The Boyne Bridge is an asymmetric cable stayed bridge with an overall length
of 352m traverses the River Boyne west of Drogheda. Cable stays, anchored in
the head of the 95m high A-frame pylon, support the 170m main span at 10m
centres. Counterbalancing cable stays tie the pylon head to the south
abutment, which consists of a cellular reinforced concrete box with mass
The angle of inclination of the pylon legs, approximately 20 degrees, is one
of the steepest ever to be specified and, as a result, has necessitated
particular attention to construction methods. The 34.5m wide dual carriageway
composite deck consists of a grillage of longitudinal and transverse steel
girders supporting a reinforced concrete slab.
The four approach spans are supported by pairs of circular reinforced concrete
columns of 2m in diameter. The deck steelwork is enclosed by a system of GRP
panels, which provides protection against corrosion and access for inspections
and maintenance. Extensive use is being made of Blast Furnace Slag Concrete,
both for its aesthetic benefits and thermal characteristics.