# Development of Analytical Model for Bonding of CFRP Rod in Concrete Subjected to Cyclic Loads
## 4 Experimental Double Pull-Out Test on G40 Concrete and UHPFRC
### Experimental Test Result Analysis
#### 4.2.3 Strain Gauge Results  
For a thorough testing procedure, accurate and homogenous load transfer was essential. To validate the load transfer uniformity, strain gauges were employed. Three strain gauges (bottom: SG1, middle: SG2, and top: SG3) were installed on the CFRP and connected to the data logger to record strain data (Figure 16). The strain gauge results for G40 concrete and Ultra-High-Performance Fibre-Reinforced Concrete (UHPFRC) are presented in Figures 17 and 18, respectively. The strain behaviour at SG1 and SG3, located at the bottom and top, respectively, exhibits remarkable consistency. However, SG2, positioned in the middle, records the highest strain. The central region of the CFRP rod, near SG3, serves as the yielding point, exhibiting the highest strain increment of 466 and corresponding strain value of 0.0013. Similarly, SG1 and SG3 exhibit peak values of 466 strain increment and strain of 0.00098, respectively. This trendline depicts a gradual increase in strain up to the peak point, followed by a subsequent decline (Figure 17). This  
Figure 14: Time–Force Result: (**a**) G40 Concrete; (**b**) UHPFRC. Figure 15: Force–Displacement Result of G40 Concrete vs. UHPFRC. trend suggests an efficient force transfer between the CFRP rod and concrete interface. Beyond strain increment 1302, the strain reduction indicates debonding. In comparison, UHPFRC outperforms G40 concrete, as illustrated in Figure 18. The peak strain value for UHPFRC reaches an impressive 632 at the middle of the CFRP, demonstrating superior performance. The bottom and top strain gauges (SG1 and SG2, respectively) in UHPFRC exhibit identical behaviour, peaking at 632. The effect of cyclic  
Figure 16: (**a**) Strain Gauges; (**b**) Data Logger; (**c**) Data Collection. Figure 17: Strain–Time Graph of G40 Concrete. Figure 18: Strain–Time Graph of UHPFRC. load, following ACT-24 guidelines, is evident, with an abrupt increase up to peak point No.1, a gradual rise up to peak point No.2, and subsequent strain reduction, indicating diminished CFRP efficiency [23]. The percentage differences clearly demonstrate the remarkable enhancement in force transfer efficiency and sustained cycles for UHPFRC compared to G40 concrete. Notably, UHPFRC exhibits a marked improvement in peak values for SG1 and SG3, with a significant increase from 466 to 632. Similarly, the peak value at SG2 (considered the yielding point) showcases a notable improvement, further supporting the overall superior performance of UHPFRC. Table 10 provides a detailed comparison of Strain Gauge Differences between G40 Concrete and UHPFRC. The peak values, incremental changes, and strains for SG1, SG2, and SG3 are presented for both materials. The data illustrates a substantial percentage difference, with UHPFRC outperforming G40 concrete across all parameters. Comparison and Validation of Experimental and FEM Result for G40 Concrete and UHPFRC Prototype without Interface Element  
To verify and authenticate the obtained results from both experimental and numerical studies, a comparison study has been conducted, with the results tabulated in Table 11 to showcase the differences in performance between UHPFRC and G40 concrete. Table 11 also provides a comparison of experimental results against numerical results for validation purposes. The analysis of the revised table reveals significant discrepancies between experimental and numerical results for both UHPFRC and G40 concrete. In the case of UHPFRC, the experimental force of 41.5 kN is noticeably lower than the numerical force of 70 kN, translating to a substantial 51.12% difference. The accompanying displacement data exhibit an even larger difference of 12.89, highlighting a remarkable deviation in predictions. For G40 concrete, the experimental force of 11.5 kN is significantly lower than the numerical force of 33.6 kN, resulting in a remarkable 98% difference. The associated displacement values further emphasise the substantial disparity, with a 44.15% difference.