Frattura ed Integrità Strutturale <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). The Journal is financially supported by Italian Group of Fracture and by crowdfunding and is completely free of charge both for readers and for authors. Neither processing charges nor submission charges will be required.<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>&nbsp;</p> <p><strong>Sister Associations help the journal managing:</strong><br>Australia: Australian Fracture Group - AFG<br>Czech Rep.: Asociace Strojních Inženýrů (Association of Mechanical Engineers)<br>Greece: Greek Society of Experimental Mechanics of Materials - GSEMM<br>India: Indian Structural Integrity Society - InSIS<br>Israel: Israel Structural Integrity Group - ISIG<br>Italy: Associazione Italiana di Metallurgia - AIM<br>Italy: Associazione Italiana di Meccanica Teorica ed Applicata - AIMETA<br>Italy: Società Scientifica Italiana di Progettazione Meccanica e Costruzione di Macchine - AIAS<br>Poland: Group of Fatigue and Fracture Mechanics of Materials and Structures<br>Portugal: Portuguese Structural Integrity Society - APFIE<br>Romania: Romania Association of Fracture Mechanics - ARMR<br>Serbia: Structural Integrity and Life Society "Prof. Stojan Sedmak" - DIVK<br>Spain: Grupo Espanol de Fractura - Sociedad Espanola de Integridad Estructural - GEF<br>Ukraine: Ukrainian Society on Fracture Mechanics of Materials (USFMM)</p> en-US <p><strong>Copyright&nbsp;</strong><br>Authors are allowed to retain both the copyright and the publishing rights of their articles without restrictions.&nbsp;&nbsp;</p> <p><strong>Open Access Statement</strong></p> <p>Frattura ed Integrità Strutturale (Fracture and Structural Integrity, F&amp;SI) is an open access journal which means that all content is freely available without charge to the user or his/her institution. Users are allowed to read, download, copy, distribute, print, search, or link to the full texts of the articles in this journal without asking prior permission from the publisher or the author. This is in accordance with the BOAI definition of open access. F&amp;SI operates under the Creative Commons Licence Attribution 4.0 International (CC-BY 4.0). This allows to copy and redistribute the material in any medium or format, to remix, transform and build upon the material for any purpose, even commercially, but giving appropriate credit and providing a link to the license and indicating if changes were made.</p> (Francesco Iacoviello) (Support) Thu, 27 Sep 2018 00:00:00 +0000 OJS 60 Considerations over the Italian road bridge infrastructure safety after the Polcevera viaduct collapse: past errors and future perspectives <p>In the last four years, Italy experienced the collapse of five road bridge: Petrulla viaduct (2014), Annone (2016) and Ancona (2017) overpasses, Fossano viaduct (2017) and Polcevera (2018) bridge.</p> <p>Although for deeply different reasons, the collapses occurred can all been gathered into the same common cause: the (lack of) knowledge of the effective structural condition, a serious problem that affects existing constructions.</p> <p>As it will be shown in the paper, different problems such as missing of the as-built designs, an appropriate construction and movement precautions, a heavy vehicle checking, and a material decay monitoring can nevertheless be addressed as an inadequate knowledge of what is happening to/in the structure.</p> <p>In the first section, the paper will report a short description of the failures for the five bridges, while in the second part a main set of problems involved in bridge safety and maintenance will be discussed. Finally, in the third part, a review on innovative and peculiar investigation and monitoring techniques will be illustrated. The collected results can shed new light on future perspectives for the Civil Engineering sector, sector that has to be ready for facing the challenges of preservation, restoration and/or replacement of the existing infrastructural constructions, worldwide.</p> Fabio Bazzucchi, Luciana Restuccia, Giuseppe Ferro Copyright (c) 2018 Fabio Bazzucchi, Luciana Restuccia, Giuseppe Ferro Thu, 27 Sep 2018 15:37:12 +0000 Experimental study on the mechanical behavior of RPC filled square steel tube columns subjected to eccentric compression <p>In order to study the mechanical behavior of reactive powder concrete (RPC) filled square steel tubular columns, this paper designs an eccentric compression experiment for 12 specimens of RPC filled square steel tubular column and studies the effects of failure form, load-displacement curve, slenderness ratio, steel ratio and eccentricity ratio of a eccentrically loaded columns on its mechanical behavior. At the same time, it also compares the experiment results with the bearing capacity calculated with relevant specifications and uses Abaqus to carry out numerical simulation of eccentrically loaded columns. The results show that, the failure form of the eccentrically loaded RPC filled square steel tubular column shows local buckling failure. Before the ultimate load is reached, there is no significant change on the surface of the specimen, and the yield stage of the load-displacement curve is not obvious, either. The results of the bearing capacity calculation formula recommended in CECS28-2012 are close to the experiment results and relatively conservative, so it is more applicable to the bearing capacity design of eccentrically loaded RPC filled square steel tubular columns. The results of the numerical simulation analysis are in good agreement with the experimental results, which can provide theoretical support for engineering practice.</p> Wenxiu Hao, Xiao Xu, Zhiqiang Niu Copyright (c) 2018 Wenxiu Hao, Xiao Xu, Zhiqiang Niu Thu, 27 Sep 2018 04:19:00 +0000 Investigation of the effect of cracks on the vibration processes in reinforced concrete structures <p>The validity of the mathematical model describing the propagation of vibrations in the reinforced concrete structures (RC structures) was verified by comparing the experimental and numerical data. The proposed model allowed us to perform numerical experiments aimed at comparing vibrorecords obtained for the structure without defects and the structure with typical fracture caused by crack formation. Based on the results of comparison, an informative diagnostic parameter was proposed. This parameter makes it possible to control the nucleation and growth of cracks in a RC structure.</p> Igor Shardakov, Aleksey Shestakov, Roman Tsvetkov, Irina Glot Copyright (c) 2018 Igor Shardakov, Aleksey Shestakov, Roman Tsvetkov, Irina Glot Thu, 27 Sep 2018 02:48:24 +0000 The impact of the temperature and exploitation time on the tensile properties and plain strain fracture toughness, KIc in characteristic areas of welded joint <p>This paper presents the analysis of the temperature and exploitation time impact on the resistant measure to brittle fracture of welded joint constituents of the new and exploited low-alloyed Cr-Mo steel A-387 Gr. B from the aspect of application of the parameters obtained by tensile testing and parameters obtained by fracture mechanics testing. The exploited parent metal is a part of the reactor mantle which has been exploited for over 40 years and is in the damage repair stage, i.e. in the stage where the part of the mantle is being replaced with new material. Basic characteristics of the material strength, as well as the stress-elongation curves required for stress analysis are obtained by tensile testing. The testing of plane strain fracture toughness is conducted in order to determine the critical stress intensity factor, K<sub>Ic</sub>, that is, assessment of behavior of the new and exploited parent metal, welded metal and heat affected zone from the side of the new parent metal and from the side of the exploited parent metal in the presence of the crack type error. Based on the research results, the analysis of the resistance to brittle fracture represents the comparison of obtained values for characteristic areas of welded joint and justification of the selected welding technology.</p> Simon Sedmak, Ivica Čamagić, Aleksandar Sedmak, Zijah Burzić, Mihajlo Aranđelović Copyright (c) 2018 Simon Sedmak, Ivica Čamagić, Aleksandar Sedmak, Zijah Burzić, Mihajlo Aranđelović Thu, 27 Sep 2018 02:41:35 +0000 Stress performance of embedded carbon fiber reinforced plastics plate consolidated reinforced concrete structure <p>With the development of the building industry, various novel building materials have emerged. Modern buildings requires higher on performance of building materials, and the performance of old buildings has not been able to keep up the pace of the times. Extending the service time of old buildings by repairing and reinforcing is inevitable. In this study, 10 reinforced concrete beams including 2 ordinary reinforced concrete beams and 8 carbon fiber reinforced plastics (CFRP) plate reinforced test beams were manufactured. Three-dimensional finite element model was established using finite element software to simulate and compare the stress performance of the strengthening beams with different number of CFRP plate, size, number of groove and shear span ratio. The results demonstrated that the ultimate carrying capacity of the embedded CFRP plate reinforced beams was obviously superior to that of the ordinary reinforced concrete beams; two plates and two grooves were appropriate; the larger the shear span ratio, the better the bearing performance and the smaller the deformation. CFRP plate consolidated reinforced concrete can effectively stabilize buildings which need repairing and reinforcement.</p> Hua Zhu Copyright (c) 2018 Hua Zhu Thu, 27 Sep 2018 02:26:40 +0000 Experimental study on concrete damage location by Computerized tomography and Acoustic Emission technology <p style="margin: 1em 0px; text-align: justify; -ms-text-justify: inter-ideograph;"><span lang="EN-US" style="font-family: 'Garamond',serif;"><span style="font-size: medium;">In order to solve the technical problem of damage localization in the concrete damage process, the Computerized Tomography (CT) scanning test and Acoustic Emission (AE) damage localization test was carried out under uniaxial compression. In addition to the three-dimensional meso model, the porosity variation law of concrete pore or cracks at different loading stages are obtained. A damage variable is created based on CT images and AE damage points. A damage variable based on CT image and AE damage point is established. The results show that the change of porosity, pore volume and damage variable is consistent with the loading process. The rapid increase of concrete pore volume and damage variable can be the precursor of concrete damage. The whole process of the development and evolution of concrete cracks was observed and analyzed comprehensively by using the three-dimensional reconstruction images and acoustic emission damage location map. A new method for analyzing the evolution and localization of cracks in concrete is presented.</span></span></p> <p>&nbsp;</p> Jinghong Liu, Jian Xie, Yongjian Liu, Panfei Shi Copyright (c) 2018 Jinghong Liu, Jian Xie, Yongjian Liu, Panfei Shi Thu, 27 Sep 2018 02:17:10 +0000 Blending Ratio of Recycled Aggregate on the Performance of Pervious Concrete <p>Recycled pervious concrete as an environment-friendly and material-saving construction material can satisfy the current development demands of circular economy and environmental protection in China. But studies concerning the performance of recycled pervious concrete are not enough, which limits its application and promotion. In this study, waste prefabricated concrete beams were taken as the source of recycled aggregate and processed by crushing and screening to obtain recycled coarse aggregate. Then pervious concrete was prepared using the recycled coarse aggregate. Taking replacement rate and grain size grade as the running parameters, five groups of mix proportion were designed. Moreover the physical, mechanical and permeability performance and the interrelation were analyzed by tests. The results demonstrated that the 24-hour water absorption rate of the recycled coarse aggregate was 12 times higher than that of natural aggregate, the porosity of the pervious concrete was between 14.2% and 20.44%, and the permeability coefficient was between 0.19 cm and 0.46 cm and increased with the increase of the porosity. The compressive strength of the pervious concrete increased with the increase of the replacement rate. When the replacement rate was 30%, the improvement amplitude was the largest. The compressive strength was improved 35.4% after double grain grade aggregate was mixed, but the permeability performance decreased.</p> yanya yao Copyright (c) 2018 yanya yao Thu, 27 Sep 2018 02:00:29 +0000 Numerical simulation of a heat generation in a layered material during ultrasonic wave propagation <p><span lang="EN-US" style="margin: 0px; font-family: 'Times New Roman',serif; font-size: 12pt;">Ultrasonic vibrothermography is an effective and non-destructive method, which can be used for a quick detection of coating defects on large surfaces. Mechanical excitation of a layered structure induces inelastic deformation and, as a consequence, energy dissipation in the defective area and local heating. In this work, a three-dimensional numerical simulation of this process is applied to the bi-metallic layered structure with an edge crack. Two models of energy dissipation are considered (hysteretic damping model and visco-elastic Maxwell’s model) for simulation of energy dissipation in a crack tip area under ultrasonic loading. The models allow us to study the effects of the loading frequency, loading direction and location of the coating defects on the heat dissipation and propose optimal regimes for the ultrasonic vibrothermography of bi-metallic layered structures</span><span lang="EN-US" style="margin: 0px; font-family: 'Garamond',serif; font-size: 12pt;">.</span></p> Anastasiia Kostina, Oleg Plekhov, Sergey Aizikovich Copyright (c) 2018 Anastasiia Kostina, Oleg Plekhov, Sergey Aizikovich Thu, 27 Sep 2018 01:45:19 +0000 Characterization of Isogrid Structure in GFRP <p>Lightening parts, maintaining also a high strength, is a request of the transport industry. Isogrid structures represent one of the best answer to face these issues, especially if composite materials are considered for their production. However, the fabrication of these structures is very complex, as defects can arise that cause the part discarding or the part failure during service. The properties of the fabricated structure depend on some process characteristics, as the forming technology, the process parameters and the tools that have to be wisely designed. Isogrid structures are characterized by the ribs, so the mould shape must be carefully planned. In fact, a common defect that usually occurs is a scarce compaction of the ribs, which involves porosity and low mechanical strength.</p> <p>In this paper, the manufacturing process peculiarities for GFRP (Glass Fibre Reinforced Polymer) isogrid structures were defined, then both the mould and the parts were produced. Structural tests were carried out on these structures in order to validate the process design methodology, paying particular attention to the structural properties of the ribs, as the compaction degree and the interlaminar shear strength. Finally, some actions were undertaken to avoid the problems found in the first production run.</p> Costanzo Bellini, Luca Sorrentino Copyright (c) 2018 Costanzo Bellini, Luca Sorrentino Thu, 27 Sep 2018 01:35:50 +0000 Fatigue crack propagation in welded joints X70 <p>Hi Dear colleague,<br>You will find enclosed in word file the text of our article entitled:<br>"Fatigue crack spread in weld seal X70"</p> Adel Deliou, Benattou Bouchouicha Copyright (c) 2018 Adel Deliou, Benattou Bouchouicha Thu, 27 Sep 2018 01:27:16 +0000 Deformation and failure of carbon fiber composite specimens with embedded defects during tension-torsion test <p>A need to timely reveal operational damages and technological defects requires a prompt control of states of structures made from composite materials and their consequent repairs aimed at service life extension. This work is devoted to the experimental study of inelastic deformation and fracture of specimens made from layer composite materials with prior introduced technological defects related to a possible inappropriate compacting and inappropriate bonding of material layers at a given restricted domain. The analysis is carried on the evolution of inhomogeneous deformation fields on the surface of carbon plastic specimens with an internal “delamination-type” defect under complex stress state. The method of active infrared thermography was used to identify the location and parameters of defects configurations. The obtained experimental data will be used for further tests related to sufficiency evaluation of signals received from the built-in sensors under complex loadings.</p> Tatyana Viсtorovna Tretyakova, Valery E. Wildemann, Elena M. Strungar, Mikhail P. Tretyakov Copyright (c) 2018 Tatyana Viсtorovna Tretyakova, Valery E. Wildemann, Elena M. Strungar, Mikhail P. Tretyakov Thu, 27 Sep 2018 01:15:47 +0000 Performance Index of Natural Stones-GFRP Hybrid Structures <p>Natural stone is a material that presents durableness over time and high aesthetic characteristic, but it is brittle and its tensile strength is significantly lower than compressive one: these peculiarities must be taken into account for material usage; in fact, for applications requiring high flexural and tensile strength, as thin sections or long spans, the particular mechanical behavior of the natural stone constitutes an issue to be overcome.</p> <p>A solution to the above mentioned problem is presented in the present paper: a natural stone tile is reinforced by bonding a sandwich structural laminate made of composite materials. In such manner, a double result is obtained: the mechanical strength increment and the and the tile specific weight decrement. In particular, two different types of sandwich structures, made of glass/epoxy laminates and honeycomb or foam core, were bonded to the lower surfaces of marble and granite tiles; then, 3-point bending tests were carried out on specimens extracted from the produced hybrid tiles. A performance index, considering both strength and weight of tiles, was introduced and the comparison with specimens extracted from traditional unreinforced tiles demonstrated that the considered reinforcement increases the structural characteristics of stone tiles up to an order of magnitude.</p> Luca Sorrentino, Costanzo Bellini, Wilma Polini, Sandro Turchetta Copyright (c) 2018 Luca Sorrentino, Costanzo Bellini, Wilma Polini, Sandro Turchetta Thu, 27 Sep 2018 01:00:44 +0000 Experimental Research on the Instantaneous and Long-Term Deflections of Pre-Cracked Concrete Beams Enhanced by Carbon Fibre Reinforced Polymer <p>This paper aims to disclose the influence law of cracks on instantaneous and long-term deflections of reinforced beam. For this purpose, four concrete beams were created, pre-loaded to varied degrees of cracking, and reinforced with carbon fibre reinforced polymer (CFRP). Then, a 300-day load test was carried out on these samples to measure the instantaneous and long-term deflections. The experimental results show that the pre-cracking degree has little influence on instantaneous deflection; whether a beam is pre-cracked or intact, the final deflection of the beam is mostly affected by its initial deflection before the reinforcement; the pre-cracking degree is negatively correlated to the magnitude of additional deflection under sustained load. The research findings lay the basis for judging whether a reinforced beam can be used normally in the long run.</p> Shiyong Jiang, Tao Cai, Shijuan Wu, Weilai Yao Copyright (c) 2018 Shiyong Jiang, Tao Cai, Shijuan Wu, Weilai Yao Wed, 26 Sep 2018 16:44:38 +0000 Micro failure analysis of adhesively bonded joints enhanced with natural cork particles: Impact of overlap length and particles volume fraction <p>In this work, the effects of natural particles on the micro failure mechanisms and static strength of an epoxy are studied using scanning electron microscope (SEM) technique. To this end, bulk specimens and adhesively bonded single lap joints (SLJs) containing different amount of micro cork particles were fabricated and tested. To investigate the toughening mechanisms, the fracture surfaces of the specimens were analyzed using SEM and a magnifying glass. It was shown that the deviation of the crack path and formation of micro-cracks generate multi fracture surfaces which is one of the main sources of energy absorption and resulted in higher fracture energy of the enhanced adhesives. Acting as a crack stopper and consequently stabilizing the crack propagation, prevents developing large and unstable cracks which is another source of energy consumption. However, the micro analysis showed that higher contents of cork lead to agglomeration of the particles which acts as a source of stress concentration, with a higher possibility of delamination between the matrix and the micro corks. Accordingly, there is an optimum amount of cork where the best adhesive fracture toughness is reached. The results showed that the optimum value of micro particles depends on the loading conditions.</p> Alireza Akhavan-Safar, Ana Queirós Barbosa, Lucas Filipe Martins da Silva, Majid Reza Ayatollahi Copyright (c) 2018 Alireza Akhavan-Safar, Ana Queirós Barbosa, Lucas Filipe Martins da Silva, Majid Reza Ayatollahi Wed, 26 Sep 2018 16:18:34 +0000 Numerical Analysis and Optimization of the Residual Stresses Distribution Induced by Cold Expansion Technique <p><strong>Abstract.</strong> This paper presents a numerical investigation about the influence of mandrel shape on residual stresses induced by the cold expansion procedure. Thus, ball and tapered pin are used for cold expanding the plate. As, the entrance face presents the lowest residual stresses throughout the hole thickness, we propose to solve this problem by varying the mandrel taper degree, instead of applying a double expansion.&nbsp; The obtained results show that the tapered pin is more suitable for the cold expansion. More, low taper increases the residual stresses at the entrance, reaching the values generated at the exit face.</p> Abdelghani BALTACH, Abdelkader Djebli, Mostefa Bendouba, El Hadj Besseghier, Abdelkrim Aid Copyright (c) 2018 Abdelghani BALTACH, Abdelkader Djebli, Mostefa Bendouba, El Hadj Besseghier, Abdelkrim Aid Wed, 26 Sep 2018 16:03:53 +0000 Management of multi-source information to identify the typology of the horizontal structures in historical masonry buildings: the case study of the Museum of Capodimonte in Naples (Italy) <p>The evaluation of the seismic safety of ancient masonry buildings usually requires compounding the need of preservation of the historical values with the need of achieving a proper level of knowledge of the parameters influencing their structural behaviour. To this aim, non-destructive techniques of instrumental investigation have lately attracted increasing attention, although the provided data are frequently not exhaustive and require to be integrated with different sources of information, such as historical documents and hypotheses of critical interpretation. Therefore, the management of this multi-source information is a crucial aspect in defining a methodological approach to the structural evaluation of the cultural heritage. This paper describes an integrated approach developed in the framework of the Project on the seismic evaluation of the Museum of Capodimonte in Naples (Italy) with reference to the typological identification of the horizontal structures at the first level of the building. The management of the data derived from the application of the infrared thermography, integrated with the information from the visual inspections, the architectural survey and the historic analysis, has allowed obtaining a complete characterization of the structures under study.</p> Alessandra Maione, Luca Umberto Argiento, Claudia Casapulla, Andrea Prota Copyright (c) 2018 Alessandra Maione, Luca Umberto Argiento, Claudia Casapulla, Andrea Prota Wed, 26 Sep 2018 14:27:28 +0000 Formulating the in-plane frictional resistances and collapse mechanisms for multi-storey masonry block walls <p>In this paper a macro-block model accounting for frictional resistances is presented to assess the lateral strength of a multi-storey masonry block wall. The kinematic approach of limit analysis is used to define the load factor causing the onset of rocking-sliding mechanism under in-plane horizontal loading. A dry frictional contact condition is assumed at the rigid block interfaces, according to the Coulomb's law with non-associated flow rule. The key aspect of the proposed approach is the introduction of a criterion to evaluate the contribution of the actual frictional resistances depending on the inclination angle of the crack line. An accurate assessment of the frictional resistances is also obtained by distinguishing two different contributions (the wall own weight and additional vertical loads) and their application points. Hence, a sensitivity analysis is performed with respect to the overloading condition, the friction coefficient, and geometrical parameters such as the shape ratios of the wall and the unit block and the number of rows.&nbsp; The analytical results of the proposed model are also validated against results from other existing macro and micro-block modelling approaches in terms of load factor. The comparison confirms the reliability of the proposed model that allows, with similar results, great simplification of the computational effort with respect to micro-block models.</p> Luca Umberto Argiento, Alessandra Maione, Claudia Casapulla Copyright (c) 2018 Luca Umberto Argiento, Alessandra Maione, Claudia Casapulla Wed, 26 Sep 2018 13:49:46 +0000 Assessment of RC Bridges integrity by means of low-cost investigations <p>Infrastructure aging is an important problem nowadays, in particular for countries like Italy in which the main motorways were built 50 years ago. Huge budgets are necessary to keep infrastructure and bridges in service. In addition, the lack of a proper and timely maintenance, entails an increase of the deterioration and therefore higher costs of repair.</p> <p>Thus, the need of methods capable of assessing the reliability of the infrastructure in the frame of Bridge Management System (BMS), is patent.</p> <p>The aim of this work is to provide a robust decision-support tool for the analysis of the data collected within the BMS with field inspection. The innovative aspect of the proposal is the introduction of two factors which take into account the location of the damage, and the mechanical characterization of the material in the definition of a Condition Rating Number (CRN).</p> <p>The analysis of an existing Reinforced Concrete (RC) bridge network is presented in order to show the accuracy of this new method.</p> Flavio Stochino, Maria Luisa Fadda, Fausto Mistretta Copyright (c) 2018 Flavio Stochino, Maria Luisa Fadda, Fausto Mistretta Wed, 26 Sep 2018 13:37:11 +0000 Resonances detected on a historical tower under bells’ forced vibrations <p>The aim of the paper is to perform a preliminary assessment of the dynamic behavior of the bell tower of Basilica Church “S.S. Medici”, one of the most important church in the town of Bitonto, Bari, Italy. The tower is 55 m tall and it is made in reinforced concrete. It is totally disconnected from the main structure of the Church. The structural behavior of the tower has been investigated by performing dynamic experimental tests, which have been executed in two different forcing conditions: recording the vibrations induced only by ambient loads, and, then the ones due to ambient loads and to the excitation produced by the bells. Four bells are housed in the lower bell chamber on a concrete bell frame, four more bells are housed at a higher level bell frame. All the bells are directly connected to the tower and swing in the same direction, so that their movement introduces a dynamic excitation on the tower. The experimental records have detected excessive movements on the tower when bells swing.</p> Dora Foti, Salvador Ivorra, Prof, Mariella Diaferio, Prof, David Bru, Prof, Vitantonio Vacca, Dr. Copyright (c) 2018 Dora Foti, Salvador Ivorra, Prof, Mariella Diaferio, Prof, David Bru, Prof, Vitantonio Vacca, Dr. Wed, 26 Sep 2018 13:15:49 +0000 Failure evidences of reduced span bridges in case of extreme rainfalls The case of Livorno <p>The heavy rainfalls occurring in Italy in the last few years focused the attention on the vulnerability of the land and the related infrastructures. Critical situations involving losses of human life and deterioration or failure of relevant structures are frequent. These events were due to: (1) improper land-use; (2) aging of infrastructures, (3) insufficient maintenance and protection; (4) climate changes causing rainstorms similar to tropical events. The failure of small bridges in road networks plays a key role in this sense. The present paper aims to analyse the behaviour of small bridges during rainfalls or floods. In particular, the recent case of Livorno is analysed. The Italian territory has about 460.000 small bridges, mostly designed without the support of technical codes or a proper interaction between the hydraulic and structural aspects. A large part of them can be submerged by water flows during rainfalls and pushed by unexpected actions.</p> <p>The failure scenarios allow identifying the hydraulic and structural vulnerabilities through a specific survey. A classification of small bridges on the basis of submergibility indexes is eventually proposed.</p> Marco Lucio Puppio, Sara Novelli, Mauro Sassu Copyright (c) 2018 Marco Lucio Puppio, Sara Novelli, Mauro Sassu Wed, 26 Sep 2018 04:54:59 +0000 An on-site teaching laboratory in a village damaged by the 2009 Abruzzo earthquake <p>This paper illustrates a two-year program of summer internships that involved forty students from the School of Engineering (University of Pisa) in 2010-2011. The activity consisted in a systematic survey of damages occurred in a village after the 2009 Abruzzo earthquake and in the preparation of documents addressed to a reconstruction plan. The historical center of San Pio delle Camere (1000 inhabitants) was fully surveyed, including about 140 hypogeal sites. Each student spent at least one month in these activities, funded by study grants provided by the Tuscany Region. Teams of two-three students performed well-defined work packages, led by a tutor, who established roles and functions. The students discussed the progress made preparing a weekly report. Moreover, preliminary structural analyses were carried out to assess the seismic vulnerability of some relevant buildings, fully available to the students. The main results were published in a book presented in a workshop. Most of the results were used to set up the official reconstruction plan of the village. During this on-site laboratory, the students could experience the effects of that destructive earthquake on the population, visiting also the damaged surrounding towns and seeing with their own eyes many cases of structural collapses.</p> Linda Giresini, Mauro Sassu Copyright (c) 2018 Linda Giresini, Mauro Sassu Wed, 26 Sep 2018 04:39:37 +0000 Analysis of cylindrical delamination cracks in multilayered functionally graded non-linear elastic circular shafts under combined loads <p>This paper is focused on delamination fracture analyses of a multilayered functionally graded circular shaft under two loading combinations (centric tension and torsion, and bending and torsion) assuming non-linear elastic mechanical behavior of the material. The loading combinations under consideration generate mixed-mode II/III delamination crack loading conditions (the centric tension and bending generate mode II crack loading, while the torsion is responsible for mode III crack loading). The shaft is made by concentric longitudinal layers. The number of layers is arbitrary. Besides, each layer has individual thickness and material properties. The material in each layer is functionally graded in radial direction. Hyperbolic laws are used to describe the continuous variation of material properties in radial direction. A cylindrical delamination crack (the crack front is a circle) is located arbitrary between layers. The delamination fracture is studied in terms of the strain energy release rate by analyzing the energy balance. In order to verify the solution obtained, the strain energy release rate is derived also by differentiating the complementary strain energy with respect to the delamination crack area. Parametric investigations of the behavior of the cylindrical delamination crack are carried-out. The present paper is a contribution in the fracture mechanics of multilayered functionally graded non-linear elastic circular shafts under combined loads.&nbsp;</p> Victor Rizov Copyright (c) 2018 Victor Rizov Wed, 26 Sep 2018 04:26:22 +0000 Fatigue Behaviour and Mean Stress Effect of Thermoplastic Polymers and Composites <p>More and more polymers and polymer composite materials are used in automotive industry to reduce cost and weight of vehicles to meet the environmental requirement. However, the fatigue behaviour for these materials is less understanding than metallic materials. The current work is focussed on the fatigue behaviour for a range of thermoplastic polymer/composite materials. It reveals that the fatigue behaviour of these materials can be described by S-N curves using the Basquin Equation. All the materials exhibit significant mean stress effect. The most commonly used mean stress correction equations developed in metal fatigue were evaluated with the current test results. It reveals that Goodman, Gerber and Soderberg cannot be used as generic equations for the materials investigated, whereas Smith-Watson-Topper can correlate the test data reasonably well, but the best correlation is given by Walker with material constant γ = 0.4.</p> Zongjin Lu, Bill Feng, Charlie Loh Copyright (c) 2018 Zongjin Lu, Bill Feng, Charlie Loh Sun, 23 Sep 2018 16:31:03 +0000 Analysis of the crack-crack interaction effect initiated in aeronautical structures and repaired by composite patch <p>In this work, we analyze three - dimensionally, by the finite element method, the performance of the repair of aeronautical structures damaged by cracking and repaired by patch of composite materials. The effect of crack-crack interaction according to their position and interdistance was analyzed. The criterion of rupture retained for this study is the factor of intensity of constraints. We show that this factor increases considerably and reaches a critical threshold when the two cracks develop towards each other. The repair of such damage using a composite patch ensures the stability of this structure during the commissioning process. The sharp fall in the stress intensity factor is characteristic of this stability.</p> Nour Chafak Ibrahim, Serier Boualem, Mechab Belaïd Copyright (c) 2018 Nour Chafak Ibrahim, Serier Boualem, Mechab Belaïd Sun, 23 Sep 2018 06:40:16 +0000 Failure behaviour of a fire protected steel element <p>In the present article the failure behaviour of a steel, beam type element supported against fire by protection boards, is studied. Three – dimensional, coupled temperature - displacement, non-linear finite element analysis models have been developed to simulate the unprotected and protected structure. A simple modelling approach is proposed for the investigation of the influence of the gradual failure of fire protection at elevated temperatures, on the structural performance of the system, under thermal and mechanical loads. Yielding of steel is depicted and force – displacement diagrams are used to evaluate the ultimate behaviour of the unprotected and protected models. It is shown that for the protected structure, yielding is less severe and the time period up to maximum strength is significantly longer. Eventually, is depicted how failure of the fire protection leads to a gradual reduction of the response, in fire conditions.</p> Georgios Drosopoulos, Siphesihle Motsa Copyright (c) 2018 Georgios Drosopoulos, Siphesihle Motsa Sun, 23 Sep 2018 06:14:53 +0000