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Old 04-06-2003, 11:01 PM
Hermann Cheruscan Hermann Cheruscan is offline
Join Date: Dec 2002
Posts: 463
When troops march across bridges....

What is the term that they use for the vibrations that are caused when troops are marched across bridges? I understand that troops are ordered to route step across bridges, because marching could cause some sort of harmonic disturbance and cause the bridge to collapse. Does anyone know anything about this?
Old 04-06-2003, 11:07 PM
Ringo Ringo is offline
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Join Date: Apr 1999
Location: Houston, TX, USA
Posts: 11,261
You used the term - if the troops march in unison they can create an acoustic energy wave that may be, in its wavelength, a harmonic of the bridge, by virtue of the bridge's length.
Old 04-06-2003, 11:08 PM
Ice Wolf Ice Wolf is offline
Join Date: Jan 2001
Location: Auckland, New Zealand
Posts: 8,379

When an army marches across a bridge, the soldiers are often told to "break step." This is to avoid the possibility that their rhythmic marching will start resonating throughout the bridge. An army that is large enough and marching at the right cadence could start a bridge swaying and undulating until it broke apart.
Old 04-06-2003, 11:19 PM
Gairloch Gairloch is offline
Join Date: Mar 2002
Location: Right there.
Posts: 105
"What is the term that they use for the vibrations that are caused when troops are marched across bridges?"

Darn. Resonance (or any equivalent term) is the right answer, but I wanted to say 'Fear.'

Reason is only the companion of emotion, after all . . .

Old 04-07-2003, 06:26 AM
UncleBill UncleBill is offline
Join Date: Jan 2001
Location: Georgia, Atlanta-ish
Posts: 4,535
Resonance is related to Constructive Interference, if my memory serves.


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