Friday, July 10, 2009

Honshu-Shikoku Bridges: Kurushima Bridge (1)

The rest of the bridges on the Honshu-Shikoku Expressway were in various stages of construction when I went on my tour in 1998.

Like the previously studied Ohmishima and Tatara Bridges, the Kurushima Bridge is part of the Nishi-Seto Expressway. It is the westernmost bridge and connects Shikoku to Oshima Island across Kurushima Strait in the Inland Sea. I say bridge, but its really three suspension bridges with four anchorages and six towers. In total, it's the world's longest suspension bridge at 4015 m (13173 ft). It's similar in construction to the west spans of the San Francisco-Oakland Bay Bridge, which has four towers and a third anchorage in the middle of the bridge.

Because of occasional rough seas and to protect the waters in the Kurushima Strait, several of the towers have energy absorbing devices to protect them and ships that may possibly collide with the towers. This has become a heated issue, especially after single hull oil tankers collide with bridges. Bridge owners are usually blamed for the resulting oil spill, even when the shipping channel under the bridge is wider than 600 m. In any event, the use of energy absorbing devices is suppose to prevent ship damage, although it is likely that a tanker going at 16.5 knots (the speed of the Exxon Valdez) would be seriously damaged by a stationary object, with or without the use of energy absorbing devices.
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Honshu-Shikoku Bridges: Kurushima Bridge (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

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