Could Tiny Sensors Detect Bridge Crises?

This undated photo provided by Los Alamos National Laboratory, shows an experimental electronic sensor that could possibly be used to detect electrical charges emitted by stress on material, such as steel-reinforced concrete. LANL scientists are working on the technology that could provide early warnings of potential failures in highway bridges, according to officials. (AP Photos/Courtesy of Los Alamos National Laboratory) (AP)

ALBUQUERQUE, N.M. -- Researchers here are hoping small sensors put on bridges _ about the size of a credit card and costing only $1 apiece _ could provide an early warning to potential failures like the one in Minneapolis.

Los Alamos National Laboratory scientists, in collaboration with the University of California at San Diego, say such a system would provide enough lead time to either shut down a bridge or perform preventive maintenance to avert serious failures.

"The idea is to put arrays of sensors on structures, such as bridges, and look for the changes of patterns of signals coming out of those sensors that would give an indication of damage forming and if it is propagating," said Chuck Farrar, a civil engineer at the lab.

The electronic sensors would be powered by microwaves or the sun and would send data via radiotelemetry to a computer for analysis. The sensors detect electrical charges emitted by stress on material, such as steel-reinforced concrete.

Researchers are in the second year of the four-year project _ funded at $400,000 a year _ and it probably will be years before the sensors are commercially available, Farrar said.

Researchers are trying to incorporate the sensors with microprocessors and wireless telemetry systems so they can work as stand-alone monitoring devices, Farrar said.

Research on wireless sensors for structures also is being conducted at the University of Michigan and Stanford University, and research on bridge monitoring is being conducted at Drexel University, he said.

One hitch is how to power the sensors. Researchers are looking at small, remote-control helicopters to do the job. They would send a pulse to provide power to the sensor, help take a reading and broadcast it back to the chopper.

The helicopter also could carry a light source that would be focused through a lens to a small solar array on the sensor node.

Researchers will be testing the helicopter power delivery and wireless sensor next month on a bridge about 10 miles north of Truth or Consequences.

Much work still remains to be done. Civil engineers must work with electrical engineers and computer scientists to bring the technology together.

"The hard part is getting data from damaged structures to use in the study. Nobody wants to give you a very expensive bridge to just test a data integration algorithm," Farrar said.