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RE: TACOMA NARROW BRIDGE

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The bridge spans a narrow part of Puget Sound with fairly high bluffs
(~100 ft) which generates considerable winds.  To deal with the winds,
the original design allowed the bridge to move UP and DOWN with the
wind.  When wind speeds reached 40-50 mph through the narrows, the deck
would oscillate creating "hills and valleys" in the road surface.  Since
these winds are not uncommon, it was also not uncommon to lose sight of
the vehicle ahead of you when crossing the bridge as the vehicle went
over a "hill".  

There are several animation clips of bridge in action.  I'll leave it to
the student to ponder what affects this might have on a bridge and, more
importantly, WHY it was acting this way (e.g. 20-foot waves in the
bridge deck instead of just uplift).

Mark

> Edward wrote:
> 
> DEAR ALL
> Why the Tacoma Narrows Bridge was  nicknamed "galloping gertie"?
> Thanks
> Edward

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