Italian Group Fracture (IGF): E-Journals / Gruppo Italiano Frattura
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Introduction and application of a drive-by damage detection methodology for bridges using variational mode decomposition
Full text linkIn this research, the variational mode decomposition (VMD) method is used for the drive-by health monitoring of bridges. Firstly, the problem of a half-trailer tractor moving over a bridge is formulated. Next, a Finite Element (FE) code is developed and verified against modal analysis results where complete agreement is found. The vehicle's output signals are decomposed through VMD and then analyzed to identify and precisely locate damage in the bridge structure. The range of applicability of this technique is examined from different perspectives by including various road classes, damage severity and location, and noise. The results prove the robustness and reliability of using VMD for drive-by damage detection. The method outcomes indicate that through the VMD method, cracks with a depth of 10% to 20% of the beam height can be detected even in the case of a rough road profile. A comparison of the results of the VMD and the well-known empirical mode decomposition (EMD) method has also been conducted. This comparison reveals that by implementing the VMD, precise damage locations can be determined, whereas the EMD fails to detect any damage under the conditions considered in this study. The effects of noise and moving vehicle speed are also investigated in the research, and it is found that processing the output signals using VMD can yield reliable estimates of the damage location(s)
Optimization of the internal structure of 3D-printed components for architectural restoration
Full text linkIn 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
An interface-based microscopic model for the failure analysis of masonry structures reinforced with timber retrofit solutions
Full text linkThis paper presents a refined Finite Element (FE) modeling strategy for analyzing the failure behavior of regular masonry structures reinforced with timber-based retrofit solutions. The proposed model schematizes the masonry as brick units, modeled using two-dimensional linear elastic plane stress elements, mutually joined through zero-thickness cohesive interface elements. These interface elements serve to reproduce the nonlinear behavior of masonry because of the occurrence of failure mechanisms of the mortar joints. Reinforced timber frame elements are modeled using truss elements that exhibit elastic brittle fracture behavior. The interaction between the masonry sub-structure and the reinforced timber frame system is accounted for using special constraint conditions that simulate the mechanical behavior of anchorage connections. The reliability of the proposed model in reproducing the failure behavior of masonry is assessed through comparisons with experimental and numerical data available in the literature. Additionally, the efficacy of the retrofit technique based on timber frame structures is investigated in detail through pushover analyses on a two-story masonry wall representative of real-life masonry buildings. The results indicate that the proposed retrofitting strategy is an effective and eco-friendly retrofit solution to enhance the in-plane bearing capacity of masonry structures subjected to horizontal forces
Tool wear evaluation of self-propelled rotary tool and conventional round tool during turning Inconel 718
Full text linkEnhancing the machinability of difficult-to-cut materials is imperative, and a non-conventional rotary tool has shown high potential when machining these materials. This work comparatively evaluates the tool wear of conventional round tools (CRTs) and self-propelled rotary tools (SPRTs) when turning Inconel 718. Tool wear progression over time was measured and analyzed, simulated for various cutting conditions by creating mathematical and ANN models. This study found a 67% increase in tool life for SPRTs over CRTs, especially at a higher cutting speed of 65 m/min, due to improved heat transmission and steady wear distribution. However, at lower cutting conditions, the tool life gain was 15–18%, indicating that SPRTs could be reliably used at higher cutting conditions to achieve a machining economy. SPRTs exhibited better chip control and reduced built-up edge formation than CRTs. The cutting speed had the largest impact on tool flank wear, with machining time, feed, and depth of cut following closely behind. However, this effect was more prominent for CRTs. The 0.2 mm tool wear criterion was found to be more feasible since tool failure was caused by cutting tool chipping at this threshold instead of progressive growth of flank wear during Inconel 718 turning
Stochastic Modeling of Structural Fatigue Damage in High Strength Steel Structures
Full text linkThe paper proposes a parallel extension of the Direct Optimized Probability Computation Method. This method can be used as an alternative to Monte Carlo – based approaches for problems of structural reliability. It does not depend on any kind of randomly generated numbers, but it requires a much higher number of computations thus it can benefit from its parallelization. The proposed parallel Direct Optimized Probability Computation method is developed and studied on the problem of fatigue damage prediction. Description of the parallel algorithm is provided, and the functionality of the method is shown in an example case. The results are also compared to the results of the more common Monte Carlo – based approach
Integrating AI and statistical methods for enhancing civil structural practices: current trends, practical issues, and future direction
No full textThe integration of artificial intelligence (AI) and statistical methods has revolutionized civil engineering by enhancing accuracy, efficiency, and reliability in various processes. This review systematically examines how advanced optimization techniques, including artificial neural networks (ANNs), Design of Experiments (DOE), and fuzzy logic (FL), are transforming civil engineering practices. It emphasizes the significant roles these methods play in addressing modern challenges such as structural health monitoring, damage detection, seismic design optimization, and concrete condition assessment. The review delves into case studies and real-world applications, showcasing the potential of these methods to create more resilient, sustainable, and cost-effective infrastructures. It critically examines the limitations and scalability of these techniques, identifying gaps in current research and practical challenges in real-world applications. The investigation also highlights the need for substantial computational resources, data privacy, security, and software interoperability. By addressing these issues, the review not only shows advancements in optimization techniques but also outlines future research directions, aiming to bridge the gap between theoretical developments and practical applications in civil engineering. This review serves as an essential resource for researchers, professionals, and policymakers interested in leveraging optimization techniques to advance civil engineering practices
Mechanical, Fracture, and Thermal Characterization of Post-Cured Hybrid Epoxy Nanocomposites Reinforced with Graphene Nanoplatelets and h-Boron Nitride
Full text linkThe post-curing process of cured composites is essential in enhancing the strength, stiffness, elevating the glass transition temperature, and reducing residual stress in polymer thermoset composites. The curing temperature and time are the key factors that affect these properties. In-situ polymerization method was used to prepare composites with varying weight percentages of graphene nanoplatelets (GNP) and hexagonal boron nitride (h-BN) nanofillers (0.1, 0.2, and 0.3 wt% GNP-based composites; 0.3, 0.4, and 0.5 wt% h-BN-based composites; 0.4, 0.5, and 0.6 wt% h-BN+GNP-based composites). The cured composites were post-cured at temperatures of 80°C, 120°C, and 160°C for 120 minutes in a hot air oven. The presence of GNPs and h-BNs in the composites is confirmed using Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Further mechanical and thermal properties were evaluated by conducting tensile, flexural, impact, fracture and differential scanning thermometry (DSC) tests. The simulation analyses were performed using Ansys software, and the results demonstrated a strong correlation with the experimental data, with discrepancies between the two consistently within a standard margin of 20%
Exploring strength and ductility responses of beam-column joints using UHPC and UHPFRC employing concrete damaged plasticity
No full textStructures subjected to severe loads, such as earthquakes, often develop cracks at the beam-column joints, underscoring the significance of these regions in design. This study focuses on a comparative analysis of beam-column joints constructed with Ultra-High-Performance Concrete (UHPC) and Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) using the Finite Element Method (FEM) within the Abaqus software, contrasting with Low-Strength Concrete (LSC) and Normal-Strength Concrete (NSC). The results underscore the superiority of UHPFRC in compressive and tensile strength, coupled with enhanced ductility. Furthermore, distinct failure mechanism are observed in the concretes, captured by concrete damaged plasticity (CDP), leading to a deeper understanding of the behavior of these high-strength materials. These findings carry significant implications for enhancing structural safety and performance, particularly in situations involving seismic or other severe loads
Ultrasonic welding of lap joints of PEI plates with PEI/CF-fabric prepregs
Full text linkIn this study, ultrasonic welding (USW) of lap joints of polyetherimide (PEI) plates (adherends) with carbon fiber (CF) prepregs impregnated with PEI was investigated. No energy director (ED) was used, so binder contents were varied in the prepregs to compensate for the lack of the polymer in the fusion zone. In addition, the effect of the USW parameters on the structure and the mechanical properties of the lap-joints were analyzed. The most homogeneous macrostructure, the maintained structural integrity of both the CF-fabric in the prepregs and the lap-joined PEI adherends, as well as the maximum strength properties (tensile strength) were revealed for the USW joints with the minimum polymer content in the prepreg. In this case, rising the USW time from 400 up to 800 ms radically changed the macrostructure of the fusion zone, while the strength properties did not vary significantly (shear stresses were 42–48 MPa). Computer simulation of the influence of the PEI/CF-fabric ratios in the prepregs on the deformation response of the USW joints showed that the prepreg thicknesses and, accordingly, the PEI/CF ratios did not exert a noticeable effect on the strain–stress (tensile) diagrams, while the determining factor was the adhesion level
Fatigue behavior of pultruded fiberglass tubes under tension, compression and torsion
Full text linkThis work is devoted to an experimental investigation of fatigue behavior of pultruded fiberglass tubes under uniaxial tension, compression and torsion. Static tests were carried out; a presence of postcritical deformation stage during torsion is noted. Regularities of inhomogeneous strain fields evolution are analyzed using digital image correlation method. Fatigue curves are built for four cyclic loading modes: tension-tension, compression-compression, tension-compression and torsion. An analysis of specimens' fractures is carried out, typical damaging mechanisms are revealed. Residual dynamic stiffness data is obtained and studied using a previously proposed fitting model. Results demonstrate model's high descriptive capability and its flexibility to describe two-staged and three-staged stiffness degradation curves. An influence of loading mode on a shape of these curves is found out. Model parameters' dependence on maximum stress value during the loading cycle is studied using the Pearson's correlation coefficient. The necessity of multiaxial fatigue behavior investigation of pultruded fiberglass tubes is concluded