Big Don <bigdon@eskimo.com> writes:
> A classic case of this is the first Tacoma Narrows bridge which was most
> certainly designed to withstand a bumper-to-bumper traffic jam of
> fully-loaded 18-wheelers in both directions in combination with *static
> loads* from some peak windstorm. Yet it failed when lightly loaded in a
> rather moderate garden-variety windstorm. For those who have never seen
> the video of what came to be known as "Galloping Gertie," the wind set up
> a swaying/twisting action in the main span that increased in amplitude
> until the whole works deposited itself in Puget Sound.
>
As I recall from engineering classes in college, the problem with the
bridge was it became a resonant structure, and therefore required very
little energy to get it swinging back and forth. It had to do with the
type of suspension and supports used. The Manhattan Bridge was quickly
"redesigned" to alter it's resonant frequency (no, not to 160 meters).
If you haven't seen the film, find it. It's really something!
--
Barry N. Kutner, W2UP Internet: barry@w2up.wells.com
Newtown, PA Packet Radio: W2UP @ WB3JOE.#EPA.PA.USA.NA
Packet Cluster: W2UP >WB2R (FRC)
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