## 5 Conclusions  
In this study, a comprehensive experimental and numerical study was performed to investigate the flexural performance of CFRP prestressed PHC pile. In addition, a simplified approach to predict flexural capacity was proposed based on a parametric study. Based on the experimental and numerical results, the following conclusions can be drawn:  
1. The proposed PHC pile system reinforced with CFRP rods exhibited superior flexural performance compared to PHC pile reinforced with 1420 steel, in terms of flexural capacity and cracking resistance.  
2. The flexural capacity of the CFRP prestressed PHC pile was dominated by the failure modes. The concrete crushing and rupture of CFRP are the two typical failure modes of CFRP prestressed PHC piles under bending. The failure mode was affected by the stress level of the CFRP and concrete strain at the ultimate stage.  
3. The increment of the reinforcement ratio and prestressing level improved the flexural capacity and the cracking resistance of CFRP prestressed PHC piles.  
4. The increment of the elastic modulus improved the flexural capacity of CFRP prestressed PHC piles. However, the high modulus of the CFRP resulted in premature rupture failure of the CFRP rods. It is suggested to perform a stress check according to the analytical approach proposed in this paper.  
5. An analytical approach for the flexural capacity of CFRP prestressed PHC pile was proposed, and 90% accuracy was achieved. The proposed analytical approach offers conservative predictions of flexural capacity.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**FE**} & \multicolumn{2}{c}{**Proposed Approach**} & \multirow{2}{*}{
\begin{tabular}{c} **Deviation Rate** \\ **(\%)** \\ \end{tabular} } \\ \cline{2-2}
**Specimen** & \begin{tabular}{c} **Capacity** \\ **(kN\(\cdot\)m)** \\ \end{tabular} & \begin{tabular}{c} **Failure** \\ **Mode** \\ \end{tabular} & \begin{tabular}{c} **Capacity** \\ **(kN\(\cdot\)m)** \\ \end{tabular} & \
\begin{tabular}{c} **Failure** \\ **Mode** \\ \end{tabular} &
\begin{tabular}{c} **Deviation Rate** \\ **(\%)** \\ \end{tabular} \\ \hline P9-1000-180 & 185 & CC & 167 & CC & \(-10\) \\ P9-1500-180 & 218 & CC & 197 & CC & \(-9.8\) \\ P9-2000-180 & 231 & CC & 226 & CC & \(-4.9\) \\ P9-1500-140 & 196 & CC & 183 & CC & \(-7.6\) \\ P9-1500-200 & 208 & R & 203 & R & \(-2.4\) \\ P9-1500-220 & 207 & R & 203 & R & \(-2.9\) \\ P10-1500-180 & 246 & CC & 229 & CC & \(-7.9\) \\ P12-1500-180 & 291 & CC & 285 & CC & \(-2.1\) \\ \hline \hline \end{tabular} \({}^{a}\)CC\({}^{a}\) is concrete crushing and \({}^{a}\)R\({}^{b}\) is rupture of CFRP.  
\end{table}
Table 5: Analytical results.  
**Author Contributions:** Methodology, X.J.; Software, M.F.; Formal analysis, C.T.; Investigation, C.T. and M.F.; Resources, X.Q.; Data curation, M.F.; Writing--review & editing, X.Q.; Supervision, X.J. and X.Q.; Project administration, X.J.; Funding acquisition, X.J. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The authors gratefully acknowledge the financial supports provided by Natural Science Foundation of China [Grant No. 52278207, 52278206], National Key R&D Program of China [Grant No. 2020 YFD1100403].  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.  
**Acknowledgments:** The help of Zhongfu Carbon Fiber Core Cable Technology Co., Ltd. is highly acknowledged.  
**Conflicts of Interest:** Author [PERSON] was employed by the company Shanghai Horse Construction Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.