Monitoring of Cultural Heritage Buildings in Seismic Area

Architectural heritage groups a wide number of historical constructions such as churches, towers, buildings, bridges, and fortresses, and all of them represent a focal point of the community’s cultural identity. Along the centuries, indeed, a series of actions have been done to preserve their integrity and consequently to enhance the value of the cultural heritage for humanity. Unfortunately, as stated in [Doglioni et al. 1994] [3], [Canuti et al. 2016] [1], [Despotaki et al. 2018] [2], and [Pavia et al. 2021] [4], such architectural cultural heritage is characterized by both structural and typological vulnerabilities often responsible of their poor performance to actions related to extreme events, like earthquakes, being it usually designed for gravity actions. Therefore, the analysis of the seismic vulnerabilities represents a relevant step for choosing and designing proper retrofitting and preservation strategies. An integrated approach is required to know these sources of vulnerability, and different disciplines provide essential contributions: historic investigations of the construction evolution; geometric and material surveys of the constructions; in situ experimental testing and characterization of the materials; structural modelling and seismic analysis. Given the intrinsic difficulties that structural engineers must face when modelling heritage buildings, non-invasive experimental testing methods are valuable tools to provide support in the identification of the structural characteristics of a building. Among the various possibilities for non-invasive experimental tests, this PhD thesis refers to these ones that can characterize the response of the structure under service conditions, commonly referred as Operational Analysis (OA). As common practice these tests are separated in dynamic and static tests. Regarding dynamic tests, the technique and methodology of Operational Modal Analysis (OMA), e.g. [Brinker and Ventura – 2015] [5], [Ranieri and Fabbrocino – 2014] [6], is a very effective tool for structural identification and for model updating to support model-based simulations for the prediction of the seismic response of heritage constructions as well as for the calibrations of advanced seismic upgrading interventions. As regards instead the static tests, e.g. [Kita et all. 2018] [37], [Cavalagli et all. 2017] [43], [Ramos et all. 2012] [38] and [Lorenzoni et all. 2015] [44], together with the dynamic tests, they give a better interpretation of how the structure has been behaves under earthquakes or extreme events making in light the deficiency of the structural system in order to make a more realistic finite element model (FEM) of the structure. In a wider comprehensive view, these analysis techniques provide a better knowledge of the structural response of cultural heritage in their operational conditions, helping in characterizing their seismic response by the evaluation of the modal properties’ changes (i.e., dynamic response), and in characterizing the evolution of kinematic mechanisms such as the over-turning mechanisms (i.e., static response). These results, inside the optical of structural health monitoring, can make in light outcomes both in modal properties and in displacement measures that can suggest potentials phenomenon of damage that may arise. For this reason, the design of embedded monitoring systems that provide either a real-time and periodic information about the structural integrity and performance is a necessary activity to provide an insight on the structural health state of cultural heritage and to characterise the seismic response. This PhD Thesis seeks to design an embedded monitoring system that acquire both dynamic physical and static quantities to identify the structural response over-time, either in operational conditions, and during seismic events including potentially destructive ones, to develop an automatic data analysis process that assesses the properties that describe the response of the structure such as modal properties which natural frequencies, modal shapes and modal damping integrated with static monitoring measures such as displacement measured across the cracks. The innovative procedures developed within this work aims at automatically selecting the seismic evets input that can give a modification on the structural response within the data acquired through continuous monitoring, exploiting information available from the Italian National Institute of Geophysics and Volcanology (INGV) relevant to seismic events. Specifically, the objectives of this PhD thesis are: • to select the most effective monitoring system by considering specific problems concerning historical buildings and the available post processing data techniques to automize the analysis process. • to set up a real-time process that continuously acquire data from different types of sensors and save them in a cloud server for the successive analyses. • to select the seismic events occurred that may have changed the structural response, evaluating the in site expected shaking intensity through a calibration of a specific attenuation law based on data available from Italian National Institute of Geophysics and Volcanology (INGV) relevant to seismic events.to develop a tool that processes the acquired data using an efficient identification algorithm coupled with a clustering analysis. • to validate the developed tools in two case-studies the Portico da Varano of Ducal Palace, and the Santa Maria in Via Church, both located in the city of Camerino, severely stroked by the 2016 central Italy seismic sequence.