Smartphone app to evaluate the structural integrity of Studio bridges

Washington, Nov 6 (PTI) There may be a smartphone app to know if San Francisco’s Golden Gate Bridge, or any other bridge, is holding up well, according to a study.
The new study shows that cell phones placed in vehicles, equipped with special software, can collect useful data on structural integrity when crossing bridges. In doing so, they could become a less expensive alternative to the sensor sets attached to the bridges themselves.
“The main finding is that information on the structural health of bridges can be extracted from accelerometer data collected from smartphones,” says Carlo Ratti, co-author of the study.
The research was conducted, in part, on the Golden Gate Bridge itself. The study, which involved researchers from the Massachusetts Institute of Technology (MIT) in the United States, showed that mobile devices can acquire the same kind of information about bridge vibrations that stationary sensors compile.
The researchers also estimate that, depending on the age of a road bridge, mobile device monitoring could add 15% to 30% more years to the lifespan of the structure.
“These findings suggest that huge and inexpensive data sets collected by smartphones could play an important role in monitoring the health of existing transport infrastructures,” the authors write in their new paper, published in Nature Communications Engineering.
Bridges vibrate naturally, and to study the essential “modal frequencies” of those vibrations in many directions, engineers typically place sensors, such as accelerometers, on the bridges themselves.
Changes in modal frequencies over time can indicate changes in the structural integrity of a bridge.
To conduct the study, the researchers developed an Android-based mobile phone application to collect accelerometer data when the devices were placed in vehicles passing the bridge.
They then could see how well that data matched up with the data recorded by the sensors on the bridges themselves, to see if the cell phone method worked.
“In our work, we designed a methodology to extract modal vibration frequencies from noisy data collected from smartphones,” said lead researcher Paolo Santi.
“As data from multiple trips across a bridge is recorded, the noise generated by the engine, suspension and vibrations from traffic and asphalt tend to cancel out as underlying dominant frequencies emerge.”
In the case of the Golden Gate Bridge, researchers crossed the bridge 102 times with their devices running, and the team also used 72 trips by Uber drivers with activated phones, the study says.
The team then compared the resulting data with that of a cluster of 240 sensors that had been placed on the Golden Gate Bridge for three months.
The result, according to the study, was that the data from the phones converged with that of the sensors on the bridge; for 10 particular types of low-frequency vibrations that engineers measure on the bridge, there was a close match and in five cases there was no discrepancy between the methods.
“We were able to show that many of these frequencies correspond very accurately to the bridge’s prominent modal frequencies,” says Santi.
However, only one percent of all bridges in the United States are suspension bridges. About 41% are much smaller reinforced concrete bridges. Then, the researchers also looked at how well their method would fare in that environment.
To do this, they studied a bridge in Ciampino, Italy, comparing 280 vehicle trips on the bridge to six sensors that had been placed on the bridge for seven months.
Again, the researchers were encouraged by the results, although they found a divergence of up to 2.3% between methods for certain modal frequencies across all 280 trips and a divergence of 5.5% over a smaller sample. This suggests that a higher volume of travel could yield more useful data.
“Our initial results suggest that only a modest amount of travel within a few weeks is sufficient to obtain useful information on the modal frequencies of the bridges,” says Santi.
Looking at the method as a whole, MIT professor Markus Buehler notes: “Vibrational signatures are emerging as a powerful tool for evaluating the properties of large and complex systems, ranging from the viral properties of pathogens to the structural integrity of bridges. , as shown in this study, “Buehler said.
“It is a universal signal found widely in the natural and built environment that we are only now beginning to explore as a diagnostic and generative tool in engineering,” said Buehler.
As Ratti acknowledges, there are ways to refine and expand the search, including accounting for the effects of smartphone holder in the vehicle, the influence of vehicle type on data, and more.
“We still have some work to do, but we believe our approach could easily be expanded to the level of an entire country,” said Ratti.
“It may not achieve the accuracy that can be achieved using fixed sensors installed on a bridge, but it could become a very interesting early warning system. Small anomalies could then suggest when to carry out further analysis,” said Ratti. PTI KRS RHL

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