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# Re: big dig structural failure - epoxy anchors overhead supporting gravity

• To: seaint(--nospam--at)seaint.org
• Subject: Re: big dig structural failure - epoxy anchors overhead supporting gravity
• From: "Robert Kazanjy" <rkazanjy(--nospam--at)gmail.com>
• Date: Sun, 16 Jul 2006 12:12:00 -0700

I agree it's not damping....that's why he called it "mass damping", acts like damping (reduces response due to dynamic input) but it's a mass effect not a true damping.  Next time I have lunch with him I'll try to get a better explanation.

If the system mass is large & the input force is small (relatively)  the system response to the input will be small.

I can jump into a small boat & give it quite an effect but me jumping onto a large suspended mass will have little effect...

>>>> Bounce at the right frequency and things will really start movin' and shakin.<<<<

but that requires either feedback or luck;  good or bad depending on ones point of view     :)

cheers
Bob

On 7/16/06, Christopher Wright <chrisw(--nospam--at)skypoint.com> wrote:

On Jul 16, 2006, at 12:59 AM, Robert Kazanjy wrote:

> The reason (I think) why it worked was the mass was increased to the
> point where the mass intertial effects were so large that the input
Probably not noticeable compared to the overall deformation and migth
reduce the natural frequency below the point where the diver's bouncing
is way above the system frequency so there isn't much dynamic response.
The effect would look like 'damping' but it isn't. Bounce at the right
frequency and things will really start movin' and shakin.'
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/~chrisw/

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