## 1 Introduction
[13] found that the angle between the grid and the axis of the longitudinal beam has an impact on the shear behavior capacity of the reinforcement system, and the arrangement angle of 45\({}^{\circ}\) is superior to the 90\({}^{\circ}\) arrangement in terms of restricting the development of diagonal cracks and suppressing the degradation of flexural stiffness. [PERSON] et al. [14] considered the influence of different stirrup spacings and found that as the stirrup ratio increases the ultimate load increases, but the strain of the BFRP grid decreases. Current studies on the shear performance of reinforced concrete beams strengthened with FRP grid-PCM composites mainly focus on experiments. However, experiments are restricted by numerous conditions and have a cumbersome process. It is difficult to precisely control variables, and conducting large-scale comparative experiments requires a substantial investment of time, effort, and financial resources. In contrast, the finite element method can simulate experimental results with relatively high accuracy. Moreover, parametric analysis and other subsequent research based on it are cost-effective and efficient, making it more convenient to carry out follow-up expandable research [15]. [PERSON] et al. [16] conducted a static performance analysis of the concrete damage plasticity model in ABAQUS and verified that this model can accurately simulate the mechanical properties of concrete materials under various stress states, and can also well predict the flexural and shear properties and failure characteristics of reinforced concrete components. [PERSON] et al. [12] conducted finite element analysis based on experimental results and confirmed the effectiveness of introducing a cohesive model of bond slip at the interface between the composite strengthening layer and concrete during modeling. [PERSON] et al. [17] used finite element software to model and analyze the strengthened beams. After verifying the correctness of the model, they carried out research on the influencing factors of the CFRP grid size. Through comparison, it was found that the difference in the shear behavior capacity between the strengthened beam in the numerical simulation and that in the theoretical model is tiny. Existing studies have, respectively, considered the influence of various parameters such as the thickness, spacing, and arrangement angle of the FRP grid, the elastic modulus of the FRP grid, the shear span ratio of the beam, the strength of the concrete, and the shear reinforcement ratio of the strengthened beam. For the beam, each part of the system jointly affects the strengthening effect. However, there are numerous influencing factors, the dominant factors are not clear, and there is a lack of comprehensive analysis. Therefore, it is of great significance to make up for the above deficiencies and obtain a more comprehensive and reliable formula for the shear behavior capacity. This paper uses ABAQUS to conduct numerical simulations of FRP grid-PCM-composite-strengthened RC beams, focusing on the effects of the amount of FRP grid reinforcement, the elastic modulus of the FRP grid, the shear span ratio of the beam, the concrete strength, and the shear reinforcement ratio on the shear performance of the strengthened beams. Based on the effective strain of the FRP grid to quantify its actual shear contribution, a calculation formula of the shear behavior Capacity of RC Beams Strengthened with an FRP grid-PCM composite is proposed, providing a solid theoretical basis for the development of the composite reinforcement technology of this system.