Britain’s 2.2 km long Humber Bridge carries the A15 dual carriageway over the Humber estuary between Hessle in East Yorkshire and Barton in North Lincolnshire. Opened in 1981, its 1410 m suspended main span it made it the world’s longest single-span bridge until 1997.
The 4.5 m deep main-span deck box are supported at the suspension towers on four steel A-frames, which carry up to 1600 t each and allow longitudinal movement of the deck. Routine inspections showed the bearings on these A-frames were wearing prematurely and at risk of seizing.
The award-winning project, which included fitting temporary pendels to allow the A-frames to be removed, involved threading 160 t of specialist steelwork and bearings into a confined environment directly under live traffic and 30 m over water. Work started on site in July 2013 and was successfully completed exactly two years later.
According to project manager Michael Nichols, ‘NEC is generally the contract suite of choice now as it provides a clear allocation of risk and responsibilities, as well as a clearly defined process to follow for the agreement of change and contract administration'.
Nichols says that despite a well-defined design being prepared prior to tender, the extremely tight constraints on site – including restricted space, the need to keep the bridge open throughout and a number of elements of the existing bridge not being as originally assumed – meant that a collaborative approach was required to resolve the issues encountered.
Benefits of NEC3
- NEC enabled a complex bearing replacement project on the UK’s longest suspension bridge to be successfully completed under live traffic conditions
- The contract facilitated a collaborative approach by bringing together the expertise of the contractor and the employer’s designer while maintaining clear lines of responsibility
- For projects with a well-defined design, ECC option A encourages the contractor to achieve savings through method-related improvements
- Changes to the contract were generally quick and simple to resolve as NEC clearly identifies where risk lies