Feb 15 2011
AECOM Technology Corporation, a leading provider of professional technical and management support services for government and commercial clients around the world, recently developed a dehumidification system to prevent corrosion on the United Kingdom’s Humber Bridge.
Under the $US9.6-million contract from the Humber Bridge Board, AECOM acted as the client’s representative on the dehumidification scheme and was responsible for designing the system and overseeing the installation and commissioning process. The dehumidification system will remove moisture from the suspension bridge’s main cables, maintain structural capacity, prolong the life-span of the bridge and prevent any further corrosion of the cables.
“Cable dehumidification systems have previously been fitted to new and relatively new suspension bridges to prevent any corrosion of the cables,” said Dave Wilkinson, AECOM resident engineer and site supervisor on the Humber Bridge project. “AECOM has developed the technology into an innovative system suitable for retro-fitting much-older suspension bridges that are suffering from corrosion of the cables.”
The cable-wrapping process was carried out from four separate gantries designed and manufactured by the contractor, C. Spencer. Work on the Humber Bridge started at the highest point of each cable and moved down to the lowest point, to prevent water being trapped as the wrapping progressed. A special wrapping machine was operated from the gantry to install Cableguard™, a flexible elastomeric membrane supplied by The DS Brown Company.
“This project was unique because the span arrangement required a bespoke design to inject dry air and remove wet air at the most efficient points on the structure,” said Mark Bulmer, AECOM project manager. “It took about half a shift for the team to wrap the cable and heat-seal it, as well as put new sealant in at the point where the wrapping met the cable bands.”
In 2007, AECOM first utilized this technology on two older suspension bridges in the United Kingdom — the Forth Road Bridge in Scotland and the Severn Bridge between England and Wales.
“The design of the system on Humber Bridge has evolved from AECOM’s recent experiences on Forth Road and Severn Bridge,” added Wilkinson. “This has allowed AECOM to maximize the efficiency of the system, reducing running costs and improving the long-term durability against severe weather that suspension bridges are typically exposed to.”
Once the wrap system was fully installed, the AECOM site team walked the entire length of the cables to inspect the wrapping for any signs of air escaping from the wrap.
“AECOM engineers, through their design and supervision work, have made a major contribution to the effective and efficient installation of the cable dehumidification system,” said John Cooper, major projects manager, Humber Bridge. “We look forward to their advice and assistance, drawing on expertise developed through their experience on previous cable dehumidification projects, in monitoring and adjusting the system as the cables begin to dry out.”
The project was completed in December 2010.
Source: http://www.aecom.com/