October 23, 2012
Revealing The Health Of Bridges Through Sound
Brett Smith for redOrbit.com - Your Universe Online
With America´s aging infrastructure in need of repair, physicists are looking for ways to address and assist in the rebuilding effort that both presidential candidates are calling for this election season.
In an attempt to better analyze the integrity of bridges, a research group from Brigham Young University has found a way to detect flaws in the structures by listening to how they resonate when struck with tiny droplets of water.
“There is a difference between water hitting intact structures and water hitting flawed structures,” said Brian Mazzeo, a professor in the Department of Electrical and Computer Engineering at BYU. “We can detect things you can´t see with a visual inspection; things happening within the bridge itself.”
According to the team´s report in the journal Non-Destructive Testing and Evaluation International, they used a method called impact-echo testing to diagnose any flaws in a bridge structure. The technique was first developed in the 1980s and has been used in the past to analyze bridge integrity. However, the current use of the technique is slow and requires lane closings on the bridge being tested–which is costly in terms of time and resources.
“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.”
In the study, the BYU researchers tested two liquid flow rates that produced different droplet sizes and acoustic responses. The slower rate was set at 22.5 mL/min and produced the equivalent of 7mm spherical drops. The faster rate occurred at 94 mL/min and produced the equivalent of 3mm droplets. Both rates allowed the researchers to detect delamination, or the separation of layers within the bridge deck.
“The response gives you an indication of both the size and the depth of the flaw,” Mazzeo said in a news release.
The professor added that, with additional testing, a refined impact-echo technique based on their method could eventually be used to analyze the integrity of other materials, including those used in the construction of aircraft. He expected a refined technique to be able to perform that analysis quickly and cheaply.
“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.”
In their report, the physicists said additional testing on concrete materials will be needed to establish the sonic frequency range and depth penetration of the technique is able to analyze.
“Additionally, the details of acoustic impact responses by droplets arriving at non-perpendicular angles and/or affected by wind together with surface roughness and hydrophobicity are areas of research that need to be explored,” the team wrote. “These considerations will be important for deployment of the technique on concrete structures in the field.”