## 5 Conclusions  
In this paper, finite element software was used to establish a model of 1 unstrengthened beam and 24 RC beams strengthened with an FRP grid-PCM composite. The influence of different parameters on the shear behavior of the strengthened beams was studied. The actual shear contribution was quantified based on the effective strain of the FRP grid. Finally, a shear behavior capacity formula for RC beams strengthened with an FRP grid-PCM composite was proposed. 1. The established finite element model has high accuracy. The error between the finite element analysis results and the test results is within a reasonable range, indicating that this model can well simulate the shear behavior of RC beams strengthened with FRP grid-PCM composites. 2. Compared with the unstrengthened beams, the shear behavior capacities of all simulated RC beams strengthened with the FRP grid-PCM composite were improved to varying degrees, with the improvement ranging from 4% to 31%, which indicates that the FRP grid plays an important role. 3. As the reinforcement amount of the FRP grid increases, the shear behavior capacity of the strengthened beam increases, and the effective strain of the FRP grid decreases, and this influencing effect gradually weakens. When the reinforcement amount is constant, the combination of small thickness and small spacing is more effective in increasing the shear behavior capacity. As the elastic modulus of the FRP grid \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline
**Beam** & \(b\times h\) & \(f_{g}\) & \(p_{ee}\) & \(\lambda\) & \(t_{g}\) & E & \(\kappa_{g}\) & \(t_{g}\) & \(t_{g}\) & \(t_{g}\) & \(t_{g}\) & \(t_{g}\) & \(t_{g}\) & \(t_{g}\) & \(t_{g}\) \\
**ID** & **(mm\(\times\)mm)** & **(MPa)** & **(\%)** & **(mm)** & **(MPa)** & **(mm)** & **(mm)** & _(m)** & _(m)_ & _(m)_ & _(m)_ & _(m)_ & _(m)_ & _(m)_ & _(m)_ & _(m)_ & _(m)_ & _(m)_ & _(m)_ & _(m)_ \\ \hline S150- & & & & & & & & & & & & & & & & \\ CGM & 250 \(\times\) 400 & 61 & 0.15 & 3.15 & 0.434 & 234,500 & 46 & 0.0047 & 0.0050 & 0.94 & 613.9 & 657.4 & 0.93 \\
[9] & & & & & & & & & & & & & & & \\ \hline BCS & & & & & & & & & & & & & & & \\ [10] & 200 \(\times\) 500 & 34.1 & 0.14 & 2.6 & 2.64 & 100,000 & 100 & 0.0155 & 0.0186 & 0.83 & 757.0 & 626.9 & 1.21 \\ \hline S20-P- & & & & & & & & & & & & & & & \\ G-0 [13] & & & & & & & & & & & & & & & \\ \hline S15-G2 & & & & & & & & & & & & & & & \\ [14] & 180 \(\times\) 300 & 48.2 & 0.21 & 2.85 & 1 & 87,000 & 100 & 0.0035 & 0.0044 & 0.80 & 209.1 & 229.9 & 0.91 \\ \hline PP-G3- & & & & & & & & & & & & & & \\ T15 [23] & & & & & & & & & & & & & & & \\ \hline Bi53R1 & & & & & & & & & & & & & & & \\ [24] & 150 \(\times\) 300 & 31.6 & 0.16 & 2.75 & 4 & 150,000 & 50 & 0.0030 & 0.0029 & 1.03 & 553.2 & 566.3 & 0.98 \\ \hline XL1 [25] & & & & & & & & & & & & & & & \\ \hline \multicolumn{10}{c}{Average value} & & & & & & & & & & & & & & \\ \multicolumn{10}{c}{Standard deviation} & & & & & & & & & & & & & & \\ \hline \multicolumn{10}{c}{Coefficient of variation} & & & & & & & & & & & & & & \\ \hline \end{tabular}
\end{table} 
Table 10: Comparison of calculated values of shear capacity of reinforced beams and experimental values. increases, the shear behavior capacity and the effective strain of the FRP grid increase slightly. As the shear span ratio increases, both the shear behavior capacity and the effective strain of the FRP grid decrease. An increase in the concrete strength and the shear reinforcement ratio can both increase the shear behavior capacity and the effective strain of the FRP grid, but the influence of the shear reinforcement ratio is relatively small. 4. Based on the finite element simulation research, through the regression analysis of the simulation result data, an expression for the effective strain of the FRP grid was established. It was substituted into the ACI 440.2R-08 to quantify its actual shear contribution.