|Bridges & Structures|
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Forth Road Bridge Replacement - Queensferry Crossing
Client: Transport Scotland
Contractors Designers: Forth Crossing Design JV
Form of Contract: Amended FIDIC Silver Book
Dates work carried out: 2011 - 2016
HOCHTIEF, as part of the FCBC consortium, are currently delivering the Forth Replacement Crossing for the Scottish Government. The structure over the Firth of Forth will be constructed as a cable stayed bridge composed of three mono towers with two main spans of 650m and associated approach viaducts to the north and south. The overall length of the bridge including the approaches will be about 2.7 km. The bridge will carry two lanes of traffic in each direction, plus hard shoulders, with the road designated to motorway standard. Besides the main structure the project also features 10km of additional highways infrastructure.
The three pylons (towers) which will jut out over 200m into the sky will carry the deck structure over the main span length by means of stay cables. While the Central Tower is based on an existing mid estuary island (Beamer Rock), the flanking towers as well as a viaduct pier ‘S1’ on the southern viaduct are founded on vast seabed concrete bases formed within permanent steel caissons.
The other piers and the Central Tower are conventionally based on spread foundations using marine and land cofferdams. HOCHTIEF, with its long experience in marine works and complex civil engineering, has been involved in the overall planning and execution of marine foundation works as well as the marine accesses.
In total 180,000m3 of soil had to be dredged for marine access channels, 46,000m3 material were removed out of the caissons during the lowering process and approximately 5,000m3 of rock (dolerite) were excavated using drill and blast method for the construction of Central Tower foundation on Beamer Rock. The marine foundations used in total 50,000m3 of underwater concrete and 38,500m3 structural concrete supported by 4,200t steel caissons structures and 1,850 sheet pile cofferdams and tubes.