Characterization, documentation and virtualization of the cultural masonry heritage using wave propagation Non-Destructive Techniques

Project Information

DocumeNDT

Grant agreement ID: 101030275

DOI

10.3030/101030275

Project terminated on 31 March 2023

EC signature date 22 April 2021

Start date 1 January 2022

End date 31 December 2023

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 172 932,48

EU contribution

€ 172 932,48

Coordinated by

AGENCIA ESTATAL CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS
Spain

Periodic Reporting for period 1 - DocumeNDT (Characterization, documentation and virtualization of the cultural masonry heritage using wave propagation Non-Destructive Techniques)

Reporting period: 2022-01-01 to 2023-12-31

Summary of the context and overall objectives of the project

Preservation of heritage buildings requires deep knowledge of architectural and archaeological masonry heritage. The EU-funded DocumeNDT project focused on developing a new methodology to characterize and document the masonry built heritage. The research motivation is that detailed information about the heritage masonry structures is essential for conservation purposes and for making informed decisions on how to intervene. To accomplish the overall research objective, the project has developed new systems and methods to inspect the interior of historical masonry walls.
The inspection of heritage structures is further limited due to the need to follow a non-invasive approach that does not harm the valuable fabric of masonry heritage. The system proposed is based on a fully non-destructive technique called tomography, which is an imaging technique that can produce images of the cross-section of an object based on the transmission of any kind of penetrating wave. The system designed and fabricated by the research team is meant to obtain images of the interior of historic walls based on acoustic (sonic) wave propagation. The research has specifically aimed to automate the inspection, which, currently, is typically performed manually, consuming much time at operational and processing level. That is why their use is limited in practice. The automation was also implemented at the level of processing the data by developing new software.
The project also aimed to characterize masonry material properties, aiming to reveal specific correlations amongst elastic properties, geometry (internal and external), and wave propagation attributes. That is why laboratory tests were performed on masonry walls to determine their modulus of elasticity. During the tests, the novel automated sonic tomography system was used to inspect the walls, which led to obtain tomographic images during loading and evaluate the evolution of damage. The research outcomes highlight the potential of the tomographic technique to obtain quantitative information about the interior of heritage structures.
The project expects to have a significant impact on the conservation community by offering ready-to-use equipment and methods for practitioners for the non-destructive evaluation of historical masonry buildings. More specifically, the novel technology can have a great impact to a variety of professionals that need to be empowered with new tools to perform inspection and document existing buildings: architects, structural engineers (to perform advanced numerical analysis and calculations), archaeologists, surveyors or professionals working in the 3D digitization and virtualization of cultural heritage (to show the interior of structures and the construction technology of the past), etc.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The first activities of the project were dedicated to the development of a novel automated sonic tomography system for the inspection of historical masonry walls. It was designed and fabricated by the research team and consists of a hitting device mounted on a frame that can be placed adjacent to the wall under analysis (Figure 1). The hitting device can move along the surface within the frame area in X, Y and Z directions, generating the sonic wave. The receiving system is a scanning laser vibrometer, able to measure from the distance the displacement of a focused point over time, recording the wave when it reaches the opposite surface (Figure 2).
The system was tested to survey different masonry walls with different interior geometries constructed at the laboratory by a professional stonemason (Figure 3). The construction of the walls was carefully documented, including the generation of detailed photogrammetric models of each single stone before they were placed (Figure 4). As a result, accurate 3D models of the walls were prepared that include their inner configuration. Thus, the resulting tomographic images could be compared with the ground truth. Results obtained show that the system is able to provide relevant information of the internal morphology of the inspected walls.
One main objective of the project was also to characterize masonry material properties using sonic inspections. Therefore, the work included an extensive experimental campaign at the laboratory, consisting of uniaxial compression tests to determine the Young’s modulus of masonry walls. Results were compared with the ones obtained through NDT. During the tests, the novel automated sonic tomography system was used to inspect the wall (Figure 5). Results show that sonic wave propagation is both sensitive to the stress state and damage level in the masonry wall (Figure 6).
The main objective of the DocumeNDT research project was to develop new systems and methods able to provide a precise characterization of the interior morphology of the masonry element, based on different wave attributes that propagate throughout the solid. The research question was whether this data can be reliably correlated with the elastic properties of the masonry, providing essential data for structural analysis and diagnosis. The activities carried out confirmed that there are positive correlations among the parameters. The main outcome was the design and fabrication of the automated sonic tomography system, which is currently available to carry out on-site tomographic surveys of existing buildings. Datasets and software are publicly available in Zenodo.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The main novelty of the proposed sonic tomography system is the automation of the inspection. Conventional methods are extremely time consuming because inspections are carried out manually. That is why their use is limited in practice and focus on local inspections of a few elements. The novel system can collect thousands of data per day of a structural element, which also allows to build 3D tomographic images of entire elements. The project builds upon the base that automating the inspection is necessary to obtain more accurate and reliable results.
Since the automated system allows to perform tomographic inspections within a few minutes, tomographic inspection could be carried out during laboratory tests. The use of sonic tests to evaluate stress level and damage evolution in masonry structures is a novel field of research that was out of the scope of the original project, but results show a promising potential. The findings reveal the potential of using sonic tomography for long term monitoring of historic masonry structures, measuring damage and stress level of masonry components over time.
In conclusion, the project has provided new tools that can be used by professionals in the field of conservation of the built heritage, namely at the inspection and documentation phase. The information obtained with these tools can help professionals to make informed decisions on how to intervene and retrofit existing structures. The rehabilitation and maintenance of the built environment is identified as a key element to reduce the great environmental impacts of the construction sector.

Automated hitting system fabricated to emit the sonic signal

Setup of the laboratory tests including the tomographic inspection during cycles

Workflow for the generation of photogrammetric models of the individual stones

Tomographic images (left) and photogrammetric reconstruction of masonry walls (right)

Progressive decrease of sonic propagation velocities during the tests

Automated sonic tomography system and inspection carried out at the laboratoy