By Michele McDonald
George Mason University engineering professor David Lattanzi was inspecting a bridge several years ago in his hometown of Pittsburgh when a drunk driver sped past “lane closed ahead” signs and slammed into the final sign—the familiar, giant flashing lighted arrow—the only barrier remaining between Lattanzi and the driver.
The driver walked away. Lattanzi and his crew were left shaken.
“I’ve almost gotten killed on the job three times,” he said. “Inspecting bridges is really dangerous for humans, and we don’t get good results.”
He knew there had to be a better way.
His innovative approach combines computer science, engineering know-how and agile flight skills to create a sophisticated 3-D computer model of a bridge.
It’s no secret that the nation’s infrastructure is crumbling—just ask HBO’s John Oliver. Inspecting bridges is hazardous, expensive and well behind schedule for the nation. 3-D modeling is more efficient, about 10 percent of the traditional cost, and offers more exact comparisons from inspection to inspection, Lattanzi said.
This summer the U.S. Forest Service took Lattanzi’s idea on a large-scale test drive in Alaska. The U.S. Forest Service manages more bridges—7,500––than any other organization in the United States, Lantanzi said.
That test drive included an unmanned aerial vehicle zipping around and snapping photographs of the 280-foot Whistle Stop Bridge—the longest timber bridge in North America—on Alaska’s Kenai Peninsula.
Results from the photographic flyby went to Lattanzi’s lab at the Volgenau School of Engineering. There, they are compiled into a sophisticated 3-D model, which takes about 700 hours of computational time.
“You can see the knots in the wood,” Lattanzi said. “You can see the grain. You can count the threads on the bolts.”
In fact, the 3-D model’s detail is so minute that the name of the bolt manufacturer is easy to read.
Lattanzi’s method is also more flexible—equipment fits into a backpack—while traditional methods rely upon heavy equipment.
That’s of particular importance to the U.S. Forest Service because, like many of the bridges under its auspices, the Whistle Stop Bridge is off the beaten path where large trucks can’t pass.
The Whistle Stop crosses the Placer River and is the only way hikers can reach the Spencer Glacier. A school bus on train tracks takes a visitor part of the way to the bridge. Then it’s on foot.
Ali Khaloo, a Mason civil engineering doctoral student, took his first trip to Alaska for the project, and found that overseeing the inspection came with some unusual guidelines, as well as sightings of moose and a black bear.
“We were told to always be in a group of two, no matter what,” said the Iranian native. “I was really surprised that the guide carried a rifle.”
Khaloo, who wants to follow in the footseps of his uncle, a civil engineer, said the Alaska trip was a one-of-a-kind experience.
“It was one of the most beautiful places I’ve ever been to in my life,” Khaloo said. “Spencer Glacier was magnificent.”
Lattanzi said he expects more organizations will follow the lead of the U.S. Forest Service in the next few years, making sure bridges are safe for drivers and pedestrians.