A Simplified Micro-Modeling Approach for Historical Stone Masonry Walls
A recent study  has discussed the accuracy of the nodal elastic stresses of zero thickness interface elements when fictitious elastic parameters (often called penalty stiffness factors) are used. These stresses, commonly used to calculate the triggering conditions of the opening of the interface simulating a discrete crack in quasi-brittle materials, are affected by non-negligible errors if the in- terfaces are embedded in unstructured/irregular meshes. A procedure to avoid these errors has been proposed for homogeneous materials  and bi-material interfaces . Accurate nodal stresses are re- covered if certain geometry-dependent pre-processed coefficients are used. In this paper, this method is proposed in the analysis of Historical Stone Masonry Walls: zero-thickness interface elements rep- resent the interaction between stones of irregular shape. The crack opening triggering conditions are calculated for two identical meshes with rigid continuous elements representing the stones and fic- titiously elastic zero-thickness interfaces representing the mortar layers. This paper shows that the use of the proposed coefficients significantly changes the values of the interface stresses leading to different configurations of the cracking onset.
Angelo Di Tommaso, Cristina Gentilini and Giovanni Castellazzi
G. Castellazzi et al., "A Simplified Micro-Modeling Approach for Historical Stone Masonry Walls", Key Engineering Materials, Vol. 624, pp. 74-79, 2015