Friday, June 09, 2006

Akashi-Kaikyo Bridge

[Something brought me here, I'll never know what...]

The Akashi-Kaikyo Bridge, also known as Pearl Bridge, is a suspension bridge in Japan that crosses the Akashi Strait; it links Maiko in Kobe and Iwaya on Awaji Island as part of the Honshu-Shikoku Highway. The central section is the longest bridge span in the world at 1991 metres (6532 ft). It was planned to be one of three Honshu-Shikoku connecting bridges, annexing two borders of the Inland Sea.

Before the Akashi-Kaikyo bridge was built, ferries carried passengers back and forth 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 children. The ensuing shock and public outrage convinced the Japanese government to draw up plans for a suspension bridge to cross the strait. The original plan was for a mixed railway-road bridge but when the bridge was begun in April 1986 it 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 and required a 1500 metre wide shipping lane.

The bridge has three spans. The central span is 1991 metres, with the two other sections each 960 metres. The bridge is 3911 metres long overall. The central span was originally only 1990 metres but was stretched by a further metre in the Kobe earthquake on January 17, 1995. It was designed on a two-hinged stiffening girder system, allowing it to withstand 286 kilometres per hour (178 mph) winds, earthquakes measuring up to 8.5 on the Richter scale, and harsh sea currents. The bridge also contains pendula which operate at the resonant frequency of the bridge to dampen forces on it.

The total cost is estimated at ¥ 500 billion (≈USD 5 billion). This cost is expected to be defrayed by charging commuters a toll to cross the bridge. However, the toll is so high that, ironically, very few drivers actually use the expensive bridge, preferring instead to use the slower-but-cheaper ferries.

Two parks in proximity of 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.


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