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Demolition of a footbridge over the A3, which was constrained by environmental concerns, the proximity of the replacement bridge and service protection requirements.
The bridge was removed over two road closures to suit the project programme.
Client: National Highways
Principal Contractor: Balfour Beatty
Demolition Contractor: TRU Demolition (formerly Clarke Demolition Company)
Project Overview
The demolition and replacement of the Wisley footbridge was part of the A3/M3 junction and infrastructure improvements. The bridge was demolished at the same time as the Cockrow bridge to minimise the impact of the road possession.
Project Constraints
Access – Due to the need to maintain pedestrian access to the the bridge to allow access to RHS Wisley from a bus stop, the replacement bridge was built before the demolition of the existing footbridge.
Service Protection and Swept Path Analysis– There was a large number of services for both phases that needed to be protected using matts and a swept path analysis was carried out to verify that the plant could do what was required.
Environmental Concerns – The ramp on the second phase was in close proximity to trees in the root protection zone for the trees within RHS Wisley. This created an access challenge in the second phase of the project.
Demolition Methodology
Phase One – Access Ramp Demolition
The first phase was the removal of the access ramp. The way the ramp sits into the span on the A3 required the bridge to be propped before the ramp was lifted out. This was repeated for the lower section.
Learning from previous schemes, identified the need to provide details for loading the cut sections onto the lorry trailer. This ensured the load was sufficiently secured, and the COG was located centrally on the trailer.
Note that the best practice is to break up sections on site and remove it as rubble. However, as the section was only going a short distance, on closed roads, the project team were comfortable moving the section in this way.
Phase Two – A3 Span and North Side Ramp
The second phase was to demolish the span over the A3 and the ramp on the North side. This was done mechanically from the road level.
The works were completed safely and to programme.
