Wireless sensors to monitor bridge structural integrity

UM engineer tests sensors on I-495 to detect stress load, vibration, temperature and crack growth

August 17, 2010

A credit-card-sized, lightweight, low-power, wireless sensor has been designed to revolutionize monitoring structural security of bridges, according to a report by the Baltimore Sun.

Mehdi Kalantari, an electrical engineer at the University of Maryland (UM), College Park, devised this sensor to be powered by the sun, ambient light or even stray radio waves.

To prevent incidents like the I-35W bridge collapse in Minneapolis, which killed 13 people in 2007, this device will constantly measure stress load, vibration, temperature and growth of cracks.

“You will have a complete, real-time picture of what’s happening on the bridge,” Kalantari told the Balitmore Sun.

Kalantari and his colleagues recognize that the product would not and should not replace human inspections. They said the products would track real-time changes between inspections, especially for older bridges with a history of structural deficiency.

“The sensor will never 100% replace human intelligence,” Kalantari told the Baltimore Sun. “We don’t want to give the impression we want to replace the bridge inspectors with our sensors."

With an abundance of older bridges built in the 1950s through the 1970s, the market for this product has great potential to be vast, particularly in areas of high earthquake activity.

Kalantari explained that what makes his device different is that it uses very little power, about 4 microwatts, or 100 million less than a light bulb.

He will have to face the challenges of attaining acceptance from engineers and showcasing the product’s superiority against its competition in order to be successful in the market.

UM’s Technology Advancement Program, however, was willing to invest in this project with the belief that Kalantari might be onto something.

Kalantari and his partner, fellow UM electrical engineer Arash Takshi, were given a free year of work space on the UM campus and won a $6,000 grant for their startup company, Resensys.

Takshi and Kalantari’s company has two pending patents for sensor technologies and plan to file for more, Kalantari stated to the Baltimore Sun.

Jeff Roberts, senior project engineer with the Maryland State Highway Administration’s Office of Structures, told the Baltimore Sun that the technology “looks promising in the laboratory, but he needs to do actual field testing.”

Roberts pointed out its advantage lies in its wireless feature and that it is not battery operated. His agency allowed the company to install sensors on the I-495 bridge over the Northwest Branch in Montgomery County.

Kalantari said the sensors have been able to detect fluctuations in stresses and, from early indications, proven to be effective.

Ultimately, Kalantari’s company would need further testing to earn approval from the Federal Highway Administration (FHWA).

“Sensor technology is evolving and can be beneficial in monitoring bridge conditions,” said FHWA spokeswoman Nancy Singer. “Such technology represents an additional tool available to bridge owners but does not replace or supercede the need for regular, comprehensive visual and physical bridge inspections.”