Companies aim for ODOT pact

If Roctest’s system is selected for the Inner Belt job, it would be the company’s first sale in Ohio.

CLEVELAND (AP) — Two companies with Ohio ties are marketing sensors they say detect strains on bridges early, perhaps preventing failures like the one that killed 13 people and injured another 145 when a Minneapolis bridge collapsed.

A sensor being tested by Cleveland Electric Laboratories Co. of Twinsburg is 11‚Ñ2 inches long. Roctest Ltd., based in St-Lambert, Quebec, with a development office in Mentor, made a pitch this month to the Ohio Department of Transportation to use its system when Cleveland’s Interstate 90 Inner Belt Bridge is repaired, tentatively scheduled to begin in two years.

The transportation department has not decided what type of sensors it will use. It has used electronic sensors on previous projects and probably will use some type of sensor on the Inner Belt job, said Michael Malloy, ODOT’s bridge inspector for Cuyahoga County. The almost mile-long bridge feeds traffic from the west and south over the Cuyahoga River into downtown.

ODOT may use the sensors during the renovation, but Malloy said it will return to the more common inspection and density tests once the project is done.

“Normally we spot a problem before it’s a problem,” Malloy said. “It’s very rare that something catches you off-guard.”

Bridges being renovated face additional or abnormal strain, such as heavy equipment or altered traffic patterns, increasing the need for sensor monitoring, Malloy said. The I-35W bridge in Minneapolis was under renovation when it collapsed Aug. 1.

Both electronic and fiber-optic sensors measure stress. Electronic sensors use wire and electric current while fiber-optic sensors use mirrors and a laser beam.

Many fiber-optic sensors, some less than an inch long, are fastened to a bridge. Each contains tiny mirrors that reflect light, said Joel Lantz, a research engineer at Cleveland Electric Laboratories. A laser beam is shot from sensor to sensor through a fiber-optic cable connecting them.

Roctest could use multiple types of sensors on one project, depending on specific needs. If ODOT decides to use Roctest’s system on the Inner Belt job, it would be the company’s first sale in Ohio, said Jim Sabin, who heads Roctest’s U.S. business development initiatives.

“It is the best technological solution to date,” Sabin said. “It’s the best solution for now. We don’t want to oversell it, but we don’t want to undersell it, either.”

Although fiber-optic sensors can provide a better understanding of strain on the bridge, collapses aren’t entirely avoidable, said Dryver Huston, an engineering professor at the University of Vermont.

“You can prevent but not eliminate” such events, Huston said. “Most of these collapses are unexpected events, so you have to be able to inspect for the unexpected, which is a bit of a paradox.”

Fiber-optic sensors are gaining traction in Europe and Asia, where the technology is built into many bridges and other large structures.

Officials here have been slower to adopt the sensors. While demonstrations have taken place throughout the country, the first real uses are just beginning.