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- Suspension Bridge
Akashi Kaikyō (Pearl)
Bridge, 1998
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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 in the world, at 1,991 meters (6,532 ft). It is located in Japan and was completed in 1998. The bridge links the city of Kobe on the mainland of Honshu to Iwaya on Awaji Island by crossing the busy Akashi Strait. It carries part of the Honshu - Shikoku Highway.
The bridge is one of the key links of the Honshū - Shikoku Bridge Project, which created three routes across the Inland Sea.
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 meter (4,921 ft) wide shipping lane.
The bridge has three spans. The central span is 1,991 m (6,532 ft), and the two other sections are each 960 m (3,150 ft). The bridge is 3,911 m (12,831 ft) long overall. The two towers were originally 1,990 m (6,529 ft) 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 kilometers 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 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 kilometers (190,000 mi) of wire: each cable is 112 centimeters (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, and 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 2300 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 Megastructures. However, it will take just over 25 years for the structure to be repaid.
Two parks in proximity to 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.