Elementi di interfaccia per l’analisi di strutture murarie

Il presente articolo riguarda la modellazione del comportamento meccanico di elementi in muratura intesi come sistemi eterogenei composti da malta, blocchi ed interfacce di connessione. La strategiacomputazionale che viene adottata consiste nel modellare separatamente i blocchi, i letti di malta ed le interfacce responsabili di fenomeni di decoesione malta-blocco; a tale scopo, si propone uno speciale modello di interfaccia che combina il danneggiamento con l’attrito. Si sviluppa una procedura numerica, basata sull’algoritmo backward di Eulero, per risolvere il problema evolutivo; per il passo temporale si utilizza invece la tecnica predictor-corrector a controllo di spostamenti. Si effettuano alcune applicazioni numeriche con lo scopodi verificare la capacità del modello e dell’algoritmo proposto nel riprodurre la risposta non lineare della muratura dovuta a fenomeni di degrado localizzati. Infine, si conduce lo studio della modellazione di un arco murario, confrontando i risultati numerici con quelli sperimentali; si dimostra la abilità del modello proposto nel simulare il comportamento globale della struttura ad arco in termini di carico ultimo e di meccanismo di collasso

Elementi di interfaccia per l'analisi di strutture murarie

Il presente articolo riguarda la modellazione del comportamento meccanico di elementi in muratura intesi come sistemi eterogenei composti da malta, blocchi ed interfacce di connessione. La strategiacomputazionale che viene adottata consiste nel modellare separatamente i blocchi, i letti di malta ed le interfacce responsabili di fenomeni di decoesione malta-blocco; a tale scopo, si propone uno speciale modello di interfaccia che combina il danneggiamento con l'attrito. Si sviluppa una procedura numerica, basata sull'algoritmo backward di Eulero, per risolvere il problema evolutivo; per il passo temporale si utilizza invece la tecnica predictor-corrector a controllo di spostamenti. Si effettuano alcune applicazioni numeriche con lo scopodi verificare la capacità del modello e dell'algoritmo proposto nel riprodurre la risposta non lineare della muratura dovuta a fenomeni di degrado localizzati. Infine, si conduce lo studio della modellazione di un arco murario, confrontando i risultati numerici con quelli sperimentali; si dimostra la abilità del modello proposto nel simulare il comportamento globale della struttura ad arco in termini di carico ultimo e di meccanismo di collasso

A multi-level interface model for damaged masonry

The aim of the present work is to propose a new micro-mechanical model in the context of the deductive approach used to derive interface models. This model, based on a previous study introduced previously by A. Rekik and F. Lebon, is used to reproduce the damage in masonry by combining structural analysis and homogenization methods. The focal point of this method is to assume the existence of a third material, called interphase, which is a mixture of the two principal constituents of masonry, brick and mortar, and that is the interface between them. This new element presents a low thickness, a low stiffness and a given damage ratio. The mechanical problem of masonry, initially a 3D problem, is solved numerically as a 2D problem using finite element methods. The properties of the interface brick-mortar material are obtained using three essentials steps. First of all, an exact homogenisation of a laminates is used to define a first homogeneous equivalent medium named HEM-1. After, the assumption of damaged material is taken into account by using the general framework given by M. Kachanov to evaluate the global behaviour of the damaged HEM-1 defining thus a second equivalent homogeneous medium noted HEM-2. The last step consists in using an asymptotic analysis technique which is performed to model HEM-2 as an interface or a joint. The properties of this joint are deduced from those of the HEM-2 material as proposed in former papers. Particularly, through the second homogenization are taken into account the variability of microcracks oriented family and simultaneously the opening-closure effects (unilateral behaviour). Numerically this interface is modelled with connector finite elements. Numerical results are compared to experimental ones available in the literature

Arbitrary order 2D virtual elements for polygonal meshes: Part II, inelastic problem

The present paper is the second part of a twofold work, whose first part is reported in [3], concerning a newly developed Virtual Element Method (VEM) for 2D continuum problems. The first part of the work proposed a study for linear elastic problem. The aim of this part is to explore the features of the VEM formulation when material nonlinearity is considered, showing that the accuracy and easiness of implementation discovered in the analysis inherent to the first part of the work are still retained. Three different nonlinear constitutive laws are considered in the VEM formulation. In particular, the generalized viscoplastic model, the classical Mises plasticity with isotropic/kinematic hardening and a shape memory alloy (SMA) constitutive law are implemented. The versatility with respect to all the considered nonlinear material constitutive laws is demonstrated through several numerical examples, also remarking that the proposed 2D VEM formulation can be straightforwardly implemented as in a standard nonlinear structural finite element method (FEM) framework

Elementi di interfaccia per l’analisi di strutture murarie

The present paper deals with the modelling of the mechanical behaviour of masonry elements regarded as heterogeneous systems, made of mortar, bricks and interfaces. Thus, the adopted computational strategy consists in modelling the brick units, the mortar joints and the interfaces responsible for the mortarbrick decohesion mechanisms; to this end, a special interface model combining damage and friction is proposed. A numerical procedure, based on the backward Euler time-integration scheme, is introduced; the time step is solved adopting a displacement driven predictor-corrector scheme. Some numerical applications are performed in order to assess the performances of the proposed model and algorithm in reproducing the nonlinear response of masonry material due to damage localization. Finally, a masonry arch model is studied, comparing the numerical results with experimental ones; it is show the ability of the proposed model to simulate the global behaviour of the arch structure in term of ultimate load and collapse mechanism

A Frame Element Model for the Nonlinear Analysis of FRP-Strengthened Masonry Panels Subjected to In-Plane Loads

A frame element model for evaluating the nonlinear response of unstrengthened and FRP-strengthened masonry panels subjected to in-plane vertical and lateral loads is presented. The proposed model, based on some assumptions concerning the constitutive behaviour of masonry and FRP material, considers the panel discretized in frame elements with geometrical and mechanical properties derived on the basis of the different states characterizing the sectional behaviour. The reliability of the proposed model is assessed by considering some experimental cases deduced from the literature