Periodic Reporting for period 1 - CRACK-IT (Numerical CRACK simulation and Identification Techniques)
Reporting period: 2021-02-01 to 2023-01-31
Stone masonry is the construction technique used to build many of Europe’s built heritage: from large and impressive Roman amphitheatres to small and modest dwellings in European cities’ historic quarters. To protect these structures and preserve them for the future generations we need to understand the structural response of stone masonry under diverse loading conditions and to develop the tools for predicting it.
The EU-funded CRACK-IT project aimed at investigating and modelling the seismic response of irregular stone masonry, which is one of the most vulnerable construction typologies against earthquakes. The objectives of the project were: i) to obtain experimental evidence on the seismic response of stone masonry walls of various sizes, ii) to correlate damage due to an earthquake with residual mechanical properties and iii) to develop the numerical tools for the simulation of the structural response of stone masonry walls.
During the project, stone masonry walls of different dimensions were tested in the laboratory under in-plane horizontal actions simulating the loading and boundary conditions within a building during an earthquake. This experimental campaign tested the hypothesis whether walls of different size, due to the distribution of openings within a stone masonry building, have a different seismic response. The results of the experimental campaign provided valuable information on engineering properties (stiffness, force and displacement capacities) that are necessary for the seismic assessment of existing stone masonry structures and the design of new ones. Damage was correlated with the global residual capacity of damaged walls through the extraction of the crack skeletons and widths at different loading states. For the first time, geometrical digital twins of the tested walls were generated. This digital representation of the exact geometry and position of the stones within the wall’s volume allowed to correlate damage with the wall’s micro-structure and opened new possibilities for the validation of numerical modelling approaches for stone masonry structures.
The results of the project bring us one step further in developing the tools for the seismic assessment of irregular stone masonry structures and, hence, the protection of built heritage. Understanding the seismic behavior of stone masonry structures aids to the renewal of the interest for the use of stone masonry as a modern construction technique, contributing to the transition towards a sustainable and circular construction industry.
The EU-funded CRACK-IT project aimed at investigating and modelling the seismic response of irregular stone masonry, which is one of the most vulnerable construction typologies against earthquakes. The objectives of the project were: i) to obtain experimental evidence on the seismic response of stone masonry walls of various sizes, ii) to correlate damage due to an earthquake with residual mechanical properties and iii) to develop the numerical tools for the simulation of the structural response of stone masonry walls.
During the project, stone masonry walls of different dimensions were tested in the laboratory under in-plane horizontal actions simulating the loading and boundary conditions within a building during an earthquake. This experimental campaign tested the hypothesis whether walls of different size, due to the distribution of openings within a stone masonry building, have a different seismic response. The results of the experimental campaign provided valuable information on engineering properties (stiffness, force and displacement capacities) that are necessary for the seismic assessment of existing stone masonry structures and the design of new ones. Damage was correlated with the global residual capacity of damaged walls through the extraction of the crack skeletons and widths at different loading states. For the first time, geometrical digital twins of the tested walls were generated. This digital representation of the exact geometry and position of the stones within the wall’s volume allowed to correlate damage with the wall’s micro-structure and opened new possibilities for the validation of numerical modelling approaches for stone masonry structures.
The results of the project bring us one step further in developing the tools for the seismic assessment of irregular stone masonry structures and, hence, the protection of built heritage. Understanding the seismic behavior of stone masonry structures aids to the renewal of the interest for the use of stone masonry as a modern construction technique, contributing to the transition towards a sustainable and circular construction industry.
The EU-funded project CRACK-IT implemented a multidisciplinary approach based on experimental testing, image and point-cloud processing and numerical modelling for the seismic assessment of irregular stone masonry walls.
The experimental activities included non-destructive and destructive testing, ranging from small scale tests on the stone-mortar interface to large-scale tests of real-sized walls. For the large-scale testing, 9 squat walls of three different heights were tested under quasi-static in-plane shear compression loading. The results of this experimental campaign gave information on the effect of the wall size on the stiffness, force and displacement capacity. Displacement fields, crack patterns and crack widths of the tested walls during the loading procedure were obtained through digital image correlation and machine learning algorithms. This made possible to correlate visual damage (i.e. cracking and crushing) with residual stiffness and strength (force and displacement). Non-destructive tests using sonic pulse velocity were carried out on the surface of all the tested walls. These tests allowed to correlate the elastic properties obtained through non-destructive and destructive tests, such as the dynamic and static elastic modulus. For the small-scale testing, in-situ X-Ray micro-CT scans were carried out during the direct shearing of stone-mortar cylindrical samples with two different surface roughness. In-situ testing in the X-Ray scanner permitted to study the effect of the stone roughness on the fracture process through digital volume correlation.
Geometrical digital twinning of stone masonry walls was possible through the implementation of two pipelines. The first is based on the use of laser-scanning and the second on photogrammetry for the surveying of the stone and wall geometry during the construction process. We used the laser-scanning methodology (developed by IBOIS lab at EPFL) to develop the digital twins of three of the tested walls. Finally, in order to decrease time and increase the accuracy of the reconstruction, we collaborated with Swiss Data Science Center for the development of the second GDT pipeline based on photogrammetry.
The results of the above activities are presented in the scientific community through open source publications in conferences and peer-reviewed journals. All generated data and codes are openly available.
The experimental activities included non-destructive and destructive testing, ranging from small scale tests on the stone-mortar interface to large-scale tests of real-sized walls. For the large-scale testing, 9 squat walls of three different heights were tested under quasi-static in-plane shear compression loading. The results of this experimental campaign gave information on the effect of the wall size on the stiffness, force and displacement capacity. Displacement fields, crack patterns and crack widths of the tested walls during the loading procedure were obtained through digital image correlation and machine learning algorithms. This made possible to correlate visual damage (i.e. cracking and crushing) with residual stiffness and strength (force and displacement). Non-destructive tests using sonic pulse velocity were carried out on the surface of all the tested walls. These tests allowed to correlate the elastic properties obtained through non-destructive and destructive tests, such as the dynamic and static elastic modulus. For the small-scale testing, in-situ X-Ray micro-CT scans were carried out during the direct shearing of stone-mortar cylindrical samples with two different surface roughness. In-situ testing in the X-Ray scanner permitted to study the effect of the stone roughness on the fracture process through digital volume correlation.
Geometrical digital twinning of stone masonry walls was possible through the implementation of two pipelines. The first is based on the use of laser-scanning and the second on photogrammetry for the surveying of the stone and wall geometry during the construction process. We used the laser-scanning methodology (developed by IBOIS lab at EPFL) to develop the digital twins of three of the tested walls. Finally, in order to decrease time and increase the accuracy of the reconstruction, we collaborated with Swiss Data Science Center for the development of the second GDT pipeline based on photogrammetry.
The results of the above activities are presented in the scientific community through open source publications in conferences and peer-reviewed journals. All generated data and codes are openly available.
CRACK-IT contributed to the progress beyond the state of the art in several domains:
- Seismic behavior of irregular stone masonry walls:
The large-scale experimental campaign of the EU-funded project CRACK-IT was the first systematic effort to investigate the size effect on the in-plane seismic response of irregular stone masonry walls. The experimental dataset gives new information related with the stiffness, force and displacement capacity of different wall sizes up to collapse.
- Correlation between damage and residual stiffness and capacity:
CRACK-IT developed a dataset correlating crack propagation and crack width with residual stiffness, force and displacement capacities. While such datasets are valuable for developing tools for the realistic post-earthquake structural assessment of damaged stone masonry buildings, they are scarce in the available literature.
- Geometrical digital twinning of irregular stone masonry walls:
CRACK-IT developed a unique dataset of geometrical digital twins (GDTs) of three of the tested stone masonry walls. The GDTs include the geometry and location of each stone within the wall volume in the form of point clouds and surface meshes. These GDTs increased the exploitation potential of the experimental tests in a way that was not possible until now through: i) the comparison between numerical simulations and experiments for benchmarking numerical modelling techniques, ii) correlation of damage with the wall’s microstructure and iii) estimation of the accuracy of the reconstruction of wall’s sections using non-destructive techniques.
- Applicability of Non-Destructive Tests on irregular stone masonry walls:
CRACK-IT investigated the accuracy of the estimation of the elastic modulus of stone masonry walls from sonic pulse velocity tests through comparison with results from destructive tests. This is dataset shows the limitations and potential of this NDT technique for the mechanical characterization of existing stone masonry walls.
The above output of the project will make possible the more accurate seismic assessment of stone masonry structures with the following socio-economic impact:
i) the protection of human life against seismic actions
ii) the preservation of heritage structures without the loss of heritage value due to inadequate retrofit interventions
iii) the reduction of material resources and costs related with retrofit interventions
- Seismic behavior of irregular stone masonry walls:
The large-scale experimental campaign of the EU-funded project CRACK-IT was the first systematic effort to investigate the size effect on the in-plane seismic response of irregular stone masonry walls. The experimental dataset gives new information related with the stiffness, force and displacement capacity of different wall sizes up to collapse.
- Correlation between damage and residual stiffness and capacity:
CRACK-IT developed a dataset correlating crack propagation and crack width with residual stiffness, force and displacement capacities. While such datasets are valuable for developing tools for the realistic post-earthquake structural assessment of damaged stone masonry buildings, they are scarce in the available literature.
- Geometrical digital twinning of irregular stone masonry walls:
CRACK-IT developed a unique dataset of geometrical digital twins (GDTs) of three of the tested stone masonry walls. The GDTs include the geometry and location of each stone within the wall volume in the form of point clouds and surface meshes. These GDTs increased the exploitation potential of the experimental tests in a way that was not possible until now through: i) the comparison between numerical simulations and experiments for benchmarking numerical modelling techniques, ii) correlation of damage with the wall’s microstructure and iii) estimation of the accuracy of the reconstruction of wall’s sections using non-destructive techniques.
- Applicability of Non-Destructive Tests on irregular stone masonry walls:
CRACK-IT investigated the accuracy of the estimation of the elastic modulus of stone masonry walls from sonic pulse velocity tests through comparison with results from destructive tests. This is dataset shows the limitations and potential of this NDT technique for the mechanical characterization of existing stone masonry walls.
The above output of the project will make possible the more accurate seismic assessment of stone masonry structures with the following socio-economic impact:
i) the protection of human life against seismic actions
ii) the preservation of heritage structures without the loss of heritage value due to inadequate retrofit interventions
iii) the reduction of material resources and costs related with retrofit interventions