Design and Engineering
Dublin City Council appointed the team of Roughan & O’Donovan Consulting Engineers and Seán Harrington Architects in May 2008 to design a new public transport bridge over the Liffey. Both have a proven track record of bridge design; Roughan O’Donovan was the engineer for the Taney LUAS Bridge in Dundrum as well as the Mary McAleese Boyne Valley Bridge at Drogheda, amongst others, and projects by Seán Harrington include the Dublin Millennium Bridge. Graham Projects Ltd (who also built the Samuel Beckett Bridge), were appointed as construction contractors with the Dublin City Council’s Road Design Division responsible for overall project management. The team was complemented by the Conservation Architect David Slattery, to ensure that the historic quay walls were properly conserved, and to advise on other matters relating to the historic and important setting.
The bridge is an elegant single span concrete structure spanning 47 metres and is 26 metres wide. The deck uses a combination of high strength concrete and post-tensioning which allows minimisation of the structural depth, thus allowing the single span across the Liffey. The bridge incorporates flood protection walls, which double up as public seating and planters for flower displays. The pedestrian walk-ways are wide, and the bridge is gently sloping to facilitate easy crossing for all, including those in wheelchairs and with children’s buggies. Balustrading is visually transparent, allowing a good view of the river from the bridge and to help give the structure an elegant and slender profile when seen from the quays and the adjacent bridges.
The use of structural concrete provides aesthetic and geometrical flexibility, robustness and longevity. The underside of the bridge has a shallow curve, which tightens before reaching the quay walls to form the abutments. This curvature resolves the bridge structurally and visually. Below the bridge, the abutments form a double-bulge on plan allowing the river to flow around them easily and limiting the protrusion of the abutment into the river. As the abutments rise, the curve gradually flattens and morphs into the gentle single-curve under-belly of the bridge. The location of the abutments in the river minimised the impact on the quays – and therefore traffic – during construction.