# Puzzle (was RE: Question on Spirals in Columns)

• To: <seaint(--nospam--at)seaint.org>
• Subject: Puzzle (was RE: Question on Spirals in Columns)
• From: "Gunnar Hafsteinn Isleifsson" <gunnarhi(--nospam--at)post4.tele.dk>
• Date: Tue, 12 Mar 2002 18:34:59 +0100
```Isn't that supposed to be 1"/(2xPI), assuming that the string hovers the same distance above the surface along the entire circumference?

Gunnar Hafsteinn Isleifsson

-----Original Message-----
From: Eric Green [mailto:egreen(--nospam--at)exponent.com]
Sent: Tuesday, March 12, 2002 18:07
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Question on Spirals in Columns

It depends. Is your deck of cards thicker than 1/3.14159 inches?

Eric Green

-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
Sent: Tuesday, March 12, 2002 10:55 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Question on Spirals in Columns

Glen Pappas made an excellent observation on the function of spiral
reinforcement.

As an illustration of the effect of strain on effective confinement, the
following puzzle is offered:

Assume the earth is a perfect sphere and a string is placed around the
sphere
at its equator.  If you increase the length of the string one inch (1"),
would you be able to slip ordinary playing cards under the string around the

entire circumference?

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

<snip>

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