Tuesday, February 22, 2011

Akashi Kaikyō Bridge

Akashi Kaikyō Bridge
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Akashi Kaikyō Bridge from the air
Akashi Kaikyō Bridge
Akashi Kaikyō Ō-hashi
(明石海峡大橋?)
Other name(s)
Pearl bridge
Carries
6 lanes of roadway
Crosses
Locale
Maintained by
Design
Total length
3,911 meters (12,831 ft)
Height
282.8 metres (928 ft) (pylons)[1]
Longest span
1,991 meters (6,532 ft)[1]
Clearance below
65.72 meters
Construction begin
1988[1]
Construction end
1998[1]
Opened
April 5, 1998
Toll
¥2,300
The Akashi-Kaikyō Bridge (明石海峡大橋, Akashi Kaikyō Ō-hashi?), also known as the Pearl Bridge, has the longest central span of any suspension bridge, at 1,991 metres (6,532 ft). It is located in Japan and was completed in 1998[1]. The bridge links the city of Kobe on the mainland of Honshū to Iwaya on Awaji Island by crossing the busy Akashi Strait. It carries part of the Honshū-Shikoku Highway.
The bridge is one of the key links of the Honshū-Shikoku Bridge Project, which created three routes across the Inland Sea.
History
Before the Akashi Kaikyō Bridge was built, ferries carried passengers across the Akashi Strait in Japan. This dangerous waterway often experiences severe storms, and in 1955, two ferries sank in the strait during a storm, killing 168 people. The ensuing shock and public outrage convinced the Japanese government to develop plans for a suspension bridge to cross the strait. The original plan called for a mixed railway-road bridge, but when construction on the bridge began in April 1986, the construction was restricted to road only, with six lanes. Actual construction did not begin until May 1986, and the bridge was opened for traffic on April 5, 1998. The Akashi Strait is an international waterway that necessitated the provision of a 1,500-metre (4,921 ft)-wide shipping lane.
Architecture
The bridge has three spans. The central span is 1,991 m (6,532 ft)[1], and the two other sections are each 960 m (3,150 ft). The bridge is 3,911 m (12,831 ft) long overall. The central span was originally only 1,990 m (6,529 ft), but the Kobe earthquake on January 17, 1995, moved the two towers sufficiently (only the towers had been erected at the time) so that it had to be increased by 1 m (3.3 ft).[1]
The bridge was designed with a two-hinged stiffening girder system, allowing the structure to withstand winds of 286 kilometres per hour (178 mph), earthquakes measuring to 8.5 on the Richter scale, and harsh sea currents. The bridge also contains pendulums that are designed to operate at the resonance frequency of the bridge to damp forces. The two main supporting towers rise 298 m (978 ft) above sea level, and the bridge can expand because of heating up to 2 metres (7 ft) over the course of a day. Each anchorage required 350,000 tonnes (340,000 LT; 390,000 ST) of concrete. The steel cables have 300,000 kilometres (190,000 mi) of wire: each cable is 112 centimetres (44 in) in diameter and contains 36,830 strands of wire.[2][3]
The Akashi-Kaikyo bridge has a total of 1737 illumination lights: 1084 for the main cables, 116 for the main towers, 405 for the girders and 132 for the anchorages. On the main cables three high light discharged tubes are mounted in the colors red, green and blue. The RGB model and computer technology make for a variety of combinations. Currently, 28 patterns are used for occasions as national or regional holidays, memorial days or festivities.[citation needed]
Use
The total cost is estimated at ¥500 billion, and is expected to be defrayed by charging commuters a toll to cross the bridge. The toll is ¥2,300 and the bridge is used by approximately 23,000 cars/day.[4]
Nearby attractions
Three parks in proximity of the bridge have been built for tourists, one in Maiko (including a small museum) and one in Asagiri. Both are accessible by the coastal train line.
See also

References
  1. a b c d e f g h i j Akashi Kaikyo Bridge at Structurae
  2. ^ Akashi Kaikyo Bridge
  3. ^ Supporting the Longest Suspension Bridge in the World
  4. ^ Megastructures. National Geographic for Channel Five.
  • This page was last modified on 17 February 2011 at 17:34.