Ricerc@Sapienza

The seismic assessment of masonry buildings requires the definition of adequate models. Simplified approaches have well known positive outcomes, but the definition of their properties to describe all the complex phenomena in which structural elements are involved, especially when subjected to dynamic loading, is not an easy task. Masonry exhibits a strongly nonlinear behaviour under both static and dynamic loading and hysteretic nature of restoring forces should be considered.

This paper presents an enriched hysteresis model with damage relying on the Bouc-Wen formulation, in which a single scalar variable is introduced to reproduce effects of strength and stiffness degradation emerging for damaging materials. First, some acknowledged limits of the original Bouc-Wen model are discussed, focusing on its thermodynamic admissibility and compatibility with Drucker's plasticity postulate, and highlighting the effects of the parameters β and γ.

In this study a seismic risk analysis of masonry buildings based on damage data of L’Aquila 2009 earthquake is presented. Typological loss curves and Expected Annualized Losses (EAL) values are presented, starting from the data collected into AeDES forms available in the Da.D.O. database. A completion is proposed for improving the sample statistical significance, and correctly including undamaged and not surveyed buildings that suffered low shaking values.

This study presents a two-scale model to describe the out-of-plane masonry response. One-dimensional (1D) structural elements, like masonry columns or strips of long wall characterized by the periodic repetition of bricks and mortar arranged in stack bond, are considered. A damage-friction plasticity law is adopted to model the mortar joint constitutive response, while the bricks are assumed as linear elastic. A 1D beam formulation is introduced at both the structural and micromechanical scale, linking the two levels by means of a kinematic map.

This paper presents a kinematic enriched finite element model for nonlinear analysis of brick masonry walls loaded in their plane. The finite element accounts for the transverse deformation of the wall and permits to reproduce mortar-brick interaction in wall thickness direction. Non-local constitutive relationships are considered both for mortar and bricks, adopting a damage-friction law for the mortar and an isotropic damage model for the bricks, both accounting for tensile failure mechanisms.