Millennium Bridge ★☆☆

This modern pedestrian suspension bridge between the City and Southwark has quickly become a beloved landmark

This pedestrian concrete-glass-and-steel suspension bridge linking The City with Southwark across the Thames—a lithe, pretty modernist structure in which the suspension cables dip below the walkway at midpoint for unobstructed river views—opened in 2000.

It had to close two days later due to synchronous lateral excitation—so many pedestrians walking on it was causing it to sway, and then everyone correcting their balance in the same direction at once increased that sway in a kind of positive feedback loop. In short, everyone was stumbling around as if drunk.

(This, by the way, is why soldiers have to "break step" shen crossing bridges, since the rhytyms of synchonous marching could cause it to fail.)

The Millennium was quickly nicknamed "the wobbly bridge," and if took two years for engineers to fix the problem by deplying two sets of passive damping systems: The typical tuned mass dampers beneath the deck (which reduce vertical movements), and viscous dampers both under the walkway and around the piers that can absorb that presky lateral movement.

The bridge has been working fine since reopening in early 2002 and—barring an attack by Death Eaters (the bridge had a cameo near the start of Harry Potter and the Half-Blood Prince)—is now perfectly safe to cross, and make for a terribly convenient link between St Paul's and the Tate Modern or Globe Theatre.

The Millenium Bridge by the numbers

• Designers: Architect Sir Norman Foster, sculptor Sir Anthony Caro, engineers Arup
• Opened: 10th June 2000
• Reopened: 27th February 2002
• Construction cost: £18m
• Subsequent modifications: £5m

• Length: 330m
• Width: 4m
• Height above river at high tide: 10.8m

• Piers: Concrete and steel
• Decking: Aluminium
• Handrail: Bead blast stainless steel
• Cables: 120mm locked coil

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