Sensors tested by Czech Technical University could prevent bridge collapse

Scientists from the Czech Technical University in Prague are testing sensors built into bridges that should be able to continually monitor the strain and tension within the construction. If successful, the system could help prevent bridge overloads and other technical problems.

Illustrative photo: ČTK/Slavomír KubešIllustrative photo: ČTK/Slavomír Kubeš The tragic collapse of Genoa’s Morandi highway bridge in August 2018 raised public awareness across Europe of the many key tunnels and crossings reaching the end of their life. The case is no different in the Czech Republic.

According to data from the Czech Transport Ministry’s Road and Motorway Directorate, the country’s primary road network currently contains six bridges which are classified as being in a severely dilapidated state, while the second tier road system contains over eighty such structures.

To prevent unexpected collapses from taking place, a special team of scientists at the Czech Technical University’s Centre for Energy Efficient Buildings (UCEEB) is working on a bridge monitoring system that uses fibre optics to measure tension.

Dr. Jan Včelák, who leads the project, explains how this system works.

“During the construction process we place strings of fibre optic sensors into specially selected points of the structure and cover them in concrete. From these points, light is reflected back through the fibre optic string into an optical analyser. The analyser then uses the reflected light frequency to measure the tension or strain of the structure.”

The system, which is currently being tested on a bridge under construction in southern Bohemia, can be used in finished bridges as well. However, whether it ends up being used is also a question of cost.

A study, presented by Czech scientists in April 2018, estimated that the total cost of bridge repair in the country, could be as high as CZK 27 billion. Dr. Včelák believes there are two options on how to use the system.

Illustrative photo: Filip Jandourek / Czech RadioIllustrative photo: Filip Jandourek / Czech Radio “The optic fibre system is not very expensive. We are talking between 10 to 20 thousand crowns. But what is much more expensive is the unit which evaluates the signal reflected from the key points in the structure.

“The other possibility is that we do not leave the unit with the bridge, but that we do a regular structure check from time to time. Of course, if you wanted an immediate warning you would need it connected permanently.”

Personally, Dr. Včelák believes that the system is more likely to be implemented in new bridges, because the price can be covered by the contract.

Introducing the fibre optic cable system into bridges under construction is also safer from a practical perspective as it can be covered in concrete and therefore protected from outside factors such as weather or theft. On old bridges, the cables would be more vulnerable.

For now the team’s cable warning system is still dependent on successfully passing its trial phase, which Včelák believes is vital for the project to be trusted and ultimately picked up by mainstream companies.