Maria Letizia Raffa

An Interface Model Including Cracks and Roughness Applied to Masonry

In this paper an interface model accounting for roughness and micro-cracks is presented and applied to masonry-like structures. The model is consistently derived by coupling a homogenization approach and arguments of asymptotic analyses. A numerical procedure is introduced and numerical results, based on a finite element formulation, are successfully compared with experimental data , obtained on masonry samples undergoing to shear tests. Finally, a parametric numerical analysis is proposed, highlighting the influence of the roughness features on the interface response.

Multiscale Modeling of Imperfect Interfaces and Applications

Modeling interfaces between solids is of great importance in the fields of mechanical and civil engineering. Solid/solid interface behavior at the microscale has a strong influence on the strength of structures at the macroscale, such as gluing, optical systems, aircraft tires, pavement layers and masonry, for instance. In this lecture, a deductive approach is used to derive interface models, i.e. the thickness of the interface is considered as a small parameter and asymptotic techniques are introduced. A family of imperfect interface models is presented taking into account cracks at microscale. The proposed models combine homogenization techniques for microcracked media both in three-dimensional and two-dimensional cases, which leads to a cracked orthotropic material, and matched asymptotic method. In particular, it is shown that the Kachanov type theory leads to soft interface models and, alternatively, that Goidescu et al. theory leads to stiff interface models. A fully nonlinear variant of the model is also proposed, derived from the St. Venant-Kirchhoff constitutive equations. Some applications to elementary masonry structures are presented.

On modelling brick/mortar interface via a St. Venant-Kirchhoff orthotropic soft interface. Part II: in silico analysis

A new strategy for the numerical modelling of brick/mortar interfaces at the macro-scale taking into account finite strains and evolving microcracking phenomena is introduced. A numerical validation of the non-linear-imperfect interface model formulated in Part I of the present paper, is proposed. Well-established experimental data concerning diagonal compression of masonry walls are simulated within the finite element method. The localisation zones of highest displacement jumps and stresses obtained through the numerical simulations are in good agreement with the experimental findings. The proposed non-linear interface model is also compared with a linear interface model for masonry structures.

On modelling brick/mortar interface via a St. Venant-Kirchhoff orthotropic soft interface. Part I: theory

In this paper, a nonlinear-imperfect interface model is proposed in order to model brick/mortar-interface behavior in small masonry assemblies. The proposed model, formulated according a micromechanical strategy, derives from a consolidated approach coupling arguments of asymptotic analysis and homogenisation method. The adopted asymptotic technique is extended to the finite strain theory. The homogenisation strategy, under the non-interacting approximation, is extended to microcracked-orthotropic-hyperelastic materials. Simple numerical simulations, developed within the framework of finite element method, highlight the model soundness and its applicability in finite-strain problems.

A nonlinear interface model applied to masonry structures

In this paper, a new imperfect interface model is presented. The model includes finite strains, micro-cracks and smooth roughness. The model is consistently derived by coupling a homogenization approach for micro-cracked media and arguments of asymptotic analysis. The model is applied to brick/mortar interfaces. Numerical results are presented.