Satellite radar data show impending bridge collapse
Currently, the stability of bridges is mostly monitored with the help of sensors , which can only record the condition selectively and do not keep an eye on the overall construction. On August 14, 2018, a collapsing pillar of the Morandi Bridge in Genoa triggered a collapse of the entire bridge, causing 43 people to die and dozens injured. Even a year later, Italy is still debating whether better surveillance could have prevented the disaster
A new monitoring method can detect disasters like the collapse of the Morandi Bridge in August 2018 much earlier than current sensors. A subsequent evaluation of satellite images showed that the stability of the bridge had already deteriorated in March 2017 and that a collapse is imminent.
For this reason, scientists from the University of Bath and the California Institute of Technology have researched an early warning system. According to the paper published in the journal Remote Sensing, radar images from satellites such as the COSMO Skymed from the Italian space agency or Sentinel-1 from ESA are used for this.
Monitor buildings continuously in the future
The Genoa tragedy is irreversible, but should at least help prevent similar disasters. The authors hope that large structures could soon be automatically monitored using satellite data and intelligent tools.
Researchers from the Nasa Jet Propulsion Laboratory (JPL) and the University of Bath have developed a satellite-based early warning system that detects minute movements in bridges. Your surveillance system combines data from a new generation of satellites with a specially programmed algorithm. The tool could be used as an automatic warning system to ensure the security of large infrastructure projects. Based on the data, a possible risk of dangerous processes in building construction is calculated.
Their technology could also be used for tunnel drilling. Giardina criticizes that a lot of data is currently being collected on the ground floor, while hardly any measurements of other structures are available. She cites the Crossrail route as an example, a subway line under construction under London.
Almost a year ago, on August 14, 2018, there was a catastrophe in Italy. A pylon of the Morandi Bridge collapsed. The four-lane autostrada A10 motorway bridge in Genoa was heavily used. 43 people died in the accident. Since then, civil engineers have asked themselves whether measurements could be used to identify critical changes before they collapse. Previous measurement techniques did not provide any indication that the Italian building was in danger.
Three-dimensional images of bridges
The images of the individual satellites, which show the bridges from different perspectives, are then merged into a single three-dimensional view. According to Giorgia Giardina, co-author of the study, “thanks to the new generation of satellites, this is now possible with millimeter accuracy.”
An artificial intelligence (AI) evaluates this data practically in real time. It is thus possible to observe the smallest changes to bridge structures from space on the basis of these recordings and to recognize an impending bridge collapse far in advance.
Historical photographs of the Morandi Bridge analyzed
Buildings have long been measured at regular intervals. Common approaches to monitoring, however, have their weaknesses: only selected areas are checked with sensors, such as those that are already considered to be at risk. “However, our method allows control of the entire infrastructure and almost in real time,” says project manager Pietro Millo from JPL.
Here’s how it works: In their research project, engineers worked with satellite images of the Morandi Bridge. Since urban regions are regularly photographed, they had an extensive fund available to examine temporal dynamics. As soon as buildings are taken from different directions, three-dimensional representations can be calculated. “Thanks to a new generation of satellites, this is now possible with millimeter precision,” says Giorgia Giardina from the University of Bath. Combined with an algorithm that evaluates this data, movements can be monitored almost in real time, reports the research team.
The early warning system passes the practical test
Using data from the Italian Space Agency, Giardina’s team documented deformations for the first time, long before the Morandi Bridge collapsed. The experts write that changes in the millimeter range were not apparent with standard measurement methods. Civil engineers had long pointed out that the structure was in a bad, but by no means threatening, condition.
With the new process, engineers looked at the dynamics of the entire structure – and not just changes at individual points. According to their results, the first deformations occurred in the area of the collapsed pylon as early as 2015, in several places. The deformations accelerated rapidly between March 2017 and August 2018. In retrospect, the catastrophe came as no surprise.
Better satellite data, more precise measurements
Millo and Giardina attribute their results primarily to advances in satellite technology. In the past, radar images could be created with an accuracy of about one centimeter. Structures in the millimeter range are now recorded. The level of detail is sufficient to detect critical deformations at an early stage.
Especially in Italy, the Cosmo-Skymed program (Constellation of small Satellites for Mediterranean basin Observation) has paid off. Four satellites orbit the earth on a sun-synchronous orbit. They are equipped with high-resolution radar systems (synthetic aperture radar). Observation satellites from the Sentinel program of the European Space Agency ESA were also added. Since they provide information about a building from different angles, time-resolved, three-dimensional reconstructions are possible using software.
Satellite surveillance would have recognized the impending collapse of the Morandi bridge
In order to check whether the early warning system also works in practice, the study authors put it to the test with old satellite images of the Morandi Bridge. Images from the last 15 years were used, from which a map with changes to the construction was created.
The evaluation showed that years before the collapse, the first signs of a sinking stability of the bridge could be seen from the satellite images. The collapsed pillar, which caused the entire bridge to collapse, had its first shifts in 2015. The images from space already showed threatening dimensions from March 2017, more than a year before the catastrophe.
Giardina notes that it has been widely reported that the bridge was in poor condition. However, the scientists have now documented for the first time the deformations that preceded the collapse. “According to the study authors, the new monitoring method in combination with the sensors already in use could prevent similar disasters.