## 3 Results and Analyses  
### Damage Process of Specimens  
Six eccentrically compressed specimens were tested in this experimental program. Due to spatial constraints and the similarity in experimental parameters among specimens, detailed data presentation and analysis will focus on two representative specimens, C-1 and C-2. C-1 is a sample with the load position 50 mm from the center axis, and C-2 is a sample with the load 100 mm from the center axis. The remaining specimen data were utilized to validate the accuracy of the automated crack classification model. The failure process of eccentrically compressed members typically comprises four distinct phases, as shown in Figure 5:  
* Phase I (Elastic Compression): Inter-particle compression within the concrete aggregate densities the internal structure. Macroscopic cracks are generally absent during this stage. * Phase II (Tensile Crack Initiation and Propagation): Visible cracks initiate on the tension face, penetrating the cross-section and propagating laterally onto adjacent side faces. * Phase III (Crack Widening and Reinforcement Yielding): Cracks on the tension face widen significantly, while propagation continues on the side faces until longitudinal reinforcement in the tension zone yields. * Phase IV (Compressive Zone Failure and Capacity Degradation): Vertical cracks develop in the concrete compression zone. The subsequent yielding of compression reinforcement and crushing of the compressive concrete precipitate a decline in the member's load-bearing capacity. The time points associated with different damage stages and their respective loads are presented in Table 1 to facilitate a comprehensive analysis. The reinforced concrete (RC) column was connected to the loading apparatus via an articulated support at its top end, while its base was fixed directly onto the ground. During loading, constraint against rotation at the base induced progressive rightward inclination in the mid-height and upper regions of the column under applied load. This deformation mode resulted in maximum displacement at the top, accompanied by slight rightward sliding motion at the base. As illustrated in Figure 6, negative displacement values correspond to movement toward the dial indicator. Notably, mid-height displacement (P2) exhibited non-linear progression during loading. This occurred due to partial displacement transfer from the central region to the upper section. Furthermore, specimen C-1 demonstrated distinct mid-height displacement behavior during initial loading: displacement initially increased (leftward) followed by subsequent reduction (rightward), culminating in lower final displacement than specimen C-2. This anomaly stems from C-1's smaller eccentricity, which maintained predominantly compressive stresses throughout most cross-sections during loading. Only \begin{table}
\begin{tabular}{c c c c} \hline \hline  & & **Time (ms)** & **Load (kN)** \\ \hline \multirow{4}{*}{C-1} & Phase I & 0–500 & 0–40 \\  & Phase II & 500–2100 & 40–180 \\  & Phase III & 2100–5200 & 180–316 \\  & Phase IV & 5200–5800 & 316–235 \\ \hline \multirow{4}{*}{C-2} & Phase I & 0–1140 & 0–60 \\  & Phase II & 1140–2470 & 40–160 \\ \cline{1-1}  & Phase III & 2470–3000 & 160–290 \\ \cline{1-1}  & Phase IV & 3000–3600 & 290–220 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Time and load ranges for different stages. Figure 5: Crack initiation process: (**a**) final crack; (**b**) cracks at each stage. Phase I: Specimen C-1 exhibited elevated AE counts yet lower energy emissions, whereas C-2 showed sparse, infrequent AE activity with signal energy intensities typically approximating 10\({}^{-1}\) KpJ. Phase II: C-1 maintained AE count accumulation rates comparable to Phase I but displayed accelerated energy accumulation. Conversely, C-2 demonstrated rapid increases in cumulative AE counts alongside gradual energy elevation. Phase III: Both specimens underwent marked transitions characterized by sustained count accumulation rates but abrupt energy surges.