PSI - Issue 64

A. Di Benedetto et al. / Procedia Structural Integrity 64 (2024) 2254–2262 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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used to highlight areas with complete detachment of the concrete cover and areas with swelling, formed due to the detachment of the concrete cover but not yet fully ejected/detached. The roughness value was associated with each individual point in the point cloud. Figure 5 displays the output of box No. 9 in the plane coordinate system. Specifically, Figure 5a shows the point cloud with associated radiometrically corrected reflectance values, Figure 5b shows the point cloud with associated roughness values. The color scale of the intensity-referred values is qualitative, as the correlation of intensity values with the humidity levels has not been studied. Regarding roughness values, negative values (shades of blue) identify swollen areas, while positive values (shades of red) identify areas with complete detachment of the material or cracks with a width congruent with the resolution of the point cloud. Low intensity values (blue color) shown in Figure 5a indicate areas characterized by a low-reflecting surface, possibly affected by high humidity or a low-reflecting material over the surface. The radiometric correction effectively highlighted areas with low intensity values, distinguishing them from areas with high intensity values. This is important for better segmentation and classification of areas characterized with possible water leakages. Analysis of the roughness values allows recognition of a regular grid pattern in Figure 5b, which may be related to possible damage to the tunnel surface associated with the expulsion of the concrete cover and its swelling. In other cases, deteriorations with orientation different from the regular orientation given by the grid may be traced back to surface damage attributed to other causes. Figure 6 depicts box No. 9 with associated roughness values and traces of the reinforcing steel bars that likely caused the distress. The image is representative, as no study was conducted to verify the correspondence with reality, but the arrangement and size of the distress are consistent with a possible arrangement of the rebar relative to the concrete wall.

Fig. 5. Box No. 9 in the plane coordinate system; (a) Intensity values; (b) Roughness values.

Fig. 6. Box No. 9 with roughness values and traces of reinforcing steel bars.