Refined Rigid Block Model for In-Plane Loaded Masonry

In this work, a refined rigid block model is proposed for studying the in-plane behavior of regular masonry. The rigid block model is based on an existing discrete/rigid model with rigid blocks and elastoplastic interfaces that already proven its effectiveness in representing masonry behavior in linear and nonlinear fields. In this case, the proposed model is improved by assuming rigid quadrilateral elements connected by one-dimensional nonlinear interfaces, which are adopted both to represent mortar (or dry) joints between the blocks and also to represent inner potential cracks into the blocks. Furthermore, the softening behavior of interfaces in tension and shear is taken into account. Several numerical tests are performed by considering masonry panels with regular texture subjected to compression and shear. Particular attention is given to the collapse mechanisms and the pushover curves obtained numerically and compared with existing numerical and laboratory results. Furthermore, the numerical tests aim to evaluate the applicability limits of the proposed model with respect to existing results

Refined Rigid Block Model for In-Plane Loaded Masonry

In this work, a refined rigid block model is proposed for studying the in-plane behavior of regular masonry. The rigid block model is based on an existing discrete/rigid model with rigid blocks and elastoplastic interfaces that already proven its effectiveness in representing masonry behavior in linear and nonlinear fields. In this case, the proposed model is improved by assuming rigid quadrilateral elements connected by one-dimensional nonlinear interfaces, which are adopted both to represent mortar (or dry) joints between the blocks and also to represent inner potential cracks into the blocks. Furthermore, the softening behavior of interfaces in tension and shear is taken into account. Several numerical tests are performed by considering masonry panels with regular texture subjected to compression and shear. Particular attention is given to the collapse mechanisms and the pushover curves obtained numerically and compared with existing numerical and laboratory results. Furthermore, the numerical tests aim to evaluate the applicability limits of the proposed model with respect to existing results

An Updated Discrete Element Model for the In-Plane Behaviour of NFRCM Strengthened Masonry Walls

Masonry strengthened with natural fabric-reinforced cementitious matrix (NFRCM-strengthened masonry) is investigated by updating an existing discrete element model. Masonry walls are modelled by rigid blocks and elastoplastic interfaces that are able to account for mortar joints and block cracking. The reinforcement is modelled in a simplified manner considering perfect adhesion between wall and reinforcement and by adopting further spring elements connecting block centres. The model is validated by comparing it with an existing FEM based on a multi-step homogenization, where reinforced masonry is considered as a whole. Both approaches are used for performing nonlinear pushover tests with an increasing shear action applied to unreinforced and reinforced panels. The updated discrete model turns out to be able to represent the strength increment given by the reinforcement, but it is less able to represent the corresponding ductility increment

Manufacturing imperfection assessment of multi-leaf masonry panels

Structural stability is a major consideration in the design of structures. The stability is affected both by structure dimensions and by geometrical and mechanical imperfections. The intrinsic heterogeneity of historical masonry affects its structural behaviour; the identification of the local homogeneity degradation allows to define a new design approach to take on the structural rehabilitation of multi-leaf masonry structures. In this paper, the imperfection effects on the performances of multi-leaf masonry walls, considered as orthotropic material, are investigated using experimental and numerical approaches based on modal analysis [1, 2]. Unavoidable imperfections of workmanship, emphasized by mechanical orthotropy, affect the application of conventional design approach. After a first identification of the dynamic parameters - such as frequencies and modal shapes, of different multi-leaf masonry panels characterized by undamaged, damaged and strengthened fill - the model updating procedure has been applied to assess the local and global modal shapes. A Finite Element Model has been built simulating the fill by mono-dimensional element with different unidirectional stiffness between the external layers to distinguish and calibrate the local modal shapes and, then, the global response [3, 4]. The experimental and numerical data have been compared to analyse the reliability of the applied method [5]; the calibrated models have been tested through the non-linear static analysis and the results have been compared with the structural performances of the multi-leaf masonry panels subjected to the compressive loads

Experimental Characterization of Masonry Panels Strengthened with NFRCM

In the last years, the interest in eco-sustainable composites has consistently increased. Such innovative materials are actually a promising sustainable solution for structural strengthening since they can be an alternative to petroleum‐based materials, which are frequently used for masonry retrofitting. This work describes an experimental campaign dedicated to investigating the behavior of Fabric-Reinforced Cementitious Matrix (FRCM) with natural fibers (NFRCM) made with eco-sustainable materials. Experimental tests are performed on unreinforced masonry panels (URM) and reinforced ones (RM), for characterizing their mechanical behavior. URM samples are compared with RM ones accounting for their response under shear actions

Non-linear continuous model for three leaf masonry walls

Three-leaf brick masonry wall is a typical technique in historical buildings. Sensitivity of three-leaf brick masonry wall to core mechanical characteristics and interface between layers is studied by reference to an experimental campaign. Experimental activities were performed on three-leaf masonry panel under compressive loads and is used to identify mechanical characteristic of three-leaf masonry wall and calibrate a 2D plain strain model (without and with interfaces between layers) for cross section of panel. A parametric analysis on inner core and interface between layers mechanical characteristic sensitivity is proposed. Numerical modeling results are presented and discussed in comparison with experimental data

Non-linear behaviour of masonry walls: FE, DE & FE/DE models

Nonlinear behavior of masonry panels is a topic of great interest in the civil engineering and architecture fields. Several numerical approaches may be found in the literature. Here, three different models are presented and compared to investigate nonlinear behavior of in-plane loaded masonry walls: Discrete Element (DE) model, combined Finite/Discrete Element (FE/DE) model, Finite Element model based on a total rotating strain smeared crack approach (FE-TRSCM). Hence, analysis of masonry is carried out at different scales to compare reliability and application fields of the models. The DE and FE/DE models adopt a micromodeling strategy based on discrete cracks, blocks modeled as independent bodies and mortar joints as elastoplastic Mohr–Coulomb interfaces. These approaches already turned out to be in good agreement for in-plane nonlinear analysis. Here, the FE/DE model adopts hypothesis of infinitely resistant and deformable blocks, with cracks occurring only along mortar joints. Deformability is assumed in the triangular FE domain discretization and embedded crack elements may be activated whether tensile or shear strength is reached. The FE-TRSCM follows a macromodeling approach based on the smeared crack theory, often adopted for concrete. Masonry is modeled as a homogeneous material, with a yield criterion based on fracture energy accounting for masonry softening response on compression and tension. Three approaches are compared and calibrated by reproducing experimental tests on masonry panels in compression and under an increasing shear action. The parametric analyses show the capacity and limit of local micromodels or continuous diffused model to represent masonry behavior

Experimental and numerical procedure for vulnerability assessment of historical masonry building aggregates

Historic buildings are a substantial part of the Italian architectural heritage; hence, standard procedure is necessary to evaluate the global and local vulnerabilities. The heterogeneity of materials and technologies combined with the complex volumetric shape of the building aggregates that is constituted by several structural typologies make the definition of a standard approach a hard challenge. This work reports two case studies of rural aggregate buildings. The complex systems were examined both with local and global tests by sonic and dynamic identification. Sonic tests were carried out on representative structural elements, while the dynamic identification considered the volume interaction by modal shapes and related frequencies. For both experimental techniques, a parametric analysis was carried out on results to define reliable 2D and 3D numerical models. This paper provides the formulation of a simplified approach of a 2D FE model based on experimental data to identify potential failure mechanisms

Experimental characterization of masonry panels strengthened with NFRCM

In the last years, the interest in eco-sustainable composites has consistently increased. Such innovative materials are actually a promising sustainable solution for structural strengthening since they can be an alternative to petroleum‐based materials, which are frequently used for masonry retrofitting. This work describes an experimental campaign dedicated to investigating the behavior of Fabric-Reinforced Cementitious Matrix (FRCM) with natural fibers (NFRCM) made with eco- sustainable materials. Experimental tests are performed on unreinforced masonry panels (URM) and reinforced ones (RM), for characterizing their mechanical behavior. URM samples are compared with RM ones accounting for their response under shear actions.(undefined