concrete breakout due to shear ACI318, maximum considered Ca1

[yavier]

Hi all, have anyone know the maximum ca1 where we need to consider shear breakout. this problem have been discussed by several guys in this forum but from what i see there still no exact answear regarding this topic.
for example the shear applied on 30cm wall with edge distance 60cm, with all spec remain the same then my Vb will only depend on (ca1)^1.5
thus
Vb =X(60)^1.5=464.758X force
Avc0 =4.5(60)^2=16200 cm2
Avc =3(60)(30)=5400 cm2
Vbg =Avc/Avc0*Vb=154.919X force
other example is the edge distance increase to 100cm
Vb =X(100)^1.5=1000X force
Avc0 =4.5(100)^2=45000 cm2
Avc =3(100)(30)=9000 cm2
Vbg =Avc/Avc0*Vb=200X force
another example is the edge distance is quite long 300 cm (which shear breakout should not govern, the govern will be steel or pryout)
Vb =X(300)^1.5=5196.152X force
Avc0 =4.5(300)^2=405000 cm2
Avc =3(300)(30)=27000 cm2
Vbg =Avc/Avc0*Vb=346.410X force
the X refer to other value in Vb which remain the same
this result show increase the edge distance from 60 to 300cm (500%) only increase the shear breakout capacity around 200% which is pretty low
is this really correct way? or is there any maximum of ca1 where we do not need to consider shear breakout?