Main expansion joint replacement
The main expansion joints on the Forth Road Bridge are programmed to be replaced in 2018/19.
Contractor American Bridge International has been appointed to carry out the works, with Forth Bridges operating company Amey managing and supervising the project on behalf of Transport Scotland.
Prior to commencing work on site, the contractor has been undertaking site surveys, preparing fabrication drawings, procuring materials and pre-fabricating components. Work on site is expected to commence in November 2018 and will take approximately ten months to complete.
The main expansion joints allow the deck of the Forth Road Bridge to expand and contract as required by weather or weight of traffic. These joints are the oldest and largest of their kind in Europe, and had originally been scheduled for replacement in 2010.
However, the Forth Estuary Transport Authority (FETA) ordered a review of the project following higher than expected tender costs and the Scottish Government’s announcement that a new Forth crossing was to be constructed. If replacement could be delayed until the new crossing opened it would allow the work to be carried out at greatly reduced cost and with minimum disruption to traffic.
The review concluded in February 2009 that the project could safely be delayed, so long as failsafe devices were installed and the condition of the joints closely monitored.
FETA’s own engineering team worked together with consulting engineers Atkins to carry out the review. A section of the joints was opened up for inspection on the weekend of 16/17 January 2009, providing an up-to-date benchmark of the components’ condition. The team then carried out a systematic analysis of possible failure modes and actions that could be taken to maintain current standards of operational safety and service. Consulting engineers Flint & Neill acted as peer reviewer.
The review team agreed that it would be possible to delay the replacement of the joints, subject to five conditions:
- Inspection and monitoring levels should be significantly increased
- A permanent access system should be installed as soon as practicable to aid inspection
- Key components such as pins and springs should be replaced and in some cases modified to improve performance
- Temporary failsafe devices should be installed as a precaution in case of failure
- Any decision to defer replacement should be reviewed annually or following any significant component failure.
The report's recommendations were approved by the FETA Board at its meeting on 20 February 2009.
Work to install a permanent access system for inspection and to fit failsafe devices was subsequently completed without disruption to traffic or local residents.