Researchers are working to help inspectors make quicker, easier and more accurate determinations about the structural integrity of bridges.
Bridge inspection is a costly business. Highway departments must divert traffic as they examine the structure and road surface, and getting a good view of the underside of bridges has, until the advent of drone-based inspections, risked the safety of workers and required specialized equipment. Yet the costs of foregoing inspections is even greater -- should a bridge fail or become unsafe, commuters and local government both pay the price.
Now, University of Texas at Arlington researchers funded by the Texas Department of Transportation (TxDOT) have developed a technology that will help inspectors make faster, easier and more accurate determinations about the structural integrity of bridges.
Currently, inspectors drag or tap on the surface of a bridge with equipment that helps them interpret sounds that could indicate potential problems. The researchers' new system uses a sensor-laden platform with a tool that automatically strikes the surface of the bridge. The mechanical waves generated and captured by the platform can be mapped to a 3D image to show hidden damage.
Because the system is mounted on a trailer, it is not necessary to close lanes for testing. Additionally, the waves can penetrate three feet down into the bridge surface and give engineers better insight into the entire structure, which can be difficult to access.
“Our goal is to help TxDOT create better, more accurate maintenance plans to prevent economic losses due to unnecessary repairs or because necessary repairs weren’t made in a timely manner,” said Suyun Ham, an assistant professor of civil engineering and the project's lead researcher. “This technology will make it easier for industry, engineers and city planners to make well-informed decisions about the way forward for bridge maintenance and repairs.”
The Federal Highway Administration’s Long-Term Bridge Performance Program has been conducting similar research. In 2014, it began testing a robotic platform that analyzed 4,000 square feet of bridge deck per hour. The Robotics Assisted Bridge Inspection Tool is about the size of a Volkswagen Beetle and can quickly collect data to assess condition of bridge decks using a number of technologies including ground penetrating radar, impact echo, ultrasonic surface waves and electrical resistivity of the concrete deck. RABIT also carries two high-resolution cameras to capture images of the deck.
The latest upgrade to RABIT includes a contactless acoustic system that will speed data collection, reducing traffic delays and increasing worker safety. According to an Autumn 2019 FWHA article, the system sends a signal through a waveform generator, into an amplifier then to an air-coupled transducer. As the propagating wave leaks from the structure to the air, microphones capture the response of the structure, and the system analyzes the surface waves to estimate the depth and size of flaws in bridge decks.
"With promising preliminary results from the air-coupled system, we hope for fast and reliable field measurements in the near future," said Jean Nehme, team leader of FHWA's Long-Term Infrastructure Performance programs. "The potential combination of the RABIT and the air-coupled acoustic system could present a huge step toward more efficient bridge deck inspections."