A geometry-based anisotropic gradient-enhanced damage model for modelling masonry failure

Abstract

While masonry is known for its simple method of construction, its computational analysis poses many challenges. Since masonry consists of two distinct materials, i.e. mortar joints and clay bricks, the use of a suitable and efficient numerical model is essential in order to accurately model the orthotropic structural behaviour. Moreover, due to the quasi-brittle nature of both constituents, a numerical masonry model should incorporate a robust and objective description of strain localisation and material failure. In our contribution, we propose a novel modelling approach in which failure of the orthotropic masonry composite is modelled in a continuous manner. Unlike traditional continuous masonry models, in which mesh-dependence of strain softening is regularised using Cosserat continua [1] or non-local models [2], an implicit gradient-enhanced damage model is used for the objective description of strain localisation and failure. In contrast to conventional isotropic gradient-enhanced damage models [3], an anisotropic interaction kernel is employed, which size and shape is not only governed by the equivalent stress level [4], but also by the underlying geometry of the structure, i.e. the masonry bond. Through several numerical examples, the proposed masonry model will be compared with detailed mesoscale models in which joints are explicitly modelled [5]. Special attention will also be addressed to the influence of the model parameters and their interaction with the orthotropic elastic properties.