On This Day in History... April 5, 2014 1998 - The world’s longest suspension bridge, Japan’s Akashi Kaikyo Bridge, opened. The $3.8 billion-bridge links Shikoku, the smallest of Japan’s four main islands, with the biggest island of Honshu. The mid-section length, between the bridge’s two massive support towers, measures 6,529 feet (about 1,990 meters). 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. Since its completion, in 1998, the bridge has the longest central span of any suspension 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. 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. 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 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 up to magnitude 8.5, 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. 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. [source:wiki]
Posted on: Sat, 05 Apr 2014 15:40:26 +0000
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