Science Fair Project Encyclopedia
Boyne River Bridge
The Boyne River Bridge is Irelandís longest cable-stay bridge . Situated just to the west of Drogheda, the bridge carries traffic from the M1, across the River Boyne, linking Dublin and Belfast. It was built as part of the Drogheda bypass, diverting traffic from the N1 around Drogheda and out of the town center.
Designing a road bridge over the Boyne was not an easy task. At the chosen point, three kilometers upstream from Drogheda, the ground level on the south side is much higher, with a sudden drop. On the north bank it slopes down gradually. The area is environmentally sensitive, especially the reed beds on the north bank and the flora and fauna of Yellow Island in the middle of the river.
On the north side, being right over the Battle of the Boyne site meant out from it, the three main Williamite crossings of the river at the battle of the Boyne in 1690 took place adjacent to the bridge location, supporting the main structure ment the engineers would have to avoid putting down large foundations. On the south bank, it was important to keep the road open along the riverside and keep away from the escarpment.
The answer was a cable-stayed bridge. Although more expensive than a standard road bridge, it could incorporate a much longer main span without the need for supports in the river, so the engineers could protect the river and the island from any interference. It would also look attractive, with a tall pylon at the south side and cable stays fanning out from it, supporting the main structure.
Opened in late summer 2003, the bridge is managed under a public private partnership between the Irish government, National Roads Authority, and the private consortium, National Toll Roads . The bridge is tolled in both north and south directions.
- 350m long
- 170m main span
- 34.5 m wide, caring two lanes of traffic in both directions
- The bridge deck is 20m above the river at its highest point
- The pylon is 95m high
- Total of 56 cable stays
Source: Meath County Council
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