Detekcja zawilgoceń i zmian materiałowych na hiperboloidalnych powłokach chłodni w oparciu o intensywność odbicia wiązki lasera

Abstract

Using a hyperboloidal cooling tower undergoing repair as an example, the paper examines the possibility of using a laser beam reflectance intensity value for the automated detection of perforations in cooling tower shells and the identification of material changes characteristic of the renovated sections of reinforced concrete structures. Due to the specific geometry of the analysed object, the practical application of the value of the fourth coordinate was preceded by its a priori modification. The applied correction solution made it possible to effectively eliminate the influence of the measurement geometry, adjusting the intensity values to correspond to the properties of the scanned surface. In the usability analyses of the corrected radiometric data, the author’s approach to eliminating information loss was applied, assuming the use of the fourth coordinate values as scalar fields. The proposed methodology was verified by comparing the obtained results with those of the commonly used unsupervised classification. The agreement, based on the similarity of the structures, between the results of the image classification and the areas extracted through the segmentation of the scalar fields, representing the corrected values of the laser beam reflectance intensity, confirmed the reliability of the proposed solutions. The usefulness of the radiometric data in 3D space was confirmed by comparing the obtained results with the analyses of the local surface curvature determined by the point cloud based on principal component analysis. Thanks to the segmentation of the scalar fields, the detection of rising damp and corrosion leaks, consistent with the results of the surface condition assessment based on the local curvature analysis, made it possible to specify the degree of degradation of the hyperboloid shell according to a seven-point scale that is consistent with the industry requirements. The values of the fourth coordinate also allowed the identification of material changes caused by the repair, and their comparison with the shell damage contours extracted from the local curvature analysis made it possible to verify the amount of repair mortar used and to assess the validity of the work carried out.