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December 19, 2008, 12:37 PM ET
Columbia U. Experiment Will Test Corrosion Sensors for Suspension Bridges
A mock-up of the cable holding up New York’s Williamsburg Bridge will be used to test sensors for monitoring corrosion. (Columbia U. photo)
What would happen if unseen corrosion caused the failure of a cable on a major suspension bridge? The short answer is, you don’t want to find out. Nor does anyone else. What you want to do instead is detect the corrosion early enough to make repairs to the cable. That’s a complex and costly job in itself, but far preferable to losing the bridge — and possibly lives as well.
So on Monday researchers at Columbia University’s Carleton Laboratory will begin a six-month experiment to test a system of corrosion sensors in a 20-foot-long mock-up of the cable that holds up New York’s 1903 Williamsburg Bridge, which crosses the East River between Manhattan and Brooklyn. The bridge, which has four main cables, has a span of 1,600 feet between the two towers and gives ships a 135-foot clearance below.
The experiment will use an environmental chamber to subject the cable mock-up — and the sensors in it — to conditions simulating decades of exposure to heat, cold, humidity, and acid rain. The mock-up, which has a diameter of 20 inches, is made up of almost 10,000 strands of steel wire and is under 1.2 million pounds of tension. Columbia says it is the world’s only cable mock-up under stress.
In recent years, sensor systems have been embedded in some new concrete bridges, but retrofitting suspension bridges with corrosion sensors is a more difficult undertaking. If the sensors survive the Columbia test, similar systems could be installed in the Williamsburg Bridge and other New York-area suspension spans — the Brooklyn Bridge, the George Washington Bridge, the Manhattan Bridge, and the Verrazano-Narrows Bridge. The experiment is being paid for by the Federal Highway Administration. —Lawrence Biemiller
The Williamsburg Bridge in 1978 (Jack Boucher, Historic American Buildings Survey/Historic American Engineering Record)
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