## 4 Results (Finite-Element Analysis)  
In this section, we illustrate the results of the load-displacement and strain-stress curves. The RC columns reinforced with steel bars are considered as a control group to compare with carbon and glass reinforcement. The load-displacement graphs are shown in Figures 7-14. As seen in these figures, the load capacity of the RC columns reinforced with FRP bars is higher than that reinforced with steel bars. Figure 7 shows the load capacity of group A (In this figure, it can be seen that AC, which is the carbon bar (according to Table 3), has a greater bearing load). As can be seen in this figure, the CFRP model has a higher load capacity compared with the control and GFRP models. Also, the OCFRP, which indicates the optimized model, shows that reducing the bar's diameter from 25 mm to 12 mm has almost the same load capacity of the control and GFRP models. Moreover, Figures 8 and 9 show groups B and C, indicating the rectangular and square cross-section, respectively. As shown in Figure 8, BG has more displacement than BC, BS, and BO. However, due to the greater ductility of steel bars, the maximum displacement value of glass bar specimens is less than it is for steel ones. In this figure, comparing the stress-strain behavior also shows that the CFRP model is more brittle and has higher modulus of elasticity than two others. This phenomenon is due the nature of composite materials. In fact, CFRP material has higher modulus of elasticity and much lower failure strain than GFRP materials. Figure 7: Group A (**a**) Load-Displacement diagram (**b**) Stress-Strain Diagram. Figure 8: Group B (**a**) Load-Displacement diagram (**b**) Stress-Strain Diagram. Figure 10: Group D (**a**) Load-Displacement diagram (**b**) Stress-Strain Diagram. Figure 9: Group C (**a**) Load-Displacement diagram (**b**) Stress-Strain Diagram. Figure 11: Group E (**a**) Load-Displacement diagram (**b**) Stress-Strain Diagram. Figure 12: Group F (**a**) Load-Displacement diagram (**b**) Stress-Strain Diagram. Figure 13: Group G (**a**) Load-Displacement diagram (**b**) Stress-Strain Diagram. Figure 9 demonstrates that FRP bars have higher load and displacement capacity performance. Looking at stress-strain diagrams of this figure indicates that the steel model (control specimen) has a better ductility factor. However, the maximum stress capacity of the control sample (about 26 MPa) is much less than the CFRP model (about 33 MPa). On the other side, the GFRP model has almost 5% more stress capacity than the control sample. In addition, by comparing Figures 10 and 11, which display groups D and E, one can notice that increasing the cross-section dimension can enhance both load capacity and displacement. In fact, by comparing CS to DS, the maximum load capacity is 8576 kN in contrast to 17,505, which confirms the effect of the cross-section. Also, by comparing the results of CC and DC, it can be noted that the maximum load capacity of the mentioned specimens is 14,407 kN and 24,778 kN, respectively. One of the most important issues can be seen in Figures 11 and 12 regarding the group of E and F. As has been shown in Table 1, the cross-section of group E and F are the same at 324 \(\times\) 324 (mm), but the height of group F is twice that of group E (1.4 m compared to 0.7 m). The results are performed according to the stop rate of the loading conditions. This loading rate for models with steel bars was stopped when the bars were at yield, and the concrete is at compression failure. To address this matter for the models in which FRP bars were embedded, simultaneous failure of the bars and concrete is considered, since FRP bars are subjected to brittle behavior in contrast to ductile steel bars. In Figure 13, the load displacement and stress-strain diagrams of group G are shown. In this figure, the CFRP model has about 40 kN load capacity, while the value for control, GFRP and OCFRP is about 30 kN, 24 kN and 28 kN, respectively.