BergerWorld: 2nd Quarter 2008

The 3,300-foot-long Forth Road Bridge, a suspension bridge located in east-central Scotland, spans the Firth of Forth, connecting Scotland's capital city, Edinburgh, with Fife. When an in-depth inspection revealed corrosion to the existing bridge's main cable, A&W, in collaboration with Flint & Neill, was selected to perform an independent analysis for the Scottish Executive (Parliament). The Team's duties included reviewing the previous inspection procedures, test results and cable strength calculations. A&W also conducted an independent analysis to assess the strength of the cable and potential bridge degradation.

Following the completion of the inspection, A&W, with Fairhurst and Partners and COWI, was commissioned by the Forth Estuary Transport Authority to evaluate options for strengthening or replacing the main cables. The Team first prepared the parameters for three replacement and three augmentation alternatives, including new cables mounted above and to the sides of the existing ones. Next, A&W identified potential construction constraints; prepared designs for the new cables, suspenders and connections to the superstructure; and developed load transfer procedures using a sophisticated computer model of the bridge. Finally, the Team developed typical details for the new cable system with supporting calculations, cost estimates and a detailed schedule for the implementation of the project.