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Broadmeadow Bridge

  • Fingal County Council
  • Dublin Airport to Lissenhall Interchange, Swords, County Dublin
  • Structural Engineers: Robert Benain & Associates, Arup Consulting Engineers.
  • €18 Million
  • June 2003

Major estuary crossing at Broadmeadow which is an environmentally sensitive area.

Broadmeadow Estuary Crossing is under construction as part of the Northern Motorway Contract 1 North of Dublin Airport.  The structure consists of twin decks each 313m long.  Its form is in essence a box girder but with a curved profile to the soffit both in section and longitudinally.

Substructure

The bridge crosses the Estuary in five spans the longest of which is 69m.  At each end are substantial abutments.  Both abutments and intermediate piers are founded by piling to rock.  The piles themselves are nominally 900mm diameter.  They are bored to the rock head and then socketed up to 3m into the rock by means of a drilled rock rocket.  The whole of the completed bore is filled with concrete reinforced with 32mm diameter reinforcement.  The concrete is poured by means of a tremmie pipe to about 0.5m above cut off level.  Piles in the Estuary are formed within pre-driven cofferdams.  These cofferdams consist of LX24 sheet piles also driven to the rock head.  The size of the cofferdam is dictated by the size of base to be formed within it.  The other constraint in this regard was limitation of the impact of construction activities on this environmentally sensitive estuary.  Pier bases in the estuary are accessed via a purpose built temporary jetty.

Superstructure

The superstructure consists of a three cell box girder with a curved soffit profile.  The crossing consists of two decks each 313m long.  The concrete boxes are constructed by the incremental launch method.  Once again to minimize environmental impacts the bulk of the superstructure construction takes place behind the South abutments.  The decks are constructed in approximately 20m sections, which are then launched over the abutment and a series of temporary supports to their final position.  Once in its final position the stressing is carried out.  Parapets, kerbs and other finishes are then applied.

It was the overall winner in The Irish Concrete Society Awards 2003.

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