Articles | Volume 17, issue 7
Research article
04 Jul 2017
Research article |  | 04 Jul 2017

Signal frequency distribution and natural-time analyses from acoustic emission monitoring of an arched structure in the Castle of Racconigi

Gianni Niccolini, Amedeo Manuello, Elena Marchis, and Alberto Carpinteri

Abstract. The stability of an arch as a structural element in the thermal bath of King Charles Albert (Carlo Alberto) in the Royal Castle of Racconigi (on the UNESCO World Heritage List since 1997) was assessed by the acoustic emission (AE) monitoring technique with application of classical inversion methods to recorded AE data. First, damage source location by means of triangulation techniques and signal frequency analysis were carried out. Then, the recently introduced method of natural-time analysis was preliminarily applied to the AE time series in order to reveal a possible entrance point to a critical state of the monitored structural element. Finally, possible influence of the local seismic and microseismic activity on the stability of the monitored structure was investigated. The criterion for selecting relevant earthquakes was based on the estimation of the size of earthquake preparation zones. The presented results suggest the use of the AE technique as a tool for detecting both ongoing structural damage processes and microseismic activity during preparation stages of seismic events.

Short summary
An architectural element of the Royal Castle of Racconigi (northwestern Italy, 17th century) is subjected to nondestructive testing for structural integrity evaluation. It is found that the so-called acoustic emissions – high-frequency vibrations emitted as tiny cracks that develop inside stone and concrete – correlate with those of small nearby earthquakes, suggesting new approaches to monitoring gradual damage accumulation inflicted by such earthquakes on architectural heritage and monuments.
Final-revised paper