History and Construction

Maintaining the Forth Road Bridge

Recent maintenance on the Forth Road Bridge has focused on the condition of the main cables and their anchoring points.

Concerns over corrosion prompted the introduction of a dehumidification system to minimise moisture inside the main cables.

They were wrapped in an airtight, waterproof covering before very dry air was injected into the spaces between the 11,618 high-tensile steel wires which make up the cables.

This work has halted corrosion to the extent that the cables are not expected to weaken significantly in the lifetime of the bridge so long as the dehumidification system is maintained and continues to function effectively.

A new inspection is tentatively planned for 2017.

Further investigations were launched in 2011 following suspicions of corrosion in the main cables’ anchoring points.

However, an in-depth inspection revealed that the anchorages were in good condition, and it’s now thought unlikely that they will need to be replaced for as long as the bridge remains in service.

Other major projects to strengthen and improve the bridge’s structure and replace major components – such as the replacement of the main expansion joints and upgrading of the acoustic monitoring system – are detailed in the 15-year programme Capital Plan.