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This scientific paper explores the use of correlation coefficients of vibration signals and machine learning algorithms for structural damage assessment in beams under moving loads. The paper discusses the challenges of maintaining structural integrity and the importance of automated, nondestructive monitoring techniques. Preprocessing techniques, such as the random decrement technique (RDT), are highlighted for improving data analysis. Machine learning algorithms are identified as valuable tools for structural damage assessment. The paper concludes by emphasizing the potential of machine learning in safeguarding critical infrastructures. The text also discusses trigger points and the vibration response of a slender beam under a moving load. An artificial neural network (ANN) is proposed as a computational model for identifying non-linear features. Experimental testing on a simulated bridge girder using accelerometers collected data to identify and locate damage in the beam. The ANN achieved high accuracy in detecting damage appearance and location, but further research is needed to improve accuracy in real-world situations. [Extracted from the article]

In recent years, many innovative optimization algorithms have been developed. These algorithms have been employed to solve structural damage detection problems as an inverse solution. However, traditional optimization methods such as particle swarm optimization, simulated annealing (SA), and genetic algorithm are constantly employed to detect damages in the structures. This paper reviews the application of SA in different disciplines of structural health monitoring, such as damage detection, finite element model updating, optimal sensor placement, and system identification. The methodologies, objectives, and results of publications conducted between 1995 and 2021 are analyzed. This paper also provides an in-depth discussion of different open questions and research directions in this area. [ABSTRACT FROM AUTHOR]

This document is a compilation of various research papers and articles that discuss the use of machine learning and other techniques to predict fatigue lifetimes in different materials and structures. The papers cover topics such as the use of neural networks, XGBoost, and physics-informed machine learning models for fatigue prediction. The research focuses on different materials, including aluminum alloys and lead-free solders, and explores the effects of factors such as wear, lubrication, corrosion, and stress on fatigue life. The papers provide insights into the application of machine learning techniques in predicting fatigue lifetime and offer potential solutions for improving the accuracy of these predictions. [Extracted from the article]

This document is a reference list for a research paper on fracture mechanics and structural integrity. The paper explores the effect of element size on fracture propagation stress using energy criteria. The research was funded by the Ministry of Higher Education Malaysia. The document also includes a Python code for an artificial neural network algorithm used in the research. The reference list contains other research papers on fracture mechanics, machine learning, and structural integrity. [Extracted from the article]

This document is a list of references to research papers and articles that focus on machining processes, specifically the machining of superalloy Inconel 718. The papers cover a range of topics including tool wear reduction, surface integrity evaluation, optimization techniques, and prediction models using artificial intelligence and machine learning. The research explores different lubrication techniques, nanofluid additives, and cutting parameters to improve the machinability of Inconel 718. The papers utilize various methodologies such as neural networks, fuzzy logic, response surface methodology, and genetic algorithms to optimize machining parameters and predict tool wear, surface roughness, and material removal rate. [Extracted from the article]

This document is a list of references related to the topic of variational mode decomposition (VMD) and its applications in various fields such as structural health monitoring, fault diagnosis, and time series analysis. The references include research papers and articles that discuss the theory, methodology, and practical applications of VMD. The document also includes a list of nomenclature used in the referenced papers. [Extracted from the article]

This article discusses a numerical study on the influence of the parameters of the statistical distribution of the ultimate strength of structural elements on the fracture processes of deformable bodies. The study uses computational methods to analyze the deformation and fracture processes of solids. The results show that the distribution and dispersion of the strength properties significantly affect the behavior and load-bearing capacity of the body. The study also highlights the importance of considering the inhomogeneity of mechanical properties in the modeling of fracture processes. The text also references two research papers and an experimental study related to stochastic response analysis and the behavior of concrete structures, which may be useful for library patrons researching related topics. [Extracted from the article]

This document provides a comprehensive overview of the integration of civil structural health monitoring and machine learning in the field of concrete structures. It discusses the importance of monitoring infrastructure condition and the challenges of manual inspection. The document highlights the increasing use of machine learning algorithms, such as computer vision methods, in optimizing maintenance and repairs. It presents case studies and applications of machine learning in civil engineering, including damage detection and load assessment. The document also emphasizes the challenges and limitations of using machine learning in this context and recommends further research and interdisciplinary collaboration. Additionally, it addresses ethical and privacy concerns, the importance of open data sharing, and aligning machine learning applications with sustainability efforts. The document includes a list of academic articles related to machine learning techniques in concrete structures, covering topics such as crack detection and structural health monitoring. It also compiles various studies and research papers on machine learning for structural health monitoring in concrete structures, exploring different methods and highlighting the potential of deep learning models and image processing techniques for crack detection. Overall, the document provides a comprehensive overview of the application of machine learning in the field of structural health monitoring for concrete structures. [Extracted from the article]

This is the first part of a short three-paper series, aiming to revisit some classical concepts of Linear Elastic Fracture Mechanics. The motive of this first paper is to highlight some controversial issues, related to the unnatural overlapping of the lips of a 'mathematical' crack in an infinite plate loaded by specific combinations of principal stresses at infinity (predicted by the classical solution of the respective first fundamental problem), and the closely associated issue of negative mode-I Stress Intensity Factor. The problem is confronted by superimposing to the first fundamental problem of Linear Elastic Fracture Mechanics for an infinite cracked plate (with stress-free crack lips) an 'inverse' mixed fundamental problem. This superposition provides naturally acceptable stress and displacement fields, prohibiting overlapping of the lips (by means of contact stresses generated along the crack lips, which force the overlapped lips back to naturally accepted position) and, also, non-negative mode-I Stress Intensity Factors. The solutions of this first paper form the basis for the next two papers of the series, dealing with the respective problems in finite domains (recall, for example, the cracked Brazilian disc configuration) weakened by artificial notches (rather than 'mathematical' cracks), by far more interesting for practical engineering applications. [ABSTRACT FROM AUTHOR]

The present paper deals with the prediction of the fatigue life of a planar tubular truss, when geometrical parameters, material properties, and live loads are non-deterministic. A multi-level calculation uncertainty quantification framework code was designed to aggregate the finite element method and fatigue-induced sequential failures. Due to the incompleteness of the aleatory-type inputs, the maximum entropy principle was applied. Two sensitivity analyses were performed to report the most influencing factors. In terms of variance, the results suggest that the slope of the curve crack growth rate x stress intensity factor range is the most influencing factor related to fatigue life. Furthermore, due to the application of the entropy concept, the fatigue crack growth boundaries and fatigue crack semi-width boundaries obtained provide the most unbiased fatigue crack design mapping. These boundaries allow the designer to select the worst-case fatigue scenario, besides being able to predict the crack behavior at a required confidence level. [ABSTRACT FROM AUTHOR]

Wood is an orthotropic material used since ancient time. A literature research about the mechanical properties of density, fracture toughness, modulus of elasticity, and Poisson's ratio has been done to have a broader view on the subject. The publications relating to the topic were found through the two search engines Scopus and Google Scholar that have yielded several papers, including articles and book sections. In general, there is no standardization on the method of analysis carried out on wood, underlining the great difficulty in studying this complex material. The parameter of density has a great variability and needs a deeper investigation; fracture toughness is not always available in literature, not even in the different directions of the wood sample. Interesting is the modulus of elasticity, which provides a correlation with density, especially in longitudinal section but, again, it needs to be studied in detail. The parameter of Poisson's ratio is provided as single values in three different directions, but mainly for softwood. All the parameters require a more in-depth study for both softwood and hardwood. Furthermore, the type of analysis, whether experimental or modelling, needs to be standardized to have more comparable results. [ABSTRACT FROM AUTHOR]

This document provides a list of references to research papers and articles related to machining techniques and optimization for specific materials like Inconel 718. The papers cover various topics such as tool wear reduction, the use of nanofluids in machining, multi-objective optimization, and the application of machine learning algorithms. These references offer diverse perspectives and approaches to the subject matter, making them valuable resources for library patrons conducting research on these topics. [Extracted from the article]

This article explores the phenomenon of ignition and explosion in high-entropy alloys (HEAs) under compression. The study focuses on specific HEAs in the Ti-Zr-Hf-Ni-Cu and Ti-Zr-Hf-Ni-Cu-Co systems, which exhibit high strength and ductility. The authors propose a model to explain the ignition and explosion, which occurs when certain critical levels of strength and ductility are reached. The article provides detailed information on the materials and methods used in the study, as well as the chemical composition and physical properties of the alloys. Additionally, the text discusses the mechanical testing and failure process of a specific alloy, highlighting the factors that contribute to ignition and explosive failure. The research was funded by the National Academy of Sciences of Ukraine and includes a list of references to related scientific articles and papers. [Extracted from the article]

This article discusses the use of Additive Manufacturing (AM) in automotive engineering, specifically focusing on the reliability of AM for advanced powertrain components. The study evaluates the mechanical behavior and microstructure features of samples made of AM 17-4PH steel, including engine exhausts, drive shafts, gearbox components, braking systems, and conrods. The researchers analyze the effects of sample geometry, size, and heat treatments on the properties of the samples. The study aims to provide insights for designing efficient prototypes using AM alloys and technology. The article also includes a list of references to other research papers and theses related to the fabrication and properties of stainless steel using AM techniques, providing valuable insights for researchers and engineers in the field. [Extracted from the article]

The reinforced concrete structure is typical and widely used in many fields. The behavior of concrete is nonlinear and complex. Especially, when cracks/crushings occurred in softening phase. Thus, It is important to find a damaged model of concrete with high reliability in the numerical simulation. The nonlinear behavior of concrete is the most feature used in the simulation. This characteristic is expressed through the parameters defining the yield surface, the flow potential, and the nonlinear relationship of stress-strain in the cases of tension and compression. This paper introduces a damaged concrete model that applies to the simulation of reinforced concrete structures. The reinforced concrete beam and flat slab are selected as examples to evaluate the reliability of the model presented. Through the results achieved, the model used in this paper shows high reliability and can be used to simulate more complex reinforced concrete structures. [ABSTRACT FROM AUTHOR]

This article explores the use of 3D printing technology in architectural restoration, specifically focusing on the optimization of the internal structure of 3D-printed components. The study investigates the structural performance of 3D-printed elements made of PLA material through experimental and numerical analyses. The findings highlight the influence of different internal structure configurations on the mechanical properties of the printed parts. The article also discusses the implications of these findings for the design process and potential applications of 3D printing in architectural restoration. Overall, this research contributes to the broader field of 3D printing technology for cultural heritage preservation. [Extracted from the article]

Safety of infrastructures represents one of the most significant concerns for governments and service providers to preserve people's wellbeing. One of the main ways to keep safe facilities (buildings, bridges, railways, etc.) involves the use of monitoring sensor systems in charge of measuring critical operating conditions. Those measurements together with periodical maintenance, contribute to minimize potential risks that the infrastructure faces. The paper aims at designing, developing, and testing a monitoring system for mechanical stresses acting on the overhead contact wire (OCW) to ensure the operational safety of the railway network. In this regard, the paper proposes two Fiber Bragg Grating (FBG) sensors-based solutions, relying on the ability of these sensors to allow real-time and continuous data acquisition. The first one consists of a polyimide-coated sensor bonded on an OCW clamp, the second one is a copper-coated sensor hanging between the two separated halves of an OCW clamp. Significant results have been obtained mechanically testing both solutions, trying to simulate the operative conditions. [ABSTRACT FROM AUTHOR]

The structural health monitoring (SHM) approach plays a key role not only in structural engineering but also in other various engineering disciplines by evaluating the safety and performance monitoring of the structures. The structural damage detection methods could be regarded as the core of SHM strategies. That is because the early detection of the damages and measures to be taken to repair and replace the damaged members with healthy ones could lead to economic advantages and would prevent human disasters. The optimization-based methods are one of the most popular techniques for damage detection. Using these methods, an objective function is minimized by an optimization algorithm during an iterative procedure. The performance of optimization algorithms has a significant impact on the accuracy of damage identification methodology. Hence, a wide variety of algorithms are employed to address optimization-based damage detection problems. Among different algorithms, the particle swarm optimization (PSO) approach has been of the most popular ones. PSO was initially proposed by Kennedy and Eberhart in 1995, and different variants were developed to improve its performance. This work investigates the objectives, methodologies, and results obtained by over 50 studies (2005-2020) in the context of the structural damage detection using PSO and its variants. Then, several important open research questions are highlighted. The paper also provides insights on the frequently used methodologies based on PSO, the computational time, and the accuracy of the existing methodologies. [ABSTRACT FROM AUTHOR]

In recent years there has been constant concern in the scientific community to identify techniques for damage detection in structures. Such apprehension has contributed to the progressive development of Structural Health Monitoring. This paper proposes a methodology using Continuous Wavelet Transform associated with interpolation and regularization techniques applied to the experimental and numerical mode shapes of the Dogna Bridge using only the damaged bridge responses. Dogna Bridge is a four-span, single-lane concrete bridge, 64m long and 4m wide. The results of the analyses are presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

This paper addresses the estimation of critical loads in FFF (Fused Filament Fabrication) printed polymers and composites containing notches. Particularly, the analysis is focused on the fracture load estimations of 39 PLA (polylactic acid) and 39 graphene reinforced PLA (PLA-Gr) printed plates containing two different types of notches (U- and V-notches) and combining different plate thicknesses and defect length to plate width (a/W) ratios. The addition of graphene (1 wt.%) increases both the yield stress and the ultimate tensile strength, also reducing the strain at rupture and, thus, generating a material whose behavior is closer to linear elasticity. Among the different assessment tools that may be used to estimate critical loads, this work applies the well-known Averaged Strain Energy Density (ASED) criterion, which compares the averaged strain energy over a certain control volume at the notch tip with the corresponding critical value, the latter being a material property. This approach has a linear-elastic nature, so its application to non-fully linear materials may require the use of specific corrections or calibrations. For the two materials analyzed here, PLA and PLA-Gr, it has been observed that the ordinary linear-elastic ASED criterion provides good estimations for the PLA-Gr material, whereas the pristine PLA, with more evident non-linear behavior, the obtainment of accurate results requires a previous specific calibration of the ASED material parameters. [ABSTRACT FROM AUTHOR]

Modern technological make it possible to produce three-dimensional (3D) reinforcement for polymer composite materials. The tasks of experimental research and analysis of the deformation process of new composite materials for aviation purposes taking into account the nonlinearity of mechanical behavior become actual. The paper presents an experimental study of the mechanical compression behavior of composite material specimens made of 3D woven carbon fiber preforms using the pressure impregnation technology (Resin Transfer Molding method with a pairwise interlayer reinforcement and a longitudinal layer). Compression mechanical tests were carried out on specimens using a universal system of electromechanical testing Instron 5882 and a system of 3D analysis of displacement and strain fields on the surface. Tests were conducted in accordance with ASTM D 3410 recommendations and using specialized tooling. Consideration of nonlinearity parameter during experimental data processing is proposed. The importance of determining the values of critical deformation in compression as a parameter characterizing the moment of the beginning of fracture is noted. The comparison of strength, elastic and deformation properties of carbon-fiber composite materials made using the same technology from fibers and binders from different manufacturers is carried out. The experimental diagrams "stress-strain" and their approximating dependences taking into account the nonlinearity function - are obtained. The type of functions - of the studied materials is defined, the linear approximation of dependence of functions - on strain is substantiated. Values of strength limits, elastic modulus, nonlinearity coefficient and critical damage were obtained, statistical processing of the obtained results and their analysis were carried out. [ABSTRACT FROM AUTHOR]

Onyx ® is a new material composed of Polyamide 6 reinforced with short carbon fiber, used in the novel additive manufacturing composites technique. This paper aims to presents the axial fatigue performance of this material with and without U-notches. The experimentally determined S-N fatigue curve was obtained under axial load with a load inversion ratio, R = 0.1, and compared to fatigue performance of U-notched samples ranging from 0.25 to 2 mm radius. In addition, the stress concentration factor was compared for static and alternative loading to obtain the notch sensitivity in terms of the U-notch radius, showing that there is indeed a difference in stress concentration between them. The advantage of the approach is that it permits using commonly used dimensioning methods for this AM material. [ABSTRACT FROM AUTHOR]

The aim of this paper is to characterize the mechanical characteristics of chlorinated PVC (CPVC). Tensile tests were carried on the compounds at different temperatures ranging from -20 to 90°C and crosshead speeds from 5 to 500 mm/min. The results were analyzed to determine how crosshead speed and temperature affected on the mechanical characteristics of CPVC specimens. Two damage models are then developed, one model obtained by adapting the unified theory version and the other quasi-experimental static model based on ultimate stress. These models allow us to evaluate the damage evolution of CPVC samples and to determine the safety and maintenance intervals of this material. [ABSTRACT FROM AUTHOR]

In this paper, an experimental and numerical study was achieved to investigate the behavior of masonry beams internally reinforced using carbon fiber-reinforced polymer (CFRP) and hybrid steel/CFRP reinforcements. Three beams were built using concrete bricks and grout mortar. The brick was designed with two holes that were filled with grout before placing the rebar inside. One beam was built without shear reinforcement, and the other two were with shear reinforcement. Material characterization tests were performed to evaluate the compressive strength of the brick and the masonry cube and the flexural strength of the masonry prism. The masonry cubes were prepared and tested to evaluate their equivalent mechanical properties. The beams were tested in three-point bending with an effective simply supported span of 840 mm where the load deformations and failure loads were monitored. Finite element models were built using ANSYS and validated with experimental results. Additional beam models were analyzed to study the effect of shear reinforcement spacing from 0.78d to 0.39d and more hybrid reinforcement configurations. Results showed that using equivalent material properties in numerical modeling instead of modeling bricks and mortar was acceptable. In addition, using shear reinforcement with a spacing of 0.78 d didn't enhance the shear behavior of the spacing. Finally, the hybrid steel/CFRP-reinforced beam with shear reinforcement achieved the highest capacity compared to the two other beams. [ABSTRACT FROM AUTHOR]

According to the research conducted, the asymmetric multistorey buildings are complex and suffer from severe damage caused by increased torsional response. This paper addresses the behavior assessment of setback building with irregularity in the plan under severe seismic events such as Kobe earthquake. Using a three-dimensional model, the structure is subjected to seismic records in the three directions through ground accelerations. Nonlinear time-history analyses are employed to evaluate the dynamic response of the building. The mechanical model describes physical nonlinear behavior with evolution of damage and plasticity showing the regions of cracking propagation, mainly the columns-beams connections, corroborating the weak column and strong beam concept. The slabs did not present significant danification with damaged regions lumped on the borders of the first floors. [ABSTRACT FROM AUTHOR]

ABSTRACT. The paper analyses the numerical algorithms for experimental data processing using a contactless video system Vic-3D, designed for threedimension analysis of displacement and strain fields, and digital image correlation method. The authors considered methodological issues of conducting an experiment using a video system. They suggested recommendations on the choice of parameters of calculation of correlation, the size of subset and step during the analysis of non-homogeneous displacement and strain fields in polymer composite materials through laminated fiberglass composite. The efficient parameters of mathematical data processing are identified according to digital image correlation method on the basis of building fields for one frame on the surface of laminated fiberglass reinforced plastic at various subset values and at fixed step value. The paper shows the impact of step value on the strain fields detail degree. The authors have identified the relation of the chosen parameters of experimental data processing using digital image correlation method with the scaled levels of consideration of composite materials strain processes. To evaluate the strains at various scale levels, the paper uses supplementary video system instruments: "virtual extensometer", "rectangular area" and "line". The authors obtained a longitudinal strain profile that allows evaluating the location of strain peak areas on the composite object surface. [ABSTRACT FROM AUTHOR]

The paper discusses some of the issues, the researchers interested in verifying various multiaxial fatigue limit estimation solutions are facing to. Even recently, newly proposed criteria have been or are tested on dozens of experimental inputs. Papuga in [1] pointed out, that applicability of the most often used test batch is limited and only half of these data items is worth using for such purposes. This paper extends that analysis by describing the weak points of various data sets used in this domain for validating new proposals on multiaxial fatigue limit estimates. The conclusion from the extensive analysis is that the researchers should adopt other test sets only if they very well know their background. [ABSTRACT FROM AUTHOR]

This paper concerns the results of research into the influence of the composition of rock inclusions on the fracture response of cement-based composite specimens. Specially designed specimens of the nominal dimensions 40 × 40 × 160 mm with inclusions in the shape of prisms with nominal dimensions of 8 × 8 × 40 mm were provided with an initial central edge notch with a depth of 12 mm. These specimens, which were made of fine-grained cement-based composite with different types of rock inclusion - amphibolite, basalt, granite, and marble - were tested in the three-point bending configuration. Fracture surfaces were examined via scanning electron microscopy and local response in the vicinity of rock inclusions was characterized via the nanoindentation technique. The aim of this paper is to analyse the influence of the chemical/petrographic composition of rock inclusions on the effective mechanical fracture parameters of cement-based composites, as well as on the microstructural mechanical parameters of the interfacial transition zone. The results of this research indicate the significant dependence of the effective fracture parameters on the petrographic and related chemical composition of the rock inclusions. [ABSTRACT FROM AUTHOR]

Porous materials are defined as materials that contain holes, voids, or spaces in their structures, which can be interconnected or isolated. In the most complex forms of these materials, the holes can have irregular shapes with a random distribution in size, location, and direction, making studying their properties a challenging problem. Additive manufacturing techniques offer opportunities to create complex structures, and in this paper, we investigate the effective mechanical properties of porous material produced by the Fused Displacement Modeling (FDM) technique. We also propose an algorithm for generating a porous body containing irregularly shaped holes with arbitrary distributions in size and location while maintaining specific porosity. Due to the orthotropic properties of bodies created by the FDM technique, Reinforced Isotropic Solid Modeling (RISM) is combined with existing theories that calculate the effective properties of isotropic materials. For the experiments, some modified standard specimen with a porosity of 0.05 to 0.40 has been fabricated, and the elastic modulus and ultimate stress have been calculated using the tensile test. Finally, the results are compared with experimental data. [ABSTRACT FROM AUTHOR]

In recent years, 3D printing technology has assumed an important role in advanced construction processes across various engineering fields. Among these, the application to the architectural restoration of historic structures is particularly fascinating. The ability to precisely reproduce the shape and surface details of complex elements, combined with the availability of a wide range of printing materials, makes 3D printing technology competitive compared to traditional techniques. In this context, the internal volume structure of 3D printed elements represents an additional design parameter to consider for enhancing interventions in terms of reducing the required material, and thus, lowering costs and environmental impact. The paper presents the outcomes of experimental tests and numerical analyses conducted on plates, which represent portions of more complex elements produced by using Additive Manufacturing (AM) technology. These plates feature various internal configurations (such as reticular and rhomboidal patterns) derived from a mono-objective design optimization process. The experimental tests aim to analyze the influence of the configuration and the pattern on the behavior of printed samples. Additionally, the paper discusses insights derived from both theoretical models and Finite Element analyses, providing a clearer understanding of the experimental results.

Strain localization is one of the key phenomena which has been extensively studied in geomaterials and for other kinds of materials including metals and polymers. This well-known phenomenon appears when structure/material is closed to failure. Numerous theoretical, experimental, and numerical studies have been dedicated to this subject for a long while. In the numerical aspect, strain localization inside periodic granular assembly has not been well studied in the literature. In this paper, we investigate the occurrence and development of strain localization within a dense cohesive-frictional granular assembly with high coordination number under bi-periodic boundary conditions by Discrete Element Modeling (DEM). The granular assembly is composed of 2D circular particles and subjected to biaxial loading scheme with constant lateral pressure. The results show that the formation of shear bands is of periodic type, consistent with the boundary conditions used. The occurrence and development of the shear band are originated from the irreversible loss of cohesive contacts. The latter is viewed as micro-cracking in the cohesive-frictional granular media, which is highly concentrated in the periodic shear zones and thus related to the strain localization observed at the sample scale. Finally, we also show that the strain localization is in perfect agreement with the kinematic field, displayed in terms of displacement fluctuation. [ABSTRACT FROM AUTHOR]

The aim of this paper is to perform the inverse identification of the material parameters of a nonlinear constitutive model intended for the modeling of concrete which is known as the Karagozian & Case Concrete model. At present, inverse analysis is frequently used because it allows us to find the optimum parameter values of nonlinear material models. When applying such parameters, the resulting response of the structure obtained from a computer simulation is very similar to the real response of the structure based on the related experimental measurement. This condition then undoubtedly constitutes one of the progressive steps to refine the current numerical approaches. For the purposes of the inverse analysis performed in this paper the experimental data was obtained from the triaxial compression strength tests carried out on the concrete cylinders. [ABSTRACT FROM AUTHOR]

In this paper experimental results of investigation on reinforced concrete (RC) beams strengthened with the near surface method (NSM) are analyzed considering the response under bending tests on two beams. One of the RC beams was damaged by bending until the yield of reinforcement and successively strengthened with carbon fiber polymer (CFRP) rod, while the second beam was strengthened with glass-FRP rod. Both the beams have been subjected to bending tests until failure. Experimental diagrams and discussion on static response are presented in the paper. It also places a particular emphasis on the non-linear response of RC sections strengthened with CFRP and GFRP rods under bending moment beyond the first elastic behavior. [ABSTRACT FROM AUTHOR]

Rocks are frequently host materials for underground structures, particularly for deep Tunnels. Their behavior plays a fundamental role in the overall stability of these structures. In fact, the erection of deep tunnels imposes rocks excavations around the defined routes. These excavations are generally carried out by various methods of which the most used are Drilland-Blast (DB) and Tunnel Boring Machine (TBM). However, regardless of the tunnelling method used, the impacts such as the perturbation of the initial stress field in rocks and the release of the stored energy are always significant. The impacts produce damage, fractures and deformations which are generally time-dependent and influence the long-term stability of deep tunnels built in rocks. Thus, by considering the aforementioned excavation methods, this paper identifies, reviews and describes the relevant factors generated during and after rock excavations. Interestingly, such factors directly or indirectly influence the long-term stability and therefore the structural integrity of deep rock tunnels. In addition, some recommendations and proposals for future works are presented. This paper can provide useful references in understanding the degradations, damage and fractures generated by tunnelling methods and facilitate suitable actions to ensure long-term stability of deep underground structures. [ABSTRACT FROM AUTHOR]

Reinforced concrete structures may need repair in order to ensure the designed durability. The assessment of the structural condition usually is made in loco, but sometimes numerical analyses are required as a low cost and effective preliminary diagnosis. Lumped damage mechanics (LDM) may be used as an alternative diagnosis procedure. In LDM approaches for reinforced concrete structures, the concrete cracking in modelled by a damage variable and the reinforcement yielding is represented by plastic deformations. Therefore, this paper presents LDM as a diagnosis tool to analyse actual structures. Then, the procedure is applied in two case studies. The first one is a former bridge arch tested in laboratory. Such bridge was deactivated after almost three decades in service and some damage were observable. The second case study deals with a reinforced concrete balcony that collapsed after fifteen years of service. In the moment of collapse, only the dead load was acting in the balcony. The results show that LDM numerical response of those structures are quite close to laboratory observations, for the former bridge arch, and to in loco measurements, for the balcony. In this sense, according to the analysed structures, LDM may be used as a diagnosis tool. [ABSTRACT FROM AUTHOR]

Timber-concrete composite beams, known as TCC beams, have been widely used in rehabilitation or in new buildings where several types of connections are commonly inserted to ensure partial composite action between the timber joist and the concrete slab. The notched connections represent an effective system due to their strength and ductility and it is simple to cut from timber joists. As a result, a small number is needed for the composite beam to achieve high performance in terms of bending stiffness and load-carrying capacity. This paper aims to develop a FE model for TCC beams with notched connections. It considers realistic interactions between different components. The developed FE model can satisfactorily predict the full range load-midspan deflection curves and the failure mechanisms. The predictions agree very well with the experimental results reported in the literature, including the stiffness and the load-carrying capacity. After the validation, a numeric study was established, it aimed to research the optimal location of a notch connection between different proposed locations, to figure out which place must be installed to ensure high performance of the TCC beams. As a result of this study, the notch installed at location P3000 was found to be the optimal location to assure the highest bending stiffness. While the maximum carrying capacity was achieved at location P3750. [ABSTRACT FROM AUTHOR]

The automotive industry is continuously looking for an innovative mix of new steels and manufacturing techniques in order to improve process chain efficiency and cost reduction. To this aim, boron steels are becoming increasingly popular thanks to their high hardenability and machinability. Due to their reduced finishing steps, boron steels are commonly processed using fine blanking technologies. The success of fine blanking on boron steel components is due to heat treatments which must be carefully designed to avoid precipitation of boronrich compounds that would lower steel hardenability. At high temperature, boron is very reactive with oxygen and nitrogen. The main focus of this paper is to show some drawbacks that can occur during heat treatments of automotive components. An experimental campaign was performed on two different boron steels, namely EN 34MnB5 and EN 22MnB5. The steel samples were previously spheroidized annealed in a neutral environment (hydrogen/nitrogen atmosphere), and then fine blanked to obtain specific automotive components which were subsequently quenched and tempered. Experimental tests revealed precipitation of nanometric compounds, causing strong grain refinement and localized decrease of steel hardenability. Hardenability problems were brought back to nitrogen pick-up during initial spheroidize annealing treatments. [ABSTRACT FROM AUTHOR]

There is a need for efficient techniques that could identify damages in structures such as in bridges, pipelines, buildings, dams, among others. In order to carry out continuous monitoring of structures, this paper proposes a new experimental methodology for the identification of damages in steel beams. The methodology is based on the variation of the fundamental frequencies caused by the application of an extra additional mass along the length of the structure. This paper proposes the association of additional masses with wavelet transform in the processing of non-stationary signals and the realization of experimental tests on commercial profiles of steel beams under support conditions close to real situations. The experimental tests of simply supported steel beams are presented and discussed in this paper. The results show that the proposed methodology can identify damages or at least give a good indication of the region where damages might be. [ABSTRACT FROM AUTHOR]

Biaxial tension-torsion fatigue tests are carried out on the membrane material Nafion 115 (perfluorosulfonic acid, PFSA). This polymeric material is used in fuel cells as proton exchange membrane, undergoing frequently mechanical loading of tension and torsion during its industrial life. In order to carry out the fatigue tests on this polymeric material a self-designed and self-constructed machine was used, working under the following conditions: from 0 to 50 degrees of torsion, 0 to 60 MPa of initial tensile stresses, from room temperature (22 to 25° C) to 80° C, and two values for relative humidity: environmental and saturated relative humidity. All fatigue tests were carried out at the frequency of 1.2 Hz. This paper presents the first results, which concerns the following testing conditions: constant torsion angle of 50 degrees, 5 initial tensile stress of 60, 55, 50, 45 and 40 MPa, room temperature (22-25° C) and environmental humidity (50 - 60 %). The experimental results show that fatigue endurance decreases noticeably when the tensile stress increases. In the final section are presented the fracture surfaces observed by SEM, in order to investigate the principal trends of crack initiation and propagation under this modality of biaxial fatigue loading. [ABSTRACT FROM AUTHOR]

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 derive the governing equations. An analytical solution is determined solving the system of differential equations. In particular, in the first part of the paper a nonlinear shear-stress slip law characterized by a brittle post-peak behavior with a residual shear strength in the post peak phase is introduced for either the lower reinforcement-mortar interface (approach 1) or both the lower and the upper interface (approach 2). In the latter approach, a calibration of the shear strength of the upper interface is proposed in order to implicitly account for the effect of the damage of the mortar on the bond behavior. In the second part of the paper it is presented the solution of the problem in the case of softening behavior by approximating the shear-stress slip law throughout a step function. Comparisons with experimental data, available in literature, are presented in order to assess the reliability of the proposed approach. [ABSTRACT FROM AUTHOR]

The article discusses the use of Structural Health Monitoring (SHM) techniques to ensure the safety and longevity of civil infrastructure. It focuses on damage identification methodologies and the use of numerical models to simulate the behavior of concrete structures under different fracture conditions. The article emphasizes the importance of accurate numerical strategies and comprehensive analysis of existing structures. It also presents the results of studies on the degradation of natural vibration frequencies and the detection of damage in plain concrete structures. Additionally, the article provides a compilation of research articles covering various topics related to vibration-based damage detection and structural health monitoring. Lastly, it includes a list of references cited in a research paper on the degradation of vibration characteristics in reinforced concrete beams and micro-fracture instabilities in granular solids. [Extracted from the article]

This article discusses a numerical investigation of an extra-deep drawing process using industrial parameters. The study focuses on the formability analysis and process optimization of the drawing process. The authors conducted experiments and simulations to understand the factors that contribute to defects such as rupture and wrinkling in the manufacturing process. They used numerical modeling and measurements to analyze the behavior of the materials and optimize the process parameters. The study provides valuable insights for manufacturers in various industries, including household appliances and automobile construction, to improve the quality and competitiveness of their products. Additionally, there is a document that provides a list of references cited in a research paper on the behavior and processes of deep drawing sheet metal. The references cover various aspects of deep drawing, such as material limits, thinning, wrinkling, spring-back, cracking prevention, lubricants, tribological behavior, and optimization of process parameters. This comprehensive list of sources can be explored by library patrons for further information on these topics. [Extracted from the article]

The paper presents the stress distribution along the plate thickness in a bimetallic steel -- titanium circular perforated plate produced in the technological process of explosion welding. The steel layer is the layer that transfers the load in the plate, while the titanium layer is used to improve the properties of the plate, e.g. corrosion resistance, thermal transmittance, etc. in the plate. Two cases of fastening were considered, i.e. a freely supported and fixed plate. Such plates are used in various engineering structures, e.g. simply supported plates can be used in loose material screens, while plates are fixed in heat exchangers. The load was assumed as a concentrated force applied perpendicularly to the plate surface. The results obtained numerically using the finite element method were compared with the results calculated according to the analytical equations. It has been shown that the difference in the results of equivalent von Mises stress calculations does not exceed 13%. The research results presented in the paper can be used by engineers to design bimetallic perforated plates perpendicularly loaded to their surface. [ABSTRACT FROM AUTHOR]