In 1999 and 2006, in the Chamonix valley (France,74), a protective device dedicated to deflect and stop snow avalanches was partially destroyed. Experimental pushover tests on a 1/6 scale model have been performed in 2005 to better understand the reasons explaining the failure mode of the defense structure. In this paper, a Finite Element (FE) model is presented and calibrated on the experimental data. Then, the FE model is used to investigate the mechanical response of a reinforced concrete structure under dynamic avalanche loading. Finally, the physical vulnerability of the structure is assessed by a suitable damage index.