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RE: Question on Spirals in Columns

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Glen Pappas made an excellent observation on the function of spiral

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

Glen Pappas wrote:

. > Don't have the time to refresh myself on research on this, but I believe
. > it has to do w/the fact that higher-yield steel will result in a lower
. > volumetric ratio of transverse reinf., which is a bad thing when the major
. > functions of that reinf are core confinement & lateral support for
. > longitudinal steel.  Also, higher-yield steels have a smaller yield
. > plateau, which is also a bad thing when you're trying to maintain
. > ductility.

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