The Garisenda Tower in Bologna: Assessing Damage Evolution Over Five years of SHM Using Nonlinear FEM, Fiber Optical Strings, and the AE Technique

The preservation of Historical Constructions is invaluable to safeguarding cultural heritage. To accomplish this task effectively, a deep understanding of the state of health of these constructions (and the factors influencing it) is paramount. In this regard, experimental and numerical methods are valuable tools especially when working in synergy. In this work, we present the newest findings with respect to the state of the health of the Garisenda tower in Bologna. These findings comprise results of nonlinear finite element (FE) analyses of the base of the tower, using the Smeared Crack material model masonry. These numerical results are correlated with experimental data from fiber optic strings (FOS) and Acoustic Emission (AE) sensors, all installed in the base of the tower in 2019. FE thermoelastic analyses allowed us to better understand the cyclic behavior of strains acquired by FOS and the eccentricity of the tower which was monitored by a pendulum. Seasonal cycles are observed and reproduced numerically. In addition, nonlinear numerical analyses are performed to study evolutive damage scenarios due to the increase of the foundation tilt. The diffuse crack pattern observed in the numerical model is compared to the in-situ AE recordings. Different monitoring information and numerical results are integrated to improve the definition of alert thresholds which should help the decision makers to set up prompt and effective public safety measures.