The Millennium Bridge London

Background  It is located between Southwark Bridge and Blackfriars Bridge.  1 st Bridge to be built over the river Thames in over 100 years (1894)  Construction started in 1998  Construction ended 10 th June 2000  2 days after opening the bridge was closed for modification due to heavy swaying  The Bridge was nicknamed the “Wobbly Bridge”

Bridge Design  Price Construction: £18mConstruction: £18m Modifications: £5mModifications: £5m Total cost: £23mTotal cost: £23m  Dimensions: Length: 330mLength: 330m Width: 4mWidth: 4m Height above river at high tide: 10.8mHeight above river at high tide: 10.8m Handrail height: 1.2mHandrail height: 1.2m  Materials Used: Piers: Concrete and steel Cables: 120mm locked coil Decking: Aluminium Handrail: Bead blast stainless steel

What went Wrong  The bridge's movements were caused by a 'positive biofeedback' phenomenon  Slight horizontal force from walking on Bridge.  More people walking, more force  pedestrians locked into the same rhythm of the bridge, increasing the amplitude of the bridge oscillations  The worst of the movement occurred on the central span where the deck was moving by up to 70mm.

Solution  Turned massed Dampers to absorb vertical and horizonatl movement

Solution  Engineers constructed a criss-crossed exo-skeleton between the decking and the cable arms.  This structure acts as a brace  At the centre points of the "x" shaped skeleton there are damping mechanisms to counter lateral movement.