Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Severn Bridge corrosion revealed

Severn Bridge suspension cable corrosion is worse than that found on the older Forth Road Bridge and more serious than the Highways Agency expected, it emerged this week.
Initial findings from intrusive investigations on the cables show that the mid-span section has suffered high levels of corrosion, affecting 50% of the cross section. The results confirmed the need to fit a £20M dehumidification system to dry out the cables and halt deterioration.Highways Agency senior bridge engineer Martin Lynch told NCE: 'The dehumidification system will be installed on the main span cables where corrosion is worst this summer.' This offers the opportunity to monitor the success of the system before installing it on the whole bridge in 2008.The dehumidification system, also known as dry air injection, works by blowing warm dry air though the gaps between the 8,322, 5mm diameter strands that make up each cable. Water ingress through cracks in the zinc-based sealant is believed to be the main cause of corrosion.Lynch said that he was 'comfortable the bridge could carry normal traffic loading'. However, load restrictions on vehicles over 7.5t to a single lane in each direction, as enforced last September (NCE 21 September 2006), will remain in place until the full testing and analysis has been completed to accurately calculate the bridge's resulting loading capacity.

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.