Case study: BridgeWatch

A good status of maintenance is necessary for any bridge. For three iconic bridges in Normandy, France - including the former longest cable-stayed structure in the world, this proved to be a major challenge. The Chamber of Commerce and Industry Territory Seine Estuary (CCITSE) asked specialist company James Fisher Testing Services (JFTS) to develop an integrated bridge monitoring system.

The challenge involved the iconic cable-stayed bridge (Pont de Normandie), Pont de Tancarville and the rigid steel Pont sur le Grand Canal du Havre. Outdated maintenance equipment made it necessary to monitor structural, acoustic and weather factors on different systems, and the validity of the data collected was in doubt.

CCITSE enlisted the help of construction integrity monitoring specialists, James Fisher Testing Services (JFTS), and asked this company to develop an integrated system that could collect large amounts of data that could then be presented and interpreted in one user-friendly interface

Topcon technology partner

"With nearly 5 km of bridge to monitor in real time, CCITSE needed an intelligent solution," said Julian Allen, director of structural health monitoring at JFTS. "We proposed our BridgeWatch® system because it can analyze a massive amount of raw data and provide relevant insights, allowing CCITSE to improve safety, manage traffic flow and minimize bridge closures. But for our BridgeWatch® software and its Smart Asset Management System interface (SAMS™) to work effectively, we needed a technology partner who could help us collect high-quality data on a large scale.

Together with Topcon, JFTS developed a unique solution for CCITSE. "Our partnership with Topcon was a true collaboration," Julian continues. "By working together, we were able to give CCITSE a successful bid and then deliver a highly intelligent, automated and intuitive monitoring system that is also cost-effective."

Future-proof GNSS constellation tracking

As part of the €1.9 million contract, 21 modular Topcon MR-2 GNSS receivers were installed on the 3 bridges to enable full constellation tracking with HD2/directional capabilities and a comprehensive set of communication interfaces. The MR-2 is capable of tracking all present and future GNSS constellations and satellite signals and has 8 GB of internal storage.

The MR-2 receivers were installed with Topcon G5-A1, a good GNSS full wave antenna that can accurately track all constellations and signals. The G5-A1 antennas were placed high on the bridges so that they are not blocked by anything and a coordinate value for the antennas' positions can be created. Coupling with Topcon's TopNet software then allows continuous monitoring for movement. Tilt sensors on the bridge are combined with the antenna data to accurately image movement

Most effective GNSS technology

"The large span of the bridges means that there is a huge area to be measured and monitored," says Simon Crowhen, national sales manager sales manager for Topcon Positioning. "To do that accurately requires measuring many different positions at the same time. For that reason, we proposed a system based on GPS rather than total stations. A total station requires a line of sight to the prisms and a measurement routine. With GPS, the antenna just needs a clear view of the sky to give a constant position. In addition, you can measure many different rovers at the same time."

BridgeWatch® System Integration.

Topcon not only advised on the most effective GNSS technology for the three bridges in Normandy, but also worked with JFTS to integrate its own equipment into the BridgeWatch® system. "Our hardware and JFTS' software together measure 145 million individual data points per hour with 15 DAUs and convert them into relevant, powerful insights for CCITSE," Simon says. "The JFTS system presents data in a very visual way, making it easy for the customer to identify bridge movement and any causes for concern. It's a huge improvement over their previous system."

After an installation period that spanned only a month, the system went into operation in September 2019, much to CCITSE's delight. "France has never seen such a system before," said Clémant Fasquel, director of CCITSE. "It is pleasant to use and adds a lot of value to our bridges. Moreover, Topcon and JFTS worked together perfectly. They were very helpful, answered all our questions and quickly solved the challenges we encountered along the way. We look forward to a long-term partnership."