Kincardine Bridge, Scotland – an engineering triumph 85 years on

When construction of Kincardine Bridge was completed in 1936, it was the longest road bridge in Scotland and the largest swing-span bridge in Europe. The bridge, listed as category A by Historic Environment Scotland, remains in service 85 years on and carries around 12 000 vehicles daily across the Forth estuary. On occasions, when the Queensferry Crossing and the Forth Road Bridge are closed simultaneously, Kincardine Bridge offers the shortest available diversion route across the estuary for unrestricted traffic. A 2019 principal inspection highlighted deterioration to some structural elements and, in 2020, bridge assessment standards in the Design Manual for Roads and Bridges were revised. As a result, a quantitative assessment was undertaken to provide confidence that the bridge remains safe for use and fit for purpose and to inform future maintenance requirements. This focus of this paper is on the multitude of structural forms that comprise the overall bridge and how they have comparably performed relating to durability over the past 85 years, have been quantitatively assessed, have comparably withstood present-day traffic loading criteria and will be maintained in the future.