- Education and Science
Super Skyscrapers & Mega Bridges Part 3
The engineering masterpiece called Akashi Kaikyo took 10 years to build, and Japanese engineers spent nearly 20 years testing different designs. Not only did they have to design a bridge to span the unprecedented 2.4-mile (4-kilometer) length of the Akashi Strait, they had to design a bridge that could withstand some of the worst weather on the planet. Japan receives 57 inches of rain per year and often gets hit with typhoons and earthquakes. The bridge also had to accommodate the busy shipping traffic in the strait, so it couldn't ride low on the water. The final design can handle 180-mph winds and an earthquake with a magnitude as high as 8.5.
It's hard to believe, but with the grand opening this summer of the Oresbund Bridge linking Denmark and Sweden, most of the large chasms or crossings in the industrialized world that can possibly be bridged by steel and concrete have been spanned.
Major bridges are still being built, of course. Another bridge has been proposed to cross the Tacoma Narrows in Washington, near the site of the ill-fated "Galloping Gertie," the bridge that undulated and eventually collapsed in high winds in 1940. The San Francisco Bay Area will have three new bridges in the next 10 years, but all are replacements for existing spans. As its economy expands, China is entering an age of bridge-building over many of its rivers. In Bangladesh, bridge builders face a challenge in constructing two long causeways over river areas that are subject to annual flooding.
But most of the mega-bridges that it is currently possible to build in the United States, Europe and Japan have been opened to traffic, most for 20 years.
Bridge engineers tend to be practical-minded, and are not a good source of fantastic ideas. Bridges are earthly things. It's not that bridge engineers don't have fertile imaginations to attempt longer bridges for more challenging crossings. The Japanese, not satisfied to rest on their laurels after the recent completion of the Akashi bridge system, dream of a series of spans that will link the islands of Honshu and Hokkaido. At an estimated cost of $16 billion, the bridges would include a single 13,200-foot (4,000-meter) span and two 6,600-foot (2,000-meter) spans.
Then there's the proposal to span the 20-mile Straits of Gibraltar, which bridge engineers have probably been dreaming about for hundreds of years, and probably will for several more centuries, according to some bridge builders. That particular span presents far too many engineering problems. Even if the designs which have been bandied actually worked, it involves massive floating piers, and it would be too difficult and costly to maintain. And, so far, the economics don't justify a span. Right now, few people even want to drive cars or trains between Morocco and Gibraltar.
There is actually only one active mega-bridge-building project in the world: a 10,890-foot (3,300-meter), $8 billion bridge that will span the Straits of Messina between Italy and the island of Sicily. However, don't make your plans to drive from Italy to Sicily anytime soon as this project has one profound fundamental flaw: It's located in politically paralyzed Italy!