In mid-March, the bridge was closed temporarily across a weekend for a very unusual maintenance task: the replacement of the Clifton articulation span. If you’re wondering what that means, the articulation span is a platform that provides a smooth transit between the road surface on terra firma and the suspended bridge deck. As the bridge deck rises and falls with the movement of wind or traffic, the span gently adjusts to ensure there is no step or lip between the two surfaces.
Replacing a section of the bridge deck in such a short period of time is complex, and requires a great deal of pre-planning, with a team of experts on site ready to rise to the challenge! Here’s what was involved:
Lifting out and replacing the span creates a huge hole in the bridge, which means it’s not possible for traffic to cross. The picture below shows the span being lifted out and revealing the access channel for maintenance, inspection, and drainage which sits below. This can usually only be reached by very flexible and adventurous engineers, so the lift presented a rare opportunity to clean and inspect the channel more thoroughly.
It might be surprising to learn that the deck of the Clifton Suspension Bridge is still made from timber – an unbeatable choice of material even for us today, as it is strong yet flexible. The deck timbers were last replaced in 2008 so are moving toward the end of their working life. With the old timber removed, fresh timber was precisely cut and installed in the frame of the articulation span.
Two layers of timber are required – and to protect them from weathering or other issues caused by water ingress, they are sealed with metal strips. This important step in the process creates a smooth, flat platform just below the surface of the bridge deck.
The timbers are then covered with mesh, which not only provides an extra layer of protection – but also acts as textured surface for fresh tarmac to adhere to. This ensures that the road surface will remain in good condition for drivers for a long time to come.
With fresh road surfacing applied, the job is complete and this work should not need to be repeated until 2051! Despite being a very complex piece of pothole prevention work, we’re pleased to say that the project was completed safely and on time – thank you to drivers for your patience during the closure.
Of course, Clifton Suspension Bridge Trust always maximise the opportunities provided by a road closure to undertake and complete other smaller maintenance tasks! The bridge was bustling all weekend as maintenance crew and contractors undertook other works on our list.