Outsourced cell phone data could keep bridges safe and strong

Outsourced cell phone data could keep bridges safe and strong

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Your cell phone could reveal the health of bridges just by being in your pocket on your daily commute.

Accelerometers and GPS sensors that are standard components of smartphones collect information that can show how bridges flex and vibrate as vehicles cross, researchers report Nov. 3 in Communications Engineering.

Apps that collect metrics could keep travelers safe by alerting engineers that a bridge needs fixing. The tools could also warn or help prevent catastrophic failures like the tragic bridge collapse in the western Indian state of Gujarat on October 30, or the bridge span that collapsed in Pittsburgh in January (SN: 11/16/07).

“It really applies to any type of bridge,” says civil engineer Thomas Matarazzo of the US Military Academy at West Point in New York. All you need, he says, is a way to mount a smartphone on it — whether in a car, in a pedestrian’s pocket, or mounted on a scooter — and a way to monitor the device (SN: 10/11/17).

Bridge failures, says Matarazzo, often come down to uncertainties about structural properties. “The only way to reduce these uncertainties is to monitor more frequently.” Crowdsourcing data from cellphones may be the best, and perhaps the only, way to get a lot of data from bridges around the world.

Over 600,000 bridges exist in the United States alone. Dedicated sensors that check for structural problems are expensive, Matarazzo says, so most bridges are inspected with the naked eye, usually every two years.

Tracking the condition of bridges using simple mobile phone apps could make maintenance more efficient than with human inspectors alone – and much cheaper than with specialized sensors. The resulting improved care would extend the life of older bridges by a few years, estimate Matarazzo and his colleagues, but new bridges could last nearly 15 years longer than if left unattended. way before it needs to be rebuilt or replaced.

To test how well cellphones could monitor bridges, Matarazzo drove across the Golden Gate Bridge in San Francisco 102 times with cellphones in his car. He and his research team also collected data from Uber drivers during 72 rides on the suspension bridge. To verify the approach on bridges more typical of overpasses that are common on roads, researchers had drivers record data during 280 passes over a nearly 30-meter-long concrete bridge in Ciampino , in Italy.

For both bridges, cellphone sensors detected vibrations in the structures that were within a few percent of the measurements that dedicated instruments attached to the bridges could provide.

A single pass with a cellphone collects as much information about a bridge as a hundred or more stationary sensors, Matarazzo says. This is because phones can take data continuously as they cross, rather than offering data from specific locations along a bridge.

If the researchers can get transportation companies, government vehicle operators, or the public to collaborate, the team could accumulate a lot more information, leading to extremely accurate measurements. Since most phones are already equipped with accelerometers and GPS, the information could be collected essentially for free.

Mobile phones could help monitor bridges without installed sensors, says Huili Wang, a civil engineer at Dalian University of Technology in China, who was not involved in the study. But he has doubts about the ultimate precision that smartphones can provide. Still, “it’s a better approach for a rough estimate without [adding] more sensors,” he says.

Crowdsourced data is unlikely to entirely replace dedicated sensors for bridge monitoring, Matarazzo agrees. But cellphones are unbeatable in many ways, he says. “The advantage is in convenience and scale…. It’s a mobile detection system that’s already in place.

Bridges are key elements of transportation infrastructure. It’s crucial to look at changes that can happen over days and weeks, Matarazzo says, rather than checking bridges every few years. “This technology allows us to do that.”

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