Dynamic and seismic health monitoring of a historic masonry tower

The paper presents some results of the continuous dynamic/seismic monitoring program carried out on the tallest historic tower in Mantua, Italy. This project follows an extensive diagnostic investigation aimed at assessing the structural condition of the tower after the Italian earthquakes of May 2012. A simple dynamic monitoring system was installed in the tower to evaluate the dynamic response especially to the expected sequence of far-field earthquakes and to check the possible evolution of the natural frequencies; the response to ambient excitation has been continuously collected in 1-hour records since late December 2012. The paper summarizes the results of the continuous dynamic monitoring for a period of 8 months, highlighting the effect of temperature on automatically identified natural frequencies, the dynamic response to few seismic events and the key role of permanent dynamic monitoring in the diagnosis of the investigated historic building

One-year dynamic monitoring of a masonry tower

The paper presents some results of the continuous dynamic monitoring program carried out on the tallest historic tower in Mantua, Italy. This project follows an extensive diagnostic investigation aimed at assessing the structural condition of the tower after the Italian earthquakes of May 2012. A simple dynamic monitoring system was permanently installed in the upper part of the building and automatic modal identification was performed. The results allow to evaluate the effects of changing temperature on automatically identified natural frequencies, to verify the practical feasibility of damage detection methods based on natural frequencies shifts and provide clear evidence of the possible key role of continuous dynamic monitoring in the preventive conservation of historic towers

One-year dynamic monitoring of a historic tower: damage detection under changing environment

The paper summarizes the conceptual development of a vibration-based strategy suitable to the structural health monitoring of ancient masonry towers and exemplifies its application in the continuous dynamic monitoring of the tallest historic tower in Mantua, Italy. The presented approach is based on the installation of low-cost monitoring systems (consisting of few accelerometers and temperature sensors) and on the combined use of automated operational modal analysis, regression models to mitigate the environmental effects on identified natural frequencies and multivariate statistical tools to detect the occurrence of abnormal structural changes. The application of the adopted strategy to 15 months of continuously collected experimental data: (1) highlighted the effect of temperature on the automatically identified natural frequencies; (2) demonstrated the practical feasibility of damage detection methods based on natural frequency shifts; (3) provided a clear evidence of the possible key role of continuous dynamic monitoring in the preventive conservation of historic towers

Detecting earthquake-induced damage in historic masonry towers using continuously monitored dynamic response-only data

The paper summarizes the results obtained during the continuous dynamic monitoring of two iconic Cultural Heritage towers -the Gabbia tower in Mantua and the San Pietro bell-tower in Perugia. The two towers, exhibiting different architectural and structural characteristics, were monitored over a similar time period (of about 2 years) by Politecnico di Milano and University of Perugia, respectively, and similar methodologies of automated operational modal analysis and structural health monitoring were adopted by the two Research Teams. During the monitoring, both the towers underwent far-field seismic events which caused slight structural damage. In both case studies, the limited number of accelerometers installed in the towers allows the tracking of automatically identified modal frequencies and to distinguish between environmental and damage effects on the natural frequencies. Furthermore, the occurrence of structural anomalies corresponding to small drops in frequencies is confirmed through multivariate statistical analysis, based on principal component analysis and novelty detection

Posturographic Analysis in Patients Affected by Central and Peripheral Visual Impairment

Abstract: Although vision loss is known to affect equilibrium maintenance, postural control in patients affected by low vision has been poorly investigated. We evaluated postural stability and the ability to use visual, proprioceptive and vestibular information in different low vision patterns. Ten adults with normal vision (NC), fourteen adults affected by central visual impairment (CLV) and eight adults affected by peripheral visual impairment (PLV) were enrolled in our study. Patients underwent visual, vestibular and postural evaluation (bedside examination, Computed Dynamic Posturograophy). Motor Control Tests were performed to analyze automatic postural adaptive re- sponses elicited by unexpected postural disturbances. Clinical evaluations did not show abnormality in all patients. In the Sensory Organization Test, CLV and PLV patients performed more poorly in conditions 3–6 and 3–4, as compared to NC subjects. The condition 5 score was significantly lower in the CLV group with respect to the PLV patients. Composite equilibrium scores demonstrated significant differences between low-vision subjects vs. NC subjects. No differences were found for somatosensorial contribution. Visual afferences showed lower values in all visually impaired subjects, while vestibular contribution was lower in the CLV patients as compared to the NC and PLV patients. MCT latencies were significantly worse in the CLV subjects. In the low-vision patients, postural control was modified with a specific pattern of strategy adaptation. Different modulations of postural control and different adaptive responses seemed to characterize CLV patients as compared to PLV subjects

Post-earthquake dynamic monitoring of a historic masonry tower

The Gabbia Tower, about 54.0 m high and dating back to the XIII century, is the tallest tower in Mantua, overlooking the historic centre listed within the UNESCO Heritage. After the seismic sequence of May 2012, an extensive research program was carried out to assess the structural condition of the tower. The post-earthquake investigation (including direct survey, historic and documentary research, testing of materials and ambient vibration tests) highlighted the poor state of preservation of the upper part of the building and suggested the installation of a dynamic monitoring system to evaluate the response of the tower to the expected sequence of far-field earthquakes and check the possible evolution of the structural behaviour. After a brief description of the tower and the post-earthquake survey, the paper presents the results of the continuous dynamic monitoring for a period of 8 months, highlighting the effect of temperature on automatically identified natural frequencies, the practical feasibility of damage detection methods based on natural frequencies shifts and the key role of permanent dynamic monitoring in the diagnosis of the investigated historic building

On Site Investigation and Health Monitoring of a Historic Tower in Mantua, Italy

The paper describes the strategy adopted to assess the structural condition of the tallest historic tower in Mantua (Italy) after the Italian seismic sequence of May–June 2012 and exemplifies the application of health monitoring using (automated) operational modal analysis. The post-earthquake survey (including extensive visual inspection, historic and documentary research, non-destructive (ND) material testing, and ambient vibration tests) highlighted the poor state of preservation of the upper part of the tower; subsequently, a dynamic monitoring system (consisting of a few accelerometers and one temperature sensor) was installed in the building to address the preservation of the historic structure, and automated modal identification was continuously performed. Despite the low levels of vibration that existed in operational conditions, the analysis of data collected over a period of about 15 months allowed to assess and model the effects of changing temperature on modal frequencies and to detect the occurrence of abnormal behavior and damage under the changing environment. The monitoring results demonstrate the potential key role of vibration-based structural health monitoring, implemented through low-cost hardware solutions and appropriate software tools, in the preventive conservation and the condition-based maintenance of historic towers

One-year dynamic monitoring of a masonry tower

The paper presents some results of the continuous dynamic monitoring program carried out on the tallest historic tower in Mantua, Italy. This project follows an extensive diagnostic investigation aimed at assessing the structural condition of the tower after the Italian earthquakes of May 2012. A simple dynamic monitoring system was permanently installed in the upper part of the building and automatic modal identification was performed. The results allow to evaluate the effects of changing temperature on automatically identified natural frequencies, to verify the practical feasibility of damage detection methods based on natural frequencies shifts and provide clear evidence of the possible key role of continuous dynamic monitoring in the preventive conservation of historic towers

Structural health monitoring of a historic masonry tower

The paper summarizes the results of the first 15 months of continuous dynamic monitoring of the Gabbia tower in Mantua. After the Italian seismic events of May 2012 a wide investigation program was performed on the tower, suggesting the installation of a dynamic monitoring system in the upper region of the building. The continuously recorded signals allowed the automated identification of the natural frequencies of the key vibration modes of the structure and the clear detection of the effects of temperature on the natural frequencies. The study of the correlation between frequencies and temperature also revealed the non-reversible structural effects determined by a far-field earthquake, proving the effectiveness of damage detection techniques based on frequency shifts

Post-earthquake continuous dynamic monitoring of the Gabbia Tower in Mantua, Italy

The Gabbia Tower, about 54.0 m high and dating back to the XIII century, is the tallest tower in Mantua, overlooking the historic centre listed within the UNESCO Heritage. After the seismic sequence of May 2012 in Italy, an extensive research program was carried out to assess the structural condition of the tower. The post-earthquake investigation (including direct survey, historic and documentary research, testing of materials and ambient vibration tests) highlighted the poor state of preservation of the upper part of the building and suggested the installation of a dynamic monitoring system to evaluate the response of the tower to the expected sequence of far-field earthquakes and check the possible evolution of the structural behavior. After a brief description of the tower and the post-earthquake survey, the paper presents the results of the continuous dynamic monitoring for a period of 8 months, highlighting the effect of temperature on automatically identified natural frequencies, the practical feasibility of damage detection methods based on natural frequencies shifts and the key role of permanent dynamic monitoring in the diagnosis of the investigated historic building