Simulating the damage of rubble stone masonry walls using FDEM with a detailed micro-modelling approach

Rubble stones are commonly found in many civil engineering components, such as foundations, walls. In general, rubble stone masonry walls are composed of irregular-shaped stone units and mortar. They are usually subjected to vertical and horizontal loads simultaneously and exhibit high degree of nonlinearity and discontinuity in service conditions. The combined finite-discrete element method (FDEM) was employed to investigate the mechanical behaviour of rubble stone masonry walls in this study. In order to overcome the disadvantages in both macro- and simplified micro-modelling, a detailed micro-modelling approach was utilised, i.e. stone, mortar and stone-mortar interface were considered explicitly, providing close approximation to physical structures. Stone units and mortar were discretised into linear triangular elements with finite element formulation incorporated in, and therefore, accurate estimate on structural deformation and contact forces can be obtained. Damage of rubble stone masonry was evaluated through cohesive fracture models. Numerical examples were validated, and further parametric discussions were performed. Influence of stone unit pattern, ratio of stone and strength of mortar on the failure behaviour of rubble stone masonry walls was revealed. A very good agreement between FDEM results and experimental data was observed. It was found that the higher the ratio of stone, the better the bearing capacity, and uniform-shaped stone units with regular distribution were recommended. In addition, use of mortar with both tensile and shear strengths higher than 0.2 MPa was suggested.