Toward Safer Spans
Few human constructs can match the inspirational power of bridges. From Trajan's second-century span over the Danube to the recent Akashi-Kaikyo Bridge in Japan, the world's great bridges have for millennia symbolized technology's triumph over the barriers -- both physical and mental -- that divide places and people from one another.
Perhaps it is this ancient sense of awe that leads many of us to view bridges as permanent features of the landscape, structures as timeless as the land or water they traverse. Big mistake, says MU's Glenn Washer, an assistant professor of civil and environmental engineering and a man who knows a thing or two about how bridges stand and, more to the point, why they fall.
"The really major collapses don't occur that frequently, but they happen," Washer says. "A major bridge failure just took place in St. Louis, for example." Thankfully that incident, in which a portion of a 69-foot overpass collapsed onto Interstate 55, only hurt one motorist.
"We got lucky," Washer says, adding that the St. Louis accident, along with recent bridge collapses in Pennsylvania and Canada, should serve as a wake-up call for those who choose to ignore our nation's aging bridge infrastructure. "There are almost 600,000 bridges in the National Bridge Inventory, a list that captures almost all of the major state-owned structures across the nation," he says. "A pretty large percentage of those have deteriorated to some extent."
Washer, 40, is one of the nation's most respected specialists in "nondestructive evaluation," a discipline devoted to analyzing and measuring various materials without, as the phrase suggests, destroying them. Thanks in part to funding from the National Academy of Sciences, he is currently leading efforts to develop electronic sensors that will continuously monitor deteriorating bridges, alerting engineers to the cracks and tilts that could signal disaster.
"These devices can be there every day," Washer says. "An inspector is there, on average, only once every two years." He ought to know. Before coming to MU in 2004, Washer spent 14 years thinking about bridge safety as a research engineer with the agency to whom inspectors answer, the U.S. Department of Transportation's Federal Highway System. He came to the highway system job soon after graduating from Worcester Polytechnic Institute, a highly-regarded Massachusetts engineering school.
While working at the system's McLean,Va.-based Turner-Fairbank Highway Research Center, Washer helped to set up, and eventually run, a non-destructive evaluation program. He also took advantage of a generous continuing education policy to earn a master's degree from the University of Maryland. A few years later he added a materials science doctorate from Johns Hopkins University, an institution that offers one of the nation's only engineering programs with an emphasis in nondestructive evaluation.
In addition, Washer found time to marry and begin raising a family of five kids. "I typed my dissertation with two fingers, our twin babies in my arms," he recalls with a smile. Washer's own parents -- his dad a lineman for a Massachusetts telephone company, his mom a homemaker -- raised a big family too: Glenn was the youngest of six Washer children. He and his siblings were the first generation of their family to attend college, a circumstance that later served as a powerful motivator for Washer to leave his federal job for an academic one.
"I was a kid who grew up in the country, not knowing what an engineer was," Washer says. "A few really good professors changed that for me, got me inspired. Teachers can be inspirational for people if they're effective at what they do. They can change the way a young person looks at the world. If you've got a hundred students in the classroom, you're not going to have that influence on all 100 of them. But there are usually a few for whom you can make a big difference."
Washer also believes his sensor research may change lives, at least the lives of those of us who hope to cross bridges safely. "What we're using is kind of an electronic version of a bubble level, one that has the ability to detect very fine degrees of tilt away from their point of reference," he says. If such sensors could be arrayed on a bridge's support piers for long periods of time, the sensors would allow technicians to detect potentially disastrous movements a human inspector might not notice.
"In a big flood, for example, piers can tilt really quickly," Washer says. "We have sensors that can detect that. But there are myriad other things that can happen -- the effects of corrosion, weather and loads -- that can cause those piers to tilt gradually over decades of use. Right now there is nothing that can detect that, so that's the part of the problem we're working on solving."
Published by the Office of Research.
©2007 Curators of the University of Missouri. Click here to contact the editor.