Marlow Suspension Bridge

Challenge

Balfour Beatty required comprehensive technical assessment and monitoring services support a major maintenance programme on Marlow Suspension Bridge. The project demanded specialist advice to define an initially unclear scope of investigation and monitoring works.

A key early requirement was to establish baseline condition monitoring of the structure including the interface with a live Thames Water main carried across the bridge. This included vibration measurements at each hanger connection supporting the pipeline. Data was needed to benchmark existing performance and provide assurance ahead of planned maintenance activities.

SOCOTEC UK & Ireland was required to act as a service provider and a trusted technical advisor to help define the appropriate scope of work for this significant infrastructure asset.

Project Description and Background

Marlow Suspension Bridge is a Grade I listed structure spanning the River Thames between Marlow and Bisham. Opened in 1832, the bridge remains a key transport link and is widely recognised as one of the country's most significant historic suspension bridges. Due to its age, heritage significance and continued use, the bridge has been subject to ongoing management and maintenance interventions throughout its life. Measures including vehicle weight and width restrictions have been introduced over time to help protect the structure from increasing traffic demands and preserve its long-term serviceability

Buckinghamshire Council initiated a major programme of maintenance and restoration works to preserve the bridge's structural integrity and historic character for future generations. The programme, delivered by Balfour Beatty, includes replacement of bridge bearings, structural repairs and refurbishment works to elements of the bridge's steelwork. The works form the most significant maintenance intervention since major works undertaken during the 1960s.

SOCOTEC was initially engaged to provide technical advisory services during the scoping phase, helping define the most appropriate investigation and monitoring strategy. As the project developed, the scope expanded into a multidisciplinary programme of geotechnical investigation, structural monitoring and specialist assessment services, delivered through collaboration between SOCOTEC UK, SOCOTEC Italy and several specialist technology partners.

Solution

Once the project scope was fully established, SOCOTEC provided a multi-disciplinary solution, bringing together several specialist teams to assist Balfour Beatty with the works.

From there, technical advisory services to define appropriate scope of works was carried out, and coordination between multiple SOCOTEC service lines to provide integrated solutions was established.

SOCOTEC’s Geotechnical Investigation team assessed foundation conditions and structural support of Marlow Suspension Bridge in advance of monitoring works taking place.

SOCOTEC UK collaborated with colleagues in Italy and from several supply chain partners, who were able to provide specialised technical input and additional capabilities through the use of Interferometric radar technology which was used to measure dynamic deflections of the bridge accurately without the need to install targets or use traditional monitoring techniques such as automated total stations. The Interferometric radar was setup on a tripod next to the abutment beneath the bridge deck with data collected in hourly samples on alternating sides of the river to monitor daily trend variations under standard loading conditions.

Finland-based Koherent’s structural heath monitoring technology was also utilised and provided continuous, high-frequency 3D displacement measurements across multiple locations on Marlow Suspension Bridge.

This enabled the project team to observe both static displacement and dynamic structural behaviour, providing valuable engineering insight into the bridge’s performance while marking the first deployment of Koherent’s bridge monitoring technology on a UK bridge.

Using patented radio-based measurement technology, the system continuously captured three-dimensional structural movement with sub-millimetre accuracy, enabling engineers to better understand structural behaviour and make informed decisions around inspection, assessment and long-term asset management.

In addition to movement monitoring of the bridge vibration sensors were also installed at key positions to measure accelerations of the bridge under daily loading conditions.

The Marlow Suspension Bridge works showcased SOCOTEC's ability to operate as an integrated technical partner, with seamless collaboration between UK geotechnical, monitoring and international teams and provided our client with valuable information which went on to inform their scheme design for the bridge maintenance works.

Conclusion

The project has delivered key benefits to the client including SOCOTEC being the single point of contact for multiple technical disciplines. It’s this coordinated approach that has helped reduce the burden of client management for Balfour Beatty.

During the critical scoping phase, SOCOTEC was able to provide expert advisory input alongside the specialised monitoring solutions that were tailored to meet the requirements demanded by the heritage infrastructure of Marlow Suspension Bridge.

The Marlow Suspension Bridge project demonstrates SOCOTEC's capability to provide high-level technical advisory services alongside practical field delivery. The successful integration of UK and international resources, with SOCOTEC Italy, highlights the scope of SOCOTEC’s global capabilities, while maintaining local client relationships.