# Development of Analytical Model for Bonding of CFRP Rod in Concrete Subjected to Cyclic Loads
## 10 Conclusions  
This comprehensive study systematically examined the bonding performance of CFRP rods embedded in conventional concrete (Grade 40) and Ultra-High-Performance Fibre-Reinforced Concrete (UHPFRC) under cyclic loading conditions. The investigation delved into developing an analytical model to accurately predict the interaction between the embedded CFRP rods and the surrounding concrete matrix. Furthermore, the study aimed to elucidate the bonding characteristics of CFRP rods in concrete structures. The key findings of this research yielded compelling insights:  
1. CFRP rods exhibited exceptional bonding performance with UHPFRC, attributed to its superior ductility and strength capacity, particularly in tensile strength. This enhanced bonding significantly minimised cyclic-loading-induced fatigue failure, making UHPFRC-CFRP composites particularly suitable for applications involving heavy cyclic loading, such as parking lots, bridges, and other superstructures. 2. A substantial disparity emerged between the maximum pull-out forces of CFRP rods embedded in UHPFRC and G40 concrete. UHPFRC exhibited a remarkable 4-fold increase in pull-out force compared to G40 concrete. Additionally, UHPFRC demonstrated a significant delay in CFRP yielding time, approximately 650 increments more than G40 concrete. 3. Upon debonding between the CFRP rod and the concrete material, the force experienced a rapid drop followed by oscillations at a lower level, indicating that the CFRP rod retained its structural integrity despite the loss of bond. 4. The findings unequivocally demonstrated the exceptional bonding between UHPFRC and CFRP rods, a testament to the superior ductility of UHPFRC. In contrast, G40 concrete exhibited inferior bonding performance due to its brittle nature, which facilitated CFRP debonding from the concrete base prematurely, even before the CFRP rod reached its yielding point. 5. A comparison between the analytical interface element and the non-analytical interface element revealed a remarkable 10% improvement in displacement and a striking 42% improvement in pull-out force for UHPFRC when utilising the analytical interface element. This significant enhancement underscores the effectiveness of the analytical interface element when combined with UHPFRC. 6. The convergence of numerical and experimental results validated the accuracy of the research methodology and the reliability of the obtained findings. The comparison and analysis of the interface element further corroborated the efficacy of the analytical interface element, which was developed based on experimental data and analytical formulations. This interface element holds immense potential for more precise predictions of CFRP-UHPFRC bonding under cyclic loading conditions. 7. The study also affirmed the capability of smooth CFRP rods to effectively bond with concrete, particularly UHPFRC, which exhibits superior ductility and mitigates the risk of sudden CFRP damage. In conclusion, this ground-breaking research has provided invaluable insights into the bonding performance of CFRP rods in conventional concrete and UHPFRC under cyclic loading. The findings demonstrate the exceptional bonding capabilities of UHPFRC-CFRP composites, making them a promising material for applications subjected to heavy cyclic loading. The developed analytical interface element has proven to be an invaluable tool for accurate predictions of CFRP-UHPFRC bonding behaviour, paving the way for enhanced design and optimisation of reinforced concrete structures incorporating CFRP reinforcement. Conceptualization, A.A. and F.H. ; methodology, A.A. and F.H. ; software, A.A.; validation, A.A. and F.H. ; formal analysis, F.H. ; investigation, A.A. and F.H. ; resources, F.H. ; data curation, A.A.; writing--original draft preparation, A.A.; writing--review and editing, F.H. ; visualization, A.A.; supervision, F.H. ; project administration, F.H. ; funding acquisition, F.H. All authors have read and agreed to the published version of the manuscript.