William Dargan Bridge

Roughan & O’Donovan provided full engineering design services for this 162m long cable-stayed bridge carrying the LUAS Green Line over the busy Taney Road junction in Dundrum in South Dublin.

• Winner of  the Association of Consulting Engineers of Ireland (ACEI) President’s Award for Excellence 2003
• Winner of the Irish Concrete Society (ICS) Infrastructural Category Award 2002

This asymetrical cable-stayed bridge was designed with spans of 21.5, 108.5, 18.0 and 14.0m and a slim, elegantly curved, prestressed concrete deck only 1.325m deep.

The deck was constructed using precast match-cast concrete outer shell segments glued and stressed together, then filled with in-situ concrete, before a further prestress was applied using grouted internal strand tendons.

The deck is supported from a 50 m high in-situ reinforced concrete pylon by 13 pairs of high tensile steel cables consisting of between 16 and 37 Nos. of 15.7 mm diameter 7-wire strands.

Limiting disturbance to traffic flow during construction was a key challenge, which was overcome through the use of a single pylon, located some distance back from the junction.

Careful positioning of the foundations for the approach spans, and its effect on the design of the superstructure, avoided the relocation of a range of services including water, gas and electricity, located under the road intersection.

• Feasibility studies
• Preliminary design
• Detailed design
• Construction supervision