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10" Concrete Col.

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When I was in school, and the code was ACI 318-56, there were minimum sizes 
for square and round columns, with a minimum number of bars in each, 4-#5's 
in square columns, 5-#5's in round columns.  IIRC, the minimum size for 
square columns was 8-inches; and I don't remember the minimum size for round 
columns.

The reason for this was that tests showed that for fewer bars, and/or smaller 
columns, creep and shrinkage caused the reinforcing to yield, or be close to 
yield, under no loading.  Therefore, the reinforcing in the column could not 
contribute to the support of superimposed loads.

While this limitation is no longer in the code, the reason for it is a good 
thing to keep in mind.

Hope this helps.

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

David Bejan Tehranchi wrote:

>>I've noticed in several publications that the smallest listing for round
concrete columns is 12" diameter.   Is there any particular reason for this?

  My situation that the Architect has spec'ed out 12" dia. columns which are
overkill.  Any reason (i.e. code) that 10" diameter wouldn't be allowed?<<