A University of Maryland researcher who has developed a new, affordable early warning system says that it's too costly to fix all the bridge spans or adequately monitor their safety even as it emerged that millions of U.S. drivers cross faulty or obsolete bridges every day, highway statistics.
This wireless technology could avert the kind of bridge collapse that killed 13 and injured 145 along Minneapolis' I-35W on Aug. 1, 2007, he says - and do so at one-one-hundredth the cost of current wired systems.
Advertisement"Potentially hundreds of lives could be saved," says University of Maryland electrical engineering researcher Mehdi Kalantari. "One of every four U.S. highway bridges has known structural problems or exceeded its intended life-span. Most only get inspected once every one or two years. That's a bad mix."
Kalantari has created tiny wireless sensors that monitor and transmit minute-by-minute data on a bridge's structural integrity. A central computer analyzes the data and instantly warns officials of possible trouble. He plans to scale-up manufacture in the fall.
"If this kind of technology had been available in Minnesota four years ago, there's a good chance the fatal bridge collapse could have been avoided," Kalantari adds. "This new approach makes preventive maintenance affordable - even at a time when budgets are tight. Officials will be able to catch problems early and will have weeks or month to fix a problem."
More than one-in-four U.S. bridges are either structurally deficient or functionally obsolete, according to a 2009 estimate by the U.S. Society of Civil Engineers.
- 72,000-plus U.S. bridges are listed by the U.S. Department of Transportation as "structurally deficient" and require extra surveillance.
- 79,000 others are functionally obsolete, exceeding their life-span and carrying loads greater than they were designed to handle.
Kalantari's sensors measure indicators of a bridge's structural health, such as strain, vibration, flexibility, and development of metal cracks. The sensors are small, wireless, rugged, and require practically no maintenance, he says. They are expected to last more than a decade, with each costing about $20. An average-sized highway bridge would need about 500 sensors for a total cost of about $10,000.
"The immediacy, low cost, low energy and compact size add up to a revolution in bridge safety monitoring, providing a heightened level of early-warning capability," Kalantari concludes.