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Application of Endurance Time Analysis Method to the Non Linear Seismic Analysis of dams: Potentialities and Limitations

pubblicazioni - Memoria

Application of Endurance Time Analysis Method to the Non Linear Seismic Analysis of dams: Potentialities and Limitations

In questo lavoro vengono presentati i risultati dell’applicazione del metodo ETA per l’analisi della sicurezza sismica di una diga esistente italiana, che confermano i vantaggi del metodo, pur evidenziando alcune limitazioni rispetto a NLTHA che necessitano di ulteriori approfondimenti.

Past experiences show that most of existing concrete dams are able to withstand with minor damages the seismic actions due to real earthquakes. Compared to the return period commonly used for the design seismic actions, starting from 2500 up to 10000 years, these experiences are too short to make general conclusions. So far, Non Linear Time History Analysis, NLTH, is the most advanced and reliable method to analyze the vulnerability of dams when subjected to Maximum Credible Earthquake where the structural behavior is expected to go well beyond the linear elastic limit. Nevertheless, in consideration of all possible loading combinations, the overall number of time history to be considered, the number of results to be interpreted and managed, makes NLTHA for the seismic safety assessment of dams a very time consuming and challenging task.

Recently, a novel method, the Endurance Time Analysis method, ETA (Estekanchi and others, 2004), has been developed and its preliminary application to real cases (Hariri-Hardebili and others, 2012) has shown a good agreement with NLTHA results, while also allowing a computational effort reduction up to 90%. The ETA method can be seen as a “virtual dynamic push over test” based on special increasing time histories able to represent seismic actions associated to different performance limit states. In this paper the application of ETA method to a real arch dam model is presented and results are compared with NLTHA, highlighting advantages, limitations and further research needs. Non linearities are accounted for by means of Coulomb friction interfaces for the joints and Lee and Fenves “Damage Plasticity Model” for the concrete behavior.

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