## 4 Parametric Study
### Effect of the Outer Fiber Types  
One of the key points of the seismic design of beams reinforced with composite bars is how to choose the suitable FRP type (different FRPs have different elastic moduli, ultimate strengths, and elongation rates). In this paper, three types of FRP fiber, including carbon fiber, basalt fiber and glass fiber, are considered to study the mechanical properties of reinforced concrete beams. When the diameter of inner steel is 12 mm, the number of outer fiber bundles in the composite bar is 30, 50 and 70 respectively. The concrete mechanical performance parameters are assumed to be the same as the beam discussed above. By changing the area of the outer FRP in longitudinal composite bar, the seismic performance of the beam is compared. The BFRP type is CBF13-4000 tex, which is different from the properties of BFRP (2400 tex) in contrast to the test above. The combination of CFRP and GFRP to steel is similar to BFRP. All the types and mechanical properties of the outer fiber in composite bars are cited from test data in [16], shown in Table 5. However, the mechanical properties of FRP in composite bars, such as the ultimate strength and the elongation at break are not the same as the mechanical properties of FRP filament. Generally speaking, the ultimate strength and elongation of composite bars are much less than that of the original fiber, which may be caused by the uneven force of the fiber when the composite bars are stretched. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Specimens**} & \(\mathbf{P_{\alpha}}\)**/**kN** & \(\mathbf{\Delta_{\mathrm{cr}}}\)**/mm** & \(\mathbf{P_{y}}\)**/**kN** & \(\mathbf{\Delta_{y}}\)**/mm** & \(\mathbf{P_{p}}\)**/**kN** & \(\mathbf{\Delta_{p}}\)**/mm** & \(\mathbf{P_{u}}\)**/**kN** & \(\mathbf{\Delta_{u}}\)**/mm** \\ \hline \multirow{3}{*}{S12B43} & test & 7.75 & 1.41 & 31.51 & 11.27 & 53.30 & 57.15 & 30.00 & 58.01 \\  & simulation & 7.78 & 1.30 & 28.45 & 5.20 & 55.08 & 56.00 & 28.42 & 59.50 \\  & Error (\%) & 0.39 & 7.80 & 9.71 & 53.86 & 3.34 & 2.01 & 5.27 & 2.57 \\ \hline \multirow{3}{*}{S12B97} & test & 10.25 & 1.67 & 30.28 & 11.24 & 76.63 & 60.14 & 57.84 & 71.88 \\  & simulation & 9.78 & 1.50 & 32.04 & 5.50 & 84.48 & 63.00 & 57.61 & 71.50 \\ \cline{1-1}  & Error (\%) & 4.59 & 10.18 & 5.81 & 51.07 & 10.24 & 4.76 & 0.40 & 0.53 \\ \hline \hline \multicolumn{2}{c}{\(P_{\mathrm{cr}}\), \(P_{y}\), \(P_{\mathrm{p}}\) and \(P_{\mathrm{u}}\) represent cracking load, yield load, peak load and ultimate load respectively; \(\Delta_{\mathrm{cr}}\), \(\Delta_{y}\), \(\Delta_{\mathrm{p}}\) and \(\Delta_{\mathrm{a}}\) represent corresponding displacements. For specimen S12B97, take the average values of positive and negative skeleton curve as the characteristic values.} \\ \end{tabular}
\end{table} 
Table 4: Comparison between simulation and experimental results for load and displacement at feature points. As shown in Figure 15, the yield displacement and initial stiffness are relatively close for each fiber type of SFCBs concrete beams. With the increase in fiber content, the post-yield stiffness of beam members increases gradually, and the FRP fracture point gradually moves backward. After FRP fracture, the beam load drops sharply. When the fiber content was increased to 70 bundles, the peak load of steel-BFRP reinforced concrete beam was the highest among the three FRP types beam models, about 120 kN. The beam reinforced with steel-GFRP composite bars was second, at 115.58 kN. The beam reinforced with steel-CFRP was last, about 75.80 kN. As the ultimate strain of CFRP is smaller than the other two fiber types, the damage caused by fiber fracture occurs firstly in steel-CFRP components. At this point, the concrete has not reached the ultimate compressive strain and the failure mode is brittle failure. The capacity of CFRP-related beam is smaller than the other two fiber types because the area per bundle is smaller.