Inspection finds Forth Road Bridge corrosion is slowing

Date: 22/2/2013

Efforts to slow the process of corrosion on the main cables of the existing Forth Road Bridge in Scotland have proved successful, the latest inspection by the (FETA) Forth Estuary Transport Authority has concluded.

Previous checks in 2004 and 2008 indicated that the issue could potentially cause significant problems, with authorities concerned that lorries would have to be banned from the bridge if its structures continued to corrode.

But attempts to address the issue have been deemed effective as workers have blown dry air through the cables to reverse the process as part of a dehumidification strategy.

FETA said that the results of the inspection give "strong comfort that the newly-installed dehumidification system is retarding the corrosion of the bridge wires."

However, the organisation also explained that corrosion on the bridge continues to be an ongoing issue and that safety will remain a concern in the coming years.

"Although wire corrosion appears to have been slowed down, there are still existing cracks in some of the wires that might propagate from corrosion pits that existed prior to installation of the dehumidification system," it added.

"These cracks may eventually lead to the wire fractures, but the rate of breakages is expected to slow significantly.

"This should result in a further slowing down of deterioration of the cables and lead to a reduction in the loss of magnitude in the factor of safety."

TRL is helping FETA with the management of the bridge, deploying the SoundPrint® acoustic monitoring system, which listens for any fractures of the many wires that form the cables, allowing FETA engineers to measure the rate of deterioration.

As work continues on the (FRC) Forth Replacement Crossing - a project launched by the authorities when the problems with the current bridge were initially highlighted - FETA appears confident that the existing Forth Road Bridge will be fit for purpose until the FRC is operational.

According to Transport Scotland, the FRC is on track to be delivered in 2016 when it will serve as the main crossing for Forth traffic once it is open.

Work on the new bridge began in autumn 2011 and was expected to cost somewhere between £1.45 billion and £1.6 billion.

Posted by Sarah Bailey

Transport Research News and Vehicle Safety News