By Melissa Silmore (TPR'85)

According to experts, 25% of the more than 607,000 U.S. bridges are “functionally obsolete” and don’t meet current standards. A third of the nation’s bridge decking is “structurally deficient”—in need of significant repair—and approximately 210 million vehicles drive across them every day in the largest metropolitan areas. U.S. bridges have an average age of 42 years, and more than 30% have exceeded their 50-year design lives. These aging, deteriorating bridges demand increasingly costly inspection and maintenance. Federal, state, and municipal funding can’t keep pace.

Jim Garrett, with his research team, thinks he can help. And, for the new dean of Carnegie Mellon’s College of Engineering, his bridge research has been his passion. “Bridges are pure structures,” he says. “They’re such massive entities, and their function is clear. You can see how they work, how the forces are being distributed, and how the materials are where they need to be with no excess.”

 His fascination with them began decades ago.

The family came upon it without warning. One of the children, “Jimmy,” is beyond awestruck. More than 3,000 feet long, the span is incredible. Two sandstone cliffs loom on each side of the half-mile chasm, and he can barely glimpse the water nearly 900 feet below. As the road speeds away beneath the tires, he shouts. “Stop the car!” The other members of the Garrett family exchange knowing glances. Here we go again. “Jimmy has to see the bridge.” They pull over at the scenic overlook. The whole group spills out of the van—parents, Jim Sr. and Marie, and their children, just one grade apart: Jim, the oldest, brothers Kevin and Noel, then the two youngest, twin sisters Lori and Lisa.

Lori sighs. She thinks about all the other stops—at bridges, at construction sites, and once at a reservoir that to her eyes “looked like a big vat made of concrete.” On this day, the Garretts are on their way to Florida and are now in West Virginia, about four hours from their Pittsburgh home. Given that this is one of Dad’s “marathon” drives, the family grabs the opportunity to stretch their legs while Jim, a teenager, gazes ahead in admiration. He appreciates a bridge the way others take in a work of art.

He studies this “beautiful” bridge, amazed by its size, “how it’s founded on both banks and how minimal the material is to support the tremendous structure.”

To the others, the New River Gorge Bridge is simply a sight to behold. On this day in the late 1970s, it’s the longest single span and highest vehicular bridge in the world. Even the younger children, generally resigned to these stops, are impressed. After a short break, they pile back into the car and get on their way. Not surprisingly, Garrett insists his parents stop on their way home. And on every future family vacation trip they’ll take on this road, both coming and going.

While this bridge is stunning, Garrett can delight in many much closer to home. Just driving into downtown Pittsburgh is a special treat because “it’s just so gorgeous, with all these different bridges.”

Garrett seemed destined to become an engineer. As a young child, he loved his construction toys and making sketches of the house. By high school, he exceled in math and science, particularly physics, and got involved in helping his accountant father renovate the family’s big white house and property. As the eldest of five, he had no trouble taking the lead, either.

One summer, Jim Sr. was sprucing up the yard with the kids, edging a few trees with gravel. Pleased with the results (and according to Lori, at the prospect of less grass to mow), young Jim convinced his father they should finish the whole property—a tree-filled suburban acre. To his siblings’ horror, truckloads of gravel soon arrived, dumped and waiting to be spread. It took all five kids an entire summer of “shoveling and sweating” over the endless loads of gravel, with Jim as both laborer and general contractor. It’s a summer they’ll teasingly never let him forget.

A few years after the first sighting of the New River Gorge Bridge, it’s time for Garrett to consider college. His mother, Marie (A’57), convinces him to attend an engineering presentation at her alma mater, which she knew as Carnegie Tech. The Garrett children are top-notch students, with Jim at the forefront. As Lori puts it, “Jim’s blood type is A-positive. We always teased him with, ‘Well, what else would you have?’ because he’s gone through school with nothing but A’s.” Hearing Professor Francis McMichael’s presentation, Garrett can see himself “as part of that community” and sets his sights on CMU, where he eventually enrolls.

Apparently, his enthusiasm is contagious. Within a year, his brother Kevin follows in his footsteps. The next year, Noel joins his brothers at CMU, and within one more year, the twins enroll. Unbelievably, in 1981-82, the Garretts have five children attending CMU. President Richard Cyert, learning of the unique situation, schedules a special lunch with the entire family. “My mom and dad, I don’t think I’ve seen them so proud,” recalls Garrett. “They were just beaming.” Appearing on the front page of the local newspaper, soon after that lunch, is a picture of all of them: Jim (E’82,’83,’86), Kevin (S’83), Noel, (*84), Lori (S’85, DC’92), and Lisa (DC’85).

As his siblings join him on campus, Garrett meets another CMU student who will soon join the family—Ruth Ann Killmeyer (E’83). Fittingly, Ruth Ann’s father, Donald (E’55, TPR’69) is a CMU alumnus, as is her brother Don (E’80). Within a few years, she’ll become Garrett’s wife. They can’t know it at the time, but one day they’ll have two CMU alumni children: Ellen (A’11) in architecture and Patrick (E’12) in, of course, civil engineering.

While Garrett is enjoying undergraduate life, he finds his academic niche. He had come to CMU to study bridges but discovers the power of computing and cognitive science, excited at the opportunity to blend those fields with engineering. He completes his senior project and master’s degree developing software for civil engineering applications. Along the way, he notices that his classmates pepper him with questions, and he enjoys the impromptu teaching opportunities. So, although he applies to a number of universities, he pointedly remains at CMU to pursue his PhD and to study with Steven Fenves and his group, “world leaders in the application of computing in civil engineering.”

After earning his doctorate in 1986, and then spending a year at Schlumberger and three years as an assistant professor at the University of Illinois at Urbana-Champaign, he joins the CMU faculty. Years pass, and he rises through the academic ranks, becoming head of the civil and environmental engineering department in 2006. He and colleague Jacobo Bielak, a recognized earthquake authority, realize the potential of combining their areas of expertise and decide to collaborate, using vibrations to examine the structural health of bridges, a pressing issue.

As bridges age, they deteriorate, developing cracks that can, at times, rapidly worsen, leading to failure. Bridge safety is monitored primarily through visual inspection conducted every two years—a costly, inefficient undertaking. “You may have a crack that initially doesn’t seem to pose a big danger,” notes Bielak. “But very small changes can eventually, and possibly rapidly, create a hazard. Within a couple of days, a support can be compromised, and if one support fails, the bridge soon collapses.”

Garrett, Bielak, and their PhD student Fernando Cerda, begin meeting weekly. They discuss whether to pursue placing vibration sensors directly on bridges. They realize the devices are expensive, difficult to install, and susceptible to weather and vandalism. Moreover, it’s still nearly impossible to interpret small—and possibly destructive—structural changes from the data. Still, the need is there.

During one weekly conversation, it hits them. Vehicles travel routinely over bridges. Why not use them to collect data? Outfitting a fleet of buses or municipal cars with sensors could provide a wealth of data at minimal cost and maintenance. Research concerns would still remain, including the number of passes necessary by the same or different vehicles, environmental effects, the impact of bridge temperature, and, most critical, the need to develop the refined mathematical tools necessary to accurately detect deterioration. Nevertheless, this approach would, at a minimum, flag structural problems and reap tremendous cost savings by prioritizing inspection and rehabilitation needs.

“You want to invest in your infrastructure to improve its condition when it’s needed, and there appears to be a sweet spot, right before it starts into aggressive degradation,” explains Garrett. “Right now, things are deteriorating and we’re often unaware that a particular structure has reached that point, meaning eventual destruction or major renovation. If we could discover more clearly and sooner when something is starting down that path of much more aggressive degradation, we could make better and more cost-effective decisions.”

As he and Bielak consider how to make their idea a reality, Garrett receives another chance to make an immediate impact. Last January, he was named dean of CMU’s College of Engineering. With his interdisciplinary interests, he’s particularly excited to be at the helm of the engineering college. And he believes that his CMU training and the university’s culture will help him most in his new position.

“I’m proud of my Carnegie Mellon heritage,” says Garrett. “CMU is interdisciplinary. People aren’t afraid to reach across disciplines nor afraid to be critical. Here, you have to have good reasons for what you do. My Carnegie Mellon education trained me to always ask questions, to think outside the box, to try to continuously improve. All of those things I got as a graduate turn out to be exactly the kind of thinking one needs to lead a high-performing, intellectually challenging organization.”

He’s right about the college’s status. It consistently ranks in the top 10 undergraduate and graduate engineering schools. Garrett anticipates continued strength in the college’s research efforts, as well as its international campuses and programs. He envisions an ongoing upward trajectory in the areas of energy, environment, information and computing technologies, nanotechnology, and cyber security, and he looks forward to identifying new growth areas, such as advanced manufacturing, and smarter infrastructure, with his colleagues.

“Jim has been a leader in research that has had an impact on the world,” says CMU Provost Mark Kamlet. “His broad experience in research, teaching, and creating meaningful partnerships with business and industry make him an excellent choice [to lead the college].”

And of course, there’s that small matter of all those relatives spurring him on. “There are so many family members whose degrees ride on what I’m doing that I get lots of personal pressure to make sure I do the best job I can,” laughs Garrett.

Meanwhile, his bridge research continues. Simulating a vehicle with a vibration sensor, a red robot on wheels travels tirelessly back and forth in the CMU parking garage. As it moves along, its accelerometers are recording vibrations for Garrett, Bielak, and their CMU interdisciplinary team that includes robotics (led by Christoph Mertz), biomedical engineering and electrical and computer engineering (led by Jelena Kovacevic), and civil and environmental engineering (Hae Young Noh). With their students, these researchers are testing their hardware’s and software’s ability to flag changes in structural conditions by placing weights at different points on the girders. At this point, they can detect change with 90% accuracy thanks to the algorithms developed by the Kovacevic team.

Garrett and the team anticipate a working procedure in a few years. Until then, there are other areas where his research can expand. “There are many different ways data is, in fact, being collected every day,” he says. “For the future, it’s important to capture data from all sources and try to use it productively to understand the state of all our infrastructure.”

So, after all these years, does a bridge still inspire that childhood wonder? “I still stop at the New River Gorge Bridge,” he says. “Now I do that to my kids. Every time we get a chance, we stop.”

Melissa Silmore (TPR’85) is a Pittsburgh-based freelance writer and a regular contributor to this magazine.

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CEE Researchers Use Sensor-Equipped Vehicles to Monitor Bridges