Smart Bridge Keeping Drivers Safe

Reported July 2009

MINNEAPOLIS (Ivanhoe Newswire) -- This month marks the two year anniversary of the Minneapolis bridge collapse, when 13 people died and more than 140 were hurt. For those who survived the tragedy, the fear is still fresh, but science is doing its part to spot structural problems years before they turn into tragedies.

It was a drive home from work Erica Gwilliam will never forget.

"I felt like I was just dropping into a bottomless pit and that's all I kept feeling in my stomach, like I was dropping," Erica Gwilliam recalled to Ivanhoe.

Two years ago, while on the I-35-W Bridge in Minneapolis, Gwilliam plunged 85 feet in her car. She landed on a slab of concrete, narrowly missing the gap where 13 people dropped to their deaths.

"I've always heard people having their life flash before their eyes and it does," Gwilliam said.

The structure that now crosses the Mississippi is dubbed a "smart bridge." Civil engineers installed nearly 400 sensors that are buried in the concrete.

Each one measures how temperature, corrosion and traffic loads impact the bridge.

"Some are to measure how it's deforming, how it's curving and deflecting under load. Other types of instruments are in there to measure vibrations," Kathy French, a Civil Engineer at the University of Minnesota in Minneapolis, told Ivanhoe.

When heat or cold causes the concrete to expand or contract, a wire inside the sensors vibrates and sends a signal back to the lab.

The goal is to pick up on subtle changes in the concrete to identify any signs of deterioration.

"What we're trying to do is combine the information from these multitudes of sensors to tell a story or to understand how the bridge is responding," French explained.

Gwilliam still has nightmares, but sleeps easier knowing science is finding ways to save lives.

"That may be the one saving grace of this whole incident is that we could try to prevent another bridge from collapsing," Gwilliam said.

This bridge is the only one in the country with so many sensors buried inside. Over the next year, engineers will collect and analyze the data coming in from the smart bridge to create a new model; one that could be used to improve the performance of bridges across the nation.

The American Society of Civil Engineers and the Institute of Electrical and Electronics Engineers, Inc.-USA, contributed to the information contained in the TV portion of this report.

Click here to Go Inside This Science or contact:

Catherine French, PhD
Minneapolis, MN
(612) 625-3877
cfrench@umn.edu

The American Society of Civil Engineers
Joan Buhrman
Reston, VA 20191-4400
(703) 295-6404
http://www.asce.org
jbuhrman@asce.org

Institute of Electrical and Electronics Engineers, Inc.
IEEE
Pender McCarter
IEEE http://www.ieee.org
IEEE-USA http://www.ieeeusa.org
p.mccarter@ieee.org

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