The maximum shear reinforcement ratio of the KCI-12 design code is based on experience and experiment results same as that of the ACI318-14 code, but those of the EC2-04 and CSA-14 codes are based on a truss model. As the maximum yield strength of shear reinforcement of the KCI-12 code was increased from 400 MPa to 500 MPa in 2012, the maximum shear reinforcement ratio of the KCI-12 code needs to be adjusted accordingly. In this study, the maximum shear reinforcement ratio of the KCI-12 code was compared with those of other design codes and the experimental test results. Compared with the experiment test results, the ratio of the KCI-12 design code was too conservative. On the other hand, the proposed simplified equation based on the truss model reasonably predicted the shear failure modes of RC members. The predictive evaluation of the shear strength of the specimens in the range of the proposed equation was similar to that in the range of the maximum shear reinforcement ratio of the KCI-12 code.