Singing in the rain: Raindrops falling on a bridge can reveal hidden structural flaws

In a new study, engineers at Brigham Young University (BYU) have shown that the sounds a bridge makes when drops of water strike its surface can be used to detect serious flaws in the bridge's structure.

"There is a difference between water hitting intact structures and water hitting flawed structures," said Brian Mazzeo, an engineering professor at BYU, according to Science Daily. "We can detect things you can't see with a visual inspection; things happening within the bridge itself."

This type of non-destructive testing used by Mazzeo and fellow BYU engineering professor Spencer Guthrie — known as the 'impact-echo method' — is nothing new to bridge engineers. They've used this method for years to detect any separation of the layers of concrete in the bridge's deck — called delamination — by dragging chains across the surface and noting where the sound becomes more hollow. Depending on the size of the bridge, this can take hours and cause severe delays in traffic over the bridge as the workers close lanes to complete the work.

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Mazzeo and Guthrie are the first to use drops of water for this purpose. By recording the sound the drops make as they hit the concrete surface, they can not only detect delamination flaws, but they can also tell both the size of a flaw and how deep down it is.

Their work is just the first stage in developing this new method, but they can see it being applied to other materials that are susceptible to delamination, such as aircraft composites.

Their study has been published in this month's issue of Non-Destructive Testing and Evaluation International, and with recent reports about America's failing infrastructure, they believe the work could help by someday reducing bridge-survey times substantially.

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"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."

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