Closing down a busy bridge for safety inspections is difficult because it can lead to traffic nightmares on either side. But at the same time, the last thing engineers want is for it to collapse with vehicles on deck. So a team of researchers has come up with a novel way to test a concrete bridge's structural integrity by simply listening to the sound of rain drops.
It sounds a little impossible that a tiny drop of water could reveal problems in a multi-tonne structure, but according to professors Brian Mazzeo and Spencer Guthrie from Brigham Young University, there's a measurable audible distinction with structures that have a flaw. The technique is known as impact-echo testing, and the use of water drops is a marked improvement over previous approaches that involved a metal chain being literally dragged across the road deck while engineers listened for dull, hollow sounds.
With this approach, instead of having to completely shut down the bridge to traffic, a vehicle could drive across at speeds of up to 30 mph while spraying it with water. On-board microphones would be used to listen for changes in sound, and scanning even a giant suspension bridge for structural flaws would take mere minutes. Or hours, depending on gridlock.