William Dargan Bridge (2004) Dundrum, Dublin
The William Dargan Bridge is a cable stayed concrete framed bridge which carries the Luas (Light Rail System) Green Line over the busy Taney Road junction at Dundrum in south Dublin. An earlier bridge carried the Harcourt rail line across the same road but the junction today is significantly wider than when that line was discontinued in the early 1960s.
When the decision was taken to run the Luas line along the same route bridging the Taney Road junction presented the greatest structural challenge on the route. Engineering firm Roughan O’Donovan were appointed to carry out a feasibility study leading to the design and construction of a suitable bridge.
The resultant design was an asymmetrical cable-stayed bridge with the main span cantilevered out over the junction from a concrete pylon located off the junction. A particular advantage of this design was that it was not necessary to locate any piers on the junction which meant that traffic flow would not be affected and very few weekend closures were necessary during the construction phase. The inverted-Y shaped pylon is 50 m (164 ft) tall and the deck is supported by 13 pairs of high tensile steel cables. The main span is 108m (354 ft) long.
The bridge was completed in 2002 at a cost of approximately €11 million and the first Luas trams crossed it when the Green Line opened on 30th June 2004.
Buildings in Dundrum are predominantly low rise and the striking bridge is now an established landmark in the surrounding area. It has also won several awards including the ACEI President’s Award for Excellence from the Association of Consulting Engineers of Ireland (ACEI) and the Irish Concrete Society Award.