Government Technology

Wireless Sensors May Help Governments Monitor Health of Aging Infrastructure



March 13, 2008 By

When the Minneapolis Interstate 35W bridge collapsed on Aug. 1, 2007, sending 88 vehicles and hundreds of people into the Mississippi River - 13 were killed and 100 injured - nobody, including state bridge inspectors, foresaw such a catastrophic event.

The collapse was a sad reminder of the aging U.S. infrastructure, which needs a $1.6 trillion overhaul over the next five years, according to the American Society of Civil Engineers. Its report graded the U.S. infrastructure as a D in 2005, down from a D+ in 2001. Bridges earned a cumulative C.

U.S. bridges are a pressing concern because stress loads have increased substantially due to a spike in traffic congestion. Since the Minneapolis I-35W bridge was built in 1967, the number of vehicles using the bridge had tripled, according to state documents. Also, truck weight limits have increased nationally, according to the U.S. Department of Transportation (DOT).

The I-35W bridge had been diligently inspected since 1993, and it always passed. Although state officials knew the bridge needed repairs, they had no idea the bridge was in danger of collapse. In January, the National Transportation Safety Board (NTSB) announced the bridge failed due to a design flaw in the gusset plates that connected steel beams; the gusset plates were only half the thickness they should have been. The NTSB investigation found no evidence that cracking or corrosion played a role in the collapse. However, the tragedy had already drawn much-needed attention to the problem of corrosion in aging bridges.

The Minnesota Department of Transportation (Mn/DOT) knew of some risks beforehand: Prior to the accident, Mn/DOT was so concerned about the bridge's structural deficiencies that officials considered replacing it. Other proposed fixes included bolting steel plates to the bridge to prevent stressed areas from cracking. Mn/DOT officials, though, ultimately decided that only more frequent visual inspections were required.

Today, U.S. bridges are almost entirely visually inspected, and if corrosion or cracks are spotted, tests using eddy currents, ultrasound or penetrating dyes are often used. However, detecting weak spots visually is an imperfect and faulty science.

 
Bridging the Monitoring Gap
A new engineering technology, structural health monitoring (SHM), is being developed to address critical infrastructure needs. SHM uses sensors embedded in structures to alert crews of defects in critical structures before catastrophic failures occur. The process uses wireless technology to monitor a structure's physical properties such as loads, stresses, strains and cracks, as well as changes in chemical and electrical properties related to deterioration - corrosion, fatigue, chlorides and humidity. Experts see wireless sensors as a cheaper, more reliable way to monitor bridges and other critical infrastructure.

New York is one of many states re-evaluating bridge inspection methods after the Minneapolis bridge collapse by turning to SHM technologies. The state department of transportation's pilot program uses wireless sensors placed on bridges to transmit data on stress and vibration, and should warn if a bridge is weak or needs repairs. The system, designed by Clarkson University associate professor Kerop Janoyan, is expected to help engineers monitor the state's 17,000 bridges.

"Providing more information is the first step to a feedback system," Janoyan said. "Without information, you can't have any feedback when ultimately you're trying to control potential damage."

A New York bridge between Canton and Potsdam is serving as a test site - 40 wireless channel sensors affixed to the bridge log in real-time data to a base station. Each sensor is about the size of a few decks of playing cards, and cost about $200. The battery-powered sensors are connected to a computer that aggregates sensor data and determines whether to alert inspectors.

Information collected by the sensors is stored in a central unit attached to the bridge that transmits the data either to a laptop nearby or an office


| More

Comments

Add Your Comment

You are solely responsible for the content of your comments. We reserve the right to remove comments that are considered profane, vulgar, obscene, factually inaccurate, off-topic, or considered a personal attack.

In Our Library

White Papers | Exclusives Reports | Webinar Archives | Best Practices and Case Studies
Cybersecurity in an "All-IP World" Are You Prepared?
In a recent survey conducted by Public CIO, over 125 respondents shared how they protect their environments from cyber threats and the challenges they see in an all-IP world. Read how your cybersecurity strategies and attitudes compare with your peers.
Maintain Your IT Budget with Consistent Compliance Practices
Between the demands of meeting federal IT compliance mandates, increasing cybersecurity threats, and ever-shrinking budgets, it’s not uncommon for routine maintenance tasks to slip among state and local government IT departments. If it’s been months, or even only days, since you have maintained your systems, your agency may not be prepared for a compliance audit—and that could have severe financial consequences. Regardless of your mission, consistent systems keep your data secure, your age
Best Practice Guide for Cloud and As-A-Service Procurements
While technology service options for government continue to evolve, procurement processes and policies have remained firmly rooted in practices that are no longer effective. This guide, built upon the collaborative work of state and local government and industry executives, outlines and explains the changes needed for more flexible and agile procurement processes.
View All

Featured Papers