 |
||||
 |
||||
|
||||
| Seven Wonders of the Modern World As a tribute to modern society's ability to achieve the unachievable, reach unreachable heights, and scorn the notion of "it can't be done," in 1994 ASCE sought nominations from across the globe for the Seven Wonders of the Modern World. The chosen projects pay tribute to the greatest civil engineering achievements of the 20th century. The Seven Wonders of the Modern World:
The 31-mile Channel Tunnel (Chunnel) fulfilled a centuries-old dream by linking Britain and the rest of Europe. More than a tunnel, it combines infrastructure and immense machinery in an underwater system of unprecedented ambition. Three 5-feet thick concrete tubes plunge into the earth at Coquelles, France, and burrow through the chalky basement of the English Channel. They reemerge behind the white cliffs of Dover at Folkstone. Through two of the tubes rush the broadest trains ever built. The double decker behemoths, which span 14-feet across, traverse the tunnel at close to 100 mph. Passengers board not on foot, but in automobiles and buses. Maintenance and emergency vehicles utilize the third tunnel, located between the rail tubes. Huge pistons open and close ducts, relieving the pressure that builds ahead of the trains' noses. Some 300 miles of cold water piping run alongside the rail tracks to drain off the heat raised by the air friction.
CN Tower  The world's tallest free-standing structure soars 1,815-feet above the sidewalks of Toronto, three times the height of its better-known cousin, the Seattle Space Needle. The CN Tower, as heavy as 23,214 large elephants, was erected at an amazing rate of 18-feet per day. During construction, concrete flowed from the bottom of the tower as it ascended, while aircraft-type bombsights kept the tower plumb as it went up. Today the tower is off by a mere 1.1-inch. Designed with the aid of a wind tunnel, the CN Tower can withstand 260-mph gusts. The SkyPod, a seven-story structure, 1,100-feet high, was built around the base of the tower and jacked into place as one unit. A pair of 10-ton counterweights is attached to the mast to keep the tower from swaying too much. A Sikorsky helicopter hoisted the crowning antenna, for which the tower was originally erected. Radio signals are broadcast from the base of the antenna, while television signals are sent from the top. Presently, 16 of Toronto's media signals are transmitted from the tower.
Empire State Building  Measuring 1,250-feet high, the Empire State Building is the best-known skyscraper in the world, and was by far the tallest building in the world for more than 40 years. The building's most astonishing feat however, was the speed in which it rose into the New York City skyline. Construction was completed in only a year and 45 days, without requiring overtime. Ironworkers set a fervent pace, riveting the 58,000-ton frame together in 23 weeks. Just below them, plumbers laid 51 miles of pipe, electricians installed 17-million ft. of telephone wire and masons finished the exterior in only eight months. The building was so well engineered that, in 1945, it was easily repaired after a B-25 twin-engine bomber plane crashed into it in the dense fog. The precise choreography of the project revolutionized the tall building construction industry. Although it has been surpassed as the world's tallest building, the Empire State Building remains the standard against which all other skyscrapers have been judged for the last 65 years.
Golden Gate Bridge  More than 66 years after its completion, the Golden Gate Bridge, once the world's longest and tallest suspension bridge, stands at the entrance of the San Francisco Bay as a beloved international icon. Hanging from two 746-foot-high towers, the bridge is suspended by two massive main cables that contain 80,000 miles of wire and measure one yard in diameter. In fact, the Golden Gate Bridge cables contain enough wire to encircle the earth three times. To leap across the mouth of an ocean harbor, something never before accomplished, civil engineers planted one pier in the open sea, 1,100-feet from the shore. Construction crews braved biting cold, 70-mph gusts and dizzying heights to complete the bridge in only four years. The bridge combines engineering strength and beauty. It survived the 1989 Loma Prieta earthquake suffering no damage, and in 66 years the bridge has only been shut briefly (longest closure was 3 hours and 27 minutes) to traffic three times due to periods of high sustaining winds. A $400 million seismic retrofit, which will allow the bridge to withstand a nearby earthquake that measures 8.3 on the Richter scale, began in August 1997. Today, the Golden Gate Bridge remains one of the world's most revered and photographed bridges.
Itaipu Dam Five-miles-wide and requiring enough concrete to build five Hoover Dams, the Itaipu Dam spans the Parana River at the Brazil/Paraguay border. During its construction, workers shifted the course of the seventh largest river in the world by digging a 1.3-mile bypass. To accomplish this they had to remove 50 million tons of earth and rock. The main dam, as high as a 65-story building, is composed of hollow concrete segments; while the flanking wings are earth and rock fill. Enough iron and steel was used at Itaipu to build 300 Eiffel Towers. Another marvel of Itaipu is its powerhouse. Measuring one-half-mile long, it is partially submerged and contains 18 hydroelectric generators, each 53-feet across. Some 160-tons of water-per-second pour onto each turbine, generating 12,600-megawatts, enough to power most of California. Itaipu supplies 28 percent of all the electric energy in Brazil's south, southeast and central-west regions, and 72 percent of Paraguay's total energy consumption.
Netherlands North Sea Protection Works  This singularly unique, vast and complex system of dams, floodgates, storm surge barriers and other engineered works literally allows the Netherlands to exist. For centuries, the people of the Netherlands have repeatedly attempted to push back the sea, only to watch brutal storm surges flood their efforts, since the nation sits below sea level and its land mass is still sinking. The North Sea Protection Works consists of two monumental steps the Dutch took to win their struggle to hold back the sea. Step one, a 19-mile-long enclosure dam, was built between 1927 and 1932. The immense dike, 100-yards thick at the waterline, collars the neck of the estuary once known as Zuiderzee. Step two, the Delta Project, was intended to control the treacherous area where the mouths of the Meuse and Rhine Rivers break into a delta. The project's crowning touch was the Eastern Schelde Barrier, a two-mile barrier of tell gates slung between massive concrete piers, which fall only when storm-waters threaten. The North Sea Protection Works exemplifies the ability of humanity to exist side-by-side with the forces of nature.
Panama Canal  The dream of Spanish conquistadors and the failed ambition of famed French canal builder Ferdinand de Lesseps, the Panama Canal is one of civil engineering's greatest triumphs. Under the direction of U.S. Col. George Washington Goethals, 42,000 workers dredged, blasted and excavated the path stretching from Colon to Balboa. They moved enough earth and rubble to bury the island of Manhattan to a depth of 12-feet, or enough to open a 16-foot-wide tunnel to the center of the Earth. The canal was finished on time and within budget. Despite this, after completion a challenge remained: How to tame the flood waters of the Chagres River, known to rise 25-feet in a single day during monsoon season? The engineers' solution was to erect a dam that, at the time, formed the world's largest man-made lake. The Canal operates as regularly today as it did in 1914. In each transit, 52 million gallons of fresh water is lost, but quickly replaced by Panama's heavy rainfall. The canal remains a testament to the combined skills of structural, geotechnical, hydraulic and sanitary engineers.
|
||||
|
||||
