Ireland’s longest bridge, part of the strategic bypass of New Ross town, provides breathtaking views of the Barrow river area. The new section of Ireland’s N25 is a crucial component of the country’s transport infrastructure, encompassing 14.9km of national road as well as the 887m extradosed bridge, which combines cable stay and pier support.
The transport link seeks to remove congestion and improve traffic flow in New Ross, where substantial delays of up to 30 minutes have been a regular occurrence. Shorter and easier to predict journey times will benefit commuters in New Ross and the surrounding area, improving quality of life and supporting economic growth in the region.
Arup was appointed by a joint venture of BAM Civil Ltd. and Dragados Ireland Ltd. as lead design consultant for this national road, including new sections of both the N25 and N30, two of Ireland’s key commercial and tourist routes.
We provided highway, bridge and geotechnical engineering, as well as environmental consultancy, hydrodynamic modelling, site supervision and project supervisor for the design process (PSDP) services.
A key feature of this transport link is the design and construction of the Rose Fitzgerald Kennedy Bridge – Ireland’s longest bridge. We worked with Spanish bridge specialist, Carlos Fernandez Casado (CFC), on this new crossing over the River Barrow estuary. Our bridge leader, Marcos Sanchez, spent the last two years of the project leading the provision of design services during the critical stages of construction, along with other members of Arup’s bridge team and CFC.
In June 2020, a special issue of e-mosty magazine focused on the history and design of this major river crossing.
887mbridge - Ireland's longest
36mheight provides clearance for shipping traffic
We were delighted to partner with world-leading cable-stayed bridge designers CFC on this complex design for Ireland, an iconic new link that is a tourist attraction in itself. ”Marcos Sanchez Director
Creating an enhanced road-user experience
Procured as a public-private partnership (PPP), the N25 New Ross bypass provides a quality transport route improving regional, national and international connectivity on the N25 Cork to Rosslare Euroroute. It also links the N25 with the N30 New Ross to Enniscorthy route.
“Taking a user led design approach, we worked closely with Transport Infrastructure Ireland and the local authorities to enhance the experience of road users, in addition to providing shorter journey times,” said Greg Zabicki, Arup Senior Engineer, Highways.
Arup designed numerous features along the 8.7km of N25 dual carriageway, 5km of N30 dual carriageway and 1.2km of N30 tie-in single carriageway. The scheme includes a grade separated junction, three at-grade junctions, an overbridge of the disused New Ross/Waterford railway line, 11 local road bridges and 13 minor structures.
Rose Fitzgerald Kennedy Bridge over the River Barrow: Ireland’s longest bridge
At 887m in length, the new bridge over the river Barrow is the longest river crossing in Ireland, connecting Pink Point in Kilkenny to Stokestown in Wexford. At 36m above the Barrow, there is ample space for shipping traffic to pass underneath the bridge into the Port of New Ross. Prior to the design of this scheme, the O’Hanrahan Bridge was the only crossing in New Ross, plagued with delays and frequent closures.
This three-tower extradosed bridge combines the main elements of both a prestressed box girder bridge and a cable-stayed bridge.
An extradosed bridge uses much shorter towers than a cable-stayed bridge and a significantly shallower deck than a box girder, resulting in a bridge which is sympathetic to its surroundings, while providing the navigational clearance required into the Port of New Ross.
The bridge consists of nine spans in total. The cross section of the deck is a single box of prestressed concrete with inclined precast solid panels to reduce the cantilever length, while providing a smooth appearance. Due to the high compressive forces associated with long span extradosed bridges, high strength concrete up to C80/95 was necessary on large parts of the deck box.
The scale of the structure is impressive in size and slenderness, rising 36m over the water. The central 650m of the crossing over the river and floodplain is spanned with only three supports, using a single plane of stay cables to support the deck, each of them having up to 125 strands. The cables went through a full scale of two million cycles of fatigue testing in a lab in Chicago, one of only two labs worldwide that can test cables of this size.
Constructing the longest bridge in Ireland required significant temporary works, including two temporary piers, a push-pull prop for the balanced cantilever construction and a temporary artificial island to facilitate construction of the main central pier. Reviewing the temporary works design was a key part of our role coordinating health and safety in the design process.
Protecting the surrounding area: designing for conservation
Arup’s flooding team carried out 2D hydrodynamic modelling to estimate the potential changes in the flow regime associated with both the temporary island and the permanent in-channel bridge pier. A detailed scour assessment was also undertaken to estimate the likely scour depths and extents related with the bridge pier.
Arup’s environmental consultants advised on the design of the scheme in order to ensure that it is sensitive to its surroundings. The River Barrow is a candidate Special Area of Conservation (cSAC), due to rare habitats and species, and the River Barrow Estuary is a proposed Natural Heritage Area.