Acoustic emission monitoring of medieval towers considered as sensitive earthquake receptors

Many ancient masonry towers are present in Italian territory. In some cases these structures are at risk on account of the intensity of the stresses they are subjected to due to the high level of regional seismicity. In order to preserve this inestimable cultural heritage, a sound safety assessment should take into account the evolution of damage phenomena. In this connection, acoustic emission (AE) monitoring can be highly effective. This study concerns the structural stability of three medieval towers rising in the centre of Alba, a characteristic town in Piedmont (Italy). During the monitoring period a correlation between peaks of AE activity in the masonry of these towers and regional seismicity was found. Earthquakes always affect structural stability. Besides that, the towers behaved as sensitive earthquake receptors. Here a method to correlate bursts of AE activity in a masonry building and regional seismicity is proposed. In particular, this method permits to identify the premonitory signals that precede a catastrophic event on a structure, since, in most cases, these warning signs can be captured well in advance.