Shear capacity (Columns: EC3 Eurocode)
The shear check is performed at the point under consideration according to clause 6.2.6(1):

for the absolute value of shear force normal to the yy axis, V_{y,Ed}, and

for the absolute value of shear force normal to the zz axis, V_{z,Ed}
The following points should be noted:

No account is taken of fastener holes in the flange or web  see 6.2.6 (7)

Shear is not combined with torsion and thus the resistance is not reduced as per 6.2.6 (8)
Shear buckling
When the web slenderness exceeds 72ε shear buckling can occur in rolled sections. Tekla Structural Designer designs for shear web buckling with accordance to EN 199315:2006.
The following should however, be noted:
 The approach to design assumes a nonrigid end post, this is more conservative than the design that takes the approach assuming a rigid end post.
 Physical support conditions have been assumed to be equivalent to “transverse stiffeners at supports only”.
 All hole cut outs must be small in accordance to section EN 199315:2006 2.3
 If a grade of steel was to be used other than S335, S355 and S460 η will be taken as 1.00 regardless of National Annex.
As we are only designing for the case where no stiffeners are being used, a → ∞ therefore c → ∞ so V_{bf,Rd} → 0, where V_{bf,Rd} is the contribution from the flange  see 5.4(1)
The design assumes negligible contribution to the design shear force V_{Ed} from shear from torque, therefore V_{Ed} is restricted to 0.5 V_{bw,Rd} . Tekla Structural Designer will warn you if this limit is exceeded  see 7.1(1)