Search Results (885)

Localized failures of structural components can lead to serious social, economic, and environmental consequences, such as the collapse of an entire structure or part of it. Therefore, it is important to thoroughly investigate and justify the acceptance criteria for these components, taking into account their performance in extreme conditions. However, the scientific literature lacks a systematic analysis of how various factors can affect the resistance of structures and influence acceptance criteria under extreme conditions. Therefore, this study investigates the typical substructures of reinforced concrete frame buildings in areas that are potentially prone to local collapse. To assess their resistance and structural robustness, an analytical model has been developed. The results of 22 tests on typical substructures of monolithic and precast frames, reported in various research studies, were used to validate this model. Further, this analytical model was used to conduct a parametric study on the impact of various factors on the performance of substructures under extreme conditions. These factors included the depth-to-span ratio of the beam, the strength of the bond between the steel reinforcement and the concrete, the stiffness of the horizontal bracing within the substructure, and the proportion of the effective depth to the total depth of the beam section. It has been found that the ultimate rotation angle in the plastic hinge of beams increases as the ratio of the beam’s cross-sectional depth to the span increases. An increase in the bond strength between the reinforcement and concrete leads to a decrease in the ultimate rotation angles in the plastic hinge at the flexural and arch stages of resistance and, in some cases, to reinforcement rupture without transitioning to the catenary stage of resistance. A decrease in the ratio of the effective depth of the beam section to its overall depth leads to an increase in the load-bearing capacity at the catenary stage of 19%. Full article

In this work, we describe a new dynamic rotational Thomson effect induced on rotating conductors exposed to a chopped laser beam which generalizes recently observed analog magneto-transverse Thomson effects. We assume the existence of an out-of-equilibrium self-induced Barnett magnetic field that depends on helical thermal fields propagating on rotating conductors, and is associated with thermoelectric vortices. We deduce, assuming the validity of the Faraday law on the rotating out-of-equilibrium conductors, a time-dependent rotational Thomson voltage, showing that it is detectable on rotating ferromagnetic samples. We then prove the existence of dynamic tunable local magnetic phase transitions on rotating conductors associated with time-dependent Curie temperature fluctuations proportional to the dynamic Thomson voltage. Finally, we outline the relevance of this new time-dependent magneto-transverse Thomson effect either for dynamic thermal management or for dynamic tunable local insulator–metal transitions on rotating nanodisks exploiting metamaterials. Full article

Metasurfaces have emerged as a powerful platform for subwavelength light manipulation, attracting widespread interest for their potential to replace bulky optical components. However, most metasurfaces are statically designed with fixed functionalities. Here, we demonstrate a high-efficiency tunable meta-waveplate by heterogeneously integrating a phase-change Sb₂Se₃ layer with a piezoelectric MEMS mirror. Leveraging the reversible amorphous–crystalline transition of Sb₂Se₃, combined with MEMS-enabled nanoscale air gap tuning, the metasurface achieves dynamic switching among zero-, half-, and quarter-waveplate functionalities at the communication wavelength of 1550 nm. The device exhibits stable polarization conversion performance under various rotation angles. Furthermore, we developed a nano-quarter-waveplate library on this platform, which provides extensive phase control over the reflected field and enables programmable beam deflection. This tunable architecture opens new avenues for adaptive photonics with dynamically switchable functionalities. Full article

The evolution of neutron scattering from reactor-based steady-state sources to high-power pulsed spallation sources has necessitated a paradigm shift in neutron optics. While pulsed sources offer high peak brilliance and energy-resolved measurements via the time-of-flight (TOF) technique, the intrinsic divergence and broad wavelength bandwidth of the incident beam pose significant challenges for focusing, particularly in the realm of very small-angle neutron scattering (VSANS, Q < 0.001 Å⁻¹). This review presents a comprehensive analysis of diverse focusing techniques, including converging multi-slit apertures, electrical and superconducting magnetic sextupole lenses, grazing-incidence focusing mirrors, compound refractive lenses with oscillation apertures, and a special multi-beam VSANS configuration. Special attention is given to the transition from permanent magnet systems to nested rotating sextupole permanent magnets (Nest-Rot-SPM) and modulated superconducting sextupoles (SSM), detailing the physical and engineering challenges involved. Furthermore, grazing-incidence reflective optics, notably toroidal Wolter mirrors, are discussed as an achromatic alternative. The integration of these technologies into world-leading pulsed neutron sources is reviewed to project the future landscape of extended Q-range coverage for SANS instruments. Full article

Rolling bearing fault diagnosis is critical for ensuring the safe operation of rotating machinery, yet it faces significant challenges in noisy environments. This paper proposes BEAM-Net (Bearing-spectrum Enhanced by EMA and Weighted Spectral Convolution Network), a lightweight neural network designed specifically for rolling bearing fault diagnosis under strong noise conditions. Classifying bearing faults from vibration signals remains a challenging task when fault-related features are subtle and easily submerged in background noise—especially when the signal-to-noise ratio (SNR) is low. To address this challenge, BEAM-Net adopts a “decompose–enhance–extract” pipeline: first, an Exponential-Moving-Average Trend Decomposer (ETD) splits the frequency spectrum into a smooth trend component and a fault-sensitive residual component; second, a Spectral Residual Gate (SRG) reinjects detailed residual information through a learnable gating mechanism; finally, a Weighted Spectrum Convolution block (WSC) incorporates a symmetric center-emphasizing prior into the convolution kernel, ensuring that local spectral patterns receive greater attention. Experimental results on the Case Western Reserve University (CWRU) bearing dataset at SNR = −6 dB show that BEAM-Net achieves an F1 score of 99.15% with only 2835 parameters. Compared to the single-convolution baseline, this represents a $+0.78\%$ improvement in F1 score and a 50% reduction in the false positive rate (from $0.18\%$ to $0.09\%$). Cross-dataset validation on the Paderborn University (PU) and Machinery Failure Prevention Technology (MFPT) datasets further confirms the generalizability of the proposed approach, achieving F1 scores of 97.83% and 98.46%, respectively, under comparable noise conditions. These findings demonstrate that combining explicit spectral trend modeling with weighted convolution is not only effective but also parameter-efficient, making it well-suited for noise-robust rolling bearing fault diagnosis. It should be noted that the current method is primarily validated on spectral-analysis-based diagnostics of rolling bearings; its applicability to other vibroacoustic diagnostic modalities (e.g., tapping or nonlinear vibration excitation) and to quantitative defect severity grading remains to be investigated in future work. Full article

During the hoisting of prefabricated segmented beams, the alignment of rods and holes mainly relies on manual operation, which suffers from low safety and efficiency. To improve the safety and efficiency of rod–hole alignment, this paper proposes a vision-based alignment method for hoisting prefabricated segmented beams. The method uses binocular vision to measure the spatial coordinates of key points on rods and holes, establishes a mathematical model for alignment, and calculates the center distance and relative rotation angle between them. An experimental platform is built and tests are conducted. The results show that the proposed method can effectively measure the center distance and rotation angle, improve measurement efficiency and safety, achieve high accuracy, and possess high practical engineering value. Full article

This paper proposes a rotation-locking alignment scheme and system based on a Gaussian beam addressing the relative displacement between the receiver and the spot center during the fine tracking phase of spaceborne laser communication APT technology caused by platform vibration, temperature variations and other factors. By rotational scanning fitting, the offset angle and offset distance of the receiver relative to the spot center can be derived and achieve high-precision adaptive tracking. The simulated result demonstrates that the fitting distance error of this scheme is less than 1%, and the fitting angle error is less than π/32. At the same time, the system prototype is developed to conduct ground-based validation experiments, including the static test and outdoor link establishment test. The system prototype features simpler structure, lower computational complexity, and easier integration, satisfying the miniaturization and lightweight design requirements for spaceborne laser communication terminals. The test results verify the system can successfully establish stable laser communication links rapidly. Full article

Reinforced concrete core walls serve as the primary lateral load-resisting system in mid- and high-rise buildings, providing stability against wind and earthquake forces. Many of these walls feature non-planar cross-sections that lead to complex deformation modes, which require discretizing the wall segments for accurate numerical simulation. This paper investigates the dynamic response of U-shaped RC core walls using state-of-the-practice micro- and macroscopic modeling techniques, namely: Three-dimensional solid elements, nonlinear Beam-Truss Models, the force–displacement version of the Multiple-Vertical-Line-Element-Model, and the Applied Element Method. These models are validated against newly obtained large-scale shake table test data, assessing both global and local structural responses. Key parameters, including displacements, shear forces, rotations, torque, strain distributions, and shear deformations, are analyzed to refine numerical modeling approaches. Findings highlight some of the limitations of the different modeling approaches and provide best-practice recommendations for engineers to improve predictive accuracy. This study advances the understanding of non-planar RC wall behavior, aiding in the development of more reliable seismic design methodologies. Full article

Glass fiber–reinforced polymer (GFRP) reinforcement provides an effective alternative to conventional steel in concrete structures due to its corrosion resistance. Nevertheless, the lower elastic modulus of GFRP necessitates careful consideration of serviceability behavior in GFRP-reinforced concrete members. This study presents a numerical sectional analysis model for predicting the flexural response and ultimate capacity of hybrid reinforced concrete beams incorporating embedded GFRP profiles in combination with either mild steel or GFRP reinforcement bars under monotonic static loading. The proposed model employs realistic nonlinear stress–strain relationships for concrete and steel, together with secant moduli of elasticity evaluated at different loading stages. Particular emphasis is placed on detailed stress distribution in flexural sections, including the contribution of tension stiffening in the post-cracking regime. The formulation integrates nonlinear constitutive material behavior with theoretical sectional equilibrium to evaluate the effective flexural secant stiffness. For practical serviceability assessment and to reduce dependence on complex analytical procedures, strain vectors and stiffness matrix components are derived using elasticity coefficients that reflect modulus degradation obtained from numerical analysis. The accuracy of the model is verified through comparison with experimental results, including ultimate flexural capacity and moment–deflection responses. Many crucial parameters were studied, such as the longitudinal reinforcement ratio, type of reinforcement, concrete compressive strength, position of the I-GFRP profile, and rotation of the I-GFRP profile. The results of this study demonstrated that both the longitudinal reinforcement ratio and the rotation of the I-GFRP profile have a significant influence on the ultimate load capacity and deflection behavior. The close agreement between numerical predictions and experimental observations demonstrates the reliability and applicability of the proposed model for structural engineering analysis and design. Full article

With continued expansion of offshore oil and gas development, the number of high-inclination wells has increased rapidly. During drilling of such wells, vibration transmission from the bottom drillstring to the wellhead is significantly attenuated. Therefore, even when severe vibration occurs at the bit, surface monitoring may not accurately reflect downhole conditions. To analyze axial and lateral vibration behavior, this study considers drillstring–wellbore contact and bit–formation interaction. Based on the Lagrange equation and the S–N fatigue curve, a dynamic model of the drillstring in offshore high-inclination wells is developed using the beam element method. A dynamic safety evaluation model is then constructed using the calculated dynamic characteristics, forming a mechanical analysis and optimization approach for drillstrings in these wells. The technique was applied in a branch well in the Bohai Oilfield. Drillstring vibration under different wellbore trajectories and drilling parameters was examined, and limit drilling parameters were selected through fatigue life analysis. The recommended configuration includes 24 drill collars, a weight on bit of 100 kN, and a rotation speed of 60 r/min. These optimization guidelines support improved drilling efficiency and help ensure drillstring safety in offshore high-inclination well applications. Full article

Giant cantilevered tree-shaped steel structures are highly susceptible to cumulative deformation and geometric deviation during staged construction due to their complex spatial configuration, long cantilever characteristics, and nonlinear load transfer mechanisms. To address these challenges, this study investigates deformation monitoring and control of such structures based on 3D laser scanning, taking the “Tree of Life” project as a representative case. A high-precision full-field monitoring system is established to acquire multi-stage point cloud data throughout the construction process. The collected data are registered with the BIM model to quantify spatial deviations and track the deformation evolution of key structural components. Meanwhile, a staged preloading–unloading strategy is implemented to simulate operational loads, reconstruct load transfer paths, and regulate structural deformation during construction. Based on continuous field measurements, the deformation characteristics of different structural regions, including ring beams, rotating platforms, and trunk–branch systems, are systematically analyzed. The results indicate that the structure exhibits a pronounced global torsional deformation pattern. The displacement of ring beams ranges from 40.35 mm to 80.15 mm, while the maximum local displacement reaches 131.37 mm in geometrically complex regions, primarily attributed to the coupling effects of complex geometry, long cantilever action, stiffness discontinuity, and load concentration. Furthermore, deformation exhibits a progressive and stage-dependent accumulation pattern under sequential loading–unloading processes. The proposed monitoring and control approach achieves millimeter-level accuracy and enables effective feedback for construction adjustment and deviation mitigation. The integration of 3D laser scanning with staged load regulation provides a reliable technical framework for deformation monitoring and control of complex cantilevered steel structures. While the findings are based on a single complex project, further validation on additional cases is required to fully establish the general applicability of the proposed framework, although its integration of 3D monitoring, BIM registration, and staged load regulation suggests potential transferability to other large-scale cantilevered steel structures with similar geometric complexity. Full article

This paper proposes a Misalignment Differential Vortex Beam Interferometer (MD-VBI) integrated with DenseNet-169 for high-precision asymmetric shaft alignment. The system employs a polarization-multiplexed differential configuration to linearly map nanometric displacement to interference-fringe rotations. Building upon the optical architecture’s intrinsic suppression of common-mode thermal drift, the DenseNet-169 model serves as a robust demodulation backend, further mitigating inherent system-level optical noise to precisely decode misalignment signatures in interferograms. Experimental results demonstrate a Mean Absolute Error (MAE) of 0.382 nm within a 0–500 nm range. By decoupling true asymmetric shaft misalignment from intrinsic system noise and common-mode drift, the system provides a robust, non-contact solution for nanometric metrology under realistic conditions. Full article

To address the issue of insufficient output voltage of the self-powered unit of intelligent bearings under low-amplitude working conditions, a piezoelectric–friction composite energy harvester driven by rotating magnetic force is proposed based on the multi-physical field coupling and synergy of magnetoelectric, piezoelectric and triboelectric effects, which effectively enhances the voltage output in low-amplitude vibration environments. The intelligent bearing adopts an extended structure, consisting of an outer ring sleeve, an inner ring extension ring, magnetic poles and a composite energy harvester. The outer ring sleeve is nested on the outer ring of the bearing and fixes the composite energy harvester, while the inner ring extension ring is fixed on the inner ring of the bearing and installs the magnetic poles. The composite energy harvester adopts a magnetic double-mass block single-crystal piezoelectric simply supported beam structure and integrates a contact-separation type triboelectric nanogenerator in the vibration direction, achieving the collaborative power supply of the piezoelectric and triboelectric units. A mechanical-electrical coupling dynamic model of the composite energy harvester is developed. Using COMSOL software, the effects of various structural dimensions and magnetic pole configurations on the output voltage are analyzed. Experimental validation confirms the model’s effectiveness. The results demonstrate that the energy harvester operates effectively under varying bearing rotational speeds. The rotational speed of the magnetic poles has little influence on the output voltage amplitude but primarily affects its frequency. Under the condition that the rotational speed is within 600 r/min, the piezoelectric module stably outputs a peak voltage of approximately 16.6 V, and the triboelectric unit stably outputs a peak voltage of approximately 4.4 V, which can effectively meet the self-driving requirements of intelligent bearings. Full article

This paper investigates the low-cycle behaviour of Concrete-Filled steel Tubes (CFTs) subjected to cyclic pure bending, a loading condition representative of large bridge and building girders. A 3D finite element model is developed in Abaqus/Explicit, combining a ductile damage law for the steel tube and Concrete-Damaged Plasticity for the infilled concrete, and is calibrated against large-scale cyclic bending tests on circular and square CFT beams. An automated Python scripting framework is then used to perform a systematic parametric study on members made of standard code-based materials, varying diameter-to-thickness ratio and span length over a wide range of practical configurations. Constant-amplitude chord rotations are imposed, and the nonlinear response is tracked in the plastic range while material damage evolves. The hysteretic behaviour is quantified in terms of cumulative plastic strains, dissipated energy and the degradation of reaction force and bending moment after 25 cycles. The results show that geometric parameters strongly affect the cyclic response: within the investigated loading layer, configurations with $D_e=100$ mm generally exhibit strength degradation values between about 10% and 60%, whereas for $D_e=400$ mm the degradation typically ranges between 50% and 100%, with most cases falling in the moderate-to-severe degradation domain. At the same time, larger diameters and thicker tubes generally lead to an increase in dissipated energy, while longer members tend to show lower energy dissipation but also reduced degradation. The study therefore provides a reproducible computational framework and comparative performance trends for the assessment of low-cycle cyclic response in CFT beams under a prescribed loading protocol. Full article

In this paper, a multi-feed transmitarray with high-gain, wide-angle beam-scanning, and low-cost features is presented. A novel hybrid phase distribution (HPD) method is proposed to improve the beam-scanning range by combining the single-focal and bifocal principles according to the actual feed illumination area. By using the proposed method, the phase distribution of the transmitarray for different scanning angles can be obtained more accurately, thereby reducing the phase error between the actual and ideal phase distributions. To construct the transmitarray, a three-layer polarization conversion unit cell, consisting of two orthogonal polarizers in the outermost layers and a polarization rotating patch in the middle layer, is designed to provide high-efficiency transmission and full 360° phase coverage. Based on the HPD method, a single-polarized transmitarray antenna with a focal diameter ratio of 0.28 is designed and simulated. The simulated results show that the enhancement of the beam-scanning range is successfully realized. This design can perform a discrete ±60° beam-scanning range with a peak gain of 24 dBi. The gain losses of 0.7 dB at ±30° and 4.7 dB at ±60° are achieved. The cross-polarization levels are about 44 dB and 35 dB at 0° and −60° scanning angles, indicating low cross-polarization of the proposed solution. A five-beam prototype is fabricated and measured for experimental verification purposes. The measured results demonstrate good consistency with the simulations in the main lobe, with slight deviations due to practical fabrication and measurement constraints. The proposed design has advantages such as low-cost, wide beam-scanning angle, high-gain, low-profile and easy fabrication. Full article