Frattura ed Integrità Strutturale 2020-01-28T12:41:46+00:00 Francesco Iacoviello Open Journal Systems <p>Frattura ed Integrità Strutturale (Fracture and Structural Integrity) is the International Journal of the Italian Group of Fracture (ISSN 1971-8993). It is an open-access journal published online every three months (January, April, July, October).&nbsp;<br>Frattura ed Integrità Strutturale encompasses the broad topic of structural integrity, which is based on the mechanics of fatigue and fracture and is concerned with the reliability and effectiveness of structural components. The aim of the Journal is to promote works and researches on fracture phenomena, as well as the development of new materials and new standards for structural integrity assessment. The Journal is interdisciplinary and accepts contributions from engineers, metallurgists, materials scientists, physicists, chemists, and mathematicians.</p> <p><strong>More details:</strong></p> <p>- The Journal is financially supported by the <a href="">Italian Group of Fracture (IGF)</a> and by crowdfunding. It is completely free of charge both for readers and for authors. Neither processing charges nor submission charges are required.</p> <p>- Papers can be published only after a preliminary plagiarism/autoplagiarism check and a blind peer-review process (two reviewers, at least). More than one reviewing rounds are possible.</p> <p>- The Journal is well indexed (e.g., Scopus, since 2012, and WoS, since 2015).</p> <p>- All the papers are published with their Visual Abstracts (2 minutes max videos with the "cores" of the papers). All the Visual Abstracts are also available in a dedicated <a href="">YouTube channel</a>.&nbsp; All the issues are also published in a browsable version. All the issue in browsable version are also published in a dedicated website (<a href="">LINK</a>).</p> Finite element analysis of the thermomechanical behavior of metal matrix composites (MMC) 2020-01-28T12:32:14+00:00 Zaoui Bouchra Baghdadi Mohammed Boualem Serier Mohammed Belhouari <p>In this work the finite element method (FEM) was used to analyze the mechanical behavior of the composite materials subjected to the mechanical loading. This behavior is studied in terms of stress intensity factor variation as a function of the applied stress intensity. The residual stresses induced in the composites, during the elaboration of these composites are taken into consideration in this study. The superimposition of these types of stresses (residuals and commissioning) is simulated here by thermomechanical stresses. The results obtained show that in the vicinity very close to the fiber-matrix interface and under the effect of this loading type, the matrix cracks propagate in modes I, II and III, and far from the interface, in mode I. The propagation kinetics is slowed down by the interface-crack interaction.</p> <p>The effects of the crack size, the orientation and propagation of the crack, commissioning stresses, the elaboration temperature, fiber physical properties, matrix stiffness and thermomechanical stresses have been highlighted in this work.</p> 2020-01-03T09:26:08+00:00 Copyright (c) 2020 Baghdadi Mohammed, Zaoui Zaoui Bouchra, Boualem Serier, Mohammed Belhouari Analysis of Printed Circuit Boards strains using finite element analysis and digital image correlation 2020-01-28T12:33:01+00:00 Liviu Marsavina Alexandru Falk Octavian Pop <p>This paper investigates the use of digital image correlation (DIC) and finite element analysis for strain measurement on Printed Board Circuits (PCBs).</p> <p>Circuit boards (PCBs) are designed to mechanically support and electrically connect an electronic component assembly. Due to screw assemblies, the surface level differences on which the PCB is placed, the process of assembling the electronic components induces a certain state of stress and deformation in the PCB. The main components affected are microprocessors due to the way they are glued to PCBs with BGA - Ball grid arrays (BGA).</p> <p>Digital Image Correlation (DIC) is a full-field contactless optical method for measuring displacements and strain in experimental testing, based on the correlation of images taken during test. The experimental setup is realized with Dantec Q-400 system used for image capture and Istra 4D software for image correlations and data analyses. The maximum level of the obtained strain is compared with the allowable limit.</p> <p>Finite element analysis (FEA) is a numerical method of analysis for stresses and strain in structures of any given geometry.</p> 2019-12-14T00:00:00+00:00 Copyright (c) 2020 Liviu Marsavina, Alexandru Falk, Octavian Pop A Numerical framework for fatigue lifetime prediction of complex welded structures 2020-01-28T12:32:37+00:00 Kris Hectors Wim De Waele Mia Loccufier Hans De Backer <p>Ageing infrastructure is of major concern for different industrial sectors across Europe. Fatigue cracking is one of the most important damage mechanisms that affect structural health of welded steel structures. Fatigue assessment of welded details in large, complex structures is a difficult and time consuming task. In this paper a numerical framework for fatigue assessment of welded details is presented. In view of industrial applications, automated hot spot stress algorithms for plate and tubular joints were developed and integrated in the framework. The framework provides practicing engineers with an effective tool for fatigue assessment of different components in conformity with leading design codes. Furthermore, apart from Miner’s rule the framework allows easy implementation of different non-linear damage accumulation models in order to account for load interaction and load sequence effects.</p> 2019-12-14T00:00:00+00:00 Copyright (c) 2020 Kris Hectors, Wim De Waele, Mia Loccufier, Hans De Backer Local scale fracture characterization of an advanced structured material manufactured by fused deposition modeling in 3D printing. 2020-01-28T12:33:25+00:00 Joseph Marae Djouda Donato Gallittelli Marouene Zouaoui Ali Makke Julien Gardan Naman Recho Jérôme Crépin <p>Additive manufacturing (AM) is a promising way to produce complex structures by adding layers. It arises great interest both in industrial and academic sectors to develop new advanced structured material. To benefit from its advantages, it is important to accurately characterize the obtained structures in order to ensure their integrity during operation. It becomes then important to characterize these structures at the local scale (micron and/or the nanometer scale). In the specific case of polymeric materials obtained by Fused Deposition Modeling (FDM), the comprehension of the mechanical behavior between adjacent layers during deformation can help improving mechanical properties. However, few studies in the literature have focused on implementing approaches to characterize local strains at the surface of these materials. In this study, an original approach based on the use of speckle pattern with particle average size of 20 microns in diameter was coupled to digital image correlation (DIC). It has been applied to the case of a SENT structure with a notch made by FDM. The successive images recorded by a digital microscope allow a qualitative analysis of the evolutions of the local strains. The kinematic fields are obtained by DIC. The strain evolutions at the tip of the notch are highlighted. The deformation mechanisms at the local scale are confronted with macroscopic behavior of the structure.</p> 2019-12-13T00:00:00+00:00 Copyright (c) 2020 Joseph MARAE DJOUDA, Donato Gallittelli , Marouene Zouaoui, Ali Makke, Julien Gardan , Naman Recho, Jérôme Crépin Rigid block and finite element analysis of settlement-induced failure mechanisms in historic masonry wall panels 2020-01-28T12:33:49+00:00 Raffaele Gagliardo Lucrezia Cascini Francesco Portioli Raffaele Landolfo Giovanni Tomaselli Marialaura Malena Gianmarco de Felice <p><span lang="EN-US" style="margin: 0px; font-family: 'Garamond',serif; font-size: 12pt;">The paper is related to the assessment of collapse mechanisms of historic masonry structures suffering settlements induced by ground movements. Two numerical strategies are adopted in order to study the influence of the settled zone on the cracking of masonry buildings: a discrete rigid block model and a continuous homogenized model. The first approach provides an estimate of the collapse load and failure pattern of masonry based on the lower bound theorem of limit analysis. The second approach is formulated in the framework of multi-surface plasticity and implemented in a FE code for the path-following non-linear analysis of masonry wall described as continuous anisotropic plate. Several settlement configurations, of masonry walls under moving ground support are investigated and the corresponding failure patterns resulting from the analysis are obtained resulting in local or global failure modes. The results of the two modeling formulations are compared and discussed in order to highlight the features of the two different approaches in the prediction of settlement-induced damage.</span></p> 2019-12-12T18:49:19+00:00 Copyright (c) 2020 Raffaele Gagliardo, Lucrezia Cascini, Francesco Portioli, Raffaele Landolfo, Giovanni Tomaselli, Marialaura Malena, Gianmarco de Felice Microstructural damage evaluation of ferritic-ausferritic spheroidal graphite cast iron 2020-01-28T12:34:15+00:00 Diego Omar Fernandino Vittorio Di Cocco Nicolas Tenaglia Costanzo Bellini Francesco Iacoviello Roberto Enrique Boeri <p>The goal of this work is to improve the understanding of the relation between the microstructural characteristics of Intercritical Austempered Ductile Cast Iron (IADI) and the damage micromechanisms observed during its tensile loading. The experimental methodology involves heat treatments to obtain IADI and the assessment of the damage mechanisms (sequence and occurrence) during step by step tensile testing. The damage evaluation was carried out by observing the surface of the tensile test specimen with optical and scanning electron microscopy.</p> <p>The results show that small cracks start forming soon after the yield stress is surpassed. The crack initiation is preferentially located at matrix-nodule interface. As loading increases, cracks also develop at the ferritic grain boundaries and the ausferritic/ferritic interfaces. Consequently, at higher strain values, a competition between the plastic deformation on internodular zones and crack propagation along ausferritic phase is observed.</p> <p>Finally, the final fracture is produced by the propagation of cracks across the internodular ligaments and through the ausferritic/ferritic interface that later coalesce into a single dominant crack leading to the material failure.</p> 2019-12-12T17:10:28+00:00 Copyright (c) 2020 Diego Omar Fernandino, Vittorio Di Cocco, Nicolas Tenaglia, Costanzo Bellini, Francesco Iacoviello, Roberto Enrique Boeri Micromodels for the in-plane failure analysis of masonry walls: Limit Analysis, FEM and FEM/DEM approaches 2020-01-28T12:34:38+00:00 Marco Pepe Marco Pingaro Patrizia Trovalusci Emanuele Reccia Lorenzo Leonetti <p>In the last decades the modeling of masonry structures has become an argument particularly appealing for many researchers and a large variety of numerical techniques have been formulated with the aim to produce practical applications in civil engineering, with special reference to the preservation and restoration of cultural heritage. Nevertheless, the question appears today still far from being resolved in a general way. The characteristics of frailty, heterogeneity and anisotropy of masonry, as well as the extreme variety of the building/construction rules strongly compromise the possibility of a unified description of its mechanical behavior.</p> <p>In this work a comparison of different models and techniques for the assessment of the mechanical behavior of two-dimensional block masonry walls subjected to the static action of in-plane loads is presented. Different approaches and numerical models are considered: a Limit Analysis approach (LA), a FEM/DEM procedure and a non-linear heterogeneous Finite Element analysis (FE). In particular, the Limit Analysis is able to provide fast and reliable results in term of collapse multiplier and related mechanism. Here a standard Limit Analysis is adopted via a homemade procedure based on Linear Mathematical Programming, considering friction at interfaces. Analyses are performed referring to benchmark examples from literature.</p> 2019-12-12T05:38:18+00:00 Copyright (c) 2020 Marco Pepe, Marco Pingaro, Patrizia Trovalusci, Emanuele Reccia, Lorenzo Leonetti 3D limit analysis of masonry pavilion domes on octagonal drum subjected to vertical loads 2020-01-28T12:35:02+00:00 Carlalberto Anselmi Filomena Galizia Eduardo Saetta <p>Within the framework of limit design applied to masonry structures, this paper aims at analyzing the different behavior of a pavilion dome according to the adopted construction and reinforcement technologies. By using the static theorem applied to the dome discretized in rigid macro-blocks of variable shape aligned along parallels and meridians, a mathematical model have been constructed in order to search for the load collapse multiplier, and thus to evaluate the degree of structural safety. Then, the associated failure mechanism is represented at the instant in which the collapse is reached. The program that implement the modeling is sufficiently versatile and, in addition to the mechanical characteristics, allows to define the intrados profile, the thickness variability, as well as to insert any window opening in the drum, the lantern at the top and the hoops at each level. The results shown here concern some numerical applications carried out on a theoretical dome, as well as those related to a first approach to the analysis of the dome of Santa Maria del Fiore in Florence by Brunelleschi.</p> 2019-12-12T05:15:09+00:00 Copyright (c) 2020 Carlalberto Anselmi, Filomena Galizia, Eduardo Saetta Simulation of the delay effect after applying a simple overload on alloys of aluminum 2024T351 using the Willemborg model 2020-01-28T12:35:26+00:00 Kaddour Bahram Mohamed Chaib Abdelkader Slimene Benattou Bouchouicha <p>The structures in service are subjected to loads whose amplitude varies most often over time. These differences in loading cycle levels will have a direct impact on the propagation of cracks that can lead to accelerations or slowdowns in the propagation speed of these cracks. Indeed, the delay of the propagation of a crack produced by the application of a simple overload depends on several parameters, such as the material, the loading, the geometry of the specimen and the environment. In this paper, we will try to master more light only on the influence of the loading parameters such as the load ratio, the overload rate on crack propagation, the propagation speed, the number of delay cycle, using the AFGROW calculation code and the willenbourg model, which describes the delay after applying overloads.</p> 2019-12-12T04:33:31+00:00 Copyright (c) 2020 kaddour bahram, Mohamed Chaib, Abdelkader Slimene, Benattou Bouchouicha Dynamic characterization of progressively damaged segmental masonry arches with one settled support: experimental and numerical analyses 2020-01-28T12:35:50+00:00 Maria Giovanna Masciotta Daniele Pellegrini Daniele Brigante Alberto Barontini Paulo B. Lourenço Maria Girardi Cristina Padovani Giovanni Fabbrocino <p>This paper aims to explore the dynamic behavior of a segmental masonry arch subjected to increasing horizontal displacements of one support. To this end, output-only dynamic identification techniques are first used to track the evolution of the dynamic features of the system under progressive damage scenarios and evaluate their sensitivity to settlement-induced cracks. Considerations on the structural response of the segmental arch up to failure are also included. Then, a numerical procedure coupling linear perturbation and modal analysis is applied to simulate the dynamic behavior of the arch over consecutive scenarios, taking into account the influence of the damage on the structure’s dynamic properties in an automatic way. The combination of experimental and numerical analyses allows to fully investigate the dynamics of the cracked masonry arch and to shed light on relevant aspects about the effects of settlement-induced cracks on the modal blueprints of masonry arches.</p> 2019-12-11T17:28:40+00:00 Copyright (c) 2020 Maria Giovanna Masciotta, Daniele Pellegrini, Daniele Brigante, Alberto Barontini, Paulo B. Lourenço, Maria Girardi, Cristina Padovani, Giovanni Fabbrocino Stress-strain assessment of plain dents in gas pipelines 2020-01-28T12:36:13+00:00 Yaroslav Dubyk Iryna Seliverstova <p>Paper presents the analytical solution of the stress-strain state for a dented pipeline, based on the method of equivalent loads. First off all solution for a harmonic imperfection is found, then using Fourier series expansion a semi-analytical procedure is proposed to assess single dent. Comparison between analytical and numerical results for the axial force and pressure load is given. Influence of the dent dimensions, shell radius to thickness ratio and initial loading to stress concentration factor are discussed.</p> 2019-12-09T03:44:57+00:00 Copyright (c) 2020 Yaroslav Dubyk, Iryna Seliverstova The hydrogen embrittlement sensitivity of duplex stainless steel with different phase fractions evaluated by in-situ mechanical testing 2020-01-28T12:36:37+00:00 Margo Cauwels Lisa Claeys Tom Depover Kim Verbeken <p>The influence of the austenite (γ) phase fraction on the hydrogen embrittlement of duplex stainless steel is investigated. Heat treatments are performed to create two duplex stainless steel specimens, containing 50% and 44% of austenite, respectively. Mechanical testing with and without hydrogen charging reveals that significant embrittlement occurs regardless of the austenite fraction. A higher austenite fraction results in a reduced ductility loss under the presence of hydrogen. Samples with a higher ferrite fraction are embrittled more due to their higher hydrogen diffusivity. In-situ tensile tests, interrupted at the ultimate tensile strength, show hydrogen-assisted cracks on the specimen surface both in austenite and ferrite and across the α/γ interface.</p> 2019-12-07T17:12:36+00:00 Copyright (c) 2020 Margo Cauwels, Lisa Claeys, Tom Depover, Kim Verbeken Interlaminar shear strength study on CFRP/Al hybrid laminates with different properties 2020-01-28T12:37:01+00:00 Costanzo Bellini Vittorio Di Cocco Luca Sorrentino <p>FML (Fibre Metal Laminate) is a hybrid material that presents outstanding structural properties, such as resistance to cyclic and dynamic loads, together with low specific weight. This material consists of metal sheets alternating to composite material layers. In the present work, the ILSS (Interlaminar Shear Strength) was evaluated for different types of carbon fibre/aluminium FML, produced varying the layer thickness and the bonding solution of layers. In fact, FMLs consisting of one or two metal sheets (a parameter strictly connected to the layer thickness, as the metal/composite volume fraction was kept at constant value) and bonded with structural adhesive or prepreg resin were considered for this study. The ILSS was determined according to the three-point bending method with short beam specimens. The experimental tests evidenced an effect of the adhesion methodology on the ILSS value, while the layer thickness did not influence the interlaminar strength. The mechanical behaviour after the maximum load point was investigated too, evaluating the trend of the shear stress as a function of the loading nose displacement.</p> 2019-12-07T17:10:19+00:00 Copyright (c) 2020 Costanzo Bellini, Vittorio Di Cocco, Luca Sorrentino Finite Element Modeling of the Behavior of a Hollow Cylinder in a Hydrogen-Containing Environment 2020-01-28T12:37:24+00:00 Assia Amina Lakhdari Serguey A. Bubnov Aissa Seddak Ilya I. Ovchinnikov Igor G. Ovchinnikov <p>The two main research orientations on the problem of hydrogen embrittlement are examined: the study of fundamental principles and the disclosure of micromechanisms and the relation between hydrogen embrittlement and metal aging; the development of models and methods for predicting the kinetics of change in stress-strain state and for evaluating the longevity of structures subjected to hydrogen embrittlement. The state of the problem of hydrogen embrittlement of metals in the first direction is briefly analyzed. More attention is paid to the importance of predicting the behavior of charged metal structures under the influence of hydrogen embrittlement. We then examine the use of finite element modeling using the ANSYS software to compute the calculation analysis of a hollow cylinder subjected to internal and external pressures and hydrogen embrittlement. The cylinder material is nonlinear elastic and its properties depend on the hydrogen concentration at each point of the cylinder. Consideration is given to the influence of the rigidity of the stress state and the hydrogen concentration on the diffusion kinetics of hydrogen in the cylinder body.&nbsp; The problem is solved in time steps. The distributions of the hydrogen concentration and the stresses for a quarter of the volume of the cylinder are given, as well as the graphs of these values ​​according to the thickness of the wall of the cylinder at different times.</p> <p>It is shown that the ANSYS software package adapted to the resolution of such problems can model the behavior of different structures in a hydrogen-containing environment, taking into account the effects caused by both the influence of hydrogen on mechanical properties of the material and by the stress state of the structures, as well as by the influence of the stress state on the interaction kinetics of hydrogen with the structures.</p> 2019-12-07T16:51:54+00:00 Copyright (c) 2020 Assia Amina Lakhdari, Serguey A. Bubnov, Aissa Seddak, Ilya I. Ovchinnikov, Igor G. Ovchinnikov Alloy Substitution in a Critical Raw Materials Perspective 2020-01-28T12:37:48+00:00 Paolo Ferro Franco Bonollo Sylvia Cruz <p><span lang="EN-US">Since many years, the European Community has been monitoring some raw materials because of their high importance to the European Union economy and their high supply risk. Such raw materials, classified as critical, form a strong industrial base, producing a lot of goods and applications used in everyday life and modern technologies. Many critical raw materials are used to produce alloys and their high supply risk may constitute a serious problem for the future world economy and technological progress. Mitigating actions are therefore needed such as recycling, material efficiency improvements and, when possible, material substitution. In the present work, a systematic approach for alloy substitution in a critical raw materials perspective is developed. The method is illustrated with an example.</span></p> 2019-12-07T06:42:52+00:00 Copyright (c) 2020 Paolo Ferro, Franco Bonollo, Sylvia Cruz The FEA and experimental stress analysis in circular perforated plates loaded with concentrated force 2020-01-28T12:38:12+00:00 Mateusz Konieczny Grzegorz Gasiak Henryk Achtelik <p>ABSTRACT. The paper presents an analysis of an isotropic circular axisymmetric perforated plate loaded with concentrated force Pi applied in the geometric center of the plate using finite element software ANSYS. The test plate with diameter D = 300 mm has holes in ten circles. The plate has holes with diameter d1 = 3.5 mm on the first inner circle, and holes on the tenth outside circle have a diameter d10 = 20.5 mm. The plate of the above geometry was free supported and loaded with different values of concentrated force. By means of numerical calculations using the finite element method, the coordinates of concentration zones of reduced stress in the perforated plate were determined. These zones were located on the plate bridges between perforation holes. The most hazardous place in the analyzed perforated plate is associated with the tenth zone Z10 with the hole radius d1 = 3.5 mm at the circle radius R1 = 22.5 mm, where the highest stress concentration occurs. In this zone, the reduced stress is σred max = 416.90 MPa (point with the coordinates x, y, z [mm], i.e. P10 [-69.9; 72.5; 0.0]). The results of numerical calculations were verified with experimental results. The differences between the results of numerical calculations of the state of stress and those obtained experimentally did not exceed 36%.<br><br><br></p> 2019-12-07T04:33:16+00:00 Copyright (c) 2020 Mateusz Konieczny, Grzegorz Gasiak, Henryk Achtelik Relationship between microscopic analysis and quantitative and qualitative indicators of moisture susceptibility evaluation of warm-mix asphalt mixtures containing modifiers 2020-01-28T12:38:35+00:00 Pooyan Farazmand Parham Hayati Hamid Shaker Sajad Rezaei <p>Given the defects of bitumen in asphalt mixtures particularly exposed to moisture, this study mainly aims to investigate the relationship between qualitative and quantitative results of moisture susceptibility tests on asphalt mixtures modified by ZycoTherm, nanoclay, nanosilica and SBS. The Marshall stability, modulus of resilience and indirect tensile strength tests are carried out. Boiling water and SEM qualitative tests are also used. Eventually, the qualitative tests results are digitalized through image processing by MATLAB and compared with the moisture susceptibility results of indirect tensile strength test.</p> <p>For modulus of resilience testing, the results show that this modifier has the maximum impact on Marshall stability, improving it by about 23%. For moisture susceptibility testing, the nanosilica-modified mixture has the maximum effect among anti-stripping additives, with an improvement by about 20%. An investigation into the results of SEM images and boiling water test via MATLAB indicates the high accuracy of SEM images and their results show the most compatibility with the results of quantitative data.</p> 2019-12-05T05:00:40+00:00 Copyright (c) 2020 Pooyan Farazmand, Parham Hayati, Hamid Shaker, Sajad Rezaei Comparison of Two Parameters Models for clay brick masonry confinement 2020-01-28T12:38:59+00:00 Giancarlo Ramaglia Gian Piero Lignola Andrea Prota <p>Masonry elements are often strengthened in order to improve their structural capacity. Generalized methods to assess the behavior of confined masonry columns are not available in the technical literature. They have been usually derived from concrete confinement models. However, concrete and masonry present several crucial differences due to their physical and mechanical properties. In fact, generalized models to assess the axial capacity of masonry columns were limited by the strong variability and heterogeneity of physical and mechanical properties. However, the recent scientific researches provided relevant information on the experimental behavior of confined masonry columns. In this paper, a confinement model has been proposed to assess the axial capacity of clay brick masonry strengthened using several strengthening systems. The model has been validated by means of comparisons with experimental results. In order to assess the potential of the proposed model, the comparison was carried out also with other available mechanical models.</p> 2019-12-05T00:00:00+00:00 Copyright (c) 2020 Giancarlo Ramaglia, Gian Piero Lignola, Andrea Prota Investigations in static response and free vibration of a functionally graded beam resting on elastic foundations 2020-01-28T12:39:23+00:00 Abdelbaki Chikh <p>In this article, an analytical study was done to predict the behavior of the beam vis-à-vis bending, buckling, and dynamic responses of isotropic homogeneous beams based on an elastic foundation. The material properties of the FG-beams vary across the thickness using the power law. In this work, the sinusoidal shear deformation beams theory is used to investigate the static and dynamic behavior of FG beams. The present theory fulfills the condition of nullity of edge stresses and does not require the use of a shear correction factor. Hamilton's principle is used to deduce equations of motion, and analytical solutions for simply supported beams were obtained using the Navier resolution method. Nondimensional displacements, eigenfrequencies and critical-buckling loadcs of isotropic homogeneous beams were obtained for various values of the foundation parameters. The numerical results obtained by the present technique have been compared with the results of literature and are in excellent agreement with them. It can be concluded that the current HSDBT is simple and accurate in solving the bending, eigenfrequency and critical-buckling load problems for FGM beams.</p> 2019-12-04T18:36:13+00:00 Copyright (c) 2020 Abdelbaki Chikh Analytical and numerical analysis on the collapse modes of least-thickness circular masonry arches at decreasing friction 2020-01-28T12:39:47+00:00 Giuseppe Cocchetti Egidio Rizzi <p>Departing from pioneering Heyman modern rational investigations on the purely-rotational collapse mode of least-thickness circular masonry arches, the hypothesis that joint friction shall be high enough to prevent inter-block sliding is released. The influence of a reducing Coulomb friction coefficient on the collapse modes of the arch is explicitly inspected, both analytically and numerically, by tracing the appearance of purely-rotational, mixed sliding-rotational and purely-sliding modes. A&nbsp;classical doubly built-in, symmetric, complete semi-circular arch, with radial joints, under self-weight is specifically considered, for a main illustration. The characteristic values of the friction coefficient that limit the ranges associated to each collapse mode are first analytically derived and then numerically identified, with self-consistent outcomes. Explicit analytical representations are provided to estimate the geometric parameters that define the limit equilibrium states of the arch, specifically the minimum thickness to radius ratio, at reducing friction. These formulas, starting from the analysis of classical Heymanian instance of purely-rotational collapse, make new explicit reference to the mixed sliding-rotational collapse mode, arising within a narrow range of limited friction coefficients (or friction angles). The obtained results are consistently compared to existing numerical ones from the competent literature.</p> 2019-12-04T18:26:48+00:00 Copyright (c) 2020 Giuseppe Cocchetti, Egidio Rizzi The role of different sliding resistances in limit analysis of hemispherical masonry domes 2020-01-28T12:40:10+00:00 Elham Mousavian Claudia Casapulla <p>A limit analysis method for masonry domes composed of interlocking blocks with non-isotropic sliding resistance is under development. This paper reports the first two steps of that work. It first introduces a revision to an existing limit analysis approach using the membrane theory to find the minimum thickness of a hemispherical dome under its own weight and composed of conventional blocks with finite isotropic friction. The coordinates of an initial axisymmetric membrane surface are the optimization variables. During the optimization, the membrane satisfies the equilibrium conditions and meets the sliding constraints where intersects the block interfaces. The results of the revised procedure are compared to those obtained by other approaches finding the thinnest dome. A heuristic method using convex contact model is then introduced to find the sliding resistance of the corrugated interlocking interfaces. Sliding of such interfaces is constrained by the Coulomb’s friction law and by the shear resistance of the locks keeping the blocks together along two orthogonal directions. The role of these two different sliding resistances is discussed and the heuristic method is applied to the revised limit analysis method.</p> 2019-12-04T17:03:22+00:00 Copyright (c) 2020 Elham Mousavian, Claudia Casapulla Crumbling of Amatrice clock tower during 2016 Central Italy seismic sequence: Advanced numerical insights 2020-01-28T12:40:35+00:00 Francesco Clementi Gabriele Milani Angela Ferrante Marco Valente Stefano Lenci <p>The dynamic behaviour and the seismic vulnerability of the ancient civic tower of Amatrice, dramatically damaged by the last shocks sequence of 2016 that occurred in Central Italy, have been studied in this paper by means of advanced 3D numerical analyses with the Discrete Element Method (DEM). Thus, a discontinuous approach has been used to assess the dynamic properties and the vulnerability of the masonry structure, through large deformations regulated by the Signorini’s law, concerning the impenetrability between the rigid bodies, and by the Coulomb’s law, regarding the dry-friction model. Afterward, different values have been assigned to the friction coefficient of the models and real seismic shocks have been applied in the nonlinear analyses. The major purpose of this study is to highlight that relevant data on the real structural behaviour of historical masonry can be provided through advanced numerical analyses. The comparison between the results of the numerical simulation and the survey of the existing crack pattern of the bell tower permitted to validate the approach used. Finally, from the results and conclusions of this case study, it is possible to affirm that the used methodology can be applied to a wide variety of historical masonry structure in Europe.</p> 2019-12-04T14:37:55+00:00 Copyright (c) 2020 Francesco Clementi, Gabriele Milani, Angela Ferrante, Marco Valente, Stefano Lenci The development and application of an original 3D laser scanning: a precise and nondestructive structural measurements system 2020-01-28T12:40:59+00:00 Kexin Li Jun Wang Dawei Qi <p>Recently, a number of non-destructive testings equipment (NDTs) which can partially replace human-conducted onsite inspections has been implemented for detecting modern civil architectural structures. However, the situation of implementing 3D laser scanning measurement technology worldwide is not optimistic: several inconvenient flaws is troubling users (e.g., heavy, costly, hard to move, hard to inspect and etc.). Therefore, a new equipment to fix those problems is urgently demanded. This paper aims to thoroughly analyze the issue and then develop a feasible. A 3D laser scanning system composed of high precision elevating platform and small 2D laser ranging sensor is designed. Manufacture Process of 3D laser scanning system is describes in detail. Based on the bending fatigue loading test, the scanning designed efficiency and feasibility had been proved by comparing and analyzing traditional measurement results. The designed 3D laser scanning system can quickly capture the information of micro-damage and depth of the structure. Its detecting performance is better than the traditional methods. To overcome the challenges of the 3D laser scanning on-site measurement technology, this article proposed the manufacture process of the 3D scanning system with a high precision, miniaturization and lightweight.</p> 2019-12-04T04:06:40+00:00 Copyright (c) 2020 Kexin Li, Jun Wang, Dawei Qi Numerical modeling based on moving mesh method to simulate fast crack propagation 2020-01-28T12:41:22+00:00 Francesco Fabbrocino Marco Francesco Funari Fabrizio Greco Paolo Lonetti Raimondo Luciano <p>An analysis to show the capability of moving mesh strategy to predict dynamic crack growth phenomena in 2D continuum media is proposed. The numerical method is implemented in the framework of the finite element method, which is coupled with moving mesh strategy to simulate the geometry variation produced by the crack tip motion. In particular, a computational procedure based on the combination of Fracture Mechanics concepts and Arbitrary Lagrangian-Eulerian approach (ALE) is developed. This represents a generalization of previous authors’ works in a dynamic framework to propose a unified approach for predicting crack propagation in both static and dynamic frameworks. The crack speed is explicitly evaluated at each time step by using a proper crack tip speed criterion, which can be expressed as a function of energy release rate or stress intensity factor. Experimental and numerical results are proposed to validate the proposed approach. Mesh dependence problem, computational efficiency and numerical complexity are verified by comparative results</p> 2019-12-03T17:31:04+00:00 Copyright (c) 2020 Francesco Fabbrocino, Marco Francesco Funari, Fabrizio Greco, Paolo Lonetti, Raimondo Luciano Retrofit assessment of masonry buildings through simplified structural analysis 2020-01-28T12:41:46+00:00 Mariateresa Guadagnuolo Marianna Aurilio Giuseppe Faella <p>The current seismic prevention strategy is based on a unitary approach aimed at a risk mitigation, also at territorial level. The Italian guidelines for the assessment and mitigation of seismic risk of cultural heritage provides indications for the seismic analysis of protected cultural heritage, with the aim of specifying a path of knowledge, assessing the level of safety and planning possible improvements. The Italian building heritage is very vast and heterogeneous and was devastated by earthquakes due to its high vulnerability; therefore, the seismic risk mitigation also requires the availability of simple and handy analysis tools. The aim of this paper is the illustration of an easy, although approximate, procedure for the evaluation of the seismic safety index and the optimization of strengthening interventions. The procedure is applied to buildings located in the province of Caserta. The analyses are performed with reference to two types of buildings that are particularly recurrent and representative of the building heritage of this area and placed in areas with different seismic hazard.</p> 2019-12-03T16:23:29+00:00 Copyright (c) 2020 Mariateresa Guadagnuolo, Marianna Aurilio, Giuseppe Faella