Seismic response analysis of Italian concrete gravity dams

The objective of this paper is to evaluate possible residual displacement of concrete gravity dams produced by an earthquake. A simple mechanical model, at rst proposed by Fenves and Chopra developed to take into account the most relevant parameters in uencing seismic response (e.g. dam-water and dam-foundation interaction), is here enriched to catch residual displacement, once having xed a threshold value for the sliding foundation resistance. In particular the attention is focused on the dam displacement demand (ductility) related to the shear strength of the foundation rock. The dam is modelled as an elastic linear single degree of freedom system. The hydrodynamic e ects of the water in the reservoir are taken into account with generalized supplementary mass and force moreover by adding supplementary damping. The foundation resistance is modelled with the Mohr-Coulomb criterion including a frictional and a cohesive component and the presence of a passive wedge resistance is considered. Parametric analysis are performed in order to evaluate the in uence of each single parameter on dam response. Variable parameters considered are: foundation resistance and Young modulus, water level in the reservoir, dam height. Considerations on the rule of each relevant parameter is discussed. As an example, seismic analysis are carried out on four typical Italian dams, with di erent height, hypnotizing for each case three types of foundation rock. As input time history 36 signals obtained by natural earthquakes registered in the Italian country and 10 earthquakes taken from the PEER and ESD database are utilized. Depending on the intensity of the seismic action the expected ductility of the dam is evaluated. At the end, the proposed methodology is used to evaluate possible residual displacement of the four dams subjected to acceleration spectra proposed by the Italian Code, obtained with reference to the site seismic hazard of the region where are located.