Determination of resistance and behavioral properties and numerical modeling of unreinforced walls using DEM approach

The complex mechanical behavior of masonry structures depends strongly on the interface between brick and mortar. The purpose of the present study is to investigate and compare the shear behavior of brick–mortar interface using experimental and numerical methods in order to model unreinforced masonry walls subjected to in–plane compressive and shear loadings. Numerical modeling of masonry walls is performed using an algorithm based on the distinct element method (DEM). Obtaining shear and normal stiffness, adhesion and friction angle of brick–mortar interface, as well as the maximum permissible load on the unreinforced walls at different compressive stresses are among the important achievement of present study. 

The fracturing mechanism in masonry is a complex phenomenon due to existing two brittle materials with distinct material properties. The mechanical behavior of masonry is strongly affected by the behavior of mortar joints. In this paper, after obtaining resistance and behavioral properties of brick-mortar interface, the behavior of unreinforced masonry walls has been investigated. 

As previously mentioned, modeling has been performed by DEM approach using 3DEC. Due to the capability of distinct element method to explicitly represent the motion of multiple, intersecting discontinuities, these methods are particularly suitable for the analysis of masonry structures in which a significant part of the deformation is due to relative motion between the blocks. In the DEM modeling, the Mohr-Coulomb failure surface with a tension cut–off is chosen for blocks and Coulomb–slip model is chosen for joints with zero thickness representing mortar bands. 

The average normal and shear stiffness of the brick–mortar interface was equal to 42.82 and 122.46 (MPa/mm). The adhesion and friction angle of the brick– mortar interface was equal to 0.7 MPa and 37.7 degrees, respectively. The relationship between shear stress and shear displacement of the brick–mortar interface is presented and the maximum permissible load of unreinforced masonry walls subjected to in–plane compressive and shear loadings was calculated using distinct element method (DEM).