Historical churches, tall ancient masonry buildings, and bell towers are structures subjected to high risks due to their age, elevation, and small base-area-to-height ratio. In this paper, the results of an innovative monitoring technique for structural integrity assessment applied to a historical bell tower are reported. The emblematic case study of the monitoring of the Turin Cathedral bell tower (northwest Italy) is herein presented. First of all, the damage evolution in a portion of the structure localized in the lower levels of the tall masonry building is described by the evaluation of the cumulative number of acoustic emissions (AEs) and by different parameters able to predict the time dependence of the damage development, in addition to the 3D localization of the AE sources. The b-value analysis shows a decreasing trend down to values compatible with the growth of localized micro and macro-cracks in the portion of the structure close to the base of the tower. These results seem to be in good agreement with the static and dynamic analysis performed numerically by an accurate FEM (finite element model). Similar results were also obtained during the application of the AE monitoring to the wooden frame sustaining the bells in the tower cell. Finally, a statistical analysis based on the average values of the b-value are carried out at the scale of the monument and at the seismic regional scale. In particular, according to recent studies, a comparison between the b-value obtained by AE signal analysis and the regional activity is proposed in order to correlate the AE detected on the structure to the seismic activity, discriminating foreshock, and aftershock intervals in the analyzed time series.

中文翻译：

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都灵大教堂钟楼声发射监测：前震和余震判别

历史悠久的教堂、古老的高大砖石建筑和钟楼，由于年代久远、海拔高、底高比小，属于高风险结构。在本文中，报告了应用于历史钟楼的结构完整性评估创新监测技术的结果。本文介绍了对都灵大教堂钟楼（意大利西北部）进行监测的标志性案例研究。首先，通过对声发射 (AE) 累积数量的评估和能够预测时间依赖性的不同参数来描述位于高层砖石建筑较低层的部分结构的损坏演变。除了 AE 源的 3D 定位之外，还包括损伤发展。b 值分析显示了下降趋势，下降到与靠近塔底部的结构部分中局部微观和宏观裂缝的增长相适应的值。这些结果似乎与通过精确 FEM（有限元模型）进行的静态和动态分析非常吻合。在将 AE 监测应用于支撑塔单元中钟声的木制框架期间，也获得了类似的结果。最后，在纪念碑尺度和地震区域尺度上进行基于 b 值平均值的统计分析。特别是，根据最近的研究，提出将 AE 信号分析获得的 b 值与区域活动进行比较，以便将在结构上检测到的 AE 与地震活动相关联，