Page Comparison

...

...

Notation

E_c = modulus of elasticity of concrete, psi
E_s = modulus of elasticity of reinforcement, psi
f_c^'₌ specified compressive strength of concrete, psi
f_y = specified yield strength for non-prestressed reinforcement, psi
ε_t = net tensile strain in the extreme layer of longitudinal tension reinforcement at nominal strength, excluding strains due to effective prestress, creep, shrinkage, and temperature
ε_ty = value of net tensile strain in the extreme layer of longitudinal tension reinforcement used to define a compression-controlled section
ϕ ₌ strength reduction factor

...

It is stated in ACI 21.2.4.4 that the value of ϕ for shear will be 0.85 for beam-column joints and diagonally reinforced coupling beams.

...