Transport Scotland has contracted Spencer to replace seven truss ends that connect the bridge deck to the tower following their failure in December 2015. A crack was found in the northeast main span link that connects the tower to the road deck, forcing the bridge to close for three weeks in 2015.
A temporary solution was put in place by Amey at the time but permanent works are now under way. Amey has a five-year term maintenance contract with Transport Scotland for the Forth Road Bridges and the neighbouring new Queensferry Crossing.
Amey’s emergency works made the bridge safe to re-open. It replaced the existing truss ends on the northeast span with a new sliding bearing. [See our previous report here.] Spencer is now entrusted with the remaining seven truss ends on the rest of the bridge. It must cut out the obsolete sections and replace them with a sliding bearing system.
Spencer has started offsite fabrication works necessary to begin the major onsite refurbishment works, which have now also started.
Spencer Group civil engineering project manager James Barnes said: “The work will involve conducting complex engineering works, high above the water. It’s a huge technical challenge manoeuvring sections of bridge weighing up to 16 tonnes into position under the bridge deck. Our top priority is creating a safe and workable solution that ensures as little disruption to the general public as possible.”
Angus Bruce, major bridge manager at Amey, said: “The quality assurance and technical requirements are very high, so it’s imperative the contractors only engage with the best available resources. One of the requirements is to have worked on long-span cable supported bridges, and Spencer are one of only a few contractors who can do that.
“Spencer are a very experienced contractor who have worked on this type of work before, they are experts at managing this type of work, assessing the situation and delivering the work as safely as possible on site.”
The truss end link replacement works require a series of complex works to be delivered to a part of the Forth Road Bridge that has limited accessibility and was never designed with replacement in mind. The tower cells adjacent to the location of the replacement works require strengthening to take the combined 14-tonne weight of the support bracket and new sliding bearing, which need to be barged out and hoisted up into their final position.
As part of the works, Spencer will also install modifications that will make future works on the bearings easier. This includes installation of new access stairs and permanent access platforms to allow easy maintenance all year round without the need to erect temporary steelwork.