The half-mile-long Champlain Bridge was abruptly closed as structurally unsafe Oct.16 when engineers learned the 80-year-old massive concrete piers were rotting away just below the waterline. Underwater diving inspections of the piers was done every five years but gave no advance hint at the rapid deterioration to come. Skip Carrier, a state Transportation Department spokesman, said that in the last four years, the amount of missing and rotted concrete in two of the 10-foot-thick piers went from 10 inches to 3 feet.
Civil engineering expert Norbert Delatte said a test may have been able to find the problem before it got so bad. The expert is a professional engineer and professor at Cleveland State University in Ohio and said the the “ultrasonic pulse test is not cheap, but it is a lot cheaper than what is going to have to happen now.” An ultrasonic pulse acts like a kind of sonar. An electrical transmitter is placed against concrete and emits a sound wave, which travels through the concrete and bounces back to a receiver. An engineer can analyze the resulting signal to determine the condition of the concrete.
Delatte is an expert on bridge failure, and is the editor of the American Society of Civil Engineers Journal of Professional Issues in Engineering Education and Practice. He reviewed DOT diving inspection records for 2000, 2003 and 2005 provided by the Times Union.
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