Engineers were this week carrying out corrosion inspections on the Humber Bridge’s main suspension cables.
Similar tests were first carried out in the UK on the Forth Road Bridge in 2004 and the Severn Bridge in 2006, and severe corrosion was found in both cases.
The Humber Bridge, which was the longest single-span suspension bridge in the world when it opened in 1981, is newer than the Forth and Severn bridges. Its cables are not expected to be as badly corroded. Regulations dictate that inspections must be undertaken after 30 years.
“We are looking at implementing a dehumidification scheme as a prevention measure.”
Peter Hill, bridgemaster
“We expect that some corrosion product will be present, based on other bridges elsewhere, but at 30 years we wouldn’t expect a significant loss of strength,” said Humber Bridge bridgemaster Peter Hill.
Dehumidification has been employed on the Forth and Severn bridges after inspections showed that load bearing capacity had already been lost as a result of corrosion. This involved wrapping the cables in an airtight neoprene membrane and pumping dry air through it in an attempt to prevent further corrosion.
Preventing further corrosion
“We are looking at implementing a dehumidification scheme as a prevention measure,” said Hill. He said it was better to use dehumidification as a damage limitation measure if corrosion is detected. “Dehumidifcation stops corrosion, but doesn’t improve anything. We are preparing contract documents so by the time we get the inspection results, with board approval, we will be capable of letting the tender.”
If implemented on the Humber bridge, the dehumidification operation would be the largest in the world.