# CNN-Based Damage Identification of Submerged Structure-Foundation System Using Vibration Data
## 6 Evaluation of 1-D CNN Models for Untrained Damage Cases
### Discussion on Damage Classification Results  
In Figure 26, the damage classification results of CNN models (shown in Figures 23 and 25) are analyzed for untrained Case 1 using the normal probability density function (PDF) [25]. In Figure 26a, the classification results are depicted in blue (based on time-history data) and red (based on SVD data), while the combined results are shown in green. The shaded region represents the range within one standard deviation \((\sigma)\) from the mean value \((\mu)\) and encompasses 68.8% of the observed values from the central tendency of the prediction. For the untrained damage D2 in Case 1, the damage classification results (see Figures 23a and 25a) were assessed as shown in the PDF chart in Figure 26a. In the figure, the blue-shaded region indicates damage level D3 based on the time-history data. The red-shaded region indicates damage level D1 based on the SVD data. Combining the two results, the green-shaded region indicates that the damage level was classified to D2. Figure 24: Loss values of the 1-D CNN model using partially untrained SVD databanks: (**a**) Case 1; (**b**) Case 2; (**c**) Case 3. For the untrained damage D4 in Case 1 (Figure 26b), the blue-shaded region indicated damage levels D4-D5 based on the time-history data, where the mean value leans towards D5. All classification results based on SVD data indicated damage level D3, hence their normal PDF chart is not shown. The combined results in the green-shaded region indicate that the damage level was classified to D4. For the untrained damage level D6 in Case 1 (Figure 26c), both blue and red-shaded regions indicate damage level D7. Consequently, the green-shaded region for the combined results indicates that the damage level belonged to D7. In Figure 27, the damage classification results (see Figures 23b and 25b) are analyzed for Case 2 using the PDF chart. For the untrained damage level D1 in Case 2, all results indicated the nearest trained damage level D3. Similar to untrained damage level D7 in Case 2 (Figure 27d), all results indicated the nearest trained damage level D6. The normal PDF chart is not shown for these cases. Figure 25: Damage classification results of the 1-D CNN model using partially untrained SVD databanks: (**a**) Case 1; (**b**) Case 2; (**c**) Case 3. The red ticks indicate the correct level of the inflicted damage. When the CNN model could not directly classify data to untrained levels, it returned the classification results in the most similar trained damage levels (green ticks). Figure 27: Probability assessment of damage classification results: Case 2: (**a**) untrained D1; (**b**) untrained D3; (**c**) untrained D5; (**d**) untrained D7. The blue-shaded region shows results based on time-history data, the red-shaded region shows results based on SVD data, and the green-shaded region shows combined results. For the untrained damage level D3 in Case 2 (Figure 27b), the results based on time-history and SVD data indicated damage levels D2 and D4, respectively. Combining the two results, the green-shaded region indicates that the damage level was classified to D3. For the untrained damage level D5 in Case 2 (see Figure 27c), all three shaded regions indicate that the damage level fell between D5 and D6, with the mean value leaning towards D6. In Figure 28, the damage classification results (see Figures 23c and 25c) are analyzed for Case 3. For the untrained damage levels D1 and D2 in Case 3 (see Figure 28a,b), almost all results based on time-history and SVD data indicated the nearest trained damage level D3. The green-shade region indicates that the damage belonged to D3. Figure 28c shows the probability assessment for the untrained damage level D5 in Case 3. In the figure, the blue-shaded region indicates the damage level D7 based on time-history data. The red-shaded region indicates the damage level D4 based on SVD data. Combining the two results, the green-shaded region indicates that the damage level belongs to D5 and D6, with the mean value leaning towards D5.