Hungerford Bridge and Golden Jubilee Bridges - The New Footbridges

The New Footbridges

The new footbridges were designed by architects Lifschutz Davidson Sandilands with engineers WSP Group. Their construction was complicated by the need to keep the railway bridge operating without interruptions, the Bakerloo Line tunnels passing only a few feet under the river bed, as well as the potential danger of unexploded World War II bombs in the Thames mud. Despite extensive surveys of the riverbed, London Underground was unwilling to accept these risks and preliminary works were stopped in 2000. The design was modified so that the support structure on the north side, which would have been within 15 m (49 ft) of the tube lines, was moved out of the river bed and onto Victoria Embankment. Excavation near the tube lines was carried out when the tube was closed and foundations were hand-dug for additional security.

The 300 m (980 ft) long decks were raised using an innovative method called incremental launching, in which each 50 m (160 ft) long section was pulled across the river using a 250 m (820 ft) long steel truss weighing 300 tonnes. This process was repeated five times until each deck spanned the river, supported by six temporary piers made of steel and concrete. The seven 25-tonne pylons were then raised over the subsequent two weeks. Once the pylons had been installed, the decks were jacked up to enable their connection with the cable stays suspended from the pylons. The concrete deck was then lowered into its final position and the temporary piers and supports were dismantled.

The design of the bridges is complex. Each of the two decks is supported by inclined outward-leaning pylons. The decks are suspended from fans of slender steel rods called deck stays—there are 180 on each deck, made up of over 4 km (2.5 mi) of cable—and are held in position by other rods called back stays. Because the pylons lean, the back stays are under tension. The deck is secured in place by steel collars fitted around (although not supported by) the pillars of the railway bridge; the collars are themselves attached to the bridge's foundations by tie-down rods. The entire structure is thus held in place by exploiting the tensions between the pylons and the various stay rods and struts.

The new bridges won the Specialist category in the Royal Fine Art Commission Building of the Year Award in 2003. It gained a Structural Achievement Award commendation in the 2004 Institution of Structural Engineers awards, and has won awards from the Civic Trust and for its lighting design.