ROD-AECOM, in partnership with subconsultant Sean Harrington Architects, developed the design of this landmark bridge crossing of the River Shannon in Athlone town centre.
Westmeath County Council received planning approval for the bridge in 2017, and ROD-AECOM Alliance was awarded the contract for the detailed design and construction stages of the project in 2019.
Work commenced on site in August 2021, with Jons Civil Engineering Ltd. as the main contractor.
The bridge was opened by Minister of State for Transport, Jack Chambers, on Tuesday, 8 August, 2023.
This 104m long, two-span, steel girder bridge has a pier in the middle of the river and end supports on the riverbanks. Modern and slender, it sits elegantly within its urban surrounds, which comprise a mix of historic buildings and structures, tourism sites and commercial properties.
Following the initial site clearance, the ground was prepared to receive the foundations, with the structures supported on piles. The contractor proposed the use of mini piles so the piling activity could be progressed outside of the permitted window (based on environmental restrictions) for construction activity in the river.
Constructing a pier in the middle of the river while maintaining navigational access and avoiding any negative impacts on water quality was challenging. The central pier was founded on a combination of steel driven piles and mini pile anchors drilled five metres into rock on the riverbed. The river pier itself is elliptical in profile and extends from below the riverbed to the underside of the bridge deck. Once the pier was finished, the cofferdam was removed, and temporary supports were installed either side of it in readiness for the erection of the bridge deck components.
The constrained nature of the site within Athlone’s town centre presented a significant challenge for the project team and careful planning of the construction logistics was required.
Substantial landside works were carried out along the narrow riverbanks, including construction of the bridge abutments and the foundations for the ramp structures linking the bridge to the proposed river boardwalks.
A complex installation
The structural steel for the bridge was fabricated in Spain by Tecade. The steel was transported to site, in 13 separate pieces, by sea and road via Dublin Port. The steelwork was assembled on site and transported downstream for installation. Openings were left in the top of the bridge deck to accommodate the final welding activity and to allow concrete to be poured into the bridge deck to stabilise the bridge when pedestrians walk across it.
Transporting the assembled units down river to the bridge location required the specialist expertise of Mammoet and Ocean Crest Marine. The bridge units weighed more than 150 tonnes each. They were slid onto a barge on skids via a temporary jetty set up at the site compound.
The skids extended out into the river until the water reached a sufficient depth to allow them to transfer onto special supports positioned on the barge. The supports incorporated jacks that helped raise the bridge deck to its final position. The jacks remained lowered during transfer and travel to ensure stability during their transportation and to facilitate the steelwork passing under the existing railway bridge between the site compound and the destination.
Multiple small motorboats were used to manage the movement of the barges, with the finest of adjustments made to the path and orientation of the assembly, when necessary.
After the installation of the main bridge components, the primary connections between the components were made, the infill concrete to the deck was poured, mortar was poured at the bearings, and the temporary supports in the river were removed.
- Detailed design - main bridge
- Detailed design - approach ramps and associated structural and civil works
- Geotechnical design
- Construction supervision
- Contract administration