London’s famous Millennium Bridge has been repainted for the first time since it opened 15 years ago, using an innovative suspended cradle and rope access system.
Project: Repainting of the London Millennium Bridge
Client: City of London Corporation
Contract value: £198,991
Main contractor: FM Conway
Specialist access: CAN Structures
Start date: 12 October 2015
End date: 11 December 2015
Spanning 325 m across the River Thames between the Tate Modern and St Paul’s Cathedral, the Millennium Bridge has become a landmark London structure. Opening in June 2000, the steel suspension bridge now carries five to seven million people over the river every year.
The footbridge was designed by a collaboration of leading sculptor Sir Anthony Caro, Arup and Foster + Partners.
It is supported by two Y-shaped armatures carrying eight steel cables. The 4-m-wide deck is clamped onto the cables at 8 m intervals.
The shallow design of the bridge ensures that the cables are never more than 2.3 m above the main deck, preserving its elegant form and the uninterrupted panoramic views of the surrounding structures.
Refurbishing the structure
To address the effects of 15 years of wear and tear, in October 2015 the City of London Corporation commissioned the bridge’s first maintenance programme.
FM Conway was contracted to repaint the main steelwork of the structure, re-condition the suspension cables with a special industrial coating, and polish and clean the steel handrails running along the bridge deck.
A scaffolding rig would normally be used to carry out repairs of this nature to an elevated structure. However, the slender design of the bridge meant that it was unable to take the weight of a full rig.
A solution to this challenge came in the form of a specialist rope access system, supplied by CAN Structures. This was used to safely access the supports and underside of the bridge without endangering the integrity of the structure.
“Originally designed for mountaineering and potholing, the rope access system’s flexibility allowed it to be adapted to suit the unique design of the footbridge”
Mobile towers were used to access the southern end of the bridge, where there was suitable space for them to be deployed.
Originally designed for mountaineering and potholing, the rope access system’s flexibility allowed it to be adapted to suit the unique design of the footbridge.
Suspended from the bridge, the painting team pulled themselves along using a lightweight aluminium cradle system. They carried out minor repairs before applying 300 litres of water and temperature-resistant paint to the steel sections of the bridge.
After being cleaned with solvent to remove dirt and debris, a specialist wax aluminium coating sourced from Italy was applied to the steel cables. Containing aluminium micro flakes, dioxide powder and resin, the wax coating is designed to prevent corrosion of the cable fibres.
The City of London Corporation was determined to maintain access to the bridge at all times and minimise disruption to the public as much as possible.
Use of the less obstructive access system had the added benefit of allowing pedestrians to continue using the popular river crossing throughout the maintenance works.
The site teams cooperated closely with the London Borough of Southwark – with whom FM Conway holds the long-term maintenance contract – to safely manage the flow of people using the crossing. Signage was installed to explain the project to passers-by, navigating them across the bridge while works to the handrails and sections of the main deck were carried out.
Constant liaison with the Port of London authority and the Environment Agency ensured that the navigable water lanes underneath the bridge also remained open at all times.
A special licence was obtained to carry out the works, and the Port Authority was notified each time the team moved between the bridge spans. A safety boat remained beneath the structure at all times to protect passing river traffic and the operatives working below the bridge.
Inclement weather presented a number of challenges. In particular, extra care had to be taken when using the suspended cradle system.
Working closely with CAN Structures, the site team maximised periods of good weather, using weekends to make up delays. A good relationship with the Port Authority meant that licences and approvals could be obtained quickly at short notice when the weather improved.
The funding for the project came from the privately managed Bridge House Estates, meaning that the City of London was able to complete the refurbishment at no cost to the tax-paying public.
The project was safely completed ahead of the Christmas period ensuring that the bridge could resume its place at the centre of London’s New Year celebrations – looking its best for the occasion.
Matt Smith is head of building and structures at FM Conway.