Break Your Step!: Lateral Vibration at the Linc

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Apparently, since all 69,000 Birds fans left the Linc at roughly the same time this glorious Sunday, the dynamic load of their combined girth, moving in step, made for some tricky descents down the facility’s ramps. Some described it as feeling like an “earthquake.” It appeared to be a case of lateral vibration or synchronous lateral excitation and a highly typical case. In classic cases the structure’s movement alters peoples’ walking patterns, exacerbating the erratic movement.

The same thing happened at the opening of London’s Millenium Bridge in 2000. For those Eagles fans who had a major freak-out, the Millenium Bridge has an entire section of their site devoted to explaining the problem under “challenge”. There’s even some video of the sway.

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Linc spokesperson Bonnie Grant believes the facility can tolerate these loads but no one should doubt the power of stepping-in-synch. Hence this worst case scenario: “For this reason, armies traditionally “break step” when they march over a bridge. In 1850, the Angers suspension bridge collapsed over the Maine (sic) [Marne] River in Angers, France, as 478 French soldiers marched in step across it, killing 226. Though a storm raged at the time of the accident, experts blame the soldiers’ marching for causing one of the anchoring cables, embedded in concrete, to tear loose.”

Read the whole Village Voice article from which this exerpt comes from — written after momentous loads caused the Brooklyn Bridge to slither in 2003.

L&I has ordered an investigation into the ramps, although the firm who originally designed the Linc, RWDI, tried to minimize movement in the spectator deck.

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