## 3 Analysis of Factors Affecting Flexural Performance of Reinforced Beams
### Modeling of Bending Load Capacity Calculation  
The results of the finite element analysis above found that the type of FRP grid material and the amount of FRP grid reinforcement are the main influencing factors when the simulated beam undergoes peeling damage, so these two factors will be taken into account to propose a formula for calculating the peeling strain of the FRP grid when the simulated beam undergoes peeling damage. Considering that beams with different FRP grid materials selected for reinforcement have different cross-sectional areas, this paper takes the axial stiffness, i.e., the product of the modulus of elasticity of the FRP grid material and the total cross-sectional area of the FRP grid in the latitudinal direction in the fitting \(E_{f}A_{f}\) to represent the difference between the FRP grid material type and the amount of reinforcement. After several attempts, the following relational assumptions are presented in the form of power functions to ensure fitting accuracy:  
\[\varepsilon_{deb}=a\left(E_{f}A_{f}\right)^{b} \tag{16}\]  
In Equation (16), \(a\) and \(b\) is the coefficient to be found; \(\varepsilon_{deb}\) is the FRP grid peeling strain; \(E_{f}\) is the modulus of elasticity of the FRP grid material; and \(A_{f}\) is the total cross-sectional area of the FRP grid in the latitudinal direction. The relationship between FRP grid debonding strain and axial stiffness was plotted in the form of scatter points, and is fitted with Equation (10). The fitting result is shown in Figure 12.  
From Figure 12, the FRP grid peeling strain relation is given as follows:  
\[\varepsilon_{deb}=2.8174\left(E_{f}A_{f}\right)^{-0.6652} \tag{17}\]  
The coefficients are obtained after retaining three significant figures:  
\[\varepsilon_{deb}=2.82\left(E_{f}A_{f}\right)^{-0.665} \tag{18}\]  
The stress-strain distribution in the midspan cross-section of the reinforced beam when debonding failure occurs is shown in Figure 12. For further analysis, the following assumptions are made: (i) during the stressing process, the strains of concrete, reinforcement, and FRP grid in the cross-section of the test beam satisfy the assumption of flat section; (ii) the bond between concrete and reinforcement as well as between the polymer-cement mortar and the FRP grid is reliable, and there is no relative slippage; (iii) the effects of the \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Beam ID**} & **Grid Warp \(\times\) Weft** & **Yield** & **Ultimate** & **Ultimate Load** & **Deflection** & **FRP Grid** & **Failure** \\  & **Spacing/mm** & **Load (kN)** & **Load (kN)** & **Increase Rate (\%)** & **Value (mm)** & **Strain** & **Mode** \\ \hline B3O50-50 & 50 \(\times\) 50 & 164.6 & 211.8 & 51.5 & 21.14 & 0.0163 & D + FR \\ B3O50-100 & 50 \(\times\) 100 & 165.1 & 211.6 & 51.4 & 23.06 & 0.0230 & CC \\ B3O100-50 & 100 \(\times\) 50 & 165.5 & 214.3 & 53.2 & 22.37 & 0.0222 & CC \\ \hline \end{tabular}
\end{table} 
Table 6: Effect of FRP grid geometry on reinforced beams. concrete in the tension zone and polymer-cement mortar on flexural capacity are neglected; (iv) after the concrete cracking, the concrete in the tension zone does not participate in the structural force; (v) the FRP constitutive model is linear before the maximum strain; (vi) the material constitutive relationship between the concrete in the compression zone and the stressed longitudinal reinforcement follows the literature [16]. At this time, the stress and strain distribution of the section is shown in Figure 13, and the mechanical expression of the section is shown in the Formulas (19)-(23).