## 5 Discussion  
Based on the parametrical investigation, the energy absorption values are shown in Figure 15. It is clear that group H holds the highest energy absorption due to its dimensions. However, the CFRP bar has better behavior in enhancing energy absorption compared to GFRP. However, the models with steel bars have better energy absorption due to yield and failure points of steel material. To investigate the effect of the cross-section, group D (648 \(\times\) 648 mm) and F (324 \(\times\) 324 mm), and the height of 1.4 m are compared. The energy absorption of DC was about 184% higher than FC. The values were 159 and 56, respectively. Also, DG has 364% more energy absorption value than FG. On the other hand, it is necessary to compare the energy absorption of each group to evaluate the effect of each specimen. In Figure 15, the circular section (Group A: 508 mm) indicates that the AS specimen has more energy absorption than AC and AG, which shows the energy absorption of (153.77 G \(\times\) 10\({}^{6}\)) 63 and 75 percent more than AC and AG, respectively. The specimen AO, which is the optimized sample of AC, has the least value of energy. By comparing group B and D, which have the same height (1.4) and different cross-sections, shows that the square cross-section has a better absorption capability. In other words, comparison between specimens reinforced with steel bars BS (\(315\times 635\) mm) and DS (\(648\times 648\) mm) represents energy absorption of 113.2 G \(\times\) 10\({}^{6}\) and 302.7 G \(\times\) 10\({}^{6}\), respectively. Moreover, the values for energy absorption of BC, BO, DC and DO are 63 G \(\times\) 10\({}^{6}\), 46.12 G \(\times\) 10\({}^{6}\), 161 G \(\times\) 10\({}^{6}\), and 118.86 G \(\times\) 10\({}^{6}\), respectively. Figure 16 shows the seismic factor of specimens. By comparing the seismic factor in Figure 16 between group B (\(315\times 635\) mm) and F (\(324\times 324\), both of which have the same height (1.4 m), it can be seen that the seismic value of BS is 90%higher than that for FS. Furthermore, comparing BG and FG, the seismic value increases with the increase in the cross-section (4.9 and 2.9, respectively). Furthermore, comparison between group E and F, which have the same cross-section \(324\times 324\) mm and different heights (E = 0.7  
Figure 15: Energy absorption of the models. and F = 1.4 m) demonstrates that the higher the height, the lower the seismic factor is. The results from groups E and F show that the seismic factor of FS is 12% higher than ES, while this difference for FG and EG is 33%. In order to compare the effect of cross-section, group D (\(648\times 648\) mm) and F (\(324\times 324\) mm) is chosen. These groups have the same height (1.4 m). The results show that the difference of the seismic factor is too closed, meaning that the cross-section does not have a big influence on the seismic factor (However, the smaller cross-section has better performance in seismic factor). As a case in point, FS is 6.6% more than DS, and this difference for optimized model FO and DO is subjected to have 0.39 and 0.38 which is less than 2.7%. In Figure 17, the stiffness of all models is shown. By comparing groups of steel, carbon and glass bars, it can be declared that carbon bars have better performance in enhancing the stiffness. This may be due to the mechanical properties of carbon fiber reinforced polymer bars. On the other side, the stiffness of steel bars is much higher than that for the glass groups. This is because of the much higher modulus of elasticity of steel (200 GPa) in comparison to 51 GPa for glass bars. In order to evaluate the detailed comparison of stiffness based on cross-section parameters, groups D and F are selected. As \(\backslash\)mentioned above, these group have the same height, but the cross-section of D is twice that of F (The comparison of FS and DS shows that DS has more stiffness than FS (about 153%); also this difference for the carbon and glass model is 120% and 215%, respectively).