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Skyway Bridge Ice Sensors Can Alert State Officials and Keep Motorists Safe

The devices are specifically attuned to identify conditions conducive to ice forming, and “shedding” from the bridge's stainless-steel coverings.

(TNS) -- Better detection of ice formations on the Veterans’ Glass City Skyway’s pylons can alert state officials to conditions that make the ice a hazard to traffic on the bridge, according to a state-commissioned study.

Twice during each of its first two winters of service, then again in February, 2011, closings have been ordered on the cable-stayed I-280 bridge over the Maumee River because of ice chunks falling from its stays, central pylon, or both after winter storms. Several vehicles were damaged in at least two of those incidents when falling ice struck them.

The ice problems prompted the Ohio Department of Transportation to commission a study, led by researchers from the University of Toledo and the University of Cincinnati, to investigate possible ways to manage, if not eliminate, the ice.

The result of their study is installation of new sensors on several of the stays’ stainless-steel coverings and a new weather station on the bridge with devices specifically attuned to identifying conditions conducive to ice forming on, and “shedding” from, those coverings.

The effort included UT researchers’ invention of a sensor capable of detecting the development of a sheen of water between ice and stay sheaths that is a strong indicator that ice chunks may break free. Their sensors use electric current to identify the different electrical resistance properties of ice, water, and ice-water mixes.

“Drivers should feel secure in the fact that these improvements are providing ODOT with the tools to make informed decisions and improve safety,” said Todd Audet, the department’s deputy director for its Bowling Green district. “The sensors provide invaluable insight on ice formation, and in the rare event that ice falls, we can efficiently manage any closures.”

According to the study’s 316-page report, researchers first hoped that an anti-icing or de-icing method might work. But heating, while effective, was deemed too slow and expensive, while coatings and de-icing chemicals were less satisfactory. The scientists found most coatings they tried were less effective at keeping simulated freezing rain from sticking and accumulating than uncoated surfaces.

Those results led to a second study phase. The team looked at better ways to monitor ice formation on the bridge and identify the roles of air temperature, wind, and solar radiation in determining when ice is about to break away.

The effects of a freezing-rain storm on the night of Feb. 20, 2011 proved to be a case study for their research and development of a computer “dashboard” to assemble weather data and set up an alert system for bridge managers.

Researchers documented readouts and field conditions starting the night of the storm and continuing through Feb. 24, when large chunks of ice broke from the stays and either fell onto the bridge deck or sailed over the side into the Maumee River.

The new weather station measures have ice-thickness and moisture detectors, a “rain bucket” for measuring precipitation, and a solar sensor to predict heating. Data from its array from more conventional weather stations at the bridge, at three other ODOT sites, and at Toledo’s two main airports are fed into a computer that calculates an ice-alert status that is reported to transportation department managers.

The research cost taxpayers $652,894.58, which ODOT officials said was federal funding.

One half of that, Mr. Audet said, was the cost of writing computer software and testing models, while one third was for equipment used in the simulations and tests. The research should be beneficial for other bridges in similar climates, he said.

The Lawrence Technological University, the Army Cold Regions Research and Engineering Lab, NASA Glenn Research Center, and HNTB, a private engineering consultant, also participated in the study.

©2014 The Blade (Toledo, Ohio)