Barbagelata, Juan Manuel (2025) Seismic performance and fragility of a concrete face rockfill dam. [Tesi di dottorato]

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Abstract

The methodologies for evaluating the safety of embankment dams under seismic actions have evolved, and regulatory agencies increasingly require risk assessments and probabilistic evaluations of seismic performance as part of dam safety evaluations. In this context, fragility functions play an essential role, as their ability to represent dam behavior can significantly influence performance and risk assessments. The need for reliable fragility functions is therefore imperative. This dissertation presents the application of a novel methodological framework for deriving case-specific fragility functions, exemplified through its implementation for Potrerillos Dam, a Concrete Face Rockfill Dam (CFRD) located in northern Mendoza Province, the most seismically active region of Argentina. The framework highlights the importance of each step and the opportunities to incorporate variability and uncertainty throughout the process. A detailed characterization of the dam and site conditions is first provided, supported by a rigorous evaluation of geotechnical laboratory and in-situ tests, and the analysis of static and seismic monitoring records. A preliminary identification of Potential Failure Modes (PFMs) is then performed to link the fragility functions with the main seismically induced damage mechanisms of the system. The definition of seismic hazard is established through a primer Probabilistic Seismic Hazard Analysis (PSHA) for the site, followed by the selection of hazard-consistent records to be used as input motion in the numerical analyses. Advanced numerical models are subsequently constructed and calibrated, and then employed to perform a large number of Nonlinear Dynamic Analyses (NDAs). The results of the NDAs support the calibration of fragility functions through different fitting methods, damage criteria, and ground motion intensity measures, all of them carefully described. The resulting fragility functions describe the vulnerability of the dam to different PFMs while also revealing the influence of damage criteria and intensity measures on seismic fragility across damage states. The derived functions, linked to PFMs and consistent with the seismic hazard, provide a robust representation of the system’s fragility. The use of the fragility functions derived within an Earthquake Early Warning System for embankment dams was also explored as a novel application of the fragility functions. The application of this framework to generate reliable case-specific fragility functions constitutes a significant advancement that enhances performance-based evaluations and seismic risk assessments.

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