The pair of Golden Jubilee footbridges lie either side of Hungerford Railway Bridge, across the River Thames in central London. Ramboll’s competition-winning design provides a replacement for the single footbridge once attached to the downstream side of the rail bridge. We developed several innovative construction methods at tender stage, and this proved key to our contractor colleagues winning the contract.
We acted as the contractor’s designer throughout the Adopt and Build Contract. We also gained approvals from a range of relevant authorities, including Port of London Authority, the Environment Agency, London Underground Ltd, British Rail and the Ministry of Agriculture, Fisheries & Food.
Design and scope of works
Each footbridge is a seven-span cable-stayed structure hung away from the rail bridge on tapered tubular steel pylons. Span lengths are typically 50m and 53m, and the width of the reinforced concrete decks is 4.7m.
This project also included:
- Construction of new island piers upstream and downstream of Brunel’s Surrey pier
- Refurbishment of the existing two masonry piers from Brunel's suspension bridge of 1845, which are now part of the rail bridge's structure
- New lifts and stairs
- Ship impact protection for the existing rail bridge caissons.
Innovative construction methods
The river foundations are designed to resist ship impacts of 30MN, and we maximised the used of precast components to minimise tidal construction work under the railway bridge. The 450-tonne beams were suspended above high water level and progressively lowered as the ‘in situ’ connections and cutwaters were added.
The decks for the mirror-image footbridges were cast in 50m lengths on purpose-built casting cells located over the southern-most river span. They were then connected to a temporary steel truss and incrementally launched across the river before final connection of the permanent cable stays.
Ground engineering challenges on a complex and historic site
The complex and historic site posed a series of challenges for the ground engineering and foundation design:
- Deep large-diameter bored piles and hand-dug caissons were required, and the design of these involved detailed modelling of their potential interaction with existing bridge substructures.
- Ship impact protection had to be devised for the existing bridge caissons for the accommodation of large vessel impact loading on the new structures without transferring significant loads to the railway bridge.
- The ground at this point is London Clay and Lambeth Group clays, overlain by river bed deposits and a thin layer of river terrace gravels. In one upstream location, the design had to allow for a scour hole up to 16m deep into the clay surface right at the site of the largest substructure element.
- A deep telecommunications tunnel runs under the site and three underground train lines run nearby Extensive negotiations and collaborative work was undertaken with the engineers responsible for the train tunnel safety in relation to the London Underground tunnels, and for the telecommunications tunnel, which runs under the site. Interaction between the new deep bridge foundations and the tunnels was analysed using a combination of closed form elastic solutions and finite element analysis.