San Francisco’s Golden Gate Bridge and New York’s Brooklyn Bridge are arguably the world’s most iconic suspension bridges. However, they are by no means the longest. Sixteen years ago today, a bridge two thousand feet longer than the former and four times the length of the latter opened in Kobe, Japan. This bridge is the Akashi Kaikyō Bridge, and, with a central span of 6,532 feet, it is twice as long as the world’s tallest skyscraper, the Burj Khalifa, is tall.
Although completed in 1998, construction began a decade earlier. It is the magnum opus of its designer, Satoshi Kashima, who has no other major bridges to his name. The Akashi-Kaikyō Bridge crosses a narrow part of the Inland Sea, which, although a shallow shipping route, is often rough and was the setting of a disastrous ferry accident in 1955. The bridge’s construction was a long and arduous process. This was in part due to the sheer scale, the fact that no construction could take place during the typhoon season, and the numerous setbacks that happened through the decade. One such setback was the 1995 Kobe earthquake, which moved the towers three feet apart, forcing the engineers to modify their design.
Everything about the Akashi Kaikyō Bridge is monumentally huge. As well as being the longest bridge in the world, it is also the tallest. There is enough cable used to stretch around the Earth over seven times. The cost is also monumental, coming in at five hundred billion yen, or about 3.6 billion US dollars, making it the most expensive bridge ever built. This massive expense seems to have paid off, for the bridge is one of the most spectacular engineering feats of recent years.
As if building the world’s longest bridge was not enough of a challenge, the engineers were faced with the problem of building it in Japan, the natural disaster capital of the world. The bridge had to be built to withstand heavy rain, hurricane-strength winds, and massive earthquakes. Numerous measures were used to counter these forces. Twenty pendulum dampers, which use inertia to keep the structure steady in winds and earthquakes, were installed throughout the bridge. A special method of construction was used to ensure the deck and cables stayed secure during construction. The aerodynamic, open-truss deck was perfected through many wind tunnel tests.
I think that the bridge is one of the great engineering achievements of recent years, and a more challenging accomplishment than any of the famous American and European suspension bridges. The Akashi Kaikyō Bridge gets only a fraction of the attention it deserves, and I can’t figure out why. It is an engineering masterpiece, and does not lack elegance. In any case, visitors to Kobe or nearby Osaka should make the short trip to the bridge, especially at night, where lights on the cables make the bridge look like a long string of pearls across the Inland Sea.
photo from Wikipedia
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