Sean O Casey Bridge
Project:Sean O Casey Bridge, Dublin. Location:Dublin Docklands, Co. Dublin Client: Dublin Docklands Development Authority
Architects:Brian O Halloran Associates Main Contractor:John Mowlem Construction Ltd (Carillion PLC).
Sean O’Casey Pedestrian Bridge is the successful result of an international competition that required a openable bridge over the River Liffey in Dublin. The solution is an exciting moveable structure that spans the 100m wide river using two 44m long balanced cantilever leaf structures plus short abutment supported cantilever spans.
Dublin’s newest bridge, the Sean O’Casey Bridge, has won a major international engineering award. The bridge, which was commissioned by the Docklands Authority, won the Best Pedestrian Bridge at the International IStructE Awards run by the UK ’s Institute of Structural Engineers .
Opened in mid-2005, the Sean O’Casey Bridge links the north and south Docklands, and has become an instant landmark on the River Liffey. The bridge has even featured in advertisements for O2, the Ryder Cup and, most recently for Guinness.
O’Connor Sutton Cronin, the structural designers of the Sean O’Casey Bridge, won the award for its work on the design of the bridge, which features a pioneering ‘swing’ action that sees the two leaves or arms of the bridge open to allow boats pass up and down the River Liffey. Each ‘leaf’ of the bridge is approximately 44 metres long and 4.5 metres wide and weighs around 160 tonnes. Each bridge leaf is a balanced cantilever and is designed to rotate on a central bearing supported on granite clad piers in the River Liffey. The piers are founded on four piles bored over 12 metres into the bedrock.
“The Sean O’Casey Bridge has not only become an architectural landmark in the Docklands area but has also made a huge difference to how people get around the area with the IFSC being only a five minute walk from Merrion Square now. The addition of the Macken StreetBridge in the next few years will reinforce the importance of these links in the city.” said Paul Maloney, Chief Executive, Docklands Authority.
The judging panel praised the structural solution for the bridge for combining lightness in design to resolve structural forces with efficiency and transparency. “The result is an aesthetic and elegant design,” it said.
The IStructE Structural Awards are one of the world’s most prestigious awards for structural engineering excellence. Run by the Institution of Structural Engineers, the annual awards celebrate the work of the world’s most talented structural designers.
Paul Healy of O’Connor Sutton Cronin said, “We are delighted and honoured to have been awarded this prestigious international award from our engineering colleagues. This is a tremendous reflection on the innovative work by the entire design team.”
The architects for the Sean O’Casey Bridge were Brian O’Halloran Associates, project cost consultants, Bruce Shaw and Partners and the contractor, John Mowlem Construction.
The Dublin Docklands Development Authority held an international competition in late 2002 for a new openable pedestrian bridge to the east of the Matt Talbot Bridge on the River Liffey.
This design was selected from over 80 entries received. It proposes a symmetrical structure of twinned cantilevered cradles suggesting a formal maritime gateway to the city. The double swing opening sequence of the bridge should be an appropriate event to compliment the arrival of sea craft into the heart of Dublin.
The structural form of the two main bridge elements is based on a simple balanced cantilevered principle which provides an intrinsically efficient structure for the scale of opening required, resulting in reduced structural mass to create a permeable and dramatic silhouette. The two central opening sections are approximately 44 metres in overall length and each rotates in plan about a central pier to allow a free 33 metre open width. Two profiled cantilever abutments complete the transition with the quay side. The balanced cantilever achieves its support via a cradle, comprised of four tapered steel sections, profiled to allow the flow of maximum load transfer.
The bridge deck is directly supported on continuous longitudinal circular sections and these in turn are supported at their extreme end via cable ties, saddled over the cradle tips and tensioned down to the support pivot.
The operating system for the rotational movement is essentially two hydraulic rams driving a slewing ring arrangement located in the void of the cradle base. The electrical distribution panels, hydraulic motors and pumps are suspended in the zone of the main structure beneath the bridge deck.