Punching Shear Unbalanced Moments

[CTSeng]

I’ve run across a vague reference stating that I need only look at the unbalanced moment in one direction for the punching shear reinforcement design of flat plate slabs on concrete columns. In the past I’ve designed for the unbalanced moments in both directions and often get more and larger stud rails.

How do others handle this situation? Can anyone point to a some definitive literature to back designing for moments in only one direction? Thanks

 

[WillisV]

See the Concrete International article published in November of 2005 "Checking Punching Shear Strength by the ACI Code" as well as several follow up letters in July of 2006. The Nov. 05 article stated that only one direction at a time needed to be checked. The follow up letters were all various dissenting opinions.

This same article is also posted in the members only section of

http://www.concrete.org

and appears to be the ACI stance on the subject.