Abstract：To improve the prediction accuracy and stability of the shear capacity of reinforced concrete (RC) shallow beams with web reinforcements, a modified variable-angle truss model considering the contribution of concrete was developed. Firstly, the shear capacity calculation formula of stirrups considering the contribution of concrete is presented based on the variable-angle truss model, and the value of diagonal crack dip angle is determined according to the plasticity lower bound theorems. Secondly, the shear capacity calculation formula considering the contribution of concrete is presented according to the splitting failure mode of RC shallow beam compression zone, and the brittle failure characteristics of concrete are also considered by the size effect coefficient. Finally, the shear capacity provided by the stirrup and concrete is superimposed to establish the shear capacity calculation formula of RC shallow beams with web reinforcement. The prediction accuracy of shear capacity calculation formulas in this study, GB50010, ACI and AASHTO standard are contrastively evaluated based on the database ACI-DAfStb of shear capacity of RC shallow beams with web reinforcement. The results indicate that the proposed shear capacity formula can not only reflect the influence rule of reinforcement ratio, shear span ratio, concrete strength and other shear parameter, but also consider the size effect and the modification of diagonal crack dip angle to the shear capacity. Furthermore, the prediction accuracy and stability of shear capacity are improved when compared with that using the methods in current standards.
