Work has begun on the £10m project to restore and strengthen Brunel’s Royal Albert Bridge.
According to Mike Palmer, the project manager for Network Rail, “this has been quite a long process, because with a bridge such as this you really have to put a huge level of detail into it. It’s not like some smaller structures where you have a quick look, do an assessment of what needs to be done, then get the job awarded within a year or so; this has taken quite a bit longer.”
Over the next two years the work will be carried out by Taziker Industrial (TI), the appointed contractor. It will take place in five stages, designed not only to minimise disruption to rail operations and local residents but also to prevent damage and undue stress on the landmark structure.
In all, over 100t of new steelwork will be added, 205 original Brunel cross girders will be repaired, 40 diagonal bracings will be strengthened, and 1,800 individual steelwork repairs will be completed. The 50,000 bolts that will be needed have been purpose-designed to look like the existing rivets.
Even getting access to undertake the required repairs is not straightforward, as the main spans are not able to take the weight of traditional scaffold in the amount needed. Instead a proprietary HAKI scaffolding system will be used which is very lightweight with modular panels and flooring that slots into place.
This can be erected around 25 per cent more quickly than standard scaffold, and according to Palmer has several other advantages, not least that “they build into the bay and basically push it out in advance of themselves, meaning there is no leading edge working, no individual putting themselves in harm’s way, and less chance of anything dropping below”.
Around a third of the project costs are taken by the scaffolding, although savings are expected from the speed of erection and the innovative encapsulation system designed to prevent environmental contamination. A particular concern is to minimise the potential wind loading on the structure while the work is being carried out, so encapsulation is restricted to 700m2 at any one time. Unlike traditional plastic sheeting, which has to be cut away if wind speeds reach a critical level, the HAKI system unclips at the top and slides down, allowing it to be raised again when the wind dies.
Rockwool insulation and acoustic screens will be used around the working areas to reduce the noise pollution caused by the grit blasting necessary to remove up to 30 layers of paint. The bridge has been painted over 20 times since it was completed in 1859, but it is expected that the new glass flake paint system, which will be supplied by Leighs Paints, will last a minimum of 25 years and probably longer.
Peter Cook, site manager for TI, explained that 35,000l of paint will be applied in four coats: a zinc primer, a strike coat all around the rivets and edges to build up the minimum thickness, a 500 micron glass flake epoxy intermediate layer, and finally a Goose Grey polyurethane finish coat to match the original colour of the bridge. Cook says the system is similar to that used on the Forth Bridge, “but with a bit more elasticity because this bridge has so much movement”.
Check out E&T's analysis of the project.