Simultaneous Biaxial Bending

[Emot]

I am running into some problems with punching at corner columns. My software designs for the maximum shear stress at a point due to biaxial bending. ACI 421.1 suggests that this may be overly conservative due to stress redistribution. They recommend designing for vu at a distance 0.4d from the max shear stress, but not to reduce more that 15% from the max. Has anyone utilized this before? Are there any other strategies for considering with biaxial moments? There was also a CI article I found on this subject saying the equations were intended for bending in one direction at a time, but I'm still a little uncomfortable neglecting it for a corner column.

Also, I am dealing with a PT slab, so I am not able to take advantage of the reduced gamma v they offer for RC slabs.