Search Results (2,517)

Concrete slabs in composite bridges are inevitably subjected to heavy vehicular loads during their service life. To evaluate the fatigue performance of the prestressed concrete slabs in composite bridges, two full-scaled models of prestressed concrete slabs were first designed and tested, with the load amplitude was selected as the variable. To simulate the damage caused by the initial passage of heavy vehicles, this was simplified into the form of a static cyclic load. The mechanical deformation state and crack distribution of the slab were analyzed. Further, a finite-element model was established, and a parametric analysis based on the variation in loading form, such as monotonic displacement loading, static cyclic loading followed by monotonic displacement loading, and cyclic displacement loading, was conducted to discuss the performance-enhancement mechanism of prestressed concrete slabs. Finally, in consideration of the influence of static cyclic damage on the fatigue performance of prestressed concrete slabs, evaluation parameters were proposed to account for static cyclic damage by considering the effects of stresses in concrete, tensile rebar, prestressed tendons, and external loading. A comprehensive fatigue performance evaluation method for prestressed concrete slabs, which neglects the tensile hardening behavior of cracked concrete in the tension zone, was established and verified by test results. The results indicate that the damage caused by static cyclic loading has a significant influence on the fatigue performance of the slab. Applying prestress can significantly mitigate the influence of initial damage on the mechanical and deformation behavior of the slab, which benefits from the prestress compensating for the cracking stress at the bottom of the slab. The proposed fatigue performance-evaluation method for prestressed concrete slabs, which considers static cyclic damage, can predict fatigue deformation behavior with an error of less than 10%, while reasonably determining the fatigue life and failure modes of prestressed concrete slabs. The parametric analysis reveals that when the prestress value exceeds 9 MPa, the failure mode of the prestressed concrete slab transfers from rebar fracture to concrete failure. Full article

The quality of heavy plates produced from low-carbon steel is directly linked to the structural characteristics inherited from the initial continuously cast thick slabs. This study explores how different casting technologies affect the morphology and distribution of allotriomorphic ferrite along prior austenite grain boundaries (PAGBs) within these slabs. Using quantitative microstructural analysis based on advanced computer vision techniques (OpenCV), the research identifies significant variations in ferrite boundary thickness and volume fraction associated with different casting methods. These microstructural differences strongly correlate with variations in Charpy V-notch impact energy (KVZ20) and susceptibility to microcrack formation during subsequent rolling processes. The results obtained allow us to evaluate the influence of the cast structure on the formation of the initial structural characteristics of the material, especially on the formation of microcracks of the slab microstructure and their propagation during further processing. Full article

This study investigates fiber content and orientation in prefabricated slab elements made of ultra-high-performance fiber-reinforced concrete (UHPFRC), using novel non-destructive measurement using a coil’s quality factor, where the coil is put to one side of the specimen only. This allows the analysis of slab specimens of arbitrary size. That then allows an accurate quality control of elements made in the prefabrication industry. This study presents an experimental campaign designed to evaluate the non-destructive principle’s accuracy and practical feasibility. Twenty-five large slab specimens were made in an industrial prefabrication plant using various casting methods to introduce different flow-induced fiber parameters. The slabs were subjected to this non-destructive testing, then destructive bending tests and CT scanning to tie the results together and validate the non-destructive results. The results showed that the coil’s quality factor values correspond well to the distribution (concentration) and orientation of fibers, and the method reliably reveals potential defects of the material and can predict the element’s mechanical properties. Full article

This study experimentally investigates the strengthening performance and failure behavior of reinforced concrete slabs coated with high elastic modulus polyurea(HEPU). To address the limited strengthening effect of conventional polyurea due to its low elastic modulus and strength, HEPU was applied to slab specimens with varying coating thicknesses (1, 2, and 3 mm). To evaluate the effectiveness of the HEPU reinforcing method, experiments were conducted with varying coating thicknesses, and the results were compared with those of unstrengthened specimens. The results showed that HEPU strengthening significantly enhanced flexural strength and stiffness, with improvements increasing proportionally with coating thickness. Additionally, the polyurea coating enhanced crack resistance and adhered well to the concrete, preventing delamination or detachment up to final failure. The slabs maintained ductile behavior even after HEPU rupture, although load resistance decreased post-rupture. However, the strengthening effect diminished due to the rupture of the HEPU, indicating limited effectiveness in improving ductility. These findings provide insights into the design and application of polyurea-based strengthening techniques for reinforced concrete structures. Full article

For urban rail vehicles operating at speeds ranging from 60 to 250 km/h, the dominant source of radiated noise is the wheel–rail interaction. Finite element modal analysis was conducted on the wheelset, rails, and track slab. A multibody dynamics model under straight-line condition was established. It was a rigid–flexible coupling dynamics model, including the rigid vehicle body, flexible wheelsets, flexible rails, and flexible track slabs. Dynamic simulation calculations were carried out in this model to obtain the wheel–rail forces. The finite element and boundary element models of wheels and rails were established using simulation software to obtain the results of wheel–rail noise. The sound pressure levels on the surfaces of wheels and rails were calculated under the operating conditions of 120 km/h, 140 km/h, 160 km/h, and 200 km/h in the straight-line condition. The variation law of the frequency distribution of wheel–rail noise with the change in speed was obtained. The variation fitting function of wheel–rail noise SPL with speeds was obtained. Within the speed of 200 km/h, as the speed increased, the total value of wheel–rail SPL basically shows a linear growth. The simulation analysis results were compared with the experiment results. It indicated that the simulation results were reasonable. The simulation models are of great significance for the noise prediction in train design and manufacturing. Full article

In the North China region, measures such as restricting groundwater extraction and promoting cross-basin water diversion have effectively alleviated the problem of excessive groundwater exploitation. Nevertheless, the continuous rise in groundwater levels may alter the mechanical properties of foundation soil layers, potentially leading to geotechnical hazards such as foundation instability and the uneven settlement of structures. This study employs FLAC3D software to simulate the displacement, deformation, and stress–strain behavior of buildings and their surrounding strata during the dynamic recovery of groundwater levels, aiming to assess the impact of this process on structural integrity. Research findings indicate that the maximum building settlement within the study area reaches 54.8 mm, with a maximum inter-column differential settlement of 8.9 mm and a peak settlement rate of 0.16 mm/day. In regions where differential settlement aligns with the interface between the floor slab and walls, tensile stress concentrations are observed. The maximum tensile stress in these zones increases progressively from 1.8 MPa to 2.19 MPa, suggesting a potential risk of tensile cracking in the concrete structures. The influence of groundwater level recovery on buildings exhibits distinct phase characteristics, and the response mechanisms of different lithological strata vary significantly. Therefore, particular attention should be given to the physical properties and mechanical behavior of strata that are highly sensitive to variations in moisture content. These findings hold significant reference value for the sustainable development and utilization of underground space in the North China region. Full article

We perform a molecular dynamics simulation of a bulk eight-component hydrocarbon mixture that roughly represents a composition of hydrocarbon fluid in a volatile oil reservoir. For that goal, we have developed a method for building molecular models of hydrocarbon mixtures which can include various branched molecules. We have used self-periodical simulation boxes with different aspect ratios. Our main focus here is the phase behavior of a multicomponent mixture in the presence of gas–liquid interfaces of different shapes: spherical, cylindrical, and slab-like gas bubbles. We have developed a method for calculating properties of coexisting phases in molecular simulations of multicomponent systems. In particular, it allows us to analyze the local composition of the mixture and to calculate the molar densities of components in liquid and gas phases, and inside the interface layer between them. For the values of model parameters that we have used so far, the mixture is homogeneous at a high pressure and undergoes liquid–gas phase separation upon decreasing the pressure. We have kept the same temperature $T=375.15 \mathrm{K}$, the same composition and the same number of molecules in all systems and used several combinations of the simulation box size and shape to control the overall density, and therefore also the pressure, as well as the presence or absence of a liquid–gas interface and its shape. The gas bubble that appears in the system is mainly composed of methane. There is also a small number of ethane and butane molecules, a tiny number of hexane molecules, and no molecules of heavier components at all. In the liquid phase, all components are present. We also show that inside the gas–liquid interface layer, which is actually quite broad, the molar density of methane is also higher than that of other components and even reaches a maximum value in the middle of the interface. Ethane behaves similarly: its molar density also reaches a maximum inside the interface. The molar density of heavier components grows monotonically from the inner part of the interface towards its outer part and shows a very small (almost not visible) maximum at the outer side of the bubble. Full article

There is a growing global trend toward reducing the consumption of natural resources and newly produced construction materials by replacing them with secondary raw materials. Concrete derived from construction and demolition waste can be recycled multiple times and is considered environmentally sustainable. This study evaluates the feasibility of reinforcing weak subsoil using crushed recycled concrete. Concrete obtained from the demolition of residential buildings was crushed under laboratory conditions to produce material with grain sizes corresponding to sands, and mixtures were subsequently prepared containing up to 30% fine fraction. The case study focuses on circular wind turbine foundations supported by symmetrically arranged columns made of four different materials, located beneath the foundation slab. The analyzed subsoil is characterized by strong stratification, low bearing capacity, and high compressibility. The calculation results indicate that the bearing capacity conditions for all foundations were met within similar ranges of the safety factor for the given loads, both for low- and high-power turbines. However, foundation deformations increased with turbine size and bending moments, and were nearly twice as large for recycled aggregates compared to recycled concrete. Numerical simulations demonstrate that recycled aggregate without fine fraction, as well as with fine fraction, and recycled concrete can provide load-bearing performance comparable to conventional concrete under low loading conditions, while offering significant environmental benefits. Full article

This study presents an amplitude-based non-destructive testing (NDT) approach for estimating reinforcement bar diameter in reinforced concrete members using ground-penetrating radar (GPR). The novelty of this work lies in the use of normalized amplitude-diameter-depth (NADD) relationships, which link the reflected electromagnetic wave amplitude to both rebar diameter and cover depth through an exponential attenuation model. Normalization was applied to remove the influence of varying signal energy and antenna coupling, thereby allowing consistent comparison of amplitudes across different depths and improving the reliability of amplitude-depth interpretation. The NADD equation was developed from GPR measurements obtained on a reinforced concrete slab containing bars with diameters ranging from 9.5 mm (#3 bar) to 25.4 mm (#8 bar) and then validated using data from three prestressed concrete box beams recovered from a decommissioned bridge managed by the West Virginia Department of Highways. The normalized amplitude prediction error (E_a) was calculated to quantify model performance. The minimum mean error of approximately 4.7% corresponded to the 12.7 mm (#4 bar), which matched the actual reinforcement used in the beams. The results demonstrate that the proposed normalization-based approach effectively captures the amplitude-depth-diameter relationship, offering a quantitative framework for interpreting GPR data and improving the evaluation of reinforcement characteristics in existing concrete structures. Full article

In slab continuous casting, achieving uniform cooling in the secondary cooling zone is essential for ensuring both surface integrity and internal quality. To optimize the process for ship plate steel, a solidification heat transfer model was developed, incorporating radiation, water film evaporation, spray impingement, and roll contact. The influence of secondary cooling water flow on slab temperature distribution was systematically investigated from multiple perspectives. The results show that a weak cooling strategy is crucial for maintaining higher surface temperatures and aligning the solidification endpoint with the soft reduction zone. Along the casting direction, a “strong-to-weak” cooling pattern effectively prevents abrupt temperature fluctuations, while reducing the inner-to-outer arc water ratio from 1.0 to 0.74 mitigates transverse thermal gradients. In addition, shutting off selected nozzles in the later stage of secondary cooling at medium and low casting speeds increases the slab corner temperature in the straightening zone by approximately 50 °C, thereby avoiding brittle temperature ranges. Overall, the proposed multi-dimensional uniform cooling strategy reduces temperature fluctuations and significantly improves slab quality, demonstrating strong potential for industrial application. Full article

Lithium-ion battery (LIB) wireless charging using inductive power transfer (IPT) represents a transformative pathway for transportation electrification. While applications in railway systems remain limited, early studies highlight significant promises for implementation. This paper presents a hybrid energy-supply framework integrating LIB, inductive battery charging (BC) charging, and battery swapping (BS) to support a 20 km heritage trolley excursion between Belmont and Gastonia, NC. A kinematic simulation was developed to estimate traction energy demand, yielding 56 kWh per trip, or 112 kWh for two daily round trips. Finite element analysis (FEA) was conducted to design an LCL-s compensated 3 kW IPT system. Two transmitter configurations were evaluated: W–I ferrite cores (peak coupling ~0.22) and magnetic concrete slabs (~0.20). Although ferrite offers higher efficiency, magnetic concrete demonstrates superior durability and integration potential. Simulation results indicate that wireless charging alone, whether static or dynamic, is insufficient; similarly, a single daily BS strategy provides only 96 kWh. Seven BC-BS hybridization scenarios were evaluated, showing that mid-day swaps combined with either static or dynamic IPT produce a 12–16 kWh surplus. The most practical approach is a one-pack swap supplemented by uniformly distributed static pads, providing energy neutrality. This hybrid pathway ensures operational sufficiency, structural resilience, and compatibility with heritage rail preservation. Full article

A contactless passive magnetoelastic sensing setup, recently proposed for detecting pest/substance accumulation in confined spaces (labs, museum reserves), is optimized for enhanced low-frequency performance. The setup uses a short flexible polymer slab, clamped at one end. There, a short Metglas^® 2826MB magnetoelastic ribbon is fixed upon the slab’s surface. The opposite end receives excitation by a remotely controlled module of ultra-low amplitude vibration. When vibrating (with the slab), the ribbon generates magnetic flux, which depends on (and reflects) the slab’s dynamics. This changes when loads accumulate on its surface. The flux induces voltage in a contactless manner in a low-cost pick-up coil suspended above the ribbon. Voltage monitoring allows for evaluation of the vibrating slab’s real-time dynamics and, consequently, the detection of load-induced changes. This work innovates by introducing a low-cost passive circuit for real-time voltage processing, thus achieving an accurate representation of the low-frequency dynamics of the magnetic flux. Furthermore, it introduces an algorithm, which statistically detects load-induced changes using the voltage’s low-frequency power characteristics. Both additions enable load detection at relatively low frequencies, thus addressing a principal issue of passive contactless sensing setups. Extensive testing at different occasions demonstrates promising load detection performance under various conditions, especially given its cost-efficient hardware and operation. Full article

Introduction: Radon is a radioactive noble gas formed from uranium decay in the Earth’s crust. The most significant isotope, 222Rn, emits alpha particles capable of damaging lung tissue and inducing cancer. Radon exposure is affected by geophysical and building characteristics and is recognized as a Group 1 carcinogen by the IARC. Despite regulatory thresholds (e.g., EURATOM standards), health risks remain. Various mitigation methods aim to reduce indoor radon exposure and its impact. Materials and Methods: This systematic review followed PRISMA guidelines. PubMed, Scopus, and Web of Science were searched up to 28 February 2025, using a defined string. Studies with original data on radon exposure and lung cancer risk or mitigation efficacy were included. Independent screening and quality assessment (Newcastle–Ottawa Scale) were conducted by multiple reviewers. Results: Of the 457 studies identified, 14 met the inclusion criteria. Eleven of these investigated the link between indoor radon and lung cancer risk, and three evaluated mitigation strategies. Radon levels were commonly measured using passive alpha track detectors. Levels varied depending on geographical location, season, building design and ventilation, these were higher in rural homes and during the colder months. Case–control studies consistently found an increased lung cancer risk with elevated radon exposure, especially among smokers. Effective mitigation methods included sub-slab depressurisation and balanced ventilation systems, which significantly reduced indoor radon concentrations. Adenocarcinoma was the most common lung cancer subtype in non-smokers, whereas squamous and small cell carcinomas were more prevalent in smokers exposed to radon. Discussion and Conclusions: This review confirms the robust association between indoor radon exposure and lung cancer. Risks persist even below regulatory limits and are amplified by smoking. While mitigation techniques are effective, their application remains uneven across regions. Stronger public education, building codes, and targeted interventions are needed, particularly in high-risk areas. To inform future prevention and policy, further research should seek to clarify radon’s molecular role in lung carcinogenesis, especially among non-smokers. Full article

Noise has detrimental effects on mental and physical health and quality of life, especially for those living in apartment buildings. Therefore, sound insulation materials are pivotal for reducing unwanted noise as well as enhancing acoustic comfort. This study offers a hybrid approach for analyzing 3D woven textile sound insulation material effectiveness, especially in residential buildings, by simulating airborne sound insulation and testing manufactured slab samples with 3D woven textile mortars in a laboratory using a tapping machine. At the same time, the JCA model and the transfer matrix method are employed to calibrate sound absorption coefficients (SAC) and simulate its airborne sound insulation effect in buildings in Seoul, South Korea. Results indicate that the maximum mean sound pressure level (SPL) of the 3D woven textile was reduced up to 9 dB in the octave band frequencies. The thickness improvement of 3D woven textiles enhances the mid- and high-frequency sound absorption effect, most pronounced in 3D woven textiles made of double-layer (DSRM) material, which demonstrated an air sound insulation efficiency around 28.5% greater than that of traditional materials. The maximum drop in impact sound pressure level (SPL) at 2 kHz is 13 dB. The study also proposes a strategy to optimize sound insulation performance, which is used as an effective solution for noise control in buildings. These findings lay the groundwork for research on the application of 3D woven textiles for sound insulation in residential buildings and offer prospects for sustainable textile composites in architectural building applications. Full article

This study investigates the mechanical behavior of a new type of link slab through experimental testing and numerical simulation. A full-scale segmental specimen of an I-shaped steel–concrete composite beam was designed, and a vertical active plus horizontal follow-up loading system was employed to realistically simulate the stress state of the link slab. In parallel, a nonlinear finite element model was established in ABAQUS to validate and extend the experimental findings. Test results indicate that the link slab exhibits favorable static performance with a ductile flexural tensile failure mode. At ultimate load, tensile reinforcement yielded while compressive concrete remained uncrushed, demonstrating high safety reserves. Cracks propagated primarily in the transverse direction, showing a typical flexural tensile cracking pattern. The maximum crack width was limited to 0.4 mm and remained confined within the link slab region, which is beneficial for long-term durability, maintenance, and repair. The FE model successfully reproduced the experimental process, accurately capturing both the crack development and the ultimate bending capacity of the slab. The findings highlight the reliability of the proposed structural system, demonstrate that maximum crack width can be evaluated as an eccentric tension member, and confirm that bending capacity may be assessed using existing design specifications. Full article