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Effective mechanical properties identification of the concrete from the historical bridge structure
Full text linkOne of the first and most important tasks in a complex and precise assessment of the current condition and load-bearing capacity of existing structures is a determination of the physical and mechanical parameters of the materials used. This problem is even more complicated when a historical concrete structure is assessed. This study shows the possible way how to perform an effective and comprehensive evaluation of the concrete taken from the historical bridge structure with the use of a wide range of non-destructive and destructive methods
Micro-scale properties of cement pastes exposed to gamma radiation
Full text linkThe extension of the lifetime of nuclear power plants is a critical issue today, raising concerns about the microscale mechanisms and mechanical changes in the individual phases of concrete that contribute to its macroscopic deterioration. Accurate quantification of these changes is essential for more reliable lifetime predictions. This paper investigates the effects of gamma irradiation on cement pastes exposed to varying relative humidity levels (RH = 11–100 %) using scanning electron microscopy (SEM) and nanoindentation. While SEM analysis did not reveal significant phase changes through image analysis, nanoindentation highlighted substantial differences in the mechanical properties of samples exposed to either low or high humidity or submerged in water during irradiation
gl3 ALGEBRA IN MIXED MATRIX REPRESENTATIONS
Full text linkIt is demonstrated that the so-called mixed realization of the gl3 algebra generators in terms of matrix differential operators in two variables, as presented by Smirnov-Turbiner (2013), can be “lifted” into the action in the Fock space associated with the five-dimensional Heisenberg algebra h5. A realization of the gl3 generators in terms of matrix finite-difference (translation-invariant) operators, matrix discrete (dilatation-invariant) operators, matrix complex operators in (z, z̄), and their mixtures is presented
Numerical verification of fracture toughness values for very thin 3D printed polyamide samples
Full text linkThis researche presents an experimental and numerical analysis of the mechanical properties of very thin polyamide (PA12) samples fabricated by 3D printing with selective laser sintering (SLS). The research methodology focuses on testing mechanical properties such as fracture toughness and simple tensile on PA12 samples ranging in size from 0.50 mm to 2.00 mm, which were then subjected to numerical analysis replicating the experiment. Significant differences between the experimental data and the numerical analysis were found, mainly due to the choice of material model and the selection of inappropriate material parameters. With the numerical analysis, these parameters were appropriately set up and the results of the numerical analysis began to agree more closely with the experimental data
Tractable descriptors for digital aggregate generation
Full text linkThis paper introduces a deep learning-based approach for generating 2D aggregate shapes using a small set of tractable and physically meaningful parameters. In contrast to existing methods that often rely on quantities without clear physical interpretations, the approach presented here leverages scale invariant moments to capture essential shape characteristics. Additionally, we introduce the idea of using scale-invariant state descriptors, such as area, to control the size of the generated shapes. The neural network is trained to generate shapes corresponding to these parameters, and its ability to learn the relationship between shape constants and state descriptors without explicit data augmentation is demonstrated. The framework thus presented provides a foundation for developing microstructure generators that offer enhanced interpretability by relying on parameters that provide meaningful insights into the description of material morphology composed of non-trivial shapes
Interface shear strength evaluation between different concrete types
Full text linkComposite concrete elements, combining different types of concrete, are widely used in modern infrastructure projects like bridge deck overlays and the reinforcement of existing structures. A critical property for ensuring effective composite action between concrete materials of different ages or types is shear strength, which must be sufficient to prevent excessive slippage or complete separation. This is a fundamental requirement for achieving composite action. This article presents an experimental study on the shear strength at the interface between two different types of concrete, assessed through a push-off test. This investigation stands directly on earlier research focused on the use of high-performance concrete as lost formwork, providing core protection for concrete with recycled aggregates. The study explored the influence of Recycled Aggregate Concrete with aggregates from bricks (RAC) and High-performance Concrete (HPC), with particular attention to the treatment of the concrete interface and the impact of interface roughness and surface treatment. The findings validated the hypothesis that shear strength at smooth, untreated interfaces is considerably lower than that at rough, treated interfaces
Research on intelligent synchronous tension monitoring of suspender of though arch bridge
Full text linkSuspender tension and cable adjustment are important construction procedures in the construction of through arch bridges. The traditional suspender tension method is asynchronous tension. Because it is tensioned in batches and manually reads, it will cause errors in the control of suspender tension, which often fails to reach the tension accuracy. Therefore, it is necessary to determine whether secondary cable force adjustment is needed according to the site conditions, which may increase the construction period, management cost and construction cost. In this paper, the overall intelligent synchronous tensioning technology is applied to a through arch bridge. By monitoring the measured suspender cable force, structural deformation and structural stress in the synchronous tensioning process and comparing them with the theoretical values, the traditional asynchronous tensioning technology and intelligent synchronous tensioning technology are compared based on the finite element software. The influence of the error caused by asynchronous tensioning on the structure is analyzed and compared with the suspender cable force, structural stress and structural deformation in the synchronous tensioning process. The results show that the bridge is relatively sensitive to the tension cable force, so it is necessary to accurately control the construction cable force. The overall intelligent synchronous tensioning technology can control the error of the suspender cable force within 3% during the bridge completion process, the geometric shape error of the whole bridge is controlled within 4mm, and the stress error is within 7MPa, avoiding the secondary cable force adjustment. It not only reduces the structural stress generated during the construction of the suspender, but also saves the construction period and construction cost, and ensures the safety of the construction process.
Received: 24.4.2024
Received in revised form: 20.6.2024
Accepted: 30.8.202
Construction monitoring analysis of the combination system bridge of cable-stayed bridge and shaped arch bridge
No full textThe combination system bridges of cable-stayed and shaped arch bridges feature innovative structures and complex force distributions, necessitating intricate construction processes. Monitoring these processes ensures that the bridge\u27s stress state aligns with designed internal forces. Measured stress values on the main girder\u27s edges align with theoretical trends but are slightly lower. Throughout construction, the middle span experiences compression, with maximum stresses of -5.1 MPa on both edges. Full support during construction minimizes the impact of stay cable and derrick tension on main girder stress. After support removal, compressive stress increases on the upper edge and decreases on the lower. The tower’s elevation is slightly above design, aiding in reducing prestress loss and deflection in later stages. At 16.5 m above the bridge girder, the tower’s left side experiences tension and the right compression, with a tensile stress of only 1.0 MPa, indicating sound design and effective construction control.
Received: 30.1.2025
Received in revised version: 14.7.2025
Accepted: 30.8.202
DEVELOPMENT OF A CUSTOM 3D-PRINTED ORTHOTIC DEVICE WITH INTEGRATED ELECTRODE INTERFACES FOR ELECTRICAL STIMULATION IN CARPAL TUNNEL SYNDROME
Full text linkThis article focuses on the design and fabrication of a customized orthotic device with the capability of applying electrical stimulation for the treatment of carpal tunnel syndrome. A 3D positive model of the affected area was obtained using a handheld optical 3D scanner. This model was used for the orthosis design in suitable CAD (Computer-Aided Design) software. Two prototypes were produced: the first by Fused Deposition Modeling (FDM) with PLA, and the second by Selective Laser Sintering (SLS) with polyamide PA2200. The FDM variant required longer time of printing and extensive post-processing, offering low cost but limited durability. In contrast, the SLS orthosis was completed in shorter time, with higher material cost but improved flexibility, comfort, and surface quality. This work demonstrates the feasibility of producing individualized orthoses that integrate dual conservative therapies using additive manufacturing. Future research should include clinical validation and testing in diverse patient populations
Bidirectional coupling of jet plume and particles in a plasma spraying process
Full text linkIn previous studies of plasma spraying, a plasma jet was considered as a constant background in which particles are fed to be heated, molten and deposited on a target. This assumption is well justified for low feeding rates. At high rates, the particles can affect the plasma jet. This effect is studied here in terms of a bidirectional interaction between the plasma jet and the injected particles. The influence on the jet temperature and velocity in the plume, and the resulting coating is analysed