9:12 a.m., Oct. 13, 2009----Three researchers at the University of Delaware have received a $1.1 million grant from the Delaware Department of Transportation (DelDOT) to design and install a structural monitoring system on the new Indian River Inlet Bridge (IRIB) in Sussex County, Del.

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The interdisciplinary team includes Michael Chajes and Harry (Tripp) Shenton, professors in the Department of Civil and Environmental Engineering, and Robert Hunsperger, professor in the Department of Electrical and Computer Engineering. The work is being carried out through UD's Center for Innovative Bridge Engineering (CIBrE).

“The concept of a structural health monitoring system for a bridge is similar to the computer-controlled sensing and diagnostic systems installed in modern cars,” Shenton says. “Just as various lights on your dashboard show you when the car is low on oil or the trunk is open, the sensing system on the bridge will provide feedback about how the structure is performing.”

According to Jim Zammataro, applications specialist with Cleveland Electric Labs, industrial partner on the project, fiber-optic structural health monitoring systems have been used widely across Europe and Asia for years but have been slow to catch on in the U.S.

“Until now,” he says, “much of the health monitoring of bridges in the U.S. has been short term and usually covers only parts of the structure. Short-term monitoring is a great way to get a snapshot of what is happening, but a long-term monitoring system with fiber-optic sensors provides a continuous real-time picture of how the structure is performing.

“We believe Indian River is the first significant bridge built in the U.S. to have an all-fiber-optic monitoring system designed into it from the beginning,” he adds. “It is significant that DelDOT and FHWA chose to go with this optical system because it signals a shift in the way structural health monitoring is viewed here in the U.S.”

According to DelDOT project manager Doug Robb, the bridge has a 100-year design life, and inspection and maintenance over that time will require a substantial investment in time and resources. “The monitoring system will enhance our ability to efficiently and effectively manage this significant resource for years to come,” he says.

The UD-Cleveland Electric team will design and install a computer-controlled fiber-optic system consisting of some 120 sensors to measure a variety of conditions, from temperature and wind speed and direction to strain, deck inclination and expansion joint movement.

Data will be collected at prescribed intervals, for example, hourly, as well as during extreme events such as high winds or the passage of overweight vehicles requiring a special permit.

“The data gathered will allow DelDOT as well as the general bridge community to understand the short- and long-term performance of this long-span cable-stayed bridge,” says Chajes. “We anticipate that the lessons learned both in instrumenting the bridge and in analyzing the data will expand our fundamental knowledge about bridge behavior and maintenance.”

Sensors will be placed in the deck and pylons, on selected stay cables, at deck level and at the top of the pylons. Some will be embedded, while others will be surface mounted. According to Hunsperger, fiber-optic systems have a number of benefits, including immunity to noise, ease of installation, redundancy and long-term durability. “We hope to learn more about not only bridge behavior but also about structural health monitoring systems from this project,” he says.

“Everyone has heard about bridge failures of the past, including the Tacoma Narrows Bridge, the Silver River Bridge and the I-35W Bridge in Minneapolis,” says Dennis Mertz, director of CIBrE. “Health monitoring systems can provide a wealth of information that has the potential to prevent such catastrophic collapses in the future.”

An open house, public workshop, and site tour will be held at the IRIB site from 1-4 p.m., Saturday, Oct. 17. The workshop will include 12 information stations about the bridge, including the monitoring capabilities. Visit the DelDOT Web site for more information about the event, which is free and open to the public.

Article by Diane Kukich