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Baraccani, Simonetta
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Baraccani, Simonetta
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- PublicationRestrictedStructural Interpretation of Data from Static and Dynamic Structural Health Monitoring of Monumental Buildings(2017-07)
; ; ; ; ; ; ; ; ; ; ; Structural Health Monitoring (SHM) has a crucial role in the diagnosis and conservation of historical buildings, which are typically characterized by articulated fabrics, constructed over decades using different materials and construction techniques. All these issues lead to very complex structural behaviour whose reliable assessment cannot disregard from a sound interpretation of data from SHM systems. SHM systems can be classified into (i) static systems, monitoring the long term time evolutions of specific quantities (such as amplitude of cracks, inclination of walls, relative distances, etc.) and (ii) dynamic systems, continuously monitoring the dynamic response (velocities, accelerations) in order to gather information upon overall dynamic properties such as natural frequencies, mode shapes and damping ratios. The recorded raw data need to be processed in order to distinguish eventual evolutionary trends from the seasonal and daily variations related to thermal effects. In the present work, a simple unified approach for data interpretation acquired from both static and dynamic SHM systems installed in historical buildings is presented. The approach is aimed at: (i) introducing reference quantities for interpretation of seasonal and daily variations, (ii) providing order of magnitudes of reference quantities and (iii) identifying eventual evolutionary trends which could be related to the presence of potential structural criticalities. The approach is illustrated referring to the “Two Towers” of Bologna.232 12 - PublicationOpen AccessIdentification through seismometric measurements of transients propagating inside the asinelli and garisenda towers (Bologna, Italy), implication on structural(Institute of Structural Analysis and Antiseismic Research School of Civil Engineering National Technical University of Athens (NTUA), 2019-06-24)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The SHM has a very important role in the diagnostic process of cultural heritage buildings, for which generally, the identification of the structural behaviour is affected by many uncer- tainties. The use of ambient vibration tests allow to characterize the dynamic behavior of the structures, providing also information to validate numerical modeling. Moreover, continuous monitoring allows to record streams of seismic ambient noise for long time intervals in order to retrieve the temporal evolution of the structural characteristics and to highlight the re- sponse of them to seasonal variations of environmental parameters (temperature, humidity) and the stresses due to the human activities or to the rapid (daily or weekly) changes in the ambient conditions (temperature, wind velocity and intensity). Three seismic monitoring experiments were performed in 2012, 2013 and 2014 at the Asinelli and Garisenda Towers, two masonry leaning tower built in the center of Bologna (Italy). The aim of this work is to present the results of the analysis of the data recorded by seismic moni- toring that allowed to clearly identify the normal modes of oscillation of the Two Towers. A particular attention was devoted to the identification of transient that, propagating inside the structures, produce beating effects at the top stations. Implication to the structural modeling and to the State of health monitoring are discussed.102 109 - PublicationOpen AccessEditorial: Urban Vibrations & Their Effects Upon Built Heritage: Measurements, Characterization, & Simulations(2020)
; ; ; ; ; ; ; ; ; The numerous sources of vibration that can be recorded in the urban environment both at ground or at the top level of buildings represent a complex and largely unexplored field, whose interpretation could provide valuable information about the buildings’ structural behavior. Urban vibrations may excite constructions in many different ways, generating discomfort, structural damage, and fatigue-related issues affecting their structural health. The characterization of such urban vibrations, and their use for dynamic identification and structural health monitoring, launched an emerging, new cross-disciplinary field known as urban seismology, which engages seismologists, structural engineers, and numerical analysts. The research contributions collected in this special issue deal with this emerging topic.130 10 - PublicationOpen AccessLong-Term Seismometric Monitoring of the Two Towers of Bologna (Italy): Modal Frequencies Identification and Effects Due to Traffic Induced Vibrations(2020)
; ; ; ; ; ; ; ; ; The rise of human activities and the constant increase of vehicles traffic in the cities, and in particular of heavy vehicles such as buses and trucks, causes continues ambient vibrations that can detrimentally affect the conservation of built artifacts, especially historical constructions. The effects of urban vibrations on buildings and monuments are far from being fully investigated. In general, peak levels of traffic-induced vibrations are rarely high enough to be the main cause of heavy structural damages. On the other hand, they contribute to the process of deterioration by adding extra stresses—through fatigue damage accumulation occurring as a result of long periods of exposure to low levels of vibration—or by contributing to soil densification—which can lead to the settlement of building foundations. As such, the estimation of threshold levels above which traffic-induced vibrations may cause damages to monumental buildings requires specific studies including long-time monitoring campaigns. Data from experimental campaign can, indeed, be used to extract information on the variation of dynamic properties of buildings, thus providing valuable pieces of information for a complete knowledge to plan effective preservation interventions. The present work aims to identify the effects of traffic induced urban vibrations on the two Towers of Bologna, particularly prone to fatigue-related damages and close to a high transit of vehicles, through a preliminary analysis of data from several dynamic monitoring campaigns conducted during the last years.156 19