Akashi Kaikyō Bridge
|Akashi Kaikyō Bridge
Akashi Kaikyō Ō-hashi (明石海峡大橋?)
Akashi Kaikyō Bridge from the air
|Other name(s)||Pearl bridge|
|Carries||six lanes of roadway|
|Locale||Awaji Island and Kobe|
|Maintained by||Honshu-Shikoku Bridge Authority|
|Total length||3,911 metres (12,831 ft; 2.430 mi)|
|Height||282.8 metres (928 ft) (pylons)|
|Longest span||1,991 metres (6,532 ft; 1.237 mi)|
|Clearance below||65.72 metres (215.6 ft)|
|Opened||April 5, 1998|
The Akashi Kaikyō Bridge (明石海峡大橋 Akashi Kaikyō Ō-hashi?), also known as the Pearl Bridge, links the city of Kobe on the mainland of Honshu to Iwaya on Awaji Island, in Japan. It crosses the busy Akashi Strait (Akashi Kaikyō in Japanese). It carries part of the Honshu-Shikoku Highway.
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 1988, the construction was restricted to road only, with six lanes. Actual construction did not begin until May 1988, 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 (4,900 ft; 0.93 mi)-wide shipping lane.
The bridge has three spans. The central span is 1,991 m (6,532 ft; 1.237 mi), and the two other sections are each 960 m (3,150 ft; 1 mi). The bridge is 3,911 m (12,831 ft; 2 mi) long overall. The two towers were originally 1,990 m (6,530 ft; 1.24 mi) apart, but the Great Hanshin earthquake on January 17, 1995, moved the towers so much (only the towers had been erected at the time) that the span had to be increased by 1 m (3.3 ft).
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 up to magnitude 8.5, and harsh sea currents. The bridge also contains tuned mass dampers that are designed to operate at the resonance frequency of the bridge to dampen forces. The two main supporting towers rise 282.8 m (928 ft) above sea level, and the bridge can expand because of heat by up to 2 m (7 ft) over the course of a day. Each anchorage required 350,000 tonnes (340,000 long tons; 390,000 short tons) 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.
The Akashi-Kaikyo bridge has a total of 1,737 illumination lights: 1,084 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.
The total cost is estimated at 500 billion yen; it is expected to be repaid by charging drivers a toll to cross the bridge. The toll is 2,300 yen and the bridge is used by approximately 23,000 cars per day. At 2,300 yen/car annual revenue would equal 19.5 billion yen. Given the interest expense on 500 billion yen, this bridge will never be repaid, according to TV series MegaStructures. But annual revenue is around 4% of investment, so with near zero interest rates in Japan, the bridge will pay for itself in 30 years, plus enable the growth of the overall economy in the region.
- Great Seto Bridge
- Honshū-Shikoku Bridge Project
- Kurushima-Kaikyo Bridge
- List of longest suspension bridges
- Akashi Kaikyo Bridge at Structurae
- Akashi Kaikyo Bridge at everything2[self-published source]
- Cooper, James D. "World's Longest Suspension Bridge Opens in Japan". United States Department of Transportation - Federal Highway Administration. Retrieved 14 February 2012.
- Supporting the Longest Suspension Bridge in the World
- Megastructures. National Geographic for Channel Five.