The Akashi-Kaikyō Bridge is also known as the Pearl Bridge. It is the world’s longest suspension bridge (measured by the length of the center span of 1,991 metres/6,532 feet). It is located in Japan and was completed in 1998. 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 the 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.
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 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).
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 metric tons of concrete. The steel cables have 300,000 km of wire: each cable is 112cm in diameter and contains 36,830 strands of wire.
The total cost is estimated at ¥500 billion (US$5 billion), and is expected to be defrayed by charging commuters a toll to cross the bridge. The toll is ¥2,300 (£11, US$20.00). It is used by approximately 23,000 vehicles a day.
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