High-level bridge works specialist Spencer Group has delivered a hugely challenging project to repair a fracture that closed the Forth Road Bridge.
A team from the Hull-based engineering business has carried out works to replace truss end links which connect the bridge deck to the towers.
The project had its origins in the discovery, in December 2015, of a major fault on the crossing, which spans the Firth of Forth, connecting Edinburgh to Fife.
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.
Spencer Group MD Gary Thornton said: “The project showcased the expertise we bring to works such as this, which pose a range of major challenges. The solutions we put in placeensured 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 weighed 7-8 tonnes, 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.”