## 7 Conclusions  
In this study, the finite element (FE) model of an axially loaded reinforced concrete column under impact load has been developed. This RC column model and verified car models were used to observe the behavior of RC columns under vehicle impact. The following specific conclusion can be drawn from this study: \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Column (\(\rho\),)**} & **Jacket** & **Longitudinal** & **Shear Capacity** & **Car Impact** & \multirow{2}{*}{**PIF (\(\kappa\)N)**} & \multirow{2}{*}{**DI**} & \multirow{2}{*}{**Observation from FE Analysis**} \\  & **Thickness** & **(mm)** & **in Jacket** & **(\(\kappa\)N)** & **(\(\kappa\)N/h)** & & \\ \hline C400 (1.13\%) & 40 & 8 \(\phi\)10.0 & 960.1 & 60 & 1505.0 & 1.57 & Minor damage in the column and jacket \\ \hline \hline \end{tabular}
* * Shear reinforcement in the jacket is \(\phi\)100\(@\)150 mm.  
\end{table} 
Table 4: _Cont._  
Figure 19: Displacement history of columns with an RC jacket with \(\phi\)100\(@\)150 mm shear reinforcement up to 1.3 m height of the column: (**a**) column size 300 \(\times\) 300 mm and impact velocity of 40 km/h; (**b**) column size 400 \(\times\) 400 mm and impact velocity of 60 km/h. 1. The axially loaded column, with a cross-section of 300 \(\times\) 300 mm\({}^{2}\) (C300), is highly vulnerable under the initial car impact with V = 40 km/h. However, the column with a cross-section of 400 \(\times\) 400 mm\({}^{2}\) (C400) is more stable under initial car impact with V = 40 km/h. This implies that increasing column shear capacity by increasing the size of the columns can improve the impact resistance of the column. 2. Impact forces do not increase linearly with the increase of car initial-impact velocity. Therefore, the estimation of design impact force using the constant stiffness factor proposed by Eurocode 1 is not valid for crashing velocities of more than 20 km/h. 3. There is no significant effect on the impact force if the car-crashing height changes from 850 to 1500 mm. However, the deformation characteristics of the column are varied with the change of impact height. 4. There is an improvement in the column performance against car impact when the longitudinal reinforcement ratio increases from 1% to 2.6%. However, adding more than 2.6% of longitudinal reinforcement, there is a minor improvement in controlling the lateral displacement of the column against car impact. 5. The slender column should be strengthened near the car impact region to avoid any permanent deformation (i.e., internal damage) of the RC column at the parking places of the building. Two systems are proposed in this study, namely, (1) retrofitting the column by AFRP and (2) reinforced concrete jackets (RC jackets) at the column base. 6. The AFRP warp can reduce maximum lateral displacement and residual displacement, but it cannot eliminate the internal damage of the column. On the other hand, the RC jacket is very effective in reducing the lateral displacement and internal damage of the column. Up to an impact velocity of 40 km/h, a 40-mm-thick RC jacket can completely eliminate any permanent damage to column C300. Similarly, with a 40-mm-thick jacket, column C400 can withstand a car impact velocity of 60 km/h without being damaged. 7. By comparing the performance of an AFRP-retrofitted column to a column with an RC jacket, it is found that the AFRP jacket is not as effective as the RC jacket for the column against car impact. 8. Using the damage index specified in Equation (8), the RC jacket can be designed to protect the column against car (SUV type) impact with specific velocities. Project administration and funding acquisition, A.A.F. ; conceptualization, methodology, software, validation, K.M.A.S. ; writing--original draft preparation, writing--review and editing, visualization, supervision, M.A. All authors have read and agreed to the published version of the manuscript.