Both flexural moment and shear strength is controlled automatically according to Codes.
Dimensions of the cross-section should be satisfy Codes. It’s automatically controlled and users are warned if the rule is not satisfied.
International Design Codes
ACI 318-19 : Diaphragm Design Strength per ACI 318-19 with ideCAD
Symbols in ACI 318-19
Mu = factored flexural moment at section, lb
Mn = nominal flexural strength at section, in.-lb
f'c = specified comprehensive strength of concrete, psi
Ac-sh = area of concrete used to determine shear stress, in2
Ag = gross area of concrete section, in2
bw = web width or diameter of circular section, in.
d = distance from extreme compression fiber to centroid of longitudinal tension reinforcement, in.
h = overall thickness, height, or depth of member, in.
s = center-to-center spacing transverse reinforcement, in
Vc = nominal shear strength provided by concrete, lb
Vn = nominal shear strength, lb
Vs = nominal shear strength provided by shear reinforcement, lb
Vu = factored shear force at section, lb