Video: ‘Major challenges’ but £10m repairs to Forth Road Bridge are complete
A major £10m repair project on the Forth Road Bridge has been completed.
The work, which involved replacing truss end links which connect the bridge deck to the towers, followed a fracture that caused the closure of the bridge in December 2015.
At that time, one of the eight truss end links on the bridge was found to have fractured, causing the bridge to be closed completely for more than three weeks while urgent repairs were carried out.
A temporary splint was applied to the fractured link, followed by a permanent structural repair to that area.
Bridge owner Transport Scotland subsequently decided to replace the other seven key links and, following a tender process, selected Spencer Group, an industry leader in complex engineering projects on major structures, for the works.
The £10m scheme has involved cutting out the truss end links and replacing them with a unique new sliding bearing system. It has required a series of complex works to be delivered to a part of the bridge which has limited accessibility and was never designed with replacement in mind.
The project posed multiple challenges, with the Spencer team working in confined spaces within the main towers and manoeuvring large new structural components to precise tolerances.
The replacement bearings were delivered to the bridge from a workboat, so the works had to be co-ordinated with tide times within the busy Forth estuary.
Ensuring effective communication via two-way radios was crucial, with engineers working below the bridge deck having to contend with significant noise and vibration as traffic passed above them.
Despite these challenges, Spencer Group team delivered the project successfully with minimal impact on normal bridge operations and with traffic flowing throughout.
Spencer Group Managing Director Gary Thornton said: “We’re delighted to have completed this important project to maintain the structural integrity of the Forth Road Bridge.
“The project showcased the expertise we bring to works such as this, which pose a range of major challenges. The solutions we put in place ensured critical components were replaced without having to interrupt traffic flows at any time.”
Spencer Group Bridges Projects Manager James Barnes said: “This project has been particularly challenging in relation to access because the truss end links and the new bearings we have fitted are below the bridge deck, about 40 metres above the water.
“No permanent access was in place, so we installed a temporary access platform to allow our personnel to reach the location of the works.
“With our supply chain we have fabricated over 200 tonnes of new steel and joined it to the existing structure in some very inaccessible areas.
“The pieces that we cut out to replace were 7-8 tonnes in weight and some of the heaviest lifts have been up to 16 tonnes. All the pieces have had to be lifted onto the bridge deck or lowered to the workboat, so there have been major lifting, hoisting and access challenges that had to be overcome.
“A key factor in the success of this project has been the collaborative approach between everyone involved. It’s been a real team effort to come up with the right solutions and undertake the works in the most efficient manner, with safety the number one priority.”
As well as installing the new bearing arrangements, Spencer Group has introduced modifications that will make future works considerably easier, including new permanent access stairs and platforms to allow easy and safe inspection and maintenance all year round.