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Endurance Time Analysis for the Seismic Vulnerability of Arch Dams

pubblicazioni - Memoria

Endurance Time Analysis for the Seismic Vulnerability of Arch Dams

In questa memoria viene presentato un metodo innovativo, Endurance Time Analysis (ETA method) per la valutazione della vulnerabilità e la verifica sismica delle dighe ad arco. Si documentano le esperienze acquisite da RSE applicando il metodo ad un significativo parco dighe di grandi produttori idroelettrici italiani e confrontando i risultati con quelli forniti dai metodi classici. Infine si propone il metodo ETA comealternativa, altrettanto valida ma molto meno dispendiosa, ai metodi tradizionali per la verifica sismica delle dighe di questa tipologia secondo i dettami del nuovo regolamento sismico italiano.

This contribution summarizes the main outcomes achieved by RSE in the last two working years on the dynamic non-linear response of arch dams aimed at their seismic vulnerability assessment. On the basis of the results obtained, an alternative approach is proposed to evaluate their seismic vulnerability. The Endurance Time Analysis (ETA) introduced in 2004 is used for this purpose. The method consists in shaking the structure using a special acceleration function with increasing intensity in time able to be spectrum compatible to limit states spectra at the so called equivalent times.

A relationship exists in fact between the time and the seismic intensity parameters. For each ETA function it is possible to track the nonlinear behaviour of the structure up to collapse. The method allows evaluating the time at which specific limit states are overpassed. These times, coming from a single analysis, can be then compared to the equivalent times.

Compared with traditional dynamic analysis performed with Time History accelerograms, more or less artificial, this approach strongly reduces the amount of time requested for a full seismic assessment of dams giving additional information on the seismic action producing the collapse of the structure. Last but not least, the comparison between the “capacity curves” of different dams for the same ETA functions clearly allows defining the vulnerability ranking of a portfolio of arch dams against earthquakes.

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