Re: pinhole natural frequencies

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From: Paul Doherty (pauld@exploratorium.edu)
Date: Thu Feb 15 2001 - 11:20:23 PST

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Message-Id: <l03110719b6b1db76c164@[192.174.2.173]>
Date: Thu, 15 Feb 2001 11:20:23 -0800
From: Paul Doherty <pauld@exploratorium.edu>
Subject: Re: pinhole natural frequencies

Hi Sally

Theory

You can predict the frequency of oscillation from computer modelling.

Practice

You can record the motion of the bridge etc in response to forces (i.e. a
large truck driving over the bridge, or a wind gust.) You'll see evidence
for resonances in the ringing that occurs after an impulsive load is
applied.

When the amplitudes of the oscillations grow large the simple linear models
we use in class can no longer be applied. We say the response goes
non-linear. This is one of the things that happened at the Tacoma Narrows
bridge.

Paul D

Paul "But it is more complicated than that!" Doherty,
Senior Staff Scientist, The Exploratorium.
pauld@exploratorium.edu, www.exo.net/~pauld

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