Ireland’s First Extradosed Bridge: Bridging the Belturbet Bypass

The River Erne Bridge in County Cavan has been awarded both the Infrastructure Award and the Overall Award for 2013 at the 32nd Irish Concrete Society Awards held on the 22 March.

The 150m River Erne Bridge is a three span extrados structure with a 70m main span over the River Erne. The crossing site is part of the Lough Oughter & Associated Loughs Special Area of Conservation (SAC). The design provides both an aesthetically pleasing structure and a very economical use of materials. It also delivers a long clear span across the river, with a relatively shallow deck profile, minimising the environmental and visual impact of the bridge. Extradosed bridges, a cross between a cable stay bridge and an externally prestressed girder bridge, are still relatively uncommon worldwide and the Erne Bridge is the first of this type to be constructed in Ireland. It is now an instantly recognisable and elegant landmark on the N3 route from Dublin to Enniskillen. The jury for the Irish Concrete Society Awards described the bridge as “an exceptional bridge design, beautifully executed with cutting edge engineering design concepts.”

RPS, led by Christy O’Sullivan, Project Director, acted as Designer’s Site Representative and Technical Advisor on the N3 Belturbet Bypass for the Design-Build contractor Ferrovial Agroman PT McWillams Joint Venture, and undertook the tender and detailed design, environmental design and assessments, supervised and certified the construction of the project.

The bridge is part of the N3 Butlersbridge to Belturbet project, which was officially opened on 3rd April 2014. The €61m project included 7km of single carriageway and a second large bridge, the 210m long balanced cantilever construction Aghnaguig Bog Bridge crossing a sensitive bog woodland habitat. The road design and environmental work was undertaken by our Galway office, led by Cian McGuinness and the bridge design was delivered from our Cork office by Kieran Ruane and his team.

The project sets a benchmark for the increasing use of long span bridges to cross sensitive environmental sites, particularly Natura 2000 sites.