Structural Health Monitoring for Preservation and Safeguard of Architectural Cultural Heritage

The preservation of architectural cultural heritage is a complex problem that requires the use of innovative Structural Health Monitoring (SHM) and non-destructive investigation methodologies to assess the integrity of decorated artworks without altering their state of conservation. A complete diagnosis of crack pattern regarding not only the external decorated surface but also the internal support is of great importance due to the criticality of internal defects and damage phenomena, which may suddenly degenerate into irreversible failures Objective of the research is to use the Acoustic Emission monitoring to assess the support of the decorated mural surfaces of the Sacred Mountain of Varallo Renaissance Complex (Italy), developing the application aspects of this technique, which has been widely studied from a theoretical and experimental point of view by some Authors in the safeguard of civil and historical buildings. Moreover, a correlation exists between the regional seismic activity and the AE signals collected during structural monitoring. Therefore, the AET can be also used for the preservation of decorated artworks from the seismic risk. Then, the assessment of damage by electrical resistance measurements on laboratory mortar specimens and terracotta statues belonging to Chapel XVII of the Sacred Mountain of Varallo experiencing different stress conditions is presented. The evolution of damage based on changing electrical resistance shows agreement with theoretical predictions of continuum damage mechanics. The continuum damage models provide also theoretical support to estimate statues’ residual lifetime by correlating in situ electrical resistance measurements with measurements on the laboratory specimens. Finally, the collapse mechanisms of sculpture and building decoration materials is investigated by means of the Overlapping Crack Model and AE technique. These methods permit to explain the size and slenderness effects on the structural ductility and to show that the energy release during the cracks evolution is a surface-dominated phenomenon.