Acoustic Emission Monitoring of the Turin Cathedral Bell Tower: Foreshock and Aftershock Discrimination

Abstract

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.

Dynamic Elastic Modulus Variability in Anisotropic and Isotropic Materials: Comparison by Acoustic Emission

“…Thus, for each design of great complexity is necessary to evaluate the typology of the composite that will be used. In contrast, structural members and components need their evaluation during their serviceable life, because of critical conditions of use environmental, seismic, or fatigue, which could cause injuries in humans [1][2][3][4][5] The previous articles [6,7] showed the behavior of the acoustic signals over filament wound composite pipes, and how the position of the signal source or, in this case, the damage occurrence could be interfered with by the interlacing of opposites filaments of roving, regarding the lamination path. Three types of This paper presents the continuation of prior studies, which comprised the verification of the variation that occurred in the dynamic elastic modulus (E 11 ) regarding the three angular winding laminations described, in comparison with an isotropic material.…”

Identifying Optimal Intensity Measures for Predicting Damage Potential of Mainshock–Aftershock Sequences

“…After that, various structural performance indicators, e.g., peak displacement response [5][6][7], behavior factor [8,9], ductility demand [8,[10][11][12][13], input energy [14], damage index [15], and collapse capacity [16], have been adopted to examine the AS effect by subjecting SDOF systems to a suite of real [11,12] or artificial [8][9][10][11]15,16] MS-AS sequences. Recently, multiple degree of free dom systems (MDOFs) have been used to investigate the structural damage caused by MS-AS sequences; the studied structures include steel frames [17] bare and infilled reinforced concrete frames [18][19][20], wood structures [21], equipped structures [22], bridges [23] and other kind of structure [24]. The aforementioned studies compare the structural damage under MSs alone and MS-AS sequences, showing the significant effect of aftershocks on structural performance under earthquakes.…”