New, affordable instant warnings of bridge collapse
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. Also, he has adapted the sensors for the purpose of monitoring cracks on bridge piers 120 feet underwater.
A few dozen tiny sensors, strategically placed on small to medium-sized bridges could measure prime factors such as strain, vibration, deformation, pressure, tilt, inclination, displacement, crack activity, humidity and temperature, Kalantari says — and for a much smaller price than current technology.
His team has equipped the system with a wide range of remote sensing functions and data analysis software capable of detecting structural anomalies. Also, the system delivers warnings to bridge maintenance engineers — by e-mail or text messaging, in the case of severe warnings.
New “smart” bridges, including the replacement span in Minneapolis, use wired networks of sensors to detect problems early, when repairs are often cheaper, providing a wide margin of safety. These wired systems, however, are generally too expensive to retrofit all the old bridges that need them, Kalantari says. Overall, he estimates that existing wired technologies cost at least ten to fifty times more than his wireless system.
The latest statistics from the Federal Bureau of Transportation (2010) list nearly 70,000 U.S. bridges as “structurally deficient,” requiring extra surveillance. In addition, more than 77,000 others are categorized as “obsolete” — exceeding their intended lifespan and carrying loads greater than they were designed to handle. Under federal requirements, structurally deficient bridges must be visually inspected once each year. Others must be inspected once every two to five years.
“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 concludes.
Ultimately, adds Fu, real-time remote sensing will serve as a valuable supplement, but not fully replace human inspections. “You can’t put sensors everywhere,” he says.
The release notes that highway officials have been paying attention to the advances in remote sensing applications. A UMD project using the Kalantari team’s system to monitor a highway bridge and sponsored by the Maryland State Highway Administration (SHA) was selected as one of the “sweet 16” most interesting developments. The results were presented this summer at the annual meeting of the American Association of State Highway and Transportation Officials (AASHTO) research advisory committee.
Kalantari hopes the system will receive the necessary approval and certifications over the next few years from AASHTO members and the U.S. Department of Transportation.
In its report on the fatal Minneapolis bridge collapse, the National Transportation Safety Board identified a faulty metal plate as a likely cause of the disaster. It notes an “inadequate use of technologies for accurately assessing the condition of gusset plates on deck truss bridges.”
Both UMD engineering teams say the new wireless monitoring technology is poised to fill that need.
The UMD Integrated Structural Health Monitoring system research is sponsored by the U.S. Department of Transportation’s Research and Innovative Technology Administration (RITA), under the Commercial Remote Sensing and Spatial Information (CRS&SI) Technologies Program, and by the Maryland Transportation Authority, Maryland State Highway Administration and the North Carolina Department of Transportation.
