Abstract
Abstract. The use of Non-Destructive Testing (NDT) applied to construction materials allows to highlight and characterize their features, especially in the case of old buildings. The multi-technique high resolution 3D modelling described here is aimed to investigate the conservation state of the central column of a colonnade in the ancient church of Saints Lorenzo and Pancratio, dating to about the second half of the thirteenth century and located in the old town of Cagliari (Italy). This column was considered of interest because its longitudinal axis deviates from its ideal position and it appears the most deteriorated. In this work we describe the integrated application of 3D diagnostic methods, i.e. Terrestrial Laser Scanner (TLS), close range photogrammetry (CRP) and ultrasonic tomography supported by petrographic investigations. They were used to improve the diagnostic process of the conservation state of the investigated column. The TLS technique was supported by CRP to obtain a natural colour texturized 3D model of the column. The geometrical anomaly maps derived from the data of the TLS-CRP survey show the presence of some anomalies worthy of attention. Starting from the 3D reconstruction with previous techniques we planned and implemented a 3D ultrasonic tomography. Ultrasonic tomography proved to be a successful tool in identifying internal defects, as well as the presence of voids and flaws within the materials through the analysis of the propagation of ultrasonic waves. The integration of the three non-invasive techniques supported by petrographical analyses demonstrates its potential in reducing ambiguities since each technique brings its clue to the overall diagnostic process.
Highlights
For an adequate evaluation of the preservation state of the cultural heritage, in recent years the trend has been the use of independent multidisciplinary non-destructive diagnostics (Adamopoulos and Rinaudo, 2019)
In this work we describe the integrated application of 3D diagnostic methods, namely Terrestrial Laser Scanner (TLS), close-range photogrammetry (CRP), and 3D ultrasonic tomography supported by petrographic investigations to produce data that can better visualize and detect defects in the shallow and inner parts of the investigated column and evaluate its state of conservation
The integrated use of different Non-Destructive Testing (NDT) such as TLS, Close Range Photogrammetry (CRP) and ultrasonic tomography corroborated by analyses of the petrographic characteristics of the carbonate materials is of paramount importance to assess the state of conservation of the shallow and deeper zones of the stone materials that make up monuments
Summary
For an adequate evaluation of the preservation state of the cultural heritage, in recent years the trend has been the use of independent multidisciplinary non-destructive diagnostics (Adamopoulos and Rinaudo, 2019). The church dates back to 1263, and shows a dedication to “Sanctum Brancasium [Pancratio]” It is a Romanesque building in calcareous ashlars of medium size with two aisles divided by arches on squat columns (Coroneo et al, 1993). One of these columns has been of prior interest and is the object of this study as its longitudinal axis deviates from its ideal position and presents many material detachments as seen from a preliminary visual inspection
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