Launched south approach viaduct in the Queensferry Crossing, UK: design and construction

Launched bridges are becoming a widely used structural solution for the construction of medium- and long-span bridges. This construction technique has been used in the erection of the approach viaducts of the new Queensferry Crossing, a major cable-stayed bridge over the Firth of Forth in Scotland, UK. A description of the approach viaduct south, a twin-girder bridge with composite section and spans ranging from 64 m to 90 m is provided in this paper. The importance of close interaction between the design (for both permanent and temporary situations) and construction methods is emphasised. The strict design assumptions leading to tight fabrication tolerances, accurate launching control and bespoke temporary works items are highlighted. Finally, the construction method for the concrete slab is presented as a practical solution between programme and structural requirements.