Large displacement response of stone masonry structures often involves the opening and closing of dry joints, or hinging behaviour. Discrete element modelling (DEM) is often used to model large displacement response as it inherently captures the interaction of discrete bodies, and allows for joint contact recognition in a more efficient manner than many finite element modelling procedures. Modelling such behaviour can be computationally demanding and the problem becomes more complicated when reinforcing, often in the form of post-tensioning, is applied to prevent collapse. This paper evaluates the ability of DEM to accurately capture the behaviour of reinforced masonry as observed in an experimental study conducted at the University of Porto. The DEM software 3DEC was used to model the response of the post-tensioned arch when subjected to gravity and a superimposed dead load, and this response was evaluated for varying levels of pre-stress in the arch. A reasonably good correlation was observed between the experimental and DEM results, and the differences that do exist are discussed.