Distinct Element Modelling of the Out-of-Plane Seismic Behaviour of Masonry Walls

The out-of-plane vulnerability of perimeter walls is one of the main issues in the seismic response of historic masonry structures. Their dynamic behaviour is highly non-linear and is influenced by the discontinuous nature of the material. A range of failure modes may occur, such as onset of a mechanism, leaf separation, disaggregation, or sliding. Simplified approaches based on rigid-block dynamics may be unconservative, especially for poor-quality masonry, which is typical of a large proportion of our built heritage. Distinct element method (DEM), in which masonry is modelled as an assembly of discrete blocks and zero-thickness joints, appears suitable to simulate the dynamic response of masonry structures. In this work, DEM is used to analyse the out-of-plane bending response of two masonry walls, a two-leaf rubble stone masonry wall and a single-leaf wall in regular tuff blocks. Their seismic behaviour is simulated through non-linear dynamic analyses and compared to shake table test results for validation. DEM provides a good description of the seismic response of the walls, despite the high sensitivity to input parameters (stiffness, friction angle, tensile strength, cohesion and damping), which need to be calibrated in a suitable way.