The Daniel Carter Beard Bridge, better known as the Big Mac Bridge, carries 100,000 vehicles a day across the Ohio River between Cincinnati and Northern Kentucky.
It’s a complex structure made of twin steel spans with 88 cables supporting eight lanes of Interstate 471 as it crosses the Ohio.
Inspecting those cables for rust, cracks, chips, and the like is typically accomplished by a rope team composed of workers accustomed to rappelling slowly down 220 feet of cable, from the top of the bridge, in conditions that can be hot, windy, and noisy.
This past September, with the temperature at 90 degrees and the humidity around 90 percent, the inspection team, with the cooperation of the Kentucky Transportation Cabinet (KYTC), tried an innovative approach to inspecting those critical cables. They used a high-tech drone that flew close and photographed the cables for wear and tear, gathering data as it went.
The drone solution was able to save time and money, improve safety, and reduce lane closures on the busy interstate during the inspection.
“It made the process more efficient,” says Alicia McConnell, the project manager and a civil engineer with Michael Baker International, the engineering firm that handled the project for the state of Kentucky.
The team was able to inspect an entire side of the bridge in an hour, she says. Doing that manually with a rappel team would have taken days.
The engineering firm used a drone manufactured by Intel called the Falcon 8+. Intel’s drone technology came to the attention of most Americans during February’s opening ceremony of the 2018 Winter Olympic Games in China, which featured a spectacular light show choreographed for 500 drones.
While not as stunning as the Olympic light show, the Big Mac inspection was just as high tech. A flight plan is loaded into the drone, which is equipped with a high-resolution camera that can rotate 180 degrees. (Most drones are mounted with cameras that are only pointed downward.) A virtual 3D model of the bridge is built that can be used for inspections in subsequent years. Changes over time can be better tracked and the quality and accuracy of the data collected is improved.
“We’re able to document the entire length of every cable and we’ll have that to compare next time,” McConnell says.
“Without this technology, it would be me looking at a piece of paper with a pencil sketch,” says Erin Van Zee, who oversees bridge inspections for the state of Kentucky.
The weather conditions were classic summer in Cincinnati — hot and humid — when the inspection took place during the third week of September. The rope team worked 20 stories up for hours, with only the food and water they could carry.
“It was a little bit difficult on them,” McConnell says.
The team still needed to scale the bridge for portions of the inspection, but the rope time was greatly reduced. In engineering jargon, it was “a reduction in man-at-risk hours,” McConnell explains.
“The less time you can have someone dangling 220 feet in the air … we’ll call that a success,” she says.
The KYTC called it a savings of public dollars.
“We can use taxpayer funds more efficiently,” Van Zee says. “We can use our time more efficiently.”
View this short video about the Falcon drone inspection of the Daniel Carter Beard Bridge. Video provided by Intel.