Title: Garisenda Tower in Bologna (Italy): health monitoring by different non-destructive testing techniques

Authors: Angelo Di Tommaso; Gian Carlo Olivetti; Giuseppe Lacidogna; Stefano Invernizzi; Oscar Borla; Alberto Carpinteri

Addresses: Alma Mater Studiorum Università di Bologna, 40126 Bologna, Italy ' Smart Monitoraggio Italia Srl, 20134 Milano, Italy ' Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, 10138 Torino, Italy ' Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, 10138 Torino, Italy ' Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, 10138 Torino, Italy ' Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, 10138 Torino, Italy

Abstract: In the Garisenda Tower of Bologna, several non-destructive (NDT) techniques are being used to examine structural damage and cracking evolution. The acoustic emission (AE) activity emerging from the masonry structures is analysed and related to surrounding temperature and strain measurements by distributed fibre optic sensors (FOSs). A seismometer was used to monitor low-frequency vibrations propagating across the ground-building foundation interface in order to examine the impact of local seismic activity or heavy vehicle traffic on tower vibration. The obtained data has led to the identification of several sources of AE activity, which apparently indicates the existence of an evolving cracking pattern. A consistent increase in the cumulated function of AE signals suggests that tower damage is caused by more than temperature changes. As a result, the origin of damage can be identified as the material's time-dependent creep behaviour under dead load and its interaction with fatigue generated by thermal fluctuations.

Keywords: non-destructive techniques; acoustic emission; fibre optic sensors; FOSs; seismicity; medieval towers; Italy.

DOI: 10.1504/IJMRI.2024.135248

International Journal of Masonry Research and Innovation, 2024 Vol.9 No.1/2, pp.54 - 66

Received: 12 May 2022
Accepted: 18 Oct 2022
Published online: 03 Dec 2023 *

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