A collaborative team of ESA and University of Nottingham (UK) researchers has used satnav sensors to monitor small movements in the Forth Road Bridge in Scotland, providing real-time information to help make the decision whether to close the bridge during extreme weather conditions.

Large structures are more susceptible to extreme weather conditions than you might think. While many only experience very small movements, bridges are much more susceptible to high winds and driving rain, and it's sometimes better to close them off entirely when conditions become dire.

Researchers at the ESA and University of Nottingham conducted a study to help make that call in a real-time basis. They placed a series of highly sensitive satnav receivers and ultrasonic anemometers (wind meters) at key locations on Scotland's Forth Road Bridge, allowing for the detection of movements as small as 1 cm (0.39 in).

The data was transmitted in real time via satellite to a processing center at the University of Nottingham, and pushed to a web-based interface as part of the Global Navigation Satellite System and Earth Observation for Structural Health Monitoring program (GeoSHM) – a joint project primarily designed to monitor bridges with a main span greater than 400 m (1,312 ft). The interface allows the bridgemaster to view detailed information on what's happening to the bridge during adverse weather conditions, showing lateral and vertical movement, as well as wind speed.

To provide a fuller picture of the situation, the information was backed up by historical satellite data detailing gradual changes in the ground surrounding the structure, as well as any past movement. The team analyzed data going back seven years, but didn't find any signs of displacement in the earth or towers.

Use of the Forth Road Bridge has increased significantly over the last few decades, from an expected 30,000 vehicles per day to a peak of around 60,000. This has caused unexpected structural deformations that have led to decisions to close the bridge on numerous occasions during adverse weather conditions such as high winds. The real time information provided by the new system will make it much easier for the bridgemaster to make that call.

"This information is extremely useful for understanding how much the bridge can move under extreme weather conditions." said Forth Road Bridgemaster Barry Colford "This allows us to decide to close the bridge based on precise deformation information."

Source: ESA

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