NZS3101 – punching shear in two way slab  

Hi, hoping someone can straighten me out on interpretation of NZS3101.

We’re working to quantify load carrying capacity of an existing 2 way slab on circular columns. Punching shear appears critical.

Clause 9.3.9.4.13 says concrete shall be shear reinforced unless phiVc >> V*. This is in the beams and one way slabs chapter. Obviously for avoidance of brittle failure.

For two way slabs, Clause 12.7 suggests shear steel is to be added to make up for the shear deficit between demand and Vc. It doesn’t appear to link back to 9.3.9.4.13, but logic suggests it should…?

Does 9.3.9.4.13 apply to punching shear in two way slabs? ie. must these be shear reinforced if punching shear demand is over half of concrete shear capacity?

When answering, it would be great if you could refer to clauses or external references that justify your opinion.

Many thanks

Andy Reid