New 'smart' bridges improve safety
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Engineering professor Samir Shoukry examines a data collection box below the new Star Bridge.
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STAR CITY, West Virginia (AP) -- Samir Shoukry talks about the 1,000-foot span over the Monongahela River as if it were alive. And in a sense, it is.
Though still unfinished, the Star City bridge is already loaded with 770 finely tuned sensors, 28 data-collection boxes and a central unit called the brain.
Together, they make up what Shoukry considers the smartest bridge in the world.
"Intelligent structures are like the human body. It's provided with millions of sensors that send signals to the brain when you're in pain," says Shoukry, an engineering professor at West Virginia University.
"Smart" bridges and roads that communicate with their makers through built-in sensors are becoming more common as engineers try to determine whether long-held construction assumptions are correct.
Several states have smart structures, and at least one span -- Florida's Sunshine Skyway Bridge -- may have more sensors than Star City. "But if we're talking about density," Shoukry says, "this would be the most. This is one of the most extensively instrumented bridges in the world."
The sensors measure minuscule, visibly undetectable changes in steel girders and support structures, in piers and abutments, in concrete and rebar. If a crack is about to occur, the sensors should detect it. If settling shifts the inclination by as little as one-millionth of a degree, that will be recorded.
"Basically, I want the structure to tell me where it hurts so I can make a quick response to the cry and come and repair it," he says. "It's like looking into the flesh and bones."
The state Division of Highways is spending nearly $18 million on the bridge and decided to invest an additional $471,000 in Shoukry's project to learn more about what causes stress and deterioration of expensive infrastructure.
The information may help the state make smaller, less costly repairs, Deputy Commissioner Norman Roush says. "I don't know of anybody worldwide who has done this much gauging and metering on a bridge," he says.
Star City is West Virginia's fourth and largest smart structure. Shoukry and his team of graduate students also installed sensors on a bridge deck in Harrison County, in concrete pavement in Monongalia County, and in a 450-foot section of highway near Elkins.
Roads and bridges face different problems. Roads have solid support and mainly move up and down as the load on the surface changes. Roads also can shift near the edge of the pavement, and inadequate drainage can affect their performance.
Bridges, meanwhile, are not rigid. "They bend, act and react under loads," Roush says. "Their actions are working with and against each other."
Already, West Virginia's projects have yielded results. On the Elkins project, the state learned that concrete slabs 20 feet long are prone to crack, while those 15 feet are not. The state of Pennsylvania, which had problems with cracks on Interstate 81, is changing its slab length based on those results, Roush says.
Shoukry's team has set up a weather station and two small sheds as a field laboratory at the Star City bridge, just a mile or so from the engineering school. They collect environmental data 24 hours a day and readings from the bridge sensors every 20 minutes.
It is a unique lab: Civil engineering students will be able to study real-world functioning on structures. Mechanical and aerospace students will learn how to install instruments and analyze data. Computer science students will be able to develop and test better types of sensors and design databases for sharing the findings.
Smart structures such as the bridge are the way of the future, Shoukry says. The technology is there, and it only makes sense to use it.
"The cost is like medical insurance," he says. "You pay whether you use it or not, but it pays off when you get sick."
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