Tuesday, January 12, 2010

Bridges That Talk

America has more than a half million bridges that are masterpieces engineering, as much a part of the American scene as are red barns and white churches of the countryside, and skyscrapers that tower over large cities. Their history, as Henry Petroski points out in “Pushing the Limits, New Adventures in Engineering" points out that some of the greatest engineering achievements have been dwarfed by later ones. For example, a pedestrian who in five minutes can walk between the towers of the Brooklyn Bridge, once the longest span in the world, would need 20 minutes to walk from tower to tower of Japan's Akashi Kaikyo Bridge, today's longest.

In addition to getting longer, America’s bridges are getting old and rickety. Engineers recognized the problem decades ago, but the technology of the day was too inadequate to allow any meaningful action. A little more than a decade ago,  engineers were exploring the idea of using acoustic-emission sensors to make wooden bridges smart, able to examine themselves. But the technology to achieve their goals was still far out of reach.

Fortunately, engineers have broken through the barrier, developing devices that can tell inspectors a bridge's aches and pains are and how severe they’ve become. University of Michigan Engineering professor Jerry Lynch, known as “the bridge whisperer,” is developing sensor technology that continuously diagnoses, monitors and reports on the health of a bridge. 

Lynch Making Bridges Smarter

University of Michigan's smart-bridge program went into high gear a year and a half after the I-35 bridge collapse in Minneapolis, undertaking a $19-million, five-year project that aims to create the ultimate infrastructure monitoring system and install it on several test bridges throughout the country. The investigative team is developing four types of data-gathering sensors that will feed a system which organizes the information into meaningful displays and communicates with inspectors.

"The technologies from this project could prove very beneficial to the citizens of Michigan in the longer lasting, smarter, safer and ultimately more sustainable roadways," said Michigan Transportation Director Kirk Steudle. "Recognizing that our nation's infrastructure is the backbone of our economy, this type of innovative research is critical to the future of Michigan and the United States. The Michigan Department of Transportation is pleased to partner with the University of Michigan on this important engineering project."

Lynch said that if smart-sensor systems were installed on all bridges, researchers could make statistical comparisons among bridges, enabling engineers to determine, for example, if all suspension bridges developed certain dangerous signs of wear after a certain age. Implementing such a system, however, would be monumentally costly. Lynch said that the next generation of sensors to monitor bridge health will be wireless, eliminating miles of wires between bridges and computers and, in the process, lowering the cost of installation.

Already a few bridges in South Korea, China and Taiwan have tested wireless sensors, with great success.

[Slide Show] "Smart" Bridges Harness Technology to Stay Safe