[ExI] david statue coincidence

[Keith Henson]

Best wishes,

Keith


On Sun, Aug 21, 2016 at 8:37 AM, spike <spike66 at att.net> wrote:
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> From: extropy-chat [mailto:extropy-chat-bounces at lists.extropy.org] On Behalf
> Of William Flynn Wallace
> Sent: Sunday, August 21, 2016 7:58 AM
> To: ExI chat list <extropy-chat at lists.extropy.org>
> Subject: [ExI] david statue coincidence
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> In today's NYTimes:
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> "The world's most famous statue may someday topple, done in by hairline
> cracks in its ankles and tremors from a quake, traffic or millions of
> tourists' feet."
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> Can you hard science guys get moving faster on antigravity, please?
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> Bill
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> No need for mysterious physics BillW; I have an idea, rather two of them,
> neither requiring anti-gravity.  Allow me to offer a mechanical engineer’s
> perspective please rather than a physics-based solution.
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> We know that stone is very strong in compressive load; that stuff is great
> for making mountains.  This explains why nearly all mountains are made of
> it.  Stone is good in shear stress, which is why rock fractures look the way
> they do (review your mechanical engineering books, that chapter on Mohr’s
> Circle and measuring ratios of shear to compressive stress using Cauchy
> stress tensor.)  Marble (and stone in general) is not good at resisting
> bending moment, which is why stone arches are arches instead of one block
> going across horizontally: arches are in compression, straight across stone
> would be in bending stress.
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> But rock is in general terrible at tensile stress, really lousy at that.
> This is why it is never used for tension elements.  The old Greeks were
> smart guys, but all they had for building material was stone.  So… the old
> timers didn’t build any structures anywhere which require tension elements.
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> OK so the real problem here is that David’s ankles are in slight bending
> moment loading, and might fail.
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> First idea: calculate the center of gravity of the sculpture, then slightly
> tilt the base so that both ankles are in compression loading only.  Or get
> it as close as we can.  It is over-constrained, so we can’t get both ankles
> in perfect compression-only loading, but it can be improved by slightly
> tilting the base.  The necessary tilt would scarcely be noticed, and
> tourists would never know Michel didn’t plan it that way to start with,
> perhaps at Mrs. Angelo’s suggestion.
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> Second idea:  Consider what David was about to do in that sculpture.  Faced
> with this enormous adversary (Goliath) most of us would piss.  So, we add on
> a urine stream in the form of structural steel painted yellow to reinforce
> the statue and reduce bending moment at the ankles.
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> spike
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