An EKG for cracking bridges

By Linda Rodriguez McRobbie, contributing writer

( -- For most people, driving over a bridge is a matter of course. For Marybeth Miceli, the experience can be frightening.

"It's very antiquated, how they inspect bridges," Miceli says. She would know: Miceli is the chief of operations for Matech, a seven-person company in Los Angeles that specializes in metal fatigue research.

Most bridge inspections in the U.S. are conducted visually, even though a 2001 study by the Federal Highway Administration -- the first and last such study -- showed that 56% of bridge condition and safety ratings gleaned from such inspections were inaccurate.

Nearly a decade later, the inspection process hasn't changed much. But several calamities -- including the I-35W Mississippi River Bridge collapse that killed 13 people in 2007 and the San Francisco Bay Bridge's partial failure in October -- have sparked a national debate over how to maintain bridges as America's infrastructure ages.

Matech wants to be part of the solution. Over the past eight years, the company has been developing a device called an Electrochemical Fatigue Sensor, or EFS, that reveals hard-to-detect flaws in metal. It works in much the same way that an electrocardiogram, or EKG, tests the human heart.

To use the EFS, inspectors first identify the vulnerable parts of a bridge. These could be the areas most susceptible to wear and tear -- say, a sharp corner or a welded connection -- or places where bridge owners already suspect a crack.

Then they wire up the areas with sensors, which are similar to the peel-and-stick versions used for an EKG reading. Finally, they apply a constant electrical current that runs between the sensors and the bridge.

By assessing the behavior of the current as it passes through the metal, the sensors can detect cracks down to a hundredth of an inch in size. And because the device is operated while the bridge is in use, it can determine how the cracks change as the structure flexes under stress. Matech's software analyzes the resulting data to determine whether cracks are staying the same size or growing.

"Other technology only tells you whether you have a crack. This one tells you whether it's growing and approximately how fast," explains Miceli. "It allows the bridge owner to make better decisions about prioritizing repairs."

The technology behind EFS was devised by researchers at the University of Pennsylvania for use in the aerospace industry. In 1993, they forged a development deal with Matech, which revamped the technology for bridge inspections between 2002 and 2006.

The sensor has already been used to detect cracks in bridges from Pennsylvania to Australia. The Federal Highway Administration is currently testing EFS, along with four other fatigue detection technologies, for potential use in U.S. bridge inspections.

Robert Ross, a professional engineer at Fatigue Diagnostics, a bridge inspection outfit owned by CAC Industries in New York, has been using Matech's technology for the last two years. He says the device is a useful "cost-saving tool" because it "can identify if a crack is not actively growing, so maintenance dollars are not allocated where they are not needed at the moment."

Matech makes money by both conducting bridge inspections and selling its full EFS kit to third-party inspectors for $75,000; replacement peel and stick sensors run $30 apiece. Though the technology is used primarily on bridges, clients also use it to assess damage in cranes, planes, railroads, ships and nuclear power plants. Last year, Matech earned roughly $250,000 in gross revenue from EFS and raised $2.3 million in capital by issuing corporate bonds.

Matech wants to see sales rise. But U.S. infrastructure development can move at a sluggish pace, making it tough for innovators to break into the market, according to Dr. Emil Aktan, a professor of civil engineering at Drexel University.

Aktan agrees that the current method for inspecting bridges feels like something out of the Stone Age. However, he warns: "The solution is not necessarily coming up with a space-age device."

Other researchers have tried to revolutionize the inspection process with technologies such as ultrasound and fiber optics, he says. Though their tools worked in the lab, many failed in the field owing to unexpected conditions such as temperature changes, metal expansion and electromagnetic interference from the metal in the bridge itself.

When it comes to the slow pace of change, Aktan may be right.

Despite the 2001 study, the Federal Highway Administration still stands by its visual methods for inspecting bridges. Spokeswoman Nancy Singer would not comment directly on EFS technology, which the agency is currently testing, but says visual inspection is "an effective and reliable way to detect bridge cracks."

Promising new technologies "may be on the horizon," but "research and testing are still necessary to determine their true usefulness as a supplemental tool in bridge inspection," she says.

In other words, for the foreseeable future, the best tool protecting commuters from aging bridges will remain inspectors' eyeballs. To top of page

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