An Innovative SHM Solution for Earthquake-Induced Damage Identification in Historic Masonry Structures

The present Ph.D. Thesis was developed within a collaboration between the Department of Civil and Environmental Engineering of the University of Perugia, Italy, and the Department of Civil Engineering of the University of Minho, Portugal. The main objective of this research work concerned the development and validation of an innovative methodology aimed at the detection, localization and quantification of earthquake-induced damages in historic masonry structures. The high cultural, economic and political value set upon historic buildings spread out all over the world has made the earthquake-induced damage identification, as well as preservation and conservation of architectural heritage, a subject of outstanding importance. The proposed methodology, called DORI, is based on the combination of data-driven, as well as innovative model-based methods, addressing the Damage identification based on Operational modal analysis (OMA), Rapid surrogate modeling and Incremental dynamic analysis (IDA) for Cultural Heritage (CH) masonry buildings subjected to earthquakes. More in detail, the DORI methodology proposes the static-and-dynamic data fusion in the OMA-based damage detection method, and extends it through the introduction and implementation of two independent and complementary innovative model-based methods, for localization and quantification of earthquake-induced damage in permanently monitored historic masonry buildings: the former is a surrogate model-based method, a rapid tool which combines long-term vibration monitoring data (i.e. OMA) and numerical modeling, while the latter is based on non-linear seismic IDA. The Thesis focuses on the validation of different aspects of the DORI methodology, through application to four case study structures: an internationally well-known laboratory masonry structure, called the Brick House, and three CH masonry buildings equipped with permanent Structural Health Monitoring systems, namely the Consoli Palace, the Sciri Tower and the San Pietro Bell Tower. The adopted enhanced vibration-based SHM tool, by introducing crack amplitudes as predictors in the dynamic MLR model, was validated in the case of the Consoli Palace, enabling rapid and automated earthquake-induced damage detection, even for small structural damages at an early stage, conceivably caused by a moderate/light seismic event. Afterwards, the surrogate model-based procedure for earthquake-induced damage detection and localization was applied in the case of the Sciri Tower, using long-term vibration monitoring data and numerical modeling. In particular, a quadratic surrogate model is used, whose objective function considers not only experimentally identified and numerically predicted damage-induced decays in natural frequencies but also on changes in mode shapes. The procedure was validated by considering both simulated damage scenarios, as well as a slight change in structural behavior experimentally observed after a seismic event. Finally, the proposed seismic IDA-based method, introduced for the first time in this Thesis and aimed at localization and quantification of earthquake-induced damages in masonry structures, is applied to the Brick House and San Pietro Bell Tower. It relies on a priori IDA carried out from a numerical model and construction of multidimensional IDA curve sets relating meaningful local damage parameters to selected seismic intensity measures. The IDA-based procedure has demonstrated to correctly localize damage in specific parts of the structures and to quantify earthquake-induced damage with a good level of approximation. The results are particularly interesting in the case of the San Pietro Bell Tower due to the integration of the IDA-based damage identification with seismic SHM data recorded during the 2016 Central Italy seismic sequence, allowing the proposal and exploitation of some original response intensity measures. In conclusion, the DORI methodology proposed in this Thesis for earthquake-induced damage detection, localization and quantification is a novel methodological approach, successfully applied and validated in historic masonry structures, constituting a promising tool for rapid post-earthquake damage assessment of CH structures under long-term SHM monitoring.