Dynamic Testing and Monitoring of Historic Towers for Seismic Damage Detection

Abstract

Abstract. Structural health monitoring (SHM) systems represent an acknowledged low-invasiveness and low-cost solution enabling real time condition assessment of civil structures, providing useful information for preventive conservation and maintenance activities. The various documented successful applications of SHM systems to bridges and large infrastructural systems has recently led many researchers to investigate their effectiveness in the case of monumental and historical buildings, often vulnerable to both anthropogenic a natural (e.g. seismic) hazards. The countries in the Mediterranean Basin are especially committed to this kind of research, being, at the same time, rich of built cultural heritage and highly exposed to seismic and other natural hazards. Among the various types of historic buildings, Italian Cities are especially characterized by an extensive presence of bell and civic masonry towers, which also deserve a special attention because of their slenderness, making them suitably monitored via vibration-based systems, and because of their seismic vulnerability.Framing in the afore-depicted scenario, the authors have started in the last years a research activity on vibration-based permanent SHM of slender historic towers, finalized at the implementation of new approaches for the optimal management of the limited available budgets for conservation and restoration activities. In the present paper the results concerning this activity are presented with specific reference to two study cases in the city of Perugia, Italy: the bell tower of the Basilica of San Pietro and the civic tower called "Torre degli Sciri". The two considered monuments present completely different characteristics and complexities from both structural and architectural points of view, making them worth interesting investigating as typological benchmarks. The work discusses both ambient vibration testing and permanent mon-itoring applications, including considerations regarding the adopted sensing hardware. The feasibility of a rapid post-earthquake damage detection via SHM is finally explored with reference to the study case of the San Pietro bell tower, with particular attention to the recent seismic events.

Synergistic application of operational modal analysis and ambient noise deconvolution interferometry for structural and damage identification in historic masonry structures: three case studies of Italian architectural heritage

“…In order to identify the modal parameters and the travelling pulses of the Sciri Tower, an AVT was carried out on May 22 2017 following the preliminary field tests reported by Kita et al 42 Figure 4(b) shows the monitoring layout, which consisted of 12 highsensitivity (10 V/g) uni-axial PCB 393B12 accelerometers installed at four different heights of the tower, namely, z = 40:5, 33:5, 24:0, 8:4 m. The acceleration data were acquired using a multi-channel data acquisition system (DAQ) model NI CompactDAQ-9184 with NI 9234 data acquisition modules for accelerometers (24-bit resolution, 102 dB dynamic range and antialiasing filters) located at the level z = 36:7 m. The ambient vibrations induced by traffic and wind actions in operational conditions were recorded for 90 min at a sampling frequency of 1652 Hz. Note that an auxiliary coordinate system with axes x 0 and y 0 is indicated in Figure 4(b) to facilitate the description of the mode shapes in the subsequent sections.…”

“…In order to identify the modal parameters and the travelling pulses of the Sciri Tower, an AVT was carried out on May 22 2017 following the preliminary field tests reported by Kita et al 42 Figure 4(b) shows the monitoring layout, which consisted of 12 high-sensitivity (10 V/g) uni-axial PCB 393B12 accelerometers installed at four different heights of the tower, namely, z = 40 . 5 , 33 . 5 , 24 . 0 , 8 . 4 m . The acceleration data were acquired using a multi-channel data acquisition system (DAQ) model NI CompactDAQ-9184 with NI 9234 data acquisition modules for accelerometers (24-bit resolution, 102 dB dynamic range and anti-aliasing filters) located at the level z = 36 . 7 m .…”

Earthquake Performance of a Cultural Heritage Building: The Jesuit College in Dubrovnik, Croatia

“…In the case of historical structures, the availability of input data is often limited either by the incompleteness of the archived documents or because of the impracticality to conduct in-situ experiments while preserving the architectural features. In this context, vibration-based techniques to evaluate the structural dynamic response appears particularly attractive [4][5][6]. In recent years, many studies demonstrate the successful application of Ambient Vibration Tests (AVT) in combination with Finite Element (FE) model updating, for the performance assessment of cultural heritage buildings [7][8][9][10].…”