April 16, 2009 By Blake Harris
Photo: Antonio Nanni (in the middle), with graduate students Rosella Ferraro and Felipe Mejia placing sensors along Miami's Grove Isle Bridge.(Credit: Richard Patterson)
Every two years, most of the nation's older bridges (many dating from the 1960 and 70s) are still inspected visually by on-the-ground inspectors. But with literally tens of thousands of bridges, that process is time consuming and costly.
The Federal Highway Administration reportedly estimates that more than 70,000 of the nation's bridges are structurally deficient.
The obvious answer is to deploy sensors which can monitor bridges continuously. And while various solutions are being explored, the issue of providing power to sensors and communications equipment is often an issue.
To meet this challenge, a team of University of Miami College of Engineering researchers are implementing a self-powered monitor system for bridges that can continuously check their condition using wireless sensors that "harvest" power from structural vibration and wind energy.
The actual technology of monitoring bridges using wireless sensors is still being explored. This Miami project forms part of the work currently being funded under the National Institute of Standards and Technology's Technology Innovation Program as a five-year project to develop a more effective system to monitor the health and predict the longevity of bridges.
Antonio Nanni, professor and chair of the Department of Civil, Architectural, and Environmental Engineering, who directs a College of Engineering Industry/University Cooperative Research Center, is the lead investigator of the nearly $14 million project. He and his team plan to place newly developed wireless sensors-some as small as a postage stamp, others no longer than a ballpoint pen-along strategic points inside the 27-year-old Long Key Bridge, in the Florida Keys and on a Northwest 103rd Street quarter-mile steel overpass that leads into Hialeah, in Florida.
The sensors the group are deploying (developed by project collaborators Virginia Tech University and New Jersey-based Physical Acoustics Corporation) record everything, from from vibrations and stretching to acoustic waves and echoes emitted by flaws such as cracks. Even the alkaline levels in the concrete of bridge supports are being measured.
The results will be fed into a website, updated in real time, according to Nanni. This way, the results can be shared with other researchers in the U.S. and overseas.
Once all the information is gathered and analyzed, Nanni and his team will diagnose the bridges' health and isolate potential dangers. The Florida Department of Transportation will then have to decide how to repair the structures.
But more importantly, the system Nanni and his team develop could be used as a national model for monitoring the structural integrity of bridges nationwide.