Spencer Group have begun preliminary work on their project to repair the truss ends on the Forth Road Bridge, following a high-profile fracture which closed the bridge for three weeks during emergency repairs.
Selected by Transport Scotland as the contractor to replace seven truss ends which connect the bridge deck to the tower, following their failure in December 2015, Spencer are tasked with cutting out the obsolete sections and replacing them with a unique sliding bearing system.
Spencer have commenced the complex offsite fabrication works necessary to begin the major onsite refurbishment works, which have now also commenced.
James Barnes, Civil Engineering Project Manager at Spencer Group said: “We’ve worked on some of the world’s most iconic bridges, so we’re excited to make these historic repairs to the Forth Bridge, which will keep this vital artery operating for many more years.
“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.”
Spencer were contracted to complete the process of replacing the old truss end links with a world-first sliding bearing system, following the discovery of a crack in the North East main span link that connects the tower to the road deck, forcing the bridge to close for three weeks in 2015. This includes removing the temporary solutions on the main deck and installing the bearings, as well as installing both the temporary solutions and the new bearings on the side decks.
Following emergency works undertaken by Amey to first make the bridge safe to re-open, then to replace the existing truss ends on the North-East span with a new sliding bearing as part of a trail operation, Spencer were entrusted with the task of conducting similar works on the remaining seven truss ends on the rest of the bridge. This will ensure that there is no repeat of the original issue, and that the systems’ lifespan will be considerably increased.
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 which 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 considerably 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. This will make future maintenance considerably safer, and will allow it to be carried out with little disruption to the normal operation of the bridge.