This article focus on the key issue of energy dissipation in passive rockfall protection structures when exposed to impact when intercepting a rock block. As an application case, a structure consisting in a wall made of articulated concrete blocks is considered. A Non-Smooth Contact Dynamics (NSCD) model of this structure was developed and calibrated with respect to the spatiotemporal impact response obtained from real-scale impact experiments. This model accounts for energy dissipation by friction between the system bodies and plasticization at contacts. The energy dissipation computation method is detailed and its correctness is demonstrated based on the simulation of two impact cases. The evolution with time of energy dissipation by each dissipative mechanism provides insights into the global structure response with time in terms of displacement and contact force amplitude. The influence of the model parameters on the contribution of these two dissipative mechanisms is evaluated. A ratio between energy dissipation by friction to energy dissipation by plasticization is proposed as a criterion for structural response evaluation. The variability in energy dissipation varying the impact conditions is addressed. In the end, this study reveals the benefits derived from a precise quantification of energy dissipation in passive rockfall protection structures with promising perspectives in terms of structure design improvement.