Search Results (398)

This paper develops an analytical treatment of vibro-acoustic wave propagation in a cylindrical waveguide containing two clamped elastic membranes and a central flexible-shell segment. The acoustic field obeys the time-harmonic Helmholtz equation, the shell motion is described by Donnell–Mushtari thin-shell theory under axisymmetric loading, and the membrane response is governed by classical membrane theory and incorporated through a tailored Galerkin scheme. The resulting coupled fluid–structure boundary-value problem is solved by the Mode-Matching Method: the acoustic potentials are expanded in orthogonal radial eigenfunctions within each subregion, and continuity of pressure, normal velocity, and structural displacement are enforced at every interface. The mirror symmetry of the configuration is exploited by an exact decomposition into symmetric and anti-symmetric sub-problems, each of which reduces to a truncated linear algebraic system of dimension $4N+4$ for the unknown modal amplitudes. Acoustic power-balance identities provide a quantitative consistency check on the numerical implementation and diagnose convergence with respect to the truncation order; structural damping is accommodated through complex-modulus substitutions for the shell and the membrane tension without altering the algebraic structure of the system. The numerical results demonstrate that the dual-membrane configuration delivers transmission-loss values exceeding $25\mathrm{dB}$ across the low-frequency band relevant to HVAC and automotive applications, with a representative plateau near $13\mathrm{dB}$ at the reference geometry, through resonance-driven modal coupling between the acoustic field and the compliant interfaces. Parametric studies identify the excitation frequency, the inner-membrane radius, the shell radius, and the chamber length as effective design parameters for tuning the attenuation. The formulation furnishes a unified and computationally efficient analytical tool for predicting and optimising noise attenuation in flexibly coupled cylindrical duct systems. Full article

Membrane roofs with saddle geometry are widely used in stadiums and public facilities that are highly exposed to rainfall. However, current design practice typically considers rainfall only in terms of seepage effects, drainage requirements, or static stability checks, while the influence of extreme rainfall on dynamic behavior and prestress loss has not been comprehensively quantified. In this study, the behavior of a restored engineering-scale saddle-shaped membrane roof under three representative rainfall intensities (50, 300, and 550 mm/h) is investigated through combined laboratory experiments (span L = 2.52 m) and numerical simulations, with particular emphasis on how supporting conditions and pretension levels affect vertical displacement, vibration propagation, and rainfall-induced edge-cable pretension loss. The findings are intended to reveal response mechanisms and trends, while quantitative extrapolation to full-size roofs should be conducted with scaling considerations. The numerical model is validated against the experimental results through comparisons of cable forces and vertical displacements. The results indicate that while the maximum vertical displacement induced by heavy rainfall is small (millimeter-level) and does not cause immediate failure, the rainfall event induces a significant permanent loss of pretension (a maximum observed relaxation of 10.4% in the edge cables for the tested specimen) in the edge cables. This relaxation degrades the structural stiffness, potentially compromising aerodynamic stability under subsequent wind events. Consequently, for the tested configuration, post-rainfall pretension inspection is recommended for events exceeding 300 mm/h, with retensioning suggested if significant tension loss is detected. This recommendation should be interpreted as an indicative engineering reference for the present specimen rather than a universal criterion for all saddle membrane roofs. Full article

This study presents a mechanics based analytical framework for predicting the flexural–shear capacity of reinforced concrete (RC) beams strengthened with Engineered Cementitious Composites (ECCs) and a hybrid ECC–GFRP near surface mounted (NSM) system. Building upon previously reported experimental observations, the present work aims to establish rational prediction models capable of capturing the interaction between flexural and shear mechanisms in strengthened beams. The analytical approach integrates sectional analysis for flexural capacity with a modified truss analogy for shear resistance, explicitly incorporating the strain hardening tensile contribution of ECC and the tensile and confinement effects of GFRP reinforcement. An interaction based failure criterion is subsequently employed to identify the governing failure mode under combined flexural shear actions. The proposed model is validated against experimental results obtained from twenty seven beam specimens with varying flexural and shear reinforcement ratios and strengthening configurations. The predicted ultimate loads show good agreement with experimental values, with an average deviation within ±10%. The analytical framework accurately captures the transition between flexural dominated, combined flexural–shear, and diagonal tension failures observed experimentally. Results demonstrate that ECC significantly enhances ductility and shear crack control, while the hybrid ECC–GFRP system provides substantial strength enhancement with a controlled shift in failure mode. Overall, the developed analytical models offer a reliable and computationally efficient tool for predicting the flexural–shear capacity and failure behavior of ECC and hybrid ECC–GFRP-strengthened RC beams, supporting performance based design and practical strengthening applications. Full article

Low tensile strength (brittleness) is a significant drawback of lightweight aggregate concrete, as it significantly limits its application. The parameters can be improved by using dispersed reinforcement. For the purpose of the study, two fractions of high-strength lightweight aggregate were used. It was produced by sintering waste material from power plants and cogeneration plants (e.g., fly ash). Hook-shaped steel fibres were used as the reinforcement. The presented tension test results apply to lightweight fibre-reinforced concrete, i.e., flexural tensile strength, splitting tensile strength and residual flexural tensile strength compared to lightweight non-reinforced concrete. It also refers to the analysis of fibre distribution using computer tomography and the microstructure of the fibre–cement slurry contact zone. The test results revealed that steel fibres are distributed correctly in lightweight concrete, creating effective reinforcement for the brittle cement matrix. The experimental work was supported by numerical simulations based on the Finite Element Method (FEM). A lightweight concrete structure with volumetric content and steel fibre distribution identical to those used in the experiment was modelled. This way, the numerical simulations were verified. The confirmation of the numerical model’s reliability shall help engineers develop the material’s strength at the product design stage. The optimisation shall be possible owing to the easy application of the fibres’ variable configuration, given their share and orientation. As a result of combining experimental tests with numerical simulations, the paper evaluates the influence of steel fibres on the strength of lightweight concrete. Ansys Workbench software was used to model a three-point bending test on lightweight concrete beams. A Menetrey–Willam constitutive model was selected to represent the mechanical behaviour of fibre-reinforced concrete; the model assumed material hardening/softening. Simulations yielded numerical responses similar to the experimental results, confirming the model’s ability to capture the fibre reinforcement’s influence on the forms of destruction. Full article

Pavement repair has become an increasingly time-critical operation as traffic volumes grow and lane-closure windows shrink. This has driven demand for materials that gain full structural strength quickly, reopen to traffic within hours, and hold up longer than conventional patches. This study evaluates polymer concrete (PC), a thermosetting resin-bound aggregate system, through combined laboratory characterization and three-dimensional finite element analysis. Compressive strength, splitting tensile strength, unit weight, and apparent porosity were measured at 1, 3, 7, and 28 days of curing. PC reached 85.97 MPa in compression and 7.63 MPa in tension by day three, with near-zero porosity (0.15%) maintained throughout. These three-day values were used directly as material inputs in the three-dimensional finite element analysis (FEA), reflecting the early traffic reopening scenario that defines rapid repair practice. Structural performance was assessed through 36 static analyses in ANSYS 2024 R2, covering flexible (Hot Mix Asphalt, HMA) and rigid (Jointed Plain Concrete Pavement, JPCP) pavement types, three patch sizes (250 × 250 mm, 500 × 500 mm, and 1000 × 1000 mm), and nine load scenarios per configuration. Safety factors (SF) against internal cracking, interfacial debonding, and compressive failure were computed for both PC and traditional patches. PC consistently outperformed HMA and Portland cement concrete patches across all metrics. On rigid pavements, interfacial safety factors exceeded 22.0, confirming that standard surface preparation is sufficient. On flexible pavements, adopting 0.78 MPa as a conservative lower-bound estimate of PC-HMA interfacial bond strength, five scenarios exhibit debonding risk (250-C, 500-C, 500-D, 1000-C, and 1000-D; SF = 0.47–0.99), while the remaining four show high interfacial risk (SF = 1.11–1.30); primer application and mechanical scarification are required for all PC repairs on flexible pavements regardless of patch geometry. Taken together, the experimental and numerical evidence positions PC as a credible, high-performance option for highway repair. Full article

Due to the asymmetry of pass profiles, F-section steel is prone to defects such as overfilling, underfilling, and twisting during production, which significantly deteriorates the dimensional accuracy, mechanical properties, and surface quality of products. To mitigate the occurrence of such defects, this study established a thermo-mechanical coupled three-dimensional finite element model for the finishing rolling process of F-section steel using ABAQUS 2022 incorporating the actual operating conditions of the steel plant’s production line. By analyzing the stress–strain fields of each pass, it was found that the maximum deformation of the rolled piece is concentrated at the junctions of the inner leg with the flange, the inner leg with the web, and the outer leg with the web. Additionally, underfilling was observed at the legs and flanges of the pass in each rolling sequence. Based on these findings, an in-depth analysis was conducted on the effects of friction coefficient, tension configuration, rolling temperature, and web reduction on pass filling degree. Conditions of low friction, small reduction, and high temperature facilitate the smooth filling of metal in the leg cavity; in contrast, conditions of high friction, large reduction, and low temperature promote the filling of surface metal and an increase in spread. Maintaining a low-tension state is a common favorable condition for improving the pass filling degree of both the legs and the surface. When the friction coefficient is 0.2, tension is 0, rolling temperature is 1040 °C, and web reduction is 4 mm, the pass filling degrees of the inner and outer legs reach their maximum values of 99.88% and 99.16%, respectively. When the friction coefficient is 0.4, tension is 0, rolling temperature is 1010 °C, and web reduction is 4 mm, the pass filling degrees of the upper and lower surfaces are maximized, reaching 98.95% and 98.22%, respectively. These findings provide data support and theoretical guidance for addressing defects encountered in F-section steel production. Full article

Cylindrical floating production storage and offloading (FPSO) units are advancing into deeper waters. Overcoming the severe challenges posed by complex deepwater environments requires the design of mooring systems that balance economic efficiency and mooring performance. This paper proposes an innovative optimization method for cylindrical FPSO mooring systems, combining the Kolmogorov–Arnold Network (KAN) with the Non-dominated Sorting Genetic Algorithm III (NSGA-III). Configuration samples are generated within predefined design variable ranges using Latin Hypercube Sampling (LHS), followed by time-domain global response simulations using OrcaFlex (version 11.3) software. A KAN surrogate model is constructed to predict the dynamic responses of the mooring system. Finally, the NSGA-III algorithm is employed for multi-objective optimization to obtain the Pareto optimal set, aiming to minimize mooring costs, maximum tension, fatigue damage, and platform offset. The results demonstrate that, compared to traditional optimization methods, the combination of KAN and NSGA-III exhibits superior prediction accuracy and generalization capabilities. The optimized configurations significantly outperform the original design in both mooring performance and economic costs. Specifically, the most economical scheme reduces mooring costs by 20.73%, the minimum tension scheme decreases mooring line tension by 46.75%, and the minimum displacement scheme reduces platform offset by 30.88%. Full article

Overhead distribution systems may experience concurrent wind and rainfall loading during typhoon events, but most existing studies still emphasize individual components, single-hazard descriptions, or network-level consequences. To address this gap, this paper develops a probabilistic assessment framework for distribution pole–line segments exposed to compound typhoon wind–rain hazards. A three-dimensional finite-element model of a representative segment with three poles, two spans, and three-phase conductors is constructed, and uncertainties in structural properties and loading-related coefficients are incorporated explicitly. Correlated turbulent wind histories are synthesized using the Davenport spectrum and harmonic superposition method, whereas rainfall actions are represented through an impact-based raindrop spectrum formulation. Nonlinear dynamic analyses are performed for multiple combinations of basic wind speed and rainfall intensity, and the resulting peak conductor tension and pole-base bending moment are used as engineering demand parameters. Logarithmic probabilistic demand models are then fitted to derive failure-probability surfaces for the conductor, the pole, and the pole–line segment. Segment failure is defined through the maximum normalized demand among the central pole and the six connected conductors, thereby extending the assessment from component-level failure to local segment-level risk. The results show that basic wind speed governs the overall evolution of failure probability, whereas rainfall acts as a secondary but non-negligible amplifying factor that shifts the probability transition zone toward lower wind-speed levels. For the adopted configuration, the segment-level failure probability is governed mainly by pole response. Additional model checks and event-based comparisons support the consistency of the proposed segment-level probability formulation. The proposed methodology can support risk screening, warning-threshold setting, and maintenance decision making for overhead distribution systems subjected to compound meteorological hazards. Full article

In high-speed train traction power supply systems, compensation ropes serve as critical transmission components to ensure system stability. These ropes are specially designed as right-hand alternating lay wire ropes. During tension compensation of the contact wire, the compensation rope undergoes repeated bending around the ratchet device, making it susceptible to fatigue fracture. This study conducted bending fatigue tests on compensation ropes with complete structural configurations in accordance with GB/T 12347-2008. The stress distribution and deformation evolution induced by bending were simulated using the finite element method, enabling fatigue life prediction under cyclic bending conditions. Given the significant convergence difficulties encountered in large-deformation bending simulations of the full structural model, this study innovatively adopts Love’s elastic thin-rod theory as an alternative approach, which avoids the computational prohibitions of full-scale helical modeling while preserving critical bending stiffness characteristics. The results demonstrate that the equivalent elastic modulus derived from Love’s elastic thin-rod theory closely matches the modulus obtained through stress–strain curve fitting from strand tensile tests. Furthermore, under identical axial tensile loads, the equivalent diameter model and the full-structure finite element model exhibit nearly identical end elongations. The predicted bending fatigue life using the equivalent diameter model agrees well with experimental results, and the fatigue fracture mechanisms are further revealed through microscopic morphology analysis, collectively confirming that the proposed equivalent modeling strategy provides an efficient and reliable solution for fatigue life prediction of complex wire rope structures under coupled tension–bending conditions. Full article

Rectangular shield tunnels demonstrate significant advantages in underground space utilization due to their optimal cross-section efficiency and enhanced spatial functionality. Furthermore, their shallow overburden construction capability minimizes environmental impact and preserves subsurface resources. However, compared with circular shield tunnels, rectangular configurations exhibit greater susceptibility to longitudinal differential torsional deformation under asymmetric external loading. This deformation mechanism may induce excessive stresses in segments and connecting bolts, potentially causing joint offsets at tunnel rings that compromise structural integrity. This paper proposes a computational method for determining the longitudinal equivalent torsional stiffness of rectangular shield tunnels under combined compression–bending–torsion loading based on an equivalent continuum model. The proposed novel theoretical solutions were systematically validated against numerical simulations through comparative analysis. Parametric studies revealed that the effective ratio of longitudinal torsional stiffness increases proportionally with segment width-to-height ratio and bolt quantity while exhibiting inverse correlations with segment thickness and bolt equivalent shear length. The effective ratio of longitudinal torsional stiffness is directly correlated with compression–torsion ratios and bending–torsion ratios, with different load combinations significantly influencing torsional performance. Consequently, design optimizations incorporating increased bolt pre-tension forces or pre-stressed segment structures are proposed to improve torsional performance in rectangular shield tunneling systems. Full article

During the global transition toward cleaner energy infrastructure, floating photovoltaic (FPV) systems have emerged as a research focus in renewable energy technologies due to their distinctive spatial utilization advantages. This study examines the hydrodynamic performance of a novel FPV system comprising multiple floating modules connected via flexible connectors to a circular frame. Three distinct connection schemes among the floating modules were designed for comparative analysis. To ensure computational accuracy, a numerical model was established and validated against existing experimental data from a 2 × 3 scaled array. Although the validation setup differs from the novel configurations proposed in this study, the results confirm the reliability of the adopted numerical method. Based on this validated model, time-domain analyses were conducted to evaluate the six-degree-of-freedom (6-DOF) motions of the FPV, as well as the dynamic responses of the flexible connectors and mooring system under various wave periods, heights, and directions. The study shows that the motion differences in FPV under different connection schemes are mainly observed in short wave periods and oblique waves. At a wave direction of 45°, the maximum differences in surge and sway motions among the schemes reach 0.2 m. The disparity in mooring tension and connector tension for different connection schemes increases as the wave period decreases and the wave height increases. Specifically, the maximum difference in connector tension attains 10 kN under a wave period of 9 s and a wave direction of 45°, while the peak difference in mooring chain tension reaches 13 kN at a wave direction of 90°. The dynamic responses of the connectors and mooring chains in the second connection scheme are superior to those of the other two schemes. The numerical simulations identify the optimal connection scheme. The results provide theoretical guidance for the design and practical application of FPV system. Full article

Therapeutic interventions within the urinary system are often limited by the complex and tortuous anatomy of the renal pelvis and ureters, restricting access to deep regions and increasing the risk of mucosal trauma. In this study, we present a multifunctional, magnetically controlled ferrofluid droplet robotic platform engineered for high deformability and precision navigation. A custom electromagnetic actuation system was developed and optimized via COMSOL Multiphysics (version 6.3, COMSOL Inc., Stockholm, Sweden) simulations to generate programmable magnetic fields. Experimental validation in both simplified environments and anatomically realistic 3D-printed urinary tract models demonstrated the droplets’ capacity for controlled locomotion, reversible deformation, and traversing constrictions significantly smaller than their resting diameter. The droplets’ locomotion and extreme deformability are governed by the dynamic balance between the applied magnetic gradient forces, the restoring interfacial tension of the ferrofluid, and the fluidic viscous drag. Quantitatively, the droplets achieved robust translational velocities up to 260 mm/s under single-coil actuation (51 mT, 20 Hz) and 108 mm/s under a more stable dual-coil configuration (51 mT, 8.3 Hz). Furthermore, two clinically relevant functionalities were successfully executed: rapid vibration-induced release of encapsulated dye for targeted drug delivery, and the precise mechanical capture and transport of artificial kidney stones. These results establish a highly versatile platform for minimally invasive urological procedures, highlighting the immense potential of soft magnetic microrobotics for integrated therapeutic applications. Full article

The scientific literature increasingly supports the use of computational models to predict fracture across a wide range of applications, which, when calibrated with experimental data, can yield highly consistent results. Although the extended finite element method (XFEM) is widely used in commercial packages, phase field (PF) methods have emerged as a robust alternative. In this study, a cohesive zone model (CZM) was implemented using both approaches (a PF model with an implicit damage initiation criterion and a standard commercial XFEM solver with an explicit damage initiation criterion) to analyze their robustness and computational efficiency. First, a standardized fracture test of a compact tension (CT) specimen was simulated and compared with experimental data to validate both methods, achieving accurate predictions under plane strain conditions with a dominant mode I fracture behavior. Subsequently, the application of both fracture models was extended to flexible thoracic prostheses across two distinct chest wall reconstruction scenarios: a single-rib unilateral model and a multi-rib bilateral configuration. An extreme-case compressive displacement was assessed to identify critical regions susceptible to fracture initiation and to evaluate the structural limits of the proposed designs. The results showed that the PF approach required a higher computational time, but exhibited more stable convergence. In contrast, the XFEM-based solver required careful mesh calibration to ensure convergence under complex conditions. These results highlight the potential of the PF approach as a practical tool for identifying and improving critical regions of implants, overcoming the limitations of commercial XFEM implementations. Full article

Underwater acoustic monitoring is a critical technology for marine resource development and modern aquaculture. The performance of acoustic sensors directly determines the effectiveness of biological behavior tracking in complex marine environments. This paper presents the design, fabrication, and characterization of a custom hydrophone utilizing a polyvinylidene fluoride (PVDF) piezoelectric film configured in a biomimetic tympanic cavity structure. Operating on the direct piezoelectric effect, the device employs a pre-tensioned PVDF diaphragm integrated with a dedicated charge amplifier circuit to condition high-impedance signals. Laboratory calibrations demonstrate a stable frequency response (with a sensitivity variation within ±1 dB) in the low-frequency range (1–200 Hz) with an average acoustic pressure sensitivity of approximately −206 dB (re 1 V/μPa), providing a higher relative voltage gain compared to a commercial reference hydrophone with a nominal sensitivity of −210 dB (re 1 V/μPa). Furthermore, extensive field evaluations were conducted in a marine net pen to analyze acoustic data across multiple fish feeding scenarios (baseline, pre-feeding, active feeding, and post-feeding). The proposed custom hydrophone exhibited a superior dynamic range and successfully locked onto a 24.4 Hz Golden Pompano (Trachinotus blochii) bioacoustic signature, maintaining remarkable feature stability even after active feeding ceased. This study validates the efficacy of the biomimetic PVDF hydrophone for low-frequency acoustic detection, providing a robust hardware foundation for automated behavioral recognition systems in aquaculture. Full article

This study combines theoretical analysis with experimental investigation to examine the hysteretic behavior and seismic mechanisms of self-centering timber frames incorporating reinforced concrete slabs through tests on two full-scale comparative specimens. One specimen was constructed with a floor slab, while the other was designed without a slab, and both were subjected to low-cycle reversed loading under identical test conditions. The seismic performance of the two specimens was comparatively evaluated in terms of hysteresis curves, load-carrying capacity, stiffness degradation, and energy dissipation capacity. The experimental results indicate that, under the adopted test configuration, the presence of the slab increases the initial stiffness of the frame by 81.25% and enhances its load-carrying capacity. In addition, prior to concrete cracking, the slab improves the energy dissipation efficiency through composite action. The slab also reduces the rate of post-tensioning loss by approximately 12.5%, indicating its beneficial role in mitigating such loss. Overall, this study provides both theoretical and experimental support for the quantitative evaluation of slab effects in self-centering timber frames. Full article