The paper describes the numerical analyses carried out on the 65-m high Licodia Eubea concrete gravity dam under Collapse Limit State (CLS) earthquake scenario. The finite difference FLAC code was employed taking into account the interaction effects between the dam, the impounded reservoir, the sediments accumulated at the bottom of the reservoir and the underlying rockmass foundation. In particular, the water was modeled as a continuum rather than with the added mass simplified approach usually applied in most of literature studies. Linear dynamic analyses were first carried out and the seismic performance of the dam has been investigated according to demand-capacity ratio and cumulative duration indices. Dynamic tensile stresses locally exceeded the allowable tensile strength, mostly close the heel of the dam. For this reason, nonlinear dynamic analyses of the dam were then carried out introducing nonlinearity at the contact damfoundation and in the foundation rockmass. It was found that the tensile principal stresses within the dam body are significantly reduced, such that cracking is prevented. The dam might experience sliding along its base: the average permanent displacement at the base of the dam is about 8 cm, only 0.12% the height of the dam. Considering also that these values are obtained under several conservative assumptions, the dam is characterized by an acceptable margin of safety under strong CLS ground shaking
