Search Results (480)

In order to study the mechanical properties of L-shaped columns of recycled aggregate concrete-filled steel tubes (L-RACFST) with a recycled aggregate concrete (RAC) coarse aggregate replacement rate of 100%, three L-RACFST columns with a RAC coarse aggregate replacement rate of 100% were made to carry out axial compression and two-way bias point load tests. The finite element numerical model was verified on the basis of the test. ANSYS was used to investigate the influence of steel strength, steel thickness, width-to-thickness ratio, and eccentricity on the mechanical properties of L-RACFST columns. Results show that: (1) The eccentricity significantly affects the compressive bearing capacity of L-RACFST columns. Compared with the axial compression specimens, the ultimate bearing capacity of the specimens with eccentricities of 40 mm and 80 mm decreases by 18.67% and 24.84%, respectively. (2) An eccentric load will exacerbate the comprehensive bending deformation of the test specimen. (3) During parameter design, eccentricity has a significant effect on the compressive load-bearing capacity of L-RACFST columns with a 100% RAC replacement ratio. However, increasing the steel’s thickness and strength and reducing the width–thickness ratio can effectively compensate for the loss of compression performance caused by eccentricity. The findings of this study provide guidance for the engineering design and application of steel tube RAC composite special-shaped columns with a high replacement rate. Full article

This study investigates the compressive performance of fiber-reinforced polymer (FRP) rebar-reinforced Seawater and Sea Sand Concrete (SSC) columns through an integrated approach combining finite element analysis, theoretical derivation, and machine learning. Finite element models were developed to quantify the influence of key parameters on the ultimate bearing capacity and lateral deflection. The results indicate that the compressive capacity decreases significantly with increasing eccentricity and slenderness ratio. Columns reinforced with steel rebars demonstrated superior load-bearing and anti-lateral displacement capabilities compared to their FRP-reinforced counterparts. A theoretical formula for predicting the compressive capacity was derived; however, it systematically overpredicted the experimental measurements by approximately 36%. To develop data-driven predictive models for the ultimate load capacity of FRP–SSC columns, four machine learning models, backpropagation neural network (BPNN), bootstrap aggregating BPNN (Bagging-BP), genetic algorithm-optimized BPNN (GA-BP), and gradient boosting regression trees (GBRT), were employed. Using sectional dimension, concrete strength, reinforcement parameters, eccentricity, and slenderness ratio as inputs, the validation sets of the models achieved R-values of 0.942, 0.918, 0.933, and 0.990, respectively. Feature importance analysis based on SHAP identified eccentricity as the most influential parameter. Results from this work can help to understand the behavior of FRP–SSC columns under compression. Full article

Background and Objectives: Executive functions (EFs) decline with aging, impacting functional independence. While resistance training (RT) is a promising non-pharmacological intervention, the optimal modality and duration for cognitive benefits remain unclear. Flywheel RT (FRT) imposes greater motor control and attentional demands than traditional RT (TRT), potentially enhancing EFs. Objective: To compare the effects of a 36-week FRT versus TRT program on executive function and serum insulin-like growth factor 1 (IGF-1) levels in healthy older women. Methods: This parallel-group randomized controlled trial allocated 64 older women (overall mean age 66.8 ± 4.6 years; FRT group: 68.0 ± 4.8 years; TRT group: 65.5 ± 4.1 years) to either FRT (n = 25) or TRT (n = 21) for two weekly sessions over 36 weeks. Executive function was assessed using the Victoria Stroop Test (inhibitory control), Digit Span Test (working memory), and Trail Making Test (cognitive flexibility). Serum IGF-1 was quantified via chemiluminescence. Intention-to-treat analyses with ANCOVA were performed. Results: After 36 weeks, both groups showed significant within-group improvements in inhibitory control (mean reduction from pre to post: FRT: 15.2 ± 10.4 to 14.8 ± 7.4 s; TRT: 20.4 ± 11.8 to 15.6 ± 7.3 s; p = 0.028, ηp² = 0.38) and working memory (Digit Span Forward: FRT: 6.2 ± 1.7 to 7.9 ± 2.0; TRT: 6.7 ± 1.5 to 8.7 ± 1.8; p < 0.001, ηp² = 0.84). The B/A ratio of the Trail Making Test improved significantly more in the FRT group (73.0 ± 65.2 to 87.5 ± 68.1 s) compared to the TRT group (67.3 ± 54.1 to 137.7 ± 83.6 s; group × time interaction: p = 0.001, ηp² = 0.13). No significant changes in serum IGF-1 concentrations were observed in either group (FRT: 112.9 ± 25.4 to 115.3 ± 21.3 ng/mL; TRT: 104.7 ± 27.5 to 103.0 ± 28.9 ng/mL; p = 0.88, ηp² = 0.002). Adherence was high (only 4 out of 46 participants did not complete all 72 sessions), and no severe adverse events were reported. Conclusions: Flywheel training appears particularly effective for enhancing cognitive flexibility, likely due to its higher cognitive-motor demands. The absence of significant changes in circulating IGF-1 suggests that the observed cognitive benefits may not be mediated by systemic endocrine pathways, although this does not exclude the possibility of local central nervous system adaptations or changes in other neurotrophic factors not assessed in this study. Full article

The purpose of this narrative review was to provide a conceptual and applied framework that distinguishes resistance training methods, strategies, and systems and clarifies how these constructs organize established training variables within contemporary recommendations for exercise prescription. The historical, conceptual, and theoretical synthesis was not restricted by publication date and included seminal studies and previous evidence syntheses. In addition, a focused descriptive mapping of primary experimental studies published between January 2021 and April 2026 was conducted using PubMed, Scopus, and Web of Science. This mapping comprised 40 studies assessing acute responses or chronic adaptations to methods including drop sets, rest–pause, pyramidal loading, eccentric training, blood flow restriction, cluster sets, and velocity-based training. Several studies reported no statistically significant between-method differences in selected strength or hypertrophy outcomes; however, their generally small samples and the absence of equivalence or non-inferiority analyses preclude conclusions of true equivalence. Individual studies also reported context-specific differences in session efficiency, fatigue distribution, movement velocity, regional hypertrophy, and contraction-specific adaptations. Given the heterogeneity of the mapped studies and the absence of formal risk-of-bias or certainty-of-evidence assessments, these observations should be interpreted as descriptive and exploratory rather than as evidence of general comparative superiority. Taken together with the broader historical and synthesized literature, the findings suggest that resistance training adaptations are primarily governed by foundational prescription variables, including load, volume, frequency, effort, density, and exercise selection. The principal contribution of this review is therefore to clarify how methods, strategies, and systems can be selected and organized according to specific goals, individual characteristics, and practical constraints. Full article

Concrete-filled steel tube (CFT) columns have been widely used in high-rise buildings and bridge structures due to their excellent composite performance. In practical applications, CFT columns inevitably experience eccentric loading due to structural imperfections, asymmetric load distributions, and seismic actions, particularly in corner columns of seismic-resistant structures where biaxial eccentric compression may occur. However, despite extensive studies on the local buckling behavior of CFT columns under axial compression and uniaxial eccentric compression, the behavior under biaxial eccentric compression remains insufficiently understood. In this paper, a theoretical study on the local buckling behavior of rectangular CFT columns subjected to biaxial eccentric compression is presented. Based on classical elastic stability theory and the energy variation method, an analytical model is developed by assuming that both the loaded and unloaded edges of the steel tube are elastically restrained against rotation and selecting an appropriate deflection function satisfying the boundary conditions and compatibility requirements. The relationship of local buckling strength of rectangular CFT columns subjected to biaxial eccentric compression and width-to-thickness ratios under different stress gradient coefficients is obtained. The results indicate that the local buckling strength σ_cr of steel tubes decreases significantly with the increasing width-to-thickness ratios b/t when the stress gradient coefficient α₀₁ and α₀₂ remain unchanged, and the local buckling strength of the broad face is much lower than that of the narrow face. As the stress gradient coefficient increases, the local buckling strength σ_cr of steel tubes increases. When the stress gradient equals 0, the steel tube is subjected to axial compression and the minimum of the local buckling coefficient can be obtained. When the stress gradient equals 2, the steel tube is subjected to pure bending and the maximum of the local buckling coefficient can be obtained. The proposed model provides a rational prediction of local buckling strength under different biaxial eccentric compression conditions. Finally, recommended width-to-thickness ratio limits for steel tube plates with different steel grades and stress gradient coefficients are proposed, which can provide practical guidance for preventing premature local buckling and improving the material utilization efficiency of rectangular concrete-filled steel tube columns. Full article

Coastal and offshore steel infrastructures such as transmission towers and wind turbine towers are prone to coating degradation after long-term exposure to salt fog, high humidity, and ultraviolet radiation. The subsequent uniform corrosion significantly reduces the cross-sectional load-carrying capacity and threatens structural safety. This paper presents a numerical parametric analysis on the compression behavior of circular steel tube (CST) members subjected to uniform corrosion induced by coating failure, based on 18 accelerated corrosion tests. The effectiveness of the wall thickness reduction method for simulating uniform corrosion after coating degradation is verified, and the influence of key parameters on load-carrying capacity degradation is systematically investigated. A simplified formula for elastic local buckling of corroded CSTs is derived, and a direct strength method (DSM) calculation framework considering both global buckling and local–global interactive buckling is established. The results show that the uniform corrosion ratio is the dominant factor affecting load-carrying capacity degradation, while sectional dimension, slenderness ratio, and eccentricity have negligible influence. The proposed DSM method achieves a prediction error within 5% compared with test and numerical results. It is primarily applicable to uniformly corroded steel tubes represented by equivalent wall thickness loss, and its applicability to scenarios with localized corrosion, pitting corrosion, weld-zone corrosion, or non-uniform wall thickness reduction requires further validation. This method provides a rapid and accurate tool for residual load-carrying capacity assessment and life cycle management of coastal steel infrastructures after coating failure. Full article

Assessment of left atrial remodeling in atrial fibrillation (AF) has traditionally relied on anteroposterior diameter, left atrial volume (LAV), and indexed left atrial volume (LAVI). Although these measures remain clinically useful, they reduce a complex, asymmetric, and anatomically constrained chamber to scalar descriptors and therefore cannot fully capture the spatial substrate that underlies AF persistence, thromboembolic risk, or arrhythmia recurrence after catheter ablation. Three-dimensional left atrial reconstruction provides a more refined framework by preserving chamber shape, regional deformation, pulmonary vein (PV) orientation, left atrial appendage (LAA) geometry, posterior wall and roof configuration, left lateral ridge anatomy, wall-thickness heterogeneity, and computational surface features. In this review, we examine how three-dimensional left atrial geometry can extend conventional remodeling assessment from measurement of atrial size toward imaging-based substrate characterization. We discuss the relative strengths and limitations of computed tomography (CT), cardiovascular magnetic resonance (CMR), three-dimensional echocardiography, and electroanatomic mapping (EAM), and summarize key geometry-derived metrics, including LAV, LAVI, left atrial sphericity, asymmetry index, atrial eccentricity index, PV anatomy, LAA morphology, posterior wall geometry, wall thickness, radiomics, and artificial intelligence (AI)-derived shape descriptors. We further synthesize evidence linking geometric remodeling with atrial cardiomyopathy, mechanical dysfunction, fibrosis, low-voltage substrate, and catheter ablation outcomes. The clinical relevance of three-dimensional left atrial geometry may be further redefined by pulsed field ablation (PFA), whose non-thermal lesion biology and tissue selectivity may modify predictors of recurrence established in radiofrequency and cryoballoon cohorts. Finally, we outline the need for standardized segmentation, harmonized metric definitions, prospective multicenter validation, and integration with AI, digital twin modeling, biomarkers, EAM data, and wearable-derived AF burden. Three-dimensional left atrial geometry is not yet a standalone determinant of ablation strategy, but it may become a central component of individualized atrial phenotyping and rhythm-control decision-making. Full article

To address the challenges of low bearing capacity in Northeast China’s paddy-field soft foundations and the limitations of summer power line construction, a standardized design method for a novel prefabricated modular steel temporary bridge is proposed. Based on the Winkler elastic foundation beam theory, the operating characteristics of rigid short beams and the subgrade reaction distribution under heavy loads were analyzed. On this basis, combined with in situ static load tests and finite element analysis (FEA), the mechanical performance of the temporary bridge under the static loads of crawler-type and six-wheel construction machinery was investigated. The results indicate that when the bridge deck is subjected to a 25-ton construction vehicle, the maximum stress and displacement in the mid-span condition remain well below the material yield strength and the allowable limits stipulated in the Specifications for Design of Highway Steel Bridges (JTG D64-2015). Furthermore, the temporary bridge structure maintains excellent operational stability under a 100-ton extreme construction load and eccentric loading conditions. This study elucidates the mechanical behavior of the temporary bridge, providing a scientific theoretical basis and engineering reference for the design of temporary transit structures in complex environments such as soft paddy field foundations. Full article

To overcome the inherent drawbacks of cast-in-place reinforced concrete bracing—such as long construction periods and difficult demolition—as well as the relatively high construction cost of steel structure bracing, while fully incorporating the respective technical advantages of these two traditional support systems, this paper proposes a novel hybrid prefabricated reinforced concrete (RC)–steel structure foundation pit bracing system. In order to investigate the overall bearing capacity variation in the standard components of this structure under complex external forces in foundation pits, a numerical model was established using the finite element software ABAQUS. The study examines the trend of the axial compressive bearing capacity of a single standard beam segment as the steel thickness of its external stiffening sleeve varies, as well as the effects of eccentric loading, oblique loading, and the presence or absence of auxiliary supports on the structural bearing capacity of multi-segment beam assemblies. The numerical analysis results show that the bearing capacity of a single beam segment exhibits a strong correlation with the variation in sleeve thickness, and a fitting curve of compressive strength as a function of thickness was derived. For the multi-segment assembly, an increase of 1 mm in the load eccentricity in the Y and Z directions reduces the ultimate peak load by approximately 20.95 kN and 23.94 kN, respectively; in the XY and XZ planes, an increase of 1° in the eccentric angle of the oblique load reduces the peak ultimate bearing capacity by about 6.02 kN and 9.67 kN, respectively. Auxiliary supports have a relatively minor influence on the structural bearing capacity. This research thoroughly explores the bearing capacity of the prefabricated steel–concrete composite and steel structure foundation pit bracing under complex working loads, providing strong support for engineering design and demonstrating broad application prospects. Full article

Reinforced concrete (RC) beams under impact are commonly assessed using central-impact configurations, but practical impacts may deviate from midspan and create unequal shear spans. This study investigates how impact eccentricity changes force transfer and damage development using a validated coupled smoothed particle hydrodynamics–finite element method (SPH-FEM) model. Concrete is modeled with SPH particles, while reinforcement, supports, and the impactor are modeled with FEM solid elements. After validation against central drop-weight tests, full-span eccentric-impact cases are compared with matched short-span references. The first contact-force peak changes only slightly with eccentricity, whereas the later response distribution changes more substantially. At the largest eccentricity, shorter-span shear reaches up to 2.23 times the central-impact value, showing shear-dominated redistribution. Absorbed energy per unit length also localizes on the shorter-span side and reaches up to 4.29 times the longer-span side value. Matched references show that full-span eccentric beams can develop up to $18.4\mathrm{kN}$ higher local shear than symmetric short-span beams. Damage fields shift from symmetric central damage to asymmetric shorter-span-side damage with clearer fragmentation in low-strength cases. For off-midspan accidental-load assessment, the central-impact force level should be considered together with side-specific shear demand, the shorter-span shear-transfer path, and asymmetric damage. Full article

This study compared the effects of variable-resistance compound training versus constant-resistance compound training on lower-limb explosive power in judo athletes, aiming to identify an effective and safe training method. Methods: Sixteen judo athletes were randomized into VRT (n = 8) or RT (n = 8) groups for a 6-week, twice-weekly intervention. Outcomes included rate of force development (RFD), counter movement jump (CMJ), squat jump (SJ), eccentric utilization ratio (EUR), reactive strength index (RSI), squat 1RM, muscle architecture, and Special Judo Fitness Test (SJFT). After 6 weeks of training intervention, the time × group interaction effects were significant between the variable-resistance compound training group and the constant-resistance compound training group in the following parameters: CMJ (p < 0.01, η² = 0.605), SJ (p < 0.01, η² = 0.391), EUR (p < 0.01, η² = 0.308), RSI (p < 0.01, η² = 0.306), RFD (p < 0.01, η² = 0.401), squat 1RM (p < 0.01, η² = 0.328), SJFT index (p < 0.01, η² = 0.537), femoral rectus feather angle (p < 0.05, η² = 0.380), femoral rectus thickness (p < 0.05, η² = 0.288), femoral rectus cross-sectional area (p < 0.01, η² = 0.868), gastrocnemius feather angle (p < 0.05, η² = 0.274), and gastrocnemius thickness (p < 0.05, η² = 0.390). No significant group effects were observed for any of the parameters (p > 0.05). Conclusion: Both variable-resistance training (VRT) and constant-resistance training (CRT) are effective in enhancing lower-body power in judo athletes; both training methods can be regarded as effective options for developing lower-body power in judo athletes, although VRT may offer a slight advantage in specific performance domains. Full article

The Pad Bench Press (PBP) is a variation of the traditional bench press used by elite throwers to meet the mechanical demands of explosive upper-body actions in throwing events. The exercise involves a deliberately rapid eccentric phase, where the athlete allows the barbell to descend at high velocity, producing a rebound effect upon impact with the pad. This technique requires years of practice and is typically introduced early in an athlete’s development and refined progressively. The PBP is commonly used during maximal strength and power phases to provide a high-intensity, velocity-specific stimulus with heavy loads. This descriptive and exploratory case study presents a kinematic analysis of two internationally competitive Spanish shot putters, each with over 15 years of experience using the PBP. Barbell velocity data were obtained via 2D video analysis across multiple loads. The descriptive data indicate that, relative to the traditional bench press profiles reported in the literature, the PBP is associated with substantially stable peak velocities and markedly reduced sticking region, particularly at heavy loads. These findings provide a preliminary kinematic characterization of the PBP and suggest that it may offer a mechanically distinct stimulus compared to the traditional bench press, warranting further controlled investigation. Full article

Background and Objectives: Persistent quadriceps weakness, muscle atrophy, and functional deficits are common following anterior cruciate ligament (ACL) reconstruction and may compromise return to sport and increase the risk of reinjury. Eccentric-oriented strength training has been widely used to enhance muscle strength and hypertrophy in various musculoskeletal conditions; however, its specific application within ACL rehabilitation remains insufficiently explored. The aim of this scoping review was to map the existing evidence on the use of eccentric-oriented strength training in ACL rehabilitation, identify gaps in the current literature, and provide suggestions for future research. Materials and Methods: A scoping review search was conducted in PubMed, Scopus, Web of Science, and PEDro from inception to February 2026 using the following keywords and Boolean operators: (“anterior cruciate ligament”, “ACL”, “anterior cruciate ligament reconstruction”, “ACLR”) AND (“eccentric training”, “eccentric exercise”, “eccentric loading”, “flywheel training”, “isoinertial training”). Eligible studies included studies that investigated eccentric exercises as part of ACL rehabilitation and reported outcomes related to muscle strength, muscle morphology, functional performance, or return to sport. Data were extracted and synthesized descriptively in accordance with the PRISMA-ScR extension for Scoping Reviews guidelines. Methodological quality and risk of bias were evaluated using the PEDro scale (RCTs) and the ROBINS-I tool (non-randomized studies). Results: Fifteen studies met the inclusion criteria. The included literature primarily examined isokinetic eccentric exercise, eccentric cycling, early progressive eccentric resistance training, Nordic hamstring exercise, eccentric ergometry, and flywheel strength training. Most studies reported improvements in quadriceps strength and muscle morphology, with additional benefits observed in functional performance measures (i.e., hop tests), gait mechanics, and limb symmetry. Evidence was unevenly distributed across rehabilitation phases, with relatively few studies focusing on the mid-phase of ACL rehabilitation. Conclusions: Eccentric-oriented strength training represents a promising but underexplored component of ACL rehabilitation. However, the existing literature lacks standardized protocols, comprehensive outcome measures, and phase-specific guidance, particularly during the mid and late stages of rehabilitation. Further high-quality studies are needed to clarify the optimal timing, dosage, and integration of eccentric training across rehabilitation phases. Full article

Objective: To examine lower-body stretch–shortening cycle (SSC) indicators across chronological age categories and playing positions in elite male youth soccer players. Methods: In a cross-sectional design, 984 male players from Slovakia (U15–U19) completed Squat Jumps (SJ), Countermovement Jumps (CMJ), and Drop Jumps (DJ) using the OptoJump photocell system. Outcomes included Eccentric Utilization Ratio (EUR), Reactive Strength Index (RSI), DJ Ground Contact Time (DJ GCT), and Jump Heights (JH). Differences were tested using factorial ANCOVA (age category × playing position) adjusted for height and weight, followed by Tukey-adjusted post hoc comparisons (p < 0.05). Results: Significant age-category main effects were observed for DJ RSI, DJ JH, CMJ JH, SJ JH, and DJ GCT. The largest effects were for DJ JH, CMJ JH, and SJ JH (ηp² = 0.096–0.112), whereas the DJ GCT effect was statistically significant but small (ηp² = 0.013). EUR showed no significant differences across age categories (p = 0.586). Positional differences were limited overall and mainly evident in selected U19 outcomes, particularly jump-height variables and DJ GCT. Conclusions: Lower-body SSC performance increased across chronological age categories, with the largest separation in jump-height and reactive strength outcomes. These differences likely reflect a combination of maturation, training exposure, and selection rather than chronological age alone. EUR remained stable across age categories and playing positions, although the JH-based ratio has limited sensitivity in the present test configuration. Positional separation emerged mainly at U19, supporting broad SSC development across earlier youth categories and position-sensitive interpretation in the oldest cohort. Full article

The bowling performance of cricket fast bowlers is highly dependent on lower limb power and stiffness. French Contrast Training (FCT) and Velocity-Based Training (VBT) are effective ways to improve rate of force development and peak power. The objective of this study was to investigate the effects of VBT-optimized FCT on the lower limb explosive power and bowling performance of cricket fast bowlers. Twenty adult male medium-fast bowlers volunteered for this study and were evenly divided into an experimental group (EG) and a control group (CG). The EG underwent an 8-week VBT-based FCT program, while the CG completed 8 weeks of traditional resistance training combined with traditional plyometric training. Before and after the intervention, subjects were tested on their Bulgarian split squat load–velocity profile, general lower limb power (countermovement jump height, squat jump height, Eccentric Utilization Ratio, and Reactive Strength Index), and bowling performance metrics (front foot contact time, peak force, impulse, front knee angle at ball release, and ball release speed). The results demonstrated that the EG showing significant advantage over the CG on movement velocity during the Bulgarian split squat at loads 20% 1RM, 40% 1RM, and 60% 1RM (p = 0.008, 0.011, 0.008, ${\eta }_p^2$ = 0.337, 0.313, 0.324). General lower limb power in the EG also improved significantly, with CMJ height, EUR, and RSI showing significant inter-group superiority compared to the CG (p < 0.001, = 0.019, 0.004, ${\eta }_p^2$ = 0.659, 0.281, 0.399). Regarding bowling performance, the EG demonstrated highly significant advantages in front foot contact impulse, front knee angle at ball release, and ball release speed (p < 0.001, ${\eta }_p^2$ = 0.572, 0.590, 0.704). In conclusion, the 8-week VBT-FCT program is more effective than the traditional resistance and plyometric training program of the same duration in enhancing lower limb power and bowling performance for medium-fast cricket bowlers. Full article