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Flat plate punching shear question

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When you have a 2-way flat plate slab, ACI 318-02
section   8.4 says that you're allowed to redistribute
(and therefore reduce) some of the negative moments at
the supports (columns). 

ACI 318-02 sections and 11.12.6 say that you
have to account for a portion of the unbalanced moment
at supports being transferred between the slab and
column by eccentricity of shear about the centroid of
the critical (punching shear) section.

My question is this:  I?ve always assumed that the
moment you use when you look at punching shear is
unbalanced moment WITHOUT and moment redistribution
(conservative interpretation).  I?ve always assumed
(conservatively) that the provisions that allow some
negative moment redistribution was for computation of
flexural reinforcing only.  Redistribution of negative
moments relies on connection ductility. Flexural
reinforcing has such ductility. I?ve always treated
punching shear as a phenomenon that has VERY LITTLE
ductility.  ACI 318-02 is somewhat vague on this
point. It states that you can redistribute the
negative moments but does not specifically state if
there are any limitations as to what you can use the
reduced negative moments for (i.e., use them for
?everything? or use them for flexural reinforcing
calculations only.)

I know that I'm taking the conservative path (in not
using the reduced negative moments for my punching
shear calculations), but I am being questioned about
whether I am being too conservative.

Any thoughts or opinions?



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