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ACI pile-raft

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I am sending this letter for the third time, but somehow it does not appear on the list. SO I am forwarding it again with some changes and apologies to anyone who may have received it before.Thanks
 
I am doing a pile supported raft per ACI for a 40-storied tower. In the
commentary, R15.5.4  I am required to check punching shear at the column face if the piles are within d/2 of column, but the enhanced limiting shear is not defined. I have an old edition of CRSI, which puts this limit at 32 times root(fc'), which appears way out of sync with current practice outside USA. 

In previous projects, I have used 5MPa (about 700psi) as the limit for ANY shear section when using BS code. A relevent shear limit appears to be minimum of 5.5MPa (about
800psi) or 0.2fc' which is the limiting stress for shear transfer, e.g. in corbels at the face of
support, in ACI.
 
It does not appear to be explicit in the code, but shouldn't this limit apply to RCC sections on all possible shear planes, regardless of whether there are concentrated loads within punching perimeter?

Also, I notice that ACI-318 does not have a reduction factor for concrete shear strength of deep  members like BS8110, or AASHTO-LRFD. Any help will be deeply appreciated?


Syed A Masroor,