The White Cart Viaduct is an elevated section of the M8, which carries the motorway over the White Cart Water close to Glasgow Airport. The bridge comprises a concrete deck supported on steel box beams with a 73m main span.
Transport Scotland implemented a scheme to improve access under the bridge deck to aid inspection of the underside, particularly the inside of the box beams to check for corrosion. This involved the design and construction of a new 2m wide walkway, spiral stairs and cross platforms under the deck.
The walkway units were constructed from Fibre Reinforced Plastic (FRP) as opposed to the more conventional steel option. Despite material costs being increased, FRP units are lightweight and durable, resulting in little or no maintenance over the 60 year lifespan required. The light weight of the FRP imposes less load on the main bridge and is much easier to construct at height, where restricted access under the bridge prevents cranes from operating .
The walkway was made up of 3m long modules each with grated floor and sidewalls lifted into position using roped access techniques and clamped to existing cross girders.
MHB carried out outline design of the overall scheme, and independent checking of the walkway units (which were designed and supplied by Pipex).
The construction of the scheme was competed by AMCOGiffen in December 2016.