Why the wiggle in a crowd’s walk can put a wobble in a bridge | Science News


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Why the wiggle in a crowd’s walk can put a wobble in a bridge

Pedestrians tend to sync their steps, resulting in the structure’s big swings

2:00pm, November 10, 2017
Millennium Bridge

SWINGING BRIDGE  When it first opened, crowds on the Millennium Bridge in London (shown) caused the bridge to sway wildly. Scientists have made improved simulations to determine the conditions that lead to such wobbly bridges.

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Some bridges could really put a swing in your step.

Crowds walking on a bridge can cause it to sway — sometimes dangerously. Using improved simulations to represent how people walk, scientists have now devised a better way to calculate under what conditions this swaying may arise, researchers report November 10 online in Science Advances.

When a bridge — typically a suspension bridge — is loaded with strolling pedestrians, their gaits can sync, causing the structure to shimmy from side to side. The new study “allows us to better predict the crowd size at which significant wobbling can appear abruptly,” says mathematician Igor Belykh of Georgia State University in Atlanta.

Engineers might eventually use the researchers’ results to avoid debacles like the

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