Monitor the stability of a bridges with a smartphone application: this is what a new study promises, coordinated by the West Point Military Academy, in New York, in the United States and published in the journal Communications engineering. In fact, researchers have developed a system that, through the vibrations detected by the movement systems of mobile phonesit allows to estimate the state of a bridge like the installation, more expensive and complex, of hundreds of fixed sensors, so as to assess the need for maintenance. According to the authors of the study, who tested the system on the Golden Gate Bridge in San Francisco and on a reinforced concrete bridge in Ciampino, near Rome, an application of this type could extend the life of these structures by 15 years.
Solve a long-standing problem
Disastrous events like the collapse of the Morandi bridge in Genoa, which took place in 2018 and in which 43 people lost their lives, recall how basic monitor the state of the bridges (especially motorway ones) e to planwhen necessary, maintenance interventionsThese facilities are usually checked with visual inspections – which can take a long time – or through the installation of specific sensors which, if mounted in a fixed manner, detect vibrations linked to the physical characteristics of the bridge itself, called modal frequencies, which are indicative of the stability of the structures, obtaining from them a assessment of their state of health. The main difficulty is that bridge maintenance is very expensive: For example, according to an estimate made in the United States (which has over 600,000), the organizations responsible for the maintenance of these structures can spend up to $ 50,000 just on fixed sensors, not counting the costs related to maintaining them and analyzing the data they record.
To solve the age-old problem of measurement of the state of the infrastructures could come to our rescue i mobile sensors: smartphones, in fact, contain dozens of sensors carried by almost 50% of the world population. In fact, crowdsourcing networks have already proved very useful for collecting information on the social, economic, civil and technological systems that regulate the urban environments in which we live, for example quantifying urban mobility or modeling and predicting the spread of disease in cities. Recently, the study authors write, in this area a great deal of attention has been paid to platforms detection they generate data based on the movement of large numbers of vehiclesboth with smartphones and with dedicated sensors: this is why the researchers thought of use data from cell phone accelerometers. Phones, in fact, would be able to pick up the natural vibrations of bridges, allowing researchers to monitor their structural changes over time and have a way, much less expensive than fixed sensors, of evaluate the state of health.
Extend the life of bridges
To test their hypothesis, the researchers have collected accelerometer data of two smartphone mounted on two cars that have crossed the Golden Gate Bridge, in San Francisco, over a hundred times, after which they developed an analytical method that would allow, starting from these data, of trace the modal frequencies of the bridge. They subsequently applied this system to data from crowdsourcing from Uber drivers who had completed more than 70 trips on the Golden Gate Bridge and data from an application developed specifically for road maintenance personnel, which recorded over 250 trips on a short reinforced concrete bridge, part of a motorway junction at Ciampino. The results showed that data from just two smartphones offered one estimation of the modal frequencies of the bridge with the same precision as 240 fixed sensors: this means, the study authors conclude, that the inclusion of this system in a maintenance plan could add over fourteen years of life to a new bridge, at no additional cost.