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This radar image of an Athens bridge shows areas of severe deterioration, colored orange and red. Much of the deterioration is invisible from the surface of the bridge. Southern Radar Imaging would not reveal the location of the bridge.
Courtesy image by Southern Radar
This radar image of an Athens bridge shows areas of severe deterioration, colored orange and red. Much of the deterioration is invisible from the surface of the bridge. Southern Radar Imaging would not reveal the location of the bridge.

Athens firm able to look below bridge’s surface

By Eric Fleischauer
eric@decaturdaily.com · 340-2435

Every day your life depends on the judgment of a bridge inspector, but the perilous fact is the bridge inspector often has no way to evaluate critical bridge components.

An Athens company, Southern Radar Imaging, is trying to solve the problem.

Southern Radar’s product is ground penetrating radar. It consists of an electromagnetic device attached to the base of a three-wheeled device about the size of a shopping cart. Also attached is a computer to collect the radar data.

Project Manager Matthew Wilbanks operates the device by pushing it along the bridge deck, creating 2-foot-wide radar images the length of the bridge, to a depth of about 18 inches.

The resulting image looks similar to a full-color topographical map with colors ranging the spectrum from red to violet.

Colors on the violet end of the spectrum make inspectors happy: the decking is solid. Orange and red are bad news. It indicates voids or weaknesses in the decking.

“It’s not cheap,” said Roy Shaw, company spokesman. “They have to have funding if they want to use modern technology.”

The cost is about 53 cents per square foot, and it does not reduce other inspection costs incurred by Alabama Department of Transportation and other bridge owners.

“They take this information along with everything else they have,” explained Shaw. “It’s another tool. It complements the bridge inspector, but does not replace him.”

The flip side, however, is products like the one offered by Southern Radar can save money. A bridge that looks lousy from the outside may be solid on the inside, a fact hidden from a bridge inspector.

“You may walk up and see a crack in the bridge,” said project specialist Roger Shireman. “That doesn’t necessarily mean the bridge is bad. If it’s got good rebar in it and it’s supported well, that may be a crack you can fill in and you’d be in good shape.”

He points to a printout of a Cullman bridge. It looks ugly, but the deterioration reflected in the printout corresponds to cracks on the surface. That’s good news, explained Shireman. Fill in the cracks and you have a sound bridge.

Then he points to a printout Southern Radar did on an Athens bridge. He declines to say which one.

“It’s in bad shape,” he said. Deep orange and red blots the image, and the colors do not correspond to visible cracks. The bridge is unstable, but neither bridge inspectors nor drivers would know it from looking at the pavement.

Bridges consist of three interdependent components, each critical to the bridge’s soundness. Below ground is the substructure. The deck — Southern Radar’s focus — includes the asphalt you drive on and the layers below it. The superstructure runs from the ground to the deck.

Problems with the deck don’t just make for a bumpy ride. A healthy deck distributes weight evenly over the supporting structures beneath it. Deficiencies in the deck cause weight imbalances that, in the worst case, can lead to a bridge collapse.

Southern Radar, owned by Ken Schaus, is in the right place at the right time. The collapse of the Interstate 35W bridge in Minneapolis on Aug. 1 has brought national attention — and lots of money — to the bridge inspection process.

“Since the Minneapolis bridge collapsed, things are going a lot faster,” said Shaw. “A lot more people are interested now.”

The most obvious shortcoming in the normal inspection process is that, with few exceptions, it is primitive. Technological innovations that have revolutionized the world in the last century have passed bridge inspectors by.

“The inspectors are doing essentially visual analysis,” said Steven Fenves, guest researcher at the National Institute of Standards and Technology. “They’re looking at it, scratching with a hammer. None of the states have implemented a systematic way of using modern nondestructive techniques in a routine fashion.”

That could change. If it does, Southern Radar is in a position to benefit.

Another problem with bridge inspections is that they are inconsistent. Different inspectors rate the same bridge differently, and that creates a headache for those who have to prioritize spending. Southern Radar’s product, however, avoids that problem. Its printouts reveal structural characteristics invisible to an inspector and demonstrate them consistently.

For a business like Southern Radar, tax dollars are everything. However much the Department of Transportation wants high-tech bridge inspections, it needs tax dollars to pay for them. Are taxpayers willing to pull out their wallets?

“I think the chances are really good this will take,” said Shaw. “I wouldn’t be here if I didn’t. It’s just going to take time. When that bridge collapsed in Minnesota, the first thing I heard was we have to go up on taxes to pay for infrastructure. That’s a fact. If people want to be safe, they have to pay for it.”

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