Bridging the Gap

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How to ensure the safety of tens of thousands of aging bridges across the U.S.? A team of UM College of Engineering researchers is testing an ingenious answer: a self-powered monitoring system made up of tiny sensors that deliver vital data in real time.

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Antonio Nanni, professor and chair of the Department of Civil, Architectural and Environmental Engineering.

A Serious Safety Issue
As the August 2007 collapse of the I-35W bridge in Minneapolis, Minn., so calamitously made clear, the structural integrity of some 70,000 older spans in our nation’s infrastructure is an urgent concern. Human inspectors check bridges visually every few years—which may not be frequent enough to catch a problem before it turns into a disaster.

A novel self-powered monitoring system being tested by a team led by Antonio Nanni, professor and chair of the Department of Civil, Architectural and Environmental Engineering at the University, could change that. Nanni and his team are placing wireless sensors, some as small as a postage stamp, others the length of a ballpoint pen, along strategic points of South Florida spans that include the 27-year-old Long Key Bridge in the Florida Keys and a quarter-mile-long, steel highway overpass that leads into Hialeah, Florida.

Developed by project collaborators Virginia Tech University and New Jersey-based Physical Acoustics Corporation, the sensors, which harvest power from structural vibration and wind energy, record vibrations, stretching, acoustic waves, even alkaline levels.

A National Model
The data will be shared online in real time, then analyzed to evaluate the bridges’ health. Should any defects be found, decisions regarding repair will be made by the Florida Department of Transportation. Study partners at the University of South Carolina at Columbia also are monitoring a series of bridges in their state and developing diagnoses collaboratively with UM engineers.

Part of the Technology Innovation Program of the National Institute of Standards and Technology, the federally funded, five-year project could serve as a national model. It’s all about common-sense maintenance, Nanni says: “Just as when someone goes to see a doctor and gets all sorts of tests done to see how healthy they are and how long they’ll live, we’re doing the same with bridges.”

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