Elio Sacco

University of Naples Federico II | UNINA · Department of Structures for Engineering and Architecture

This study adopts an enhanced multiscale approach to investigate the effects of the damaging process on the structural behavior of masonry vaults with regular texture, in view of their safety assessment. The model, recently developed by the authors, links two different structural models at macro and microscale, exploiting the advantages of each for...

Fabric Reinforced Cementitious Matrix (FRCM) composites are currently considered a very effective solution for strengthening masonry constructions. However, the mechanical interactions governing the response and the strength of FRCM reinforced masonry structures are very complex, especially in the case of curved structures. Moreover, these interact...

With in mind microstructures exhibiting unconventional macroscopic mechanical behaviors, characterized by overall auxetic responses and strain localization due to local elastic instabilities, in this work we conceived a simple two-dimensional non-chiral architecture in the form of a periodic lattice, whose drawing is decided by varying the thicknes...

The paper presents a numerical procedure for the nucleation and evolution of cohesive fracture in two-dimensional bodies. The procedure is based on the development of a 12-node virtual element. Initially, the construction bases of the virtual element method (VEM) are illustrated, with specific reference to a four sides 12-node element. The recovery...

The chapter presents recently developed two-dimensional Virtual Element Method (VEM) methodologies for problems of nonlinear inelastic material behavior, linear/nonlinear material homogenization and cohesive fracture mechanics. A rational approach ranging from theoretical foundations to implementation and code optimization details is provided, toge...

This paper aims at investigating the matrix-to-textile stress transfer in a fabric reinforced cementitious matrix FRCM system, not bonded to any substrate, under shear loads. To this end, direct shear tests are performed on a basalt FRCM specimen introduced into an innovative properly designed four-hinge frame loaded by a universal testing machine....

In the present paper five beam models are presented to reproduce the experimental response of the End Notch Flexure (ENF) test. In particular, a specific ENF scheme is considered; it is made of two symmetric laminates partially bonded by a adhesive layer, whose thickness is not negligible. The failure occurs at the interface between one laminate an...

In this paper, a first-order virtual element method for Reissner–Mindlin plates is presented. A standard displacement-based variational formulation is employed, assuming transverse displacement and rotations as independent variables. In the framework of the first-order virtual element, a piecewise linear approximation is assumed for both displaceme...

In this chapter, the contribution of the AIMETA community to the development of masonry mechanics over the past five decades is illustrated. A review of the contributions to this field within the AIMETA conferences, as well as in the journal Meccanica, is presented by discussing no-tension models, limit analysis-based models, phenomenological model...

Fabric Reinforced Cementitious Matrix (FRCM) composites represent an innovative and effective retrofitting solution for masonry structures. The use of FRCMs as an external retrofitting technique requires an insight knowledge of their mechanical behavior, failure modes and masonry-to-FRCM bond properties. A Round Robin Test (RRT) programme was launc...

In the present work, we present a linear poroelastic model for a quasi-static oscillating bilayer beam made by two thick strata in perfect bond at their interface, characterized by different elastic moduli and permeability, both directly influenced by porosity. The solution is built up by considering the structure as a three-dimensional object and...

In this paper, the Fiber Reinforced Cementitious Matrix (FRCM) material is considered as a composite material obtained embedding a fiber grid into the mortar matrix. The mechanical response of the FRCM is, hence, derived through an homogenization procedure for periodic composite materials, considering the nonlinear behavior of the constituents. In...

One of the crucial issues in the still open problem of seismic analyses of masonry constructions is the study of the structural capacity for cyclic loadings; the difficulties are even more pronounced when constructions embedding curved elements like arches, vaults and domes have to be studied. In order to develop effective nonlinear numerical model...

In this paper, a new beam model based on a 5-parameter displacement field, accounting for an enhanced kinematics and able to reproduce the Poisson effect, is proposed. The displacement field enriches the classical three-parameter Timoshenko beam with two new parameters capable to simulate the shortening effect over the thickness. The related differ...

In the present paper a mathematical model able to reproduce the mechanical response of a shape memory alloy (SMA) helical spring is presented. The proposed model is based on a simplified but effective theory of the helix that assumes small strains and large displacements. The kinematics of the helix and the related generalized strain measures are i...

In this paper, an enhanced Virtual Element Method (VEM) formulation is proposed for plane elasticity. It is based on the improvement of the strain representation within the element, without altering the degree of the displacement interpolating functions on the element boundary. The idea is to fully exploit polygonal elements with a high number of s...

The paper presents two reduced order homogenization techniques for studying the response of nonlinear composite materials. The first approach is based on Transformation Field Analyses, which considers the presence of eigenstrains to account for inelastic strains, while the second approach is derived from Hashin-Shtrikman variational principle, whic...

A novel two-scale modeling approach, linking different structural models at macro and microscale, is proposed to describe response of masonry walls with periodic texture. At the higher macroscopic scale, the real heterogeneous material is modeled as a homogenized medium, considering the classical Mindlin-Reissner theory for flat shells. At the lowe...

In this paper, an enhanced Virtual Element Method (VEM) formulation is proposed for plane elasticity. It is based on the improvement of the strain representation within the element, without altering the degree of the displacement interpolating functions on the element boundary. The idea is to fully exploit polygonal elements with a high number of s...

Composite adhesive bonded joints are widely used in various industrial and technological applications, including aerospace, electronics, biomedical, automotive, ship building and construction. In this paper, the attention is focused on layered structures consisting of two adherent beams bonded together by an adhesive layer. For such structures, a m...

This chapter focuses on three-dimensional (3D) constitutive modeling for shape memory alloys (SMA) and on finite element analysis of SMA plate and composite laminate devices. The discussion starts with a review of SMA macroscopic constitutive models with internal variables, based on the thermodynamics of irreversible processes. Subsequently, a fini...

Aim of this work is to suggest a modelling approach based on the implementation of non-linear interface modelling for reproducing the tensile constitutive law of Fibre Reinforced Cementitious Matrix (FRCM) materials and for assessing the damage pattern. The numerical modelling is described and the obtained numerical stress-strain curves are compare...

Optimization of materials and structures is a crucial step in the design of man-made mechanical components for a wide field of engineering applications. It also plays a key role in mechanobiology of living systems, being involved by nature across the scales, from single-cell to tissues and organs, as a strategy to minimize metabolic cost and maximi...

Aim of this paper is to proposed a micro-scale numerical approach for the evaluation of the mechanical behavior of Fiber Reinforced Cementitious Mortar (FRCM) composites. As a matter of fact, the FRCM constitutive behavior is affected by micro-mechanisms, such as the cracking of the mortar and the slippage of the fibers within the mortar. The repet...

The present work is focused on the analysis of the double-cap dome of St. Januarius Chapel, in Naples (Italy). Three different approaches based on the limit analysis for unilateral (no-tension) material has been applied to evaluate the dome stability. In the first approach, the overall stability of the dome has been investigated through a method of...

Under horizontal loadings, such as seismic actions, buckling phenomena can strongly affect the bearing capacity of masonry walls to gravity loads. Indeed, due to the low tensile strength of the mortar, when vertically loaded masonry members are subjected to bending moments induced by load eccentricity, out-of-plane collapse mechanisms often prevail...

Fracture is one of the most commonly encountered failure modes of engineering materials and structures. Prevention of cracking-induced failure is, therefore, essential to save lives and contain costs and should be considered a social commitment. However, the understanding of nucleation and propagation of complex crack patterns in real structures is...

The present paper proposes an innovative nucleation and propagation algorithm for fracture evolution in 2D cohesive media, based on virtual element method (VEM) technology. Initially, an interface cohesive law is described, which is able to account for the crack opening due to the evolution of a damage variable in mode I, mode II, and in mixed mode...

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A R T I C L E I N F O Keywords: Masonry wall Stability analysis Multiscale model Micromechanical approach Damage Corotational approach A B S T R A C T This paper presents two micromechanical and a multiscale finite element models for the analysis of masonry walls under out-of-plane instability effects. A two-dimensional modeling of the wall is cons...

Aim of the present study is to propose an enhanced method for the domain decomposition (clustering) of the representative volume element (RVE) of composite materials to be used with homogenization techniques, based on the PieceWise Uniform Transformation Field Analysis (PWUTFA). With PWUTFA, both constitutive and evolutive equations for the constit...

Recently, many studies showed the opportunity to use a CO2 laser for treating the surfaces for structural bonding. In this work, a study on the effectiveness of a laser texturing on ENF bonded joints made with CFRP and epoxy adhesive has been developed. The experimental results showed that the use of this technology allows obtaining mechanical resi...

The present work deals with the analysis of unreinforced and FRCM reinforced masonry walls subjected to out-of- plane loading. In particular, numerical simulations of full scale experimental clay brick walls, previously tested, are developed. The out of plane behaviour is relevant not only for flat walls, but also for curved structures, like as dom...

The present paper proposes an innovative nucleation and propagation algorithm for fracture evolution in 2D cohesive media, based on virtual element method (VEM) technology. Initially, an interface cohesive law is described, which is able to account for the crack mouths separation due to the evolution of a damage variable in mode I, mode II, and in...

Masonry structures, although classically suitable to withstand gravitational loads, are sensibly vulnerable if subjected to extraordinary actions such as earthquakes, exhibiting cracks even for events of moderate intensity compared to other structural typologies like as reinforced concrete or steel buildings. In the last half-century, the scientifi...

Few design oriented models on strengthening of unreinforced masonry (URM) panels under in-plane actions with composite systems are currently available (among them, the pioneers researches [1, 2] and the guidelines [3, 4] for FRPs). Usually, the in-plane shear capacity of a strengthened panel is evaluated as the sum of two terms: the contribution of...

In this work, a numerical model for analyzing the mechanical behavior of a reinforced concrete slab subjected to a direct contact explosion was developed, using the explicit finite element code LS-DYNA and facing the following issues: generation and propagation of the blast wave, interaction with the solid structure, and mechanical behavior of the...

In this paper a new numerical approach for determining admissible thrust curves for masonry arches is proposed. Arbitrary loading conditions, including distributed loads applied to the extrados and to the intrados of the arch, but also horizontal inertial forces simulating the effects of seismic actions are considered for arches of any geometry. Th...

In this paper a new numerical approach for determining admissible thrust curves for masonry arches is proposed. Arbitrary loading conditions, including distributed loads applied to the extrados and intrados of the arch, but also horizontal inertial forces simulating the effects of seismic actions are considered for arches characterized by any geome...

Several tools for the prediction and the assessment of the structural behavior of masonry buildings have been developed in recent decades. Numerical tools have been favorably developed and preferred over analytical approaches, given the complex mechanical response of masonry and the irregular geometries of historic masonry buildings. In this chapte...

Aim of the paper is to present a one dimensional simple model for the study of the bond behavior of Fabric Reinforced Cementitious Matrix (FRCM) strengthening systems externally applied to structural substrates. The equilibrium of an infinitesimal portion of the reinforcement and the mortar layers composing the strengthening systems allows to deriv...

The paper proposes a mixed strain- and stress-based topology optimization method for designing the ideal geometry of carbon fibers in composite laminates subjected to either applied tractions or prescribed displacements. On the basis of standard micromechanical approaches, analytical elastic solutions for a single cell, assumed to be a Representati...

In this paper the capacity of an innovative composite basalt grid with inorganic matrix (FRCM) has been evaluated both in terms of repairing pre-damaged and strengthening clay brick walls under out-of-plane loads. Experimental tests have been performed on full scale clay brick walls subjected to out-of-plane loads. A wall, damaged after a test, has...

The present paper deals with the modeling of bonded interfaces adopting the asymptotic expansion technique. The equilibrium problem of a composite body made of two adherents issn perfect contact with an elastic interface is considered and a classical rescaling technique is introduced. The asymptotic expansion method is reviewed; in fact, the repres...

Masonry arches are amongst the most fascinating structures of the World's historical and architectural heritage. Their vulnerability to earthquakes pointed out the necessity of their preservation. Fiber Reinforced Cementitious Mortar (FRCM) composites have been recently used as a more sustainable alternative to FRPs in the strengthening of masonry...

A growing interest in the preservation of historical and architectural heritage led to the necessity of developing efficient and reliable methods for the structural analysis. Most of our built heritage is made of masonry buildings; in particular, masonry arches are one of the most valuable, but also one of the most vulnerable, part of those constru...

This paper presents a Timoshenko beam finite element for nonlinear analysis of planar masonry arches. Considering small displacement and strain assumption, the element governing equations are defined according to a force-based formulation that adopts three different parametrizations of the axis planar curve, permitting the exact description of the...

A high-order virtual element method (VEM) for homogenization of long fiber reinforced composites is presented. In particular, periodic composites are considered studying square or rectangular unit cell arrays and circular inclusions. A suitable displacement representation form is adopted reducing the three-dimensional problem to an equivalent two-...

During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in...

In this paper a new multiscale approach is presented for the analysis of structures made of composite material characterized by elastoplastic or viscoplastic nonlinear response. Scale separation is assumed so that the homogenization theory can be applied: at the structural scale (macroscale) the material appears as homogeneous, while at the microsc...

A homogenized model based on simplified kinematic assumptions for the analysis of masonry columns subjected to axial forces is presented. A Unit Cell (UC) characterized by different arrangements of clay bricks and mortar joints is modeled and analyzed. The kinematic unknown fields are approximated by cubic interpolation functions and the compatible...

Recent experimental studies involving Fabric Reinforced Cementitious Matrix (FRCM) strengthening systems externally applied to structural supports have underlined important aspects characterizing their response. In particular, failure mechanisms quite different from the ones emerged in case of traditional Fiber Reinforced Polymers (FRP) have been o...

The introduction of composites in engineering applications led to a need for tools that can predict the mechanical response with account for the heterogeneities in the materials in order to safely design complex structures. These predictions are required to be sufficiently accurate yet computationally inexpensive, especially when dealing with nonli...

This paper presents the latest advances in the development of multiplane cohesive-zone models that are able to account for damage, friction and interlocking, including in particular their extension to a general three-dimensional (3D) case. Starting from the work proposed in a recent article by some of the authors, a simplified micromechanical formu...

In the present paper two constitutive models, able to reproduce the mechanical behavior of shape memory alloy (SMA), are proposed. The constitutive laws allow considering the simultaneous presence of normal and shear stresses, accounting for its coupling without developing a full three-dimensional (3D) model. In such a way, two different models sui...

The paper presents an interphase cohesive zone model (CZM) incorporating stress multi-axiality devised to capture, by simplified micro-modeling, the influence of the in-plane strain and stress state in the mechanical response of the CZM. Moreover, the model is able to account for the Poisson-related effect in the interphase, which can play an impor...

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 constit...

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...

Aim of the present paper is to develop an efficient multiscale procedure for studying the mechanical response of structural elements made of elastoplastic or viscoplastic composite materials. The micro and the macro scales are considered separated. At the microscale a PieceWise Uniform Transformation Field Analysis (PWUTFA) homogenization technique...

Multi-plane Cohesive-Zone Models (M-CZMs), based on the concept of Representative Multiplane Element (RME), provide an intermediate option between macroscale CZMs and full multiscale approaches for the analysis, within the mechanics of generalized continua, of mixed-mode fracture over micro-structured interfaces where initiation and propagation is...

This work aims at highlighting critical issues that occurs in the modeling of mono-symmetric non-prismatic thin walled beams. In particular, even considering the simplified assumption of planar behavior, it is possible to demonstrate that the shear stress distribution within non-prismatic beams is substantially different from the one that occurs in...

The present paper deals with the problem of stability of masonry arches. In particular, the problem is approached invoking the lower bound theorem of Limit Analysis; thus, the existence of a thrust-line entirely contained in the thickness of the arch ensures that the arch does not collapse under the assigned load. With this aim, the Milankovitch th...

The present work deals with the formulation of a Virtual Element Method (VEM) for two dimensional structural problems. The contribution is split in two parts: in part I, the elastic problem is discussed, while in part II [3] the method is extended to material nonlinearity, considering different inelastic responses of the material. In particular, in...

Aim of this work is the evaluation of FRCM capacity in repairing pre-damaged clay brick walls under out of plane loads. Full scale experimental tests have been performed damaging clay brick walls subjected to out of plane loads; then, tests are performed on damaged walls repaired with innovative composite grids with inorganic matrix (FRCM). The bou...

The paper presents a study concerning the local bond behavior of FRCM strengthening systems externally applied to structural supports. The aim of the study is to analyze the main parameters influencing the interaction between the reinforcement and the mortar layer and their role. To this purpose, a theoretical approach is performed in order to anal...

A 3D microstructured composite Interphase Formulation (IF) based on a Multiplane Cohesive-Zone Model (M-CZM) is proposed for describing the behavior of quasi-brittle joints. The IF is devised so as to reproduce an initial linear elastic behavior, corresponding to the elastic parameters of a thin layer of finite thickness and stiffness, followed by...

A new homogenization technique, based on the Transformation Field Analysis, able to determine the overall behavior of viscoplastic heterogeneous materials, is proposed. This method is derived developing a variational formulation of the compatibility and evolution equations governing two classical elastic-viscoplastic models, i.e. Perzyna and Perić...

The present work describes a number of cohesive zone models (CZMs) developed over the last decade; the models are derived from a simplified approach to the micro-mechanics of the fracture process. The models are able to separately consider damage and frictional dissipation; moreover, the most recent proposed models account also for intelocking and...

A 3D multi-scale cohesive-zone model (CZM) combining friction and finite dilation by a multi-plane approach (M-CZM), based on the concept of Representative Multiplane Element (RME), is developed within the mechanics of generalized continua for the analysis of mixed-mode fracture. The proposed M-CZM formulation captures the increase of measured fr...