Explaining Why the Millennium Bridge Wobbled

[Celebration]

http://www.sciencenewsdaily.org/story-7807.html

Strogatz, who has studied the collective behavior of biological oscillators from neurons to fireflies, describes each of the factors that contributed to the bridge's swaying in his paper. Cornell graduate student Daniel Abrams is one of the paper's co-authors.

The problem, says Strogatz, was one of crowd dynamics as much as engineering. The bridge surpassed standards for withstanding weight and wind. Every nonhuman element had been tested.

Instead of focusing on the structure, Strogatz examines the strange phenomenon of people unknowingly working together, simply by walking.

..............snip................

"If the people are initially disorganized and random, if a few of them get into sync by accident, the bridge would become unstable," he says. With a certain critical number of pedestrians, the wobbling becomes marked enough to force everyone into stride -- thus compounding the problem.

[RobertSeattle]

1. "Route Step, March"

Old Army command when troops were about to cross a bridge, it tells the troops it is OK (and desired) to not be in step to prevent any strange bridge harmonic issues.

[Orsino]

2. Used anytime the troops have to cover a lot of ground.

Marching in cadence is tiring (requires everyone to use the same pace length and rhythm), and is for looking good. Route step keeps the troops in formation, but is less taxing, and allows the troops to talk, smoke and joke.

But it may be that route step does significantly reduce the risk of harmonic oscillation.

[RobertSeattle]

3. You are correct sir!

Now that I think about it, my memories of it being called most when approaching bridges.

Thanks!