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Engineers Dance to Structure’s Song

Monday, December 24, 2012

More items for Quality Control

Listen up: Tuning into how a highway bridge sings in the rain can tell engineers a lot about the span's structural integrity, engineers at Brigham Young University have determined.

And they're not just whistling "Dixie." Using impact-echo testing, professors Brian Mazzeo and Spencer Guthrie say they can diagnose flaws in a bridge's deck based on the acoustic footprint produced by a few drops of water.

Simply put, drops of water are dropped on to the bridge deck, and the sound is recorded. The acoustic response indicates both the size and depth of flaws.

Photos: BYU

BYU professors Brian Mazzeo (left) and Spencer Guthrie (right) are using drops of water to acoustically determine structural flaws on bridge decks.

"There is a difference between water hitting intact structures and water hitting flawed structures," Mazzeo said. "We can detect things you can't see with a visual inspection; things happening within the bridge itself."

The BYU researchers are the first to use water droplets to produce acoustic responses on bridges, the university said. Testing usually uses objects such as hammers and chains and marking spots where a dull, hollow sound is produced.

However, such methods can require lane closures and take hours to perform.

In Tune with Efficiency

The new study, on the other hand, presents an efficient and cost-effective way of addressing mounting safety concerns over aging and corroding bridges, the scientists say.

"The infrastructure in the U.S. is aging, and there's a lot of work that needs to be done," Guthrie said. "We need to be able to rapidly assess bridge decks so we can understand the extent of deterioration and apply the right treatment at the right time."

Researchers hope that water droplets will provide a fast, cost-efficient alternative to hammer and chain tests now used in bridge testing.

The research is still in the preliminary stages, but the researchers are hopeful that one day bridge surveys will only take a few moments using this method.

"We would love to be able to drive over a bridge at 25 or 30 mph, spray it with water while we're driving, and be able to detect all the structural flaws on the bridge," Mazzeo said. "We think there is a huge opportunity, but we need to keep improving on the physics."

Mazzeo said the method could potentially be used to test other materials, too.

The study results were published in the October issue of Non-Destructive Testing and Evaluation International.