Starting from the critical failure inclined section of reinforced concrete beam without stirrups, this study analyzed the force of each part on the critical failure inclined section. Through theoretical derivation and rational simplification, the value of calculation parameters was obtained, and the calculation model of shear capacity of based on mechanical balance for the reinforced concrete beam without stirrups. On the basis of the classical mechanics principle, the model has a clear physical meaning and can better reflect the influences of shear parameters including concrete strength, shear-span ratio, longitudinal reinforcement ratio and size effect, respectively. Then, the prediction accuracy and stability of the proposed shear model were evaluated based on 9 test specimens by comparing with the GB 50010—2010, ACI 318-14, EC 2, JSCE 2007 and Zsutty calculation formula. Finally, the applicability of the proposed model in the calculation of shear capacity of FRP reinforced concrete beams without stirrups was verified. The results show that the proposed model based on mechanical balance can effectively predict the shear capacity of reinforced concrete beams without stirrups and exhibit the shear failure mechanism of beam oblique section. Moreover, the proposed shear model has a higher prediction accuracy and stability, and can better reflect the nonlinear relationship between shear capacity versus shear-span ratio and longitudinal reinforcement ratio. In addition, the predicted results have a consistent stability with the change of shear parameters, so it can be applied to the shear capacity calculation of FRP reinforced concrete beams without stirrups.

In order to investigate the effect of flange on the shear capacity of reinforced concrete (RC) beams without stirrups, this study took into the contribution of compression zone, dowel action, and aggregate interlock in tension zone, and proposed a shear capacity calculation formula for RC beams without stirrups based on the crack sliding model. To verify the accuracy of the formula, the study used the formula and major design codes to calculate the collected experimental data of 444 rectangular beams and 172 T-shaped beams, and the results were compared with the results of major design codes. Five commonly used machine learning algorithms were used for regression analysis on the collected dataset, to verify the fit of each algorithm with a small dataset to analysis on the collected data, and the fitness of each algorithm was validated with a small dataset. The results show that: the shear capacity calculation method proposed by the codes of each country is in good agreement with the test results; compared to the calculation of the codes, the addressed calculation method herein is more accurate and can effectively account for the contribution of the T-beam flange to the shear capacity; the five machine learning models selected in this paper exhibit a desirable accuracy on the test set, and the results show the same trend as calculations; it also demonstrates the applicability of the machine learning models in the calculation of the shear capacity for reinforced concrete beams.