Spencer Group bridges a gap with cantilever walkway on cantilever bridge

Bridges specialist Spencer Group is to cantilever a temporary walkway off the side of what is itself a historic cantilever bridge while it carries out major deck replacement works.

Spencer Group is carrying out the design, construction, installation and maintenance of the walkway on the Grade II listed A828 Connel Bridge, near Oban in Scotland.

It said the walkway is expected to be completed in four months, and may be retained, depending on a feasibility study and full public consultation.

It will be cantilevered off the east side of the bridge and will allow for pedestrian and cyclist access during the works to replace the entire deck, which will take place over the next two years.

Luke Fisher, sector lead for bridges and structures at Spencer Group, said: ‘Our designers proposed a traditional steel walkway design that was in-keeping with the heritage of the bridge, clamping to the existing structure where possible, to minimise invasive construction works to the bridge interface points.'

The Connel Bridge was the second largest cantilever bridge in Europe when it was built by Sir William Arrol in 1903. It links the villages of Connel and North Connel, the site of Oban airport. Originally a railway bridge, it was used for both rail and road traffic from 1914, until the railway closed in 1966.

Spencer Group, which is also self-delivering integrated street lighting, said the new steel walkway design will be in-keeping with the heritage of the bridge.

Mr Fisher said that a key element of the project was to minimise the impact on local residents and traffic, both on Connel Bridge and on the A85 below.

‘The original design intent was to install support brackets over the side of the masonry viaducts that would require rope access for installation, meaning traffic management would have needed to be in place on the A85,' he said.

‘We’ve come up with an alternative design solution that mitigates this, with brackets that can be installed from the confines of the bridge parapets. In addition, we’ve developed an installation methodology that allows our teams to install the new walkway progressively from the leading edge, almost eliminating the requirement for traffic management on the bridge during the works.’

Spencer Group is carrying out the project for BEAR Scotland, which operates the trunk road network in the region on behalf of Transport Scotland.

Eddie Ross, BEAR Scotland’s North West representative, said: ‘We appreciate the historical importance of the A828 Connel Bridge and the vital transport link it provides to local communities.

‘This project will allow teams to install a temporary footway on the east side of Connel Bridge, in advance of the deck replacement works which are scheduled to take place next year. The temporary walkway will maintain a route across the bridge whilst the bridge deck is replaced, as we will need to close the existing footpath and carriageway.’

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