• Transport and infrastructure

Checking movement on Bristol's iconic bridge

The bridge, designed by acclaimed Victorian engineer, Isambard Kingdom Brunel has been standing for 156 years – its design a much-admired feat of engineering.  

For the past seven years, JFTS has been closely monitoring the structure and checking for excessive movement and potential damage, but last year the team was asked to design an upgrade to the existing system which would also monitor the roller-mounted ‘saddles’ which sit at the top of each of the bridge’s twin stone towers.  

These saddles are designed to securely clamp the wrought iron chains which maintain the structural integrity of the bridge. They are designed to allow movement of the chains, allowing ‘give’, both as loads pass over the bridge and as the chains expand and contract with temperature change. Though their total travel is minuscule (depending on the weather and traffic flow), these saddles absorb forces created by chain movement and so prevent damage to both tower and chain. 

The consultant agency responsible for the bridge, COWI was concerned that the towers could be exposed to excessive shear forces if the saddle bearing rollers seized.  

The bridge is used as a testbed for asset management and monitoring technology research by the University of Bristol. However, in order to manage the structural risk, a robust, reliable, industrial-standard monitoring system was needed and this was sourced commercially.  

The new system consists of strain gauges, linear displacement sensors and temperature sensors which measure structural and ambient temperature on the saddles, providing early warnings of seizure or developing flat spots, and sending this information to a secure, web-based platform.  

Nick Townsend JFTS project manager says:

‘Brunel’s Clifton Suspension Bridge is an icon of the city, recognised across the world, especially amongst the engineering community, and this was a great opportunity to continue our relationship with the team which manages the bridge and provide an up to date upgrade to the existing monitoring system. We are really proud to be able to support the ongoing operation of this important structure.

'Many of our bridge monitoring projects are located all over the UK and occasionally overseas, so it is great to have the opportunity to work much closer to our Bristol base!’