Science, Maths & Technology

Millennium Bridge science

Updated Friday 2nd June 2006

The Millennium Bridge is the longest pedestrian suspension bridge in the world. What made it wobble on its first day?

Lynda and Ruth’s Straw Bridge Copyrighted image Icon Copyrighted image Copyright: Production team

The Millennium Bridge is the first bridge to be built across the Thames for a hundred years. It links St Paul's Cathedral and the City of London on the north bank with the new Tate Modern and Shakespeare Globe on the south bank.

The Millennium Bridge spans some 320 metres. The designers call it a marriage of architecture, sculpture and engineering and it cost eighteen million pounds.

But, In spite of all their tests and projections, the engineers were still caught out. After all the excitement on the first day of opening, it wobbled!

Its wobble has a psychological and social explanation as well as a purely mechanical one. This is why:

People synchronise their step in small crowded spaces so they don't bump into each other. This is an automatic action we do without thinking but was not well known among engineers before the bridge opened. The engineers had not made adequate allowances for this action so, when a few people started walking in step, the bridge started swaying. This is because, as well as producing a downward force, the pedestrians were producing a sideways force as their weight transferred from foot to foot. Once a sway starts to develop, other people readjusted their step to walk in time with the sway. This further exacerbates the sideways movement.

All structures are designed to move and engineers had made allowances for the bridge moving. They had also made sure that the natural frequency the bridge would move at - called the resonance - was different to the frequency caused by people walking on the bridge. But the bridge still wobbled.

 

For further information, take a look at our frequently asked questions which may give you the support you need.

Have a question?

Other content you may like

Science, Maths & Technology 

Finding creativity in orbit?

Has space tourist Trevor Beattie got it wrong by suggesting that it's time to send creative people to space?

Article

Science, Maths & Technology 

Millennium Bridge Diary

Science Shack takes on the Millennium Bridge wobble, aided by a Vauxhall Astra and some olive oil. Their diary will take you behind the scenes, warts and all.

Article

Science, Maths & Technology 

Blade Runner: What's the balance between science and fiction?

How does Blade Runner shape up as a piece of work when real scientists look at its workings?

Video
10 mins

Science, Maths & Technology 

Balloon diary

It's just a lot of hot air, really, but the balloon goes up for the Science Shack Team while Adam Hart-Davis gets a lift from their latest project.

Article

Science, Maths & Technology 

Nanotechnology and paper batteries

Chemist James Bruce is excited by the ideas that come when scientists from different disciplines interact.

Article

Science, Maths & Technology 

What would happen if you went into space without a space suit?

If you go out into space without your space suit would you expect to explode, snap-freeze or boil?

Article

Science, Maths & Technology 

60-Second Adventures in Astronomy

Ever wondered where the Universe came from? Or more importantly, where it's headed? Voiced by David Mitchell, this series of 60 second animations examines different scientific concepts from the big bang to relativity, from black holes to dark matter. The series also explores the possibility of life beyond Earth and considers why David Bowie is still none the wiser about life on Mars.

Video
30 mins

Science, Maths & Technology 

Build a thunderstorm predictor

How to build your own thunderstorm predictor.

Activity

Science, Maths & Technology 

Be a Lab Rat

Try some experiments for yourself - we've got some simple Lab Rats science for you to try

Activity