## 5 Results and Discussions
### Displacement Time History  
In the event of car crushing, the RC column experiences lateral deflection. Figure 14 displays the lateral deflection-time history of the columns (C300 and C400) at 1740 mm height for a car impact velocity of 40 km/h. The deflection histories of the columns were obtained for two different cars (Econoline and Explorer). It can be seen that the maximum displacements in the columns for both cars are almost the same. The difference in the maximum displacements is less than 6 percent. These negligible differences in the displacements indicate that the frontal stiffness of similar types of cars is almost the same. It is found from the FE analysis that when the impact velocity is 35 km/h or higher, there is residual deflection in column C300. On the other hand, column C400 did not experience any residual deflection when impact velocity is less than or equal to 40 km/h. The FE results showed that elements at the base of column C300 surpass the plastic yield strength at impact speeds greater than 35 km/h. As a result, at these velocities, the column base undergoes plastic rotation, causing permanent deformation in the column. A similar type of plastic deformation occurs for column C400 when the car impact velocity exceeds 40 km/h. Figure 14: Lateral displacement time histories at 1740 mm height of the columns during the car crash with a velocity of 40 km/h: (**a**) column size 300 \(\times\) 300 mm; (**b**) Column size 400 \(\times\) 400 mm. Figure 13: Effect of crushing height on the impact force. Figure 15 shows the column displacement profile at maximum impact force for columns C300 and C400. Despite the fact that the car collides with the column at the height of 850 mm, the maximum displacement occurs at the height of 1600 to 1800 mm. The displacement profiles of the columns for both car-crashing cases are identical. Figure 15c,d shows the effect of car-crashing velocity on the displacement at 1740 mm height of the column. As anticipated, the column deflection increases with the increase of impact velocity. The column also experiences residual displacement at higher impact velocity, which indicates that the column experiences more damage at higher impact velocity. Figure 15: Deformation profile of column at maximum impact force (V = 40 km/h): (**a**) column size 300 \(\times\) 300 mm; (**b**) column size 400 \(\times\) 400 mm; (**c**) variation in column displacement history with car impact velocity; (**d**) effect of car (Econoline) impact velocity on the maximum displacement of column. Figure 16 shows the effect of reinforcement ratio on lateral displacement at 1740 mm height of columns C300 and C400, as caused by an SUV (Econoline) car impact with a velocity of 40 and 60 km/h, respectively. The axial load was set to the full capacity of the column during the simulation. Column C300 has four longitudinal reinforcements. On the other hand, column C400 has eight longitudinal reinforcements. However, the area of the reinforcement was altered by changing the diameter of the bars. It is found that the maximum displacement of column C300 is reduced with the increase of the reinforcement ratio. A similar phenomenon can also be seen for residual displacement. In the case of column C400, the maximum displacement is slightly decreased as the reinforcement ratio increases. However, there was no significant improvement in the residual displacement at a higher level of enforcement. The average residual displacement of C400 is approximately 1.5 mm, which indicates the plastic damage in the columns. The additional reinforcement increases the axial and flexural capacity of the column. However, the additional longitudinal reinforcement has a minimal contribution to the shear capacity of the RC column. For this reason, after a certain percentage of longitudinal reinforcement, there is no improvement in controlling the lateral displacement of the column against car impact. It is worth mentioning that the impact angle of the car may have an effect on the performance of the RC column.