Client: Dublin Port Company
DBFL was lead consultant providing civil, structural and transportation engineering services on the Terminal 4 Alexandra Road bridge project from inception to handover. DBFL were also project managing the provision of external services such as architectural, mechanical & electrical etc.
The bridge structure spans over Alexandra Road, linking the existing CDL Yard space to the north and the existing Terminal 4 Yard space to the south.
The bridge consists of five spans of 20m, 20m, 30m, 20m, 20m lengths. In addition, there are Mechanically Stabilised Earth (MSE) embankment approaches at each longitudinal. The mid span columns are located on either side of Alexandra Road with the centreline of the columns positioned approximately 10m from rail centreline.
The ground conditions led to a significant geotechnical challenge. Friction piles were ultimately selected to support the abutments, piers, and embankments. Due to the significant depth to bedrock, the piles were hung up in the gravel stratum, with piles lengths that would be traditionally shorter than usual for a bridge of this magnitude. DBFL carried out extensive design reviews of third party proposals to ensure that long term and differential settlement would be within acceptable limits over the design life of structure. The bridge deck design was also successfully altered to accommodate the differential settlement between spans.
The excavations for the substructure of the bridge were carried out in recent concrete yard constructions. This means that the arisings (concrete pavements, unbound subbase, 6F2 capping) contained a great deal of suitable infill material. DBFL supervised a rigorous sampling and testing regime to ensure the arising met TII acceptability limits. This minimised both waste material leaving the site and import fill material.
Project Director
