MU Researcher Developing Sensors to Monitor Structural Safety of Bridges

COLUMBIA, MO - Nationwide, motorists rely on an infrastructure of bridges to help them reach their destinations. Issues related to the structural safety of bridges have become a concern of Glenn Washer, a University of Missouri-Columbia researcher, who is building a high-tech sensor system that will help transportation officials in New York identify potential dangers.

Washer, assistant professor of civil and environmental engineering in the College of Engineering, has received $109,500 from the National Academy of Sciences to develop a system that can continuously monitor piers - the primary support systems of a bridge - and warn of structural weaknesses. The device will consist of about 20 sensors and a computer processor to relay data to highway and transportation officials. The network of sensors, which Washer said would work on any bridge, will be placed on piers to detect cracks and tilts, which are caused most frequently by scour, a hole left behind when sediment is washed away from the bottom of a river. Upon completion of a prototype, the New York Department of Transportation will select a bridge to conduct a six-month test of the system.

"The system is intended to allow departments of transportation to continuously monitor the safety of bridges to detect long-term deterioration that may lead to structural collapse," said Washer, who expects testing to begin at the end of 2007.

If successful, it could prove beneficial on a larger scale, considering nearly 14 percent of the nation's bridges were classified as "structurally deficient," meaning they are deteriorating, as of 2004, according to the latest report issued by the Federal Highway Administration (FHWA). Another 13 percent were classified as "functionally obsolete," meaning they are structurally sound but no longer meet transportation standards and demands. In Missouri, 31 percent of the state's bridges are either structurally deficient or functionally obsolete, according to the November 2006 issue of Better Roads magazine, which is geared toward the governmental highway and bridge construction industry.

"This is a national problem, regardless of geographical location. There are nearly 600,000 bridges in the U.S.," Washer said. "When a pier tilts, there's a potential for a bridge to collapse without warning. This is definitely a safety issue for travelers."

Washer said current inspection requirements are insufficient and sporadic because they require bridges only to be inspected and rated every couple of years. He said numerous structural problems can occur during such an interval, underscoring the importance of a system similar to his that can provide more frequent data.

"This device will be there every day," he said. "That inspector is there only once every two years. "The instrument that we're developing will monitor tilt over long periods of time, between 10 and 20 years."

Washer began working on the system in 2005 following a partial collapse of the Dunn Memorial Bridge, which spans the Hudson River in New York. A portion of one of its access ramps slipped off its bearings and fell several inches. Investigators determined the near-collapse of the bridge was caused by tilting and cracking of the support pier.