Punching shear Staad Pro

Hi

Trying to understand the Staad shear stresses: 

1. SQx (local) and SQy(local) being the beam (One -way) shear stresses calculated along strip faces

2. Mxy/ yx is the wood armer moment (twisting) and resultant stress will be again a beam (One -way) stress which will be additive to above. Staad example shows e.g. Sxy =Mxy/ S

Question 1: How does Staad calculate SQx and SQy.

Question 2: How to work our the punching shear (two -way) shear using the above. Or this will have to be done using a reaction and manual calcs.

Thanks.