereby a tower is usually erected on either side of the gorge and cables temporarily radiate out from it to support individual sections of the arch until the two halves are joined in the middle. With Tensho, the roadway and support spandrels were built outward at the same time as the arch. To prevent the two halves of the arch from falling into the gorge, several cables were attached from an anchor to the road deck and then down to the arch segments. Once the next vertical spandrel support was built up to deck level and connected to another short span of roadway, then another diagonal cable was connected to the arch rib within the next spandrel and the process repeated itself. When the two sides of the arch were closed in the middle, the temporary cable stays were then removed from the inside of the spandrel panels.

With a span length to rise ratio of just 8 to 1, the Tensho arch is so flat it looks lighter than its size would suggest. This desire to make the bridge an invisible presence is all part of the Japanese ethic to harmonize man and mother nature while maintaining the natural beauty of the environment.



Tensho Bridge Elevation


2TenshoBridge.jpg