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The researchers started with a controlled experiment, in which they collected data by driving across the Golden Gate Bridge with their smartphones perched on their dashboards. They knew all the variables: the type of car they were in, the speed, their location at any given time, and the exact location of the phones in the car. During the driving, phones collected data from their accelerometers, instruments that measure the movement, in this case the vibrations of the car. This allowed the researchers to accurately measure the modal frequency of the bridgewhich corresponded to the data collected by traditional sensors distributed throughout the structure.
After the scientists asked Uber to provide the accelerometer readings of its drivers on the Golden Gate: “I don’t know what kind of phone they have, I don’t know what kind of car they have, I have no idea how fast they are going”says Matarazzo. However, Uber’s data has also been able to accurately estimate the modal frequency. That’s because, while Uber’s data isn’t necessarily consistent — drivers use many different vehicles and phones — the Golden Gate Bridge is.
The weight of e-commerce
But while measuring a change in modal frequency can help ascertain that a bridge has a problem, engineers still need to figure out what causes it. It can prove to be a difficult task because even thenatural environment it can affect the frequency by changing the state of steel and concrete, for example as outside temperatures rise and fall. Matarazzo however observes that the past searches have shown that it is possible to isolate and account for these signals.
Every year the need for adequate monitoring is growing the thousands of aging bridges. Some facilities are far exceeding their originally projected life cycles, and all are now burdened with more and larger vehicles, such as the legions of trucks delivering our online orders. “It’s like asking an eighty-year-old to carry a bigger load than he carried when he was young – explains the engineer Nasim Uddin of the University of Alabama of Birmingham, who she studies the use of smartphones to detect the modal frequencies of bridges –. That’s why bridges are collapsing everywhere. Unless you have a system like this, I don’t think we’ll be able to handle it.”.
Privacy and data ownership
If you are concerned about the idea that municipalities can start to record the location of your smartphone and the accelerometer data to monitor the bridges, according to Matarazzo you have nothing to fear. His team plans to use city vehicles, such as police cars, for data collection. Ride-sharing companies like Uber could provide data about their drivers, while logistics companies could allow researchers to draw on information from semi-trailers and other large vehicles.
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