## 2 Experimental Program
### Implementation of the Retrofitting Technique Monitoring Framework  
In this study, an EMI-based wireless SHM system was implemented. As mentioned, the EMI method exploits piezoelectric materials, such as PZTs, due to their inherent ability to generate surface electric charges when subjected to mechanical stress while simultaneously experiencing mechanical deformation in response to an electric field. Hence, any conversions observed in the electrical impedance of an attached PZT transducer stem from alterations in the mechanical impedance of the area under examination. The impedance response of the PZT is routinely captured to oversee the structural integrity of a structural component. Variations in the PZT's impedance response measurements within a specified excitation frequency range suggest deterioration in the monitoring element's structural integrity. In the proposed methodology, PZT patches are epoxy attached to the C-FRP ropes to assess the performance of the employed retrofitting technique. The imposed beam's deformation induces stress in the joint of the specimen. As the joint's stress increases with each successive loading step, the formation of cracks is progressively intensified in the joint's body due to the developed shear deformation. The C-FRP ropes undergo tensile strain as they restrain the crack width of the joint's cracks. Thus, a PZT patch mounted in the C-FRP rope can capture the formation of cracks in the restrained concrete and the possible debonding of the synthetic reinforcement. Hence, two PZT transducers were epoxy-bonded in the outer surface of the C-FRP ropes, as illustrated in Figure 5. The PZT transducers were obtained from PI Ceramics and designated as PIC 151. The thickness of the transducers was 5 mm, and their length and width were 20 mm. Furthermore, two WiAMS devices were employed to acquire the EMI response of the PZT transducers. The WiAMS device is a custom-made impedance analyzer initially developed by [PERSON] et al., and it has been widely utilized in numerous studies within the broader literature [67]. At this point, it is worth mentioning that in real-world cases/applications, ensuring long-term stability and reliability requires periodic calibration measurements. These measurements are typically performed on prototype PZTs using impedance analyzer stations that are either certified or calibrated by accredited laboratories. Figure 5: Epoxy-bonded PZTs for SHM of BCJ specimens. Regular calibration is essential to account for any deviations in performance due to environmental factors, material degradation, or other operational stresses. By maintaining accurate and consistent calibration standards, the integrity of the monitoring system is upheld, thus ensuring precise measurements and reliable performance over extended periods of use. Each WiAMS device captures the EMI response of a PZT patch in a predefined frequency range, which was set to 10-250 kHz with a resolution of 1 kHz. The acquired EMI responses of the PZTs were stored in an online database for post-processing. As mentioned above, the EMI measured identifies degradation of the mechanical impedance of the monitoring area through the alterations they cause in the EMI response of an attached PZT transducer. Hence, the EMI response of each PZT patch in the pristine condition of the specimens was captured and used as a baseline. Additionally, to assess the performance of the retrofitting technique, the EMI response of the attached PZT patches was captured after the end of each loading step. The literature review revealed that the EMI method usually employs statistical indices to evaluate and/or quantify the variation in EMI responses induced by alteration of the monitoring area's mechanical impedance. Thus, statistical indices, such as RMSD, can quantify the variation of the EMI response of a PZT patch between the pristine state and the examined state. The equation of the commonly used damage index RMSD is presented in Equation (1).