From the Economist:
Adding sensors and other devices to bridges, tunnels and buildings can turn them into “smart structures” capable of sensing and, in some cases, even responding to problems.
ON AUGUST 1st 2007, as commuters were driving home from work on the I-35W Mississippi River Bridge near Minneapolis, it abruptly collapsed. Thirteen people died and over a hundred were injured. The bridge had opened in 1967 and had not been scheduled for replacement until 2020. What had gone wrong? In 2008 the National Transport Safety Board concluded that extra concrete, which had been added to the bridge over the years as the level of traffic increased, had helped cause the collapse. After an inspection in 2005 engineers had classified the bridge as “structurally deficient”, and repairs were planned. But many other bridges in the area were thought to be in an even worse condition, so the work was not prioritised, and the true state of the bridge became apparent only when it failed, with tragic results.
Such catastrophes are rare, but the Mississippi River Bridge highlights a wider problem: old infrastructure is often exposed to much greater loads than it was originally designed for. British trains routinely run on arched bridges dating back to the Victorian era, for example. Old structures can be rebuilt or reinforced, of course, but the standard approach to assessing their condition is regular inspections, and these may not be frequent or detailed enough to spot problems.
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Researchers at the University of South Carolina are using $4 million in federal grant money to develop a specialized sensor that can detect bridge damage, the school announced Thursday. Paul Ziehl, an associate professor at the university’s Department of Civil and Environmental Engineering, will be the lead researcher on USC’s portion of the project, which is part of an overall effort to improve the nation’s infrastructure.
“Many of our bridges were built 50 years ago, and many of these structures have a life expectancy of 50 years,” Ziehl said. “This project focuses on steel and concrete bridges. What we learn will help us more quickly determine the health of a bridge and the length of time that it can be used.”
The National Institute of Standards and Technology has funded a $14 million infrastructure project that combines work being done at the University of Miami, Virginia Tech and USC.
The Federal Highway Administration estimates that more than 70,000 bridges in the U.S. are structurally deficient, meaning they need to be monitored or repaired.
Slightly more than 12 percent of South Carolina’s 8,343 bridges are structurally deficient, according the S.C. Department of Transportation.
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From IEEE Spectrum online:
Sensors are starting to prove themselves in the biggest, most complex bridges, but the technology isn’t ready for the hundreds of thousands of smaller ones
The 2.9-kilometer Rion-Antirion Bridge in Greece, with its 300 sensors, is a testament to how smart a piece of infrastructure can be. It routinely tells operators when an earthquake, frequent in those parts, or high winds warrant shutting down traffic.
“The bridge tolls are meant to collect thousands of euros per day,” says Alexandre Chaperon, an engineer at the company that designed the system, Advitam, in Vienna, Va. “Without the monitoring system, the bridge would be closed after every earthquake, more than three days in some cases, instead of 5 minutes.”
Dozens of the largest and most complex bridges in the world are already studded with strain and displacement gauges, three-dimensional accelerometers, tiltmeters, temperature sensors, and other instruments. They are wired to central data-acquisition units—though some newer bridges have wireless systems—which collect and analyze the information and relay it to engineers, in hopes of catching signs of distress before human inspectors could. With the United States injecting US $27.5 billion into revamping the country’s roadways and bridges as part of an $800 billion economic stimulus effort, it might seem like a perfect opportunity to add smarts to more bridges.
Rad the complete article here.