Exciting world of civil engineering - II

Greater Kashmir

Modern engineering is characterized by the broad application of what is known as systems engineering principles. Human imagination and creativity have given a new direction to Engineering, comments Gouseya Shahnaaz
When Gustav Lindenthal, who had built an impressive bridge in Pittsburgh in the early 1880s, proposed an enormous suspension bridge across the Hudson River at New York City in 1885, there were plenty of pessimists (as there always are with great projects). At 3,500 feet [1067 meters], the bridge’s span was to be over twice that of the Brooklyn Bridge, then the longest in the world. And some people, perhaps recalling Galileo’s caveats, raised the legitimate question of whether such a long span could even support itself. Yet Lindenthal held on to his dream for almost 40 years, modifying it as times and circumstances changed. Its price tag also changed with the times, rising to as high as $500 million when land acquisition and terminal facilities were included, a price that no one seemed willing to pay. To his critics who said that such a massive bridge could not be built, Lindenthal responded that “it was possible to bridge the Atlantic Ocean, but impossible to finance such an undertaking.”
Although Linden Hal’s great bridge was never built as he had dreamed it, a more modest crossing of the Hudson was engineered by his assistant Othman Amman. But if Amman’s bridge did not live up to Linden Hal’s aesthetic expectations, it did to more practical ones: at one tenth the cost of Linden Hal’s monstrosity, the George Washington Bridge, which opened to traffic in 1931, was such a technological feat as well as a financial success that in the following decade it served as a sleek model for suspension bridges built across the U.S., including the Golden Gate Bridge in San Francisco.
The ill-fated Tacoma Narrows Bridge, another descendant of Amman’s George Washington Bridge, was completed in 1940 across an arm of Puget Sound south of Seattle. At the time it was the third longest bridge in the world and narrower than any before it. The bridge had been designed according to a theory developed by Leon Moisseiff, who had served as consulting engineer to the project, as he had to virtually all large suspension bridges built after 1900
Only three months after it opened, however, the Tacoma Narrows Bridge collapsed in a 42-mile-an-hour wind. The physical phenomenon of aerodynamic instability, which had not revealed itself in heavier and wider bridges, dominated the behavior of the Tacoma Narrows. In the aftermath of this disaster, mid-20th-century engineers responded by proposing more comprehensive theories of bridge behavior. Today suspension bridges more than twice as long as the Tacoma Narrows are built safely, in no small part due to the lessons learned from the initial catastrophe. The Akashi-Kaikyo Bridge in Japan, which spans 6,529 feet [1990 meters]—a mile and a quarter—between its towers is testimony to this fact.
In the 1990s, after decades of successful experience with cable-stayed bridges, beginning with those built in Germany after the war, significantly longer spans began to be built. Even though cable-stayed bridges were originally meant to span no more than 1,200 feet [366 meters], with longer crossings expected to be suspension bridges, two modern cable-stayed bridges—the Pont de Normandie in France and the Tatara Bridge in Japan—now extend over as great distances as the Tacoma Narrows suspension bridge did.
Willy Ley, in his 1954 book Engineers’ Dreams, described some of the grandest schemes imagined by engineers up until that time: damming the Congo River to create the largest lake in Africa; draining the Mediterranean Sea to reclaim land for crowded Europe; building a tunnel between England and France. This last dream was, of course, realized when the Channel Tunnel opened in 1994, more than two centuries after the idea was first articulated by French engineer Nicolas Desmaret. Whereas the Congo is not likely to be dammed in the foreseeable future, the Three Gorges Dam in China will soon back up water on the Yangtze River and displace more than a million people. Today the decision whether to dam a river is often more political than technical. Engineers can dream, but it takes political savvy and resolve, not to mention money, to move the machinery that moves the earth.
The ultimate triumph of mega-engineering schemes, from gigantic ships to monumental skyscrapers, is also frequently limited by issues tangential to the main idea, by details that can seem decidedly low-tech or even non technical—matters such as politics, aesthetics and safety. When engineers ignore these factors or treat them as undeserving of the same careful analysis as the main technological challenge, disaster can result. The sinking of the Titanic might not have been nearly as great a tragedy had the ship’s vulnerability been acknowledged by having enough lifeboats on board. The Three Mile Island and Chernobyl accidents might not have progressed to the point that they did had nuclear power generation not come to be viewed as so commonplace as to breed a casual and careless attitude among some operators. The space shuttle Challenger might not have exploded had managers heeded engineers’ warnings about the behavior of O-rings in cold weather, rather than becoming emboldened by the two dozen successful space shuttle missions that proceeded Flight 51L. In short, colossal accidents happen when overconfidence and complacency prevail.
Engineers and managers of technology, being human, can come to believe in themselves and their creations beyond reasonable limits. When failures do occur, they naturally cause setbacks but usually do not force the abandonment of dreams for ever grander and more ambitious projects. As soon as the cause of a failed effort is sufficiently understood and the sting of its tragedy sufficiently remote, engineers want to pick up where they left off in their pursuit of greater goals. This is as it should be in engineering—as in life—for it is as much a part of the human spirit to build longer and to fly faster as it is to probe the universe further and the atom deeper than our ancestors did. Just as by standing on the shoulders of giants we can become even bigger giants, so it is that by climbing on the spires of skyscrapers, engineers can reach for ever taller skyscrapers. If this be hubris, it is an admirable trait that has, on balance, led to cumulative progress in which engineers and non engineers alike take pride.

–Concluded

(The author is 6th semester student of civil engineering department at NIT, Srinagar.)