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Technology could bridge safety gap

The Minneapolis span's collapse and a federal study may spur the use of exotic, but available, new inspection tools.

August 15, 2007|Stephanie Simon | Times Staff Writer

Civil engineer Tripp Shenton likens current bridge inspection practices to "a doctor working without a stethoscope, without X-rays or EKGs."

The collapse of an interstate highway bridge in Minneapolis -- and the frightening images of cars plunging into a river -- may force a high-tech update.

Most bridge inspections now are conducted just as they were decades ago, with binoculars to scour for cracks and a hammer to knock against trusses to test for hollow spots.

The 21st century version?

Imagine a web of sensors capable of measuring hairline cracks in steel -- and sending out an alarm when one of those cracks begins to widen. Another network might continuously check stress loads on the bridge, recording the data on a seismograph that would spike at the first sign of trouble.

For The Record
Los Angeles Times Saturday, August 18, 2007 Home Edition Main News Part Page News Desk 1 inches; 52 words Type of Material: Correction
Bridge tests: An article in Wednesday's Section A about bridge inspection technology misspelled the name of a German company that maps unstable land. The company is Geoka, not Goeka. The article also said Geoka's maps cost up to $10,000 but did not make clear that bridge maps typically cost less than $2,500.

"You could set it up so the bridge can call you if something abnormal occurs," said James A. Swanson, an engineering professor at the University of Cincinnati.

This technology is being used on bridges in a few states, including Pennsylvania, Ohio and Utah. Other diagnostic tools are also under development -- often with federal grants -- in engineering labs from coast to coast.

"There are people everywhere working on this," said Shenton, associate professor of engineering at the University of Delaware.

Mississippi State University professor Charles A. Waggoner rigged his inspection device from an unlikely assortment of household items: a jogging stroller, a lampshade, a microphone and a laptop computer.

The contraption drags metal chains across a bridge deck and analyzes the sound vibrations, mapping the pings and clunks into a grid that indicates which sections are corroding from within.

That's not even the most offbeat device.

At New Mexico's Los Alamos National Laboratory, engineer Chuck Farrar developed sensors that can tell when a bolt is coming loose or a weld is weakening. But how are the sensors powered? With a remote-controlled model helicopter, of course. The toy chopper hovers over the bridge, shoots microwave beams to activate the sensors and then records the data to an onboard computer.

If all this sounds a bit far out, it's supposed to. Promoters say it's long past time to leap into a new era of bridge inspection.

Their best sales pitch: A 2001 federal study that put traditional hammer-and-binoculars inspections to the test.

For that study, the Federal Highway Administration convened 49 inspectors from 25 states and asked them to examine bridges that had been thoroughly examined for defects. The inspectors identified only 4% of emerging cracks and 24% of suspect bolts.

The results also showed how subjective visual inspection could be. One team rated the superstructure of a test bridge at four on a zero-to-nine scale, indicating poor condition. Another team rated the same aspect of the bridge at eight, deeming it near-perfect. (The federal government gave it a five.) Wide variations also showed up in the ratings for other bridges.

The federal test drew scant attention when it was released. Now, however, it's being reviewed against the backdrop of daily updates from Minneapolis, where recovery workers are still struggling to pull victims and crushed vehicles from the wreckage.

Transportation Secretary Mary E. Peters has ordered the department's inspector general to conduct a "top-to-bottom review of the bridge inspection program"; the report should be completed within the year.

Nearly 75,000 bridges nationwide -- including about 2,800 in California -- are rated "structurally deficient," as was the Interstate 35W span in Minneapolis that tumbled into the Mississippi River. Another 80,000 are considered "functionally obsolete," meaning they are not up to handling the demands of modern traffic. Many states still use bridges built in the 1920s, '30s and '40s. (The failed bridge in Minnesota opened in 1967.)

Federal law requires that bridges be visually inspected every other year. But the amount of funding states dedicate to such exams varies wildly.

Minnesota spent $2.3 million last year on bridge inspections. California -- with 76 inspectors -- spent $15 million.

"Every state right now is reviewing their inspection program," said Malcolm T. Kerley, chief engineer for Virginia's Department of Transportation. Virginia spent $13.5 million on inspections last year. "If we think we need to put more money in there, we will."

The intense interest in bridge inspection has been boon and bane to vendors of new diagnostic devices.

Robert M. Bernstein, CEO of Material Technologies Inc., says that since the evening the Minneapolis bridge collapsed, he's been bombarded with so many inquiries, he hasn't even had time to read his e-mail.

"There's got to be 200 messages piled up," he said. He was on TV twice -- once on NBC and once on Fox. "My chief engineer has been on three times. It's been a real nightmare," he said.

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