The Golden Jubilee Footbridges lie either side of Hungerford Railway Bridge, across the River Thames in central London.The competition-winning design provides a replacement for the single footbridge once attached to the downstream side of the rail bridge. The site is complex and historic — two piers from Brunel's suspension bridge of 1845 are now part of the rail bridge's structure. A deep telecommunications tunnel runs under the site, and three underground train lines run nearby, posing extra challenges for our ground and structural engineers.
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. In addition, new island piers have been constructed upstream and downstream of Brunel’s Surrey pier, and the existing masonry piers refurbished. New lifts and stairs have been provided, and ship impact protection for the existing rail bridge caissons devised.
We developed several innovative construction methods at tender stage, and this proved key to our contractor colleagues winning the contract. We subsequently 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.
One innovation concerns the main river foundations. They 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.
Deep large-diameter bored piles and hand-dug caissons were required. The close proximity of tunnels meant extensive negotiations and collaborative works with the engineers responsible for them, and the design had also to take into account a very large scour hole in the river bed.