The Queensferry Crossing comprises three approximately 200m high main towers which support two 650m main spans with associated approach viaducts with a total crossing length of 2 638m .
It is located slightly to the west of the existing bridges , making use of Beamer Rock , a natural dolerite outcrop in the middle of the Forth . It allows the wide estuary with two navigation channels to be crossed by a pair of 650m cablestayed spans , with an approach viaduct to the south .
The client , Transport Scotland , appointed the Jacobs Arup Joint-Venture ( JAJV ) in 2008 to assist with procurement and scheme preparation of a Design and Build contract . Although the final design would be undertaken by the successful tenderer , Forth Crossing Bridge Constructors ( FCBC ), a highly developed specimen design was undertaken pre-tender by the JAJV . This design was more detailed than is usual for design and built contracts and was commissioned by Transport Scotland because of the importance of aesthetics in the context of the two adjacent iconic bridges , and also to give tenderers confidence that what they were being asked to bid for could actually be built .
3 . SPECIMEN DESIGN 3.1 Basis of design
The Queensferry Crossing is the first major bridge in Scotland to be designed to Eurocodes . It was necessary to provide rules and criteria appropriate to the bridge as well as clarify how some of the Eurocode rules should be interpreted . Aspects such as the site specific wind climate and the rules for ship impact criteria were defined as well .
3.2 Analyses
The overall structural analysis was carried out using 3D global computer models . Additional local and semi-local analysis models were established to examine more closely the distribution of stresses and to aid in calibration of the behaviour of the global models .
3.3 General Arrangement
The bridge is divided into a cable-stayed bridge and a southern approach viaduct ; the structure is continuous from abutment to abutment with no intermediate movement joints . Longitudinal fixity is provided by a monolithic connection at the central tower located on Beamer Rock , with transverse support to the deck provided at all towers and piers .
The towers are vertical reinforced concrete elements located in the centre of the deck with two planes of stay cables anchored centrally in the ‘ shadow ’ of the tower between the carriageways . The stay cables overlap in the centre of the main spans to stabilise the central tower . The deck itself is a streamlined box girder and stay cables are multi-strand type .
Figure 1 : General Arrangement
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