Acoustic monitoring of the main cables of the Forth Road Bridge has revealed three wire breaks since the system was commissioned earlier this year. The new system was installed in August, after corrosion was discovered in the cable of the bridge following similar discoveries in American suspension bridges. The system provides continuous monitoring of noise within both cables and analysis of the data provides information on wire breaks and their position. Two of the latest breaks are located on the west cable near the southeast main tower, with the other on the east cable on the south side span.
Alastair Andrew, bridgemaster, said it was too early to draw conclusions. He said: ‘Continuous monitoring gives us the comfort of an ongoing health check into the condition of the cables. And given the extent of the breaks identified from internal inspections last year, these results confirm what we suspected.
‘The real value of the acoustic system is that it helps us build up an in-depth picture of the scale of the problem while measures are being put in place to halt and prevent further corrosion.’
The Forth Estuary Transport Authority has commissioned a feasibility study into the installation of a dehumidification system, based on dry air injection, to dry out the main cables.
Such systems are typically built into new suspension bridges being designed and constructed today.
A tender process is under way to appoint a contractor to install the system, and the successful bid will be announced in December, with work due to start in spring 2007. Since the discovery, corrosion has also been found in the Severn Bridge, which is now being monitored, too.
The Severn Bridge is under extra pressure after plans were revealed for rail to carry more passengers away from the beleaguered crossing have been hit with the news a train operator is to slash services.
First Great Western has decided to press ahead with cuts to services at the Severn Tunnel Junction station, which provides an alternative to Severn Crossing tolls and expensive commuter car parking in either Bristol or Cardiff.
The decision comes despite the route experiencing increased patronage over the last two years, with 10.3% more passengers.