#38. Akashi Kaikyô Bridge
Akashi Kaikyo Bridge
The following video “Akashi Kaikyo Bridge” is a property of (owned by) History Channel [us] and is a part of a TV-Show series “MegaStructures.”
Akashi Kaikyô Bridge Location: Kobe, Japan Architect: Year: 1998
World’s longest bridge. The Akashi Kaikyô Bridge, also known as the Pearl Bridge, boasts the longest central span of any bridge and connects Kobe to the island of Awaji.
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 onAwaji Island, in Japan. It crosses the busy Akashi Strait (Akashi Kaikyō in Japanese). It carries part of the Honshu-Shikoku Highway.
Since its completion, in 1998, the bridge has the longest central span of anysuspension bridge in the world, at 1,991 metres (6,532 ft)
It 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 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 (4,921 ft)-wide shipping lane.
Structural Form
Main supporting Towers
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 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 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.
Use
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. 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.
