Vibration-based monitoring of complex architectural heritage buildings

Structural Health Monitoring (SHM) can play an important role in the preservation of architectural heritage, especially when it can support a rapid and reliable assessment of structural damage and degradation. More specifically, vibration-based monitoring may help to predict the dynamic response of a structure during seismic events, as well as the damage mechanisms activated by ground motions. This information will in turn allow the selection and development of effective protection strategies. In the case of heritage buildings, non-invasive techniques are of paramount interest, especially those that can exploit the natural vibration of the structure. However, the monitoring of architectural heritage still raises several unanswered issues, including: i) the complex optimisation problems due to the spatial characters and features of the buildings; ii) the need for distributed sensing systems with optimized configurations; iii) the possible effects of damage degradation on the sensing system’s design. This thesis provided a few theoretical, numerical and experimental answers to the above mentioned questions, proposing solutions that are applicable to a wide range of architectural heritage buildings. Under these premises, two case studies have been selected as representative of different structural typologies: an historic masonry building and a modern heritage architecture in concrete. For masonry structures the “Chiarugi” building, a former neuropsychiatric hospital in Racconigi, has been selected. The Chiarugi is a large multi-wing building characterized by extended crack patterns. The behaviour of this structure has been investigated by means of dynamic tests. The tests were designed so as to maximise: i) the spatial resolution of the experimental modal shapes associated with the main structural movements; ii) information about the parameters that govern the seismic response; iii) the efficiency of the model calibration process to be conducted on the numerical model of the building. Finally, by means of a newly proposed heuristic model-updating, the identified experimental modal properties have been compared to the numerical results, e.g. modal frequencies and shapes. Dynamic tests also provided qualitative information about the severity of the damage in the various wings of the building. As a last step, the novel heuristic method for model updating was compared with standard modelupdating techniques for validation. For the case of modern architectural heritage, the vaulted structures built by Pier Luigi Nervi in the Turin Exhibition Centre were assumed to represent a relevant and challenging example, especially in view of defining their optimal sensor configurations. The optimal sensor placement criteria, in such complex and peculiar structures, were chosen so as to include the possible damage in nonstructural elements. In this application, the objective function formulation in the algorithm was modified in order to account for the damage progression in the infill walls. In fact, the numerical analyses have shown that these elements, when they undergo seismic damage or degradation, may significantly affect the global dynamic response, and consequently the optimal monitoring configurations