Simone Tiberti1, Corrado Chisari2, Alejandro Barrero Bilbao2, Lorenzo Macorini2, and Gabriele Milani1
1)  Department of Architecture, Built Environment and Construction Engineering, Politecnico di Milano
Piazza Leonardo Da Vinci 32, 20133 Milan, ITALY
{simone.tiberti, gabriele.milani}
2)  Department of Civil and Environmental Engineering, Imperial College London
South Kensington Campus, London SW7 2AZ, United Kingdom
{c.chisari12, alejandro.barrero-bilbao09, l.macorini}

Keywords: Digital image processing, Vectorisation, Masonry, Nonlinear analysis, Finite element model.

Abstract. The paper presents an effective strategy for creating realistic 3D microscale finite element meshes for masonry components with generic bond. Microscale masonry modelling, which considers separate representations for masonry units and mortar joints, offers an accurate description of masonry components providing that the actual masonry bond is properly represented. This may be problematic in the case of rubble masonry, where stone units are often randomly assembled and connected by highly irregular mortar joints. The proposed discretisation strategy utilises a vectorisation procedure retrieving the basic geometry of a raster image of the analysed masonry component, which reveals the geometry of each stone block on the external face of the element. A Matlab script properly developed utilises proprietary image processing tools and considers the raster image as the input parameter, providing a numerical description of the external bond. It comprises the position of the vertex of the stone units with a specific level of simplification (e.g. number of vertexes for each unit) which influences the refinement of the finite element mesh. The developed script is linked to the automatic mesh generator Gmsh which creates 3D finite element meshes for both mortar and stone units. Numerical examples are presented, where nonlinear simulations of a rubble masonry test-window are performed using ADAPTIC, a nonlinear finite element code. The numerical results confirm the potential of the proposed meshing strategy to obtain accurate response predictions of rubble masonry components using microscale modelling.