Kuan-Du Bridge, Taiwan: One of the world’s largest half-through continuous steel tied arch bridges, and crosses over the scenic Tan Shui River between Kuan-Du and Pali.
Artist rendition of T.Y. Lin’s proposal to bridge the Strait of Gibraltar with two 16,000 foot spans. Each of the bridge’s cantilevered towers would be 3,000 feet tall, twice the size of the world’s tallest skyscraper.
Daniel S., Strait of Gibraltar as seen from the “Mirador del Estrecho” Lin calculated the optimum deck length for the 220 double
cantilever spans stayed by two pairs of heavy duty steel cables for the superstructure at about 1,200 feet (with 80’ vertical clearances to water). However two spans of 1,800 feet east and west of the Diomede Islands that have 200’ vertical clearance would be required for ship traffi c. Lin spoke of the plan to coat everything, including the cables in
concrete. “T at’s important from two points of view; Number one, the concrete protects the steel. It simplifi es maintenance in an icy area. Number two, it stiff ens the bridge, so it’s not just hanging from rope.” T e only concrete-free portion would be the expansion joints – but even they would be rust coated. Superstructure lightweight concrete total? 3,330,000 cubic
yards. Steel? 100 pounds of pre-stressing tendons plus 120 pounds of reinforcing steel per cubic yard. Estimates of 4 to 5 years were given to manufacture and assemble the 20,000 ton spans that would be transported to the site via catamaran. But, as it’s only possible to work in the Bering Strait for 5 months of the year, the whole process would likely resemble a very intricate, choreographed dance. T e Discovery Channel recently estimated the costs to build Lin’s
Intercontinental Peace Bridge at about $25 Billion. However, they also estimated a further $110 Billion to build the necessary infrastructure to get there. Although recent reports have emerged that a tunnel is the more
likely reality for the Bering Strait, with T e Daily Mail reporting on Aug. 22, 2011 that Russia had given the green light to a 65 mile long tunnel, it couldn’t even be constructed without using T.Y. Lin’s research.
Gibraltar Strait Bridge T e Strait of Gibraltar separates the British colony of Gibraltar in Spain from Morocco, Africa, by a mere 8 miles at its shortest distance. T e famed “Rock of Gibraltar” rises 1398 ft from the sea and, adorned with silver columns, marked safe navigation limits for ancient Mediterranean navigators. Lin’s dream would link the Christian and Islamic cultures and promote trade. T e bridge would feature 5 traffi c lanes and accommodate a break-down lane in each direction.
CHALLENGES
Although Gibraltar certainly doesn’t have the Bering Strait’s ice or darkness issues, there are two others that have proved insurmountable until Lin’s design solutions. Water and wind.
Water depth in the Gibraltar Strait ranges between 980 and 3,000
feet. Winds have been clocked at 140 miles per hour. Engineers hired by the Spanish government to research the feasibility of a bridge discovered the bottom of the Strait was extremely hard rock. As well, fog, Sahara Desert dust storms, strong currents and the frequency of ship collisions in the busy Strait are also dangerous issues.
DESIGN So what does a bridge builder suggest when faced with trying to place piers in 3,000 ft depths? Span it. Instead of even attempting to set piers in 3,000 ft of water, Lin’s hybrid cable-stayed/suspension bridge would have two spans of an incredible 16,400 ft each. T at would allow piers to be set in the relatively (emphasis on the word relatively) easy depths of 1500 ft and 500 ft. Each of the bridge’s two cantilevered towers would have to be 3,000 ft tall, and cant out slightly from the centerline. T e cables run from the tops of the towers would be transversely set at 660 ft. To deal with the winds, Lin would stiff en the structure by drawing the main cables together with transversely placed, post-tensioned bracing cables. At mid-span they would be only 130’ apart. Suspender cables would angle inward from the main suspension cables to carry the fi berglass bridge deck. Total amount of wire cable? 1,000,000 miles – or enough to go
around the world almost 30 times. T e last estimate given to build Lin’s Gibraltar Bridge was $15 Billion. If man had never dreamed of going to the moon, we wouldn’t
have GPS or satellites. And if T.Y. Lin hadn’t dreamed of linking the world, millions may have died in buildings unable to withstand earthquakes. T anks to T.Y. Lin, the question isn’t “can we build it?” but “can we aff ord to build it?” T.Y. Lin left the world with a lasting legacy of ingenuity and inspiration. T.Y. Lin died of a heart attack in 2003 at the age of 91. ❙
WIRE ROPE EXCHANGE MARCH-APRIL 2012 31
T.Y. LiN INTERNATIONAl
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