Suspension Bridges

By Murray Bourne, 13 Nov 2004

There have been some embarrassments involving suspension bridges - the Tacoma Narrows bridge in the US spectacularly fell down in the 1940s because when the wind hit it at a certain velocity, it began to oscillate at its natural frequency. It kept vibrating until it shook itself to pieces. The solution was to build bridges which were aerodynamic - so they actually 'flew' when the wind hit. See more at Univ of Washington Library.

More recently, the Millenium Bridge in London suffered from "synchronous lateral excitation" when people started to walk across it. What happened was as they walked, the people felt a sideways motion and then they all started to walk in step - something the designers never expected. The solution was to install dampeners which would dissipate the sideways energy.

So is this more about physics than mathematics? No - the whole problem with maths education has been that it is seen as a bunch of algebraic manipulations, rather than a tool to solve real-world problems, like suspension bridges...

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