The combination of Unreinforced Masonry (URM) and Reinforced Concrete (RC) walls is widely used as bracing system in several countries. This paper deals with the implementation of a numerical model in a commercial finite element software package. The calibration process is described. The objective is to enhance the knowledge of the structural performance of mixed URM-RC systems and, in a subsequent stage, to optimise their design. In this study, we focus on the lateral bracing resistance under statically applied loads. The present numerical campaign fits within a larger project, which aims at optimising the general design of hybrid URM-RC solutions (i.e. the proportion of concrete vs. masonry) as well as the connections used in these hybrid solutions. The long-term objective of the project is the optimisation of the overall lateral load-bearing system.