The project also includes associated work to strengthen the landmark crossing in north east England.
The A-frames each weigh 5t and are beneath the 1,410m main span of the bridge. They have to be replaced because their bearings, which allow them to move as the bridge contracts and expands, have become worn over time.
The contract follows Spencer Group winning tenders to project manage an inspection of the suspension cables in 2009 and to use a gantry system to enable vital main cable dehumidification work to prevent corrosion of the cables in 2010.
The latest project will be carried out in cramped areas below the carriageway.
Spencer is applying a design solution developed by Arup. It will involve Spencer fitting two ‘wind shoes’ that are designed to absorb wind loading on the bridge deck and reduce the associated loads on the new bearing system.
Spencer is working with a number of sub-contractors on the project, including ESL, which is carrying out the strip-out works; scaffolder Harsco; electrical contractor Pennine Control Systems and steel fabricator Allerton Steel.
There will be a full article on this project in the next issue of Bridge design & engineering.
