Project Overview

The Chetwynd Bridge, a Grade II* listed three-arch cast-iron structure, located in Staffordshire, England, is the largest surviving pre-1830s cast-iron bridge in England and the second largest in the world. Due to the historical significance and age of the bridge, a detailed restoration project was initiated to repair the ironwork and restore the paintwork in a way that aligned with its historical importance. Once the repairs were completed, it became necessary to monitor the bridge’s structural health, especially its reaction to the heavy traffic running over it daily. The goal of the project was to continuously monitor one arch initially, with plans to expand monitoring to all three arches, ensuring early detection of any deterioration or damage caused by traffic.

Monitoring system and challenges

The structural health monitoring of the Chetwynd Bridge presented several challenges due to its historic and protected status. The project team had to adhere to strict regulations regarding the installation of sensors on the bridge.

• Non-invasive sensor placement: since the bridge is listed as a Grade II* heritage site, no bolts or adhesives could be used to attach the sensors. As a solution, high-strength magnets were utilized to secure the sensors without altering the structure.

• Power supply management: due to the location and lack of space for an off-grid solar panel system, powering the system posed another challenge. The team ingeniously used the existing 24V street lighting to charge a backup power unit, ensuring uninterrupted monitoring.

• Flood risk: the River Tame, flowing beneath the bridge, is prone to flooding. The sensors had to be carefully positioned above historical flood levels to ensure their continued functionality during adverse weather conditions.

• Aesthetic considerations: to preserve the historical appearance of the bridge, the sensors were painted to match the existing structure, allowing them to blend in and meet regulatory approval.

Sensors deployed

The monitoring system employed a variety of advanced Move Solutions wireless sensors to capture a wide range of data:

• 36 Accelerometers

• 9 Dynamic Displacement Sensors (DDS)

• 15 Tiltmeters

• 2 Gateways

The sensors were strategically placed to monitor the structural behavior and vibrations of the bridge, ensuring real-time data collection on the impact of daily traffic. Three cameras were also installed for visual remote monitoring as well.  

Outcome

Since the installation in early September 2023, the system has provided continuous, real-time monitoring of the first arch of the Chetwynd Bridge.

• Modal Frequency Analysis: in February 2024, six months of accelerometer data was analyzed to assess the behavior and trends of the bridge’s structural health. The analysis helped to understand how the bridge responded to regular traffic loads and environmental conditions.

• Vehicle movement detection: the sensors immediately recorded every vehicle passing over the bridge. With the help of the Dynamic Displacement Sensors (DDS) and video footage, the system identified illegal overweight vehicles, which could potentially damage the bridge.

• Data-driven insights: while no new damage has been detected yet, the data revealed a more detailed picture of the structural stresses on the monitored arch. This information is vital in justifying the need for a new bridge to ensure long-term preservation, as it highlighted the gradual deterioration despite the lack of visible damage.

This case study demonstrates the capability of Move Solutions’ wireless monitoring technology to safeguard critical infrastructure by providing real-time data and actionable insights, especially in historically significant structures.