Seismic Fragility Analysis of Two Earth Dams in Southern Italy Using Simplified and Advanced Constitutive Models

The seismic performance of earth dams can be assessed using various proce-dures spanning from simple deterministic methods to fully-probabilistic ap-proaches, such as fragility analyses. In this study, analytical seismic fragility functions (i.e., based on results of numerical analyses) for two earth dams (the Farneto del Principe and the Angitola dams) in the Calabria region (Southern Italy) are developed. The Farneto del Principe dam does not have liquefaction-related issues, while the Angitola dam is founded on soils sus-ceptible to liquefaction. The analyses are performed using numerical simula-tions based on the so-called multiple-stripe method. This framework takes inputs from site-specific probabilistic seismic hazard analysis results and it is used here to develop fragility functions for intensity measure (IM) values at the same return period of the seismic action. Separate calculations are pre-sented, using the relatively simple hysteretic soil model implemented in the 2D finite difference method software FLAC and two advanced constitutive models (PM4Sand and PM4Silt) specifically developed to simulate the stress-strain response of sands and silts in geotechnical earthquake engineering ap-plications. Fragility functions for several damage mechanisms and IMs are obtained. The analyses show that the IMs with the highest predictive power (i.e., those with the lowest fragility function standard deviations) are the peak ground acceleration and velocity (PGA and PGV) for the Farneto del Principe dam and the cumulative absolute velocity (CAV), the cumulative absolute velocity above 5 cm/s2 (CAV5), and PGV for the Angitola dam.