New “smart bridge” technologies being developed by engineering teams at the University of Maryland may help prevent catastrophic failures like the one that befell the I-35 Bridge in Minneapolis five years ago, researchers say.
A new wireless sensor technology, being commercialized by a spinoff startup called Rensensys, drives a system of tiny, long-lasting, energy-efficient, low-maintenance wireless sensors and software that collect and analyze real-time data, the team reports.
University of Maryland
|Rensensys says its new probe is far less expensive than the current wired monitoring technology.|
Meanwhile, a second team is pursuing a total “smart bridge” package with multiple technology innovations.
The goal is better monitoring for the one in four U.S. highway bridges that the federal government now classifies as structurally deficient or obsolete, the researchers say.
They hope that earlier indicators of weaknesses could head off disasters like the one in Minneapolis, where 13 people were killed and 145 injured.
Rolling the Dice
"We no longer need to roll the dice when it comes to the structural integrity of the nation's highway bridges," said UM research engineer Mehdi Kalantari, who initiated the wireless sensor research with the support of the university’s Mtech incubator and went on to found Rensensys. "Technical advances in wireless sensors make real-time monitoring both affordable and practical."
Kalantari is in the second year of testing his system on a Maryland interstate bridge along the Capital Beltway in suburban Washington, D.C. Over the past 12 months, he has upgraded his system, making it fully operational, and expanded its use to the private sector.
A few U.S. and international firms are using it on transportation projects, as well as for monitoring the safety of building facades and the safety of large construction cranes, the university reports. Kalantari has also adapted the sensors for the purpose of monitoring cracks on bridge piers120 feet underwater.
Tiny Sensors, Delicate Measurements
Kalantari says that a few dozen strategically placed tiny sensors could measure strain, vibration, deformation, pressure, tilt, inclination, displacement, crack activity, humidity, temperature and other prime factors on small and medium-sized bridges—and do so much less expensively than current options.
His system is equipped with a wide range of remote sensing functions and data analysis software capable of detecting structural anomalies. The system also delivers warnings to bridge maintenance engineers—by email or text messaging, in the case of severe warnings.
Kalantari says his system costs 10 to 50 times less than wired networks of sensors now installed on some bridges, including the replacement span in Minneapolis.
The second engineering team is developing a multifaceted system called Integrated Structural Health Monitoring system, key elements of which are now being tested by Maryland State Highway officials, the Maryland Transportation Authority and the North Carolina Department of Transportation.
|Researchers hope better monitoring can prevent another failure like the I-35 bridge collapse of August 2007.|
Supported by federal and state funding, that project also involves researchers from North Carolina State University and San Francisco-based URS Corp., a global engineering, construction and technical services concern.
"Wireless technology definitely makes bridge structural health monitoring more efficient and more effective," says UMD civil and environmental engineering research professor Chung Fu, director of Maryland's Bridge Engineering Software & Technology Center and a leader of the project team.
Fu says that bridge safety technology is far more advanced, and far less expensive, than it was a decade ago.
"If the prices for system hardware and software are further reduced and standardized, we may see more widespread application in the next five to 10 years," he adds.
Inspection and Innovation
The new technologies are meant to supplement, not replace, human bridge inspection, the researchers emphasize. The massive, high-stakes task needs all available resources, they say.
"Limited, in-person inspections are not sufficient to provide highway maintenance authorities with an adequate margin of safety when compared with real-time monitoring," Kalantari says.
And yet, technology has its limits, too, acknowledges Fu: "You can't put sensors everywhere," he says.
In its report on the Minneapolis bridge collapse, the National Transportation Safety Board identified a faulty metal plate essential to the bridge's structural integrity as a likely cause of the disaster. The report notes an "inadequate use of technologies for accurately assessing the condition of gusset plates on deck truss bridges."
Both Maryland engineering teams say the new wireless monitoring technology is poised to fill that need.