Search Results (138)

To improve the seismic performance of prefabricated structures, this study suggested putting grouted sleeves at the half-height of the column (at the point of contraflexure). A quasi-static test under constant axial load was conducted on the full-scale cast-in-place column and the full-scale prefabricated column connected in half-height. The hysteresis loops, skeleton curves, ductility, stiffness degradation, and energy dissipation capacity were compared. The test results indicate that the prefabricated column connected in half-height exhibited reliable seismic performance. Compared with the cast-in-place specimen, the bearing capacity of the prefabricated column decreased by only 1.45%, the energy dissipation decreased by 5.61%, and the initial secant stiffness and ductility coefficient increased by 8.88% and 9.09%, respectively. ABAQUS finite element software was used to establish finite-element models based on the experimental results. The damage pattern and seismic performance indicators of the two types of columns were verified by resolving issues related to the bonding interface model of sleeve-connected columns and the convergence of the multidimensional constitutive model. The formula for calculating the shear bearing capacity was put forward to evaluate the failure pattern. The study provides a basis for further investigation of the seismic performance of sleeve-connected columns with different connection positions under extreme conditions. Full article

This study presents a novel approach for interpreting static load tests (SLT) of piles using Artificial Neural Networks (ANNs) integrated with the Meyer and Kowalow load-settlement mathematical model. Reliable estimation of pile bearing capacity and settlement behavior is critical for safe and economical geotechnical design, particularly given the nonlinear and heterogeneous nature of soils. Traditional SLT interpretation methods, such as Chin-Kondner, Decourt, and hyperbolic fitting approaches, provide useful extrapolation of the ultimate capacity but are sensitive to test termination levels and parameter estimation uncertainties. The Meyer and Kowalow function offers a robust mathematical representation of the load-settlement curve, allowing decomposition of the total pile resistance into the shaft and base components. In this work, ANN models were trained to solve both the direct and inverse forms of the Meyer and Kowalow problem, enabling rapid identification of constitutive parameters (initial stiffness, nonlinearity coefficient, and ultimate capacity) from measured SLT data. Numerical experiments demonstrated that networks with a single hidden layer achieved accurate predictions with low RMSE for both training and test sets. The proposed ANN-based framework facilitates improved parameter identification, supports partial-load SLT interpretation, and provides a practical tool for engineers seeking the reliable prediction of pile performance under service loads. Full article

Hydrostatic bearings are extensively utilized in precision and ultra-precision machinery. Owing to the small oil film clearance of such bearings, they are prone to tilting under eccentric loads, which may ultimately lead to bearing failure. To investigate the eccentric load characteristics of hydrostatic bearings, a typical rectangular hydrostatic oil pad unit was selected as the research object. First, an analytical model for the eccentric load-carrying capacity of the rectangular oil pad was established. This model was then validated through computational fluid dynamics (CFD) simulations. On this basis, the static and dynamic characteristics of the rectangular hydrostatic oil pad were systematically studied. The results indicate that oil supply pressure, orifice diameter, and oil pad dimensions exert significant influences on the angular stiffness and angular damping of hydrostatic bearings. Specifically, increasing the oil supply pressure to above 3 MPa can facilitate the enhancement of anti-eccentric load capacity. Under the premise of ensuring static load-carrying capacity, a moderate increase in orifice diameter is conducive to improving anti-eccentric load capacity. When the oil pad area is fixed, adjusting the width-to-height ratio of the oil pad can modify the angular damping coefficient in the corresponding direction. However, the adjustment tends to reduce the angular damping coefficient in other directions, necessitating a comprehensive evaluation in practical applications. Full article

Joint connections are critical to the overall performance of prefabricated structures. This paper proposes a novel reverse-rotation locking sleeve connection method, designed to ensure the safety of joint engineering while optimizing construction processes, improving operational efficiency, and endowing the joints with excellent seismic energy dissipation performance. To evaluate the performance of this connection method, quasi-static tests under displacement-controlled lateral loading were designed and conducted on three reinforced concrete column specimens (Specimen A: conventional reinforcement–cast-in-place monolithic; Specimen B: conventional reinforcement–reverse-rotation locking sleeve connected; Specimen C: enhanced reinforcement–reverse-rotation locking sleeve connected). The failure modes, hysteretic characteristics, skeleton curves, ductility, energy dissipation capacity, load-bearing capacity, and stiffness degradation patterns of the specimens were systematically examined. The results indicate that Specimen B exhibited the most severe damage extent, while Specimen A demonstrated the best integrity; in contrast, Specimen B showed significant and rapid degradation in energy dissipation capacity during the intermediate-to-late stages of testing; the hysteretic curves of Specimens B and C were full in shape, without obvious yield plateaus; the skeleton curves of all specimens exhibited S-shaped characteristics, and the peak loads of Specimens A and C corresponded to a lateral displacement of 21 mm, while that of Specimen B corresponded to a lateral displacement of 28 mm; compared to the cast-in-place monolithic Specimen A, the reverse-rotation locking sleeve–connected Specimens B and C showed increases in ultimate load under positive cyclic loading by 18.7% and 5.5%, respectively, and under negative cyclic loading by 40.8% and 2.0%, respectively; the ductility coefficients of all three specimens met the code requirement, being greater than 3.0 (Specimen A: 5.13; Specimen B: 3.56; Specimen C: 5.66), with Specimen C exhibiting a 10.3% improvement over Specimen A, indicating that the reverse-rotation locking sleeve–connected specimens possess favorable ductile performance; analysis revealed that the equivalent viscous damping coefficient of Specimen C was approximately 0.06 higher than that of Specimen A, meaning Specimen C had superior energy dissipation capacity compared to Specimen A, confirming that the reverse-rotation locking sleeve connection can effectively absorb seismic energy and enhance the seismic and energy dissipation characteristics of the specimens. The load-bearing capacity degradation coefficients of all specimens fluctuated between 0.83 and 1.01, showing an initial stable phase followed by a gradual declining trend; the stiffness degradation coefficients exhibited rapid initial decline, followed by a deceleration in the attenuation rate, and eventual stabilization. This indicates that the reverse-rotation locking sleeve-connected specimens can maintain relatively stable strength levels and favorable seismic performance during the plastic deformation stage. Full article

Tall-pier, long-span continuous rigid-frame bridges are prone to wind-induced vibration due to their large spans and pier heights; during cantilever erection, the maximum double-cantilever stage has reduced stiffness and buffeting becomes more evident. Accordingly, a time-domain framework driven by three-component aerodynamic coefficients and their angle-of-attack derivatives is adopted. Code-based target spectra are used to synthesize multi-point fluctuating wind time histories via harmonic superposition, followed by statistical and spectral consistency checks. Buffeting forces are then computed under the quasi-steady assumption, mapped to finite-element nodes, and integrated in time to obtain global responses (displacement and acceleration). In parallel, static six-component wind tunnel tests provide mean force and moment coefficients and their derivatives for comparison. The results indicate that the three-component time-domain approach captures the buffeting features dominated by vertical and torsional responses. When pronounced along-span sectional variation and high angle-of-attack sensitivity are present, errors associated with the strip assumption increase, whereas the force–moment coupling revealed by the six-component data helps explain discrepancies between simulation and tests. These response patterns and error characteristics delineate the applicability and limits of the three-component time-domain evaluation for variable-depth continuous rigid-frame bridges, offering a reference for wind resistance assessment and construction-stage checking of similar bridges. Full article

In this study, the seismic performance of reinforced concrete (RC) L-shaped columns, strengthened with 100 mm and 150 mm wing walls, was determined using quasi-static tests. A total of nine L-shaped column specimens were designed and tested under cyclic loading. This study found that strengthening with wing walls increased the lateral stiffness and horizontal load bearing capacity of L-shaped columns. Notably, such improvement was found to be more significant under higher axial compression ratios, exhibiting maximum increases of 254% and 194% in load bearing capacity, in the positive and negative loading directions, respectively. Additionally, ductility was influenced by the wing wall length and axial compression ratios. Under a low axial compression ratio, the ductility coefficient first increased and then decreased with an increase in the wall length. Conversely, under a high axial compression ratio, ductility was consistently improved with increasing wall length. Furthermore, finite element (FE) models were established, and they successfully validated the experimental results, such as load–displacement responses, hysteresis behavior, skeleton curves and ultimate bearing capacity. The numerical results further strengthened the significant effect of the wing wall addition on the seismic performance of the L-shaped columns. Based on the results, a lateral capacity calculation formula is developed, providing a reliable method for assessing the seismic performance of the strengthened L-shaped columns. Therefore, the findings of this study present theoretical insights and practical guidance for the seismic retrofitting of existing RC structures with special-shaped columns. Full article

To address the insufficient adaptability of imported peanut harvesting equipment’s soil-engaging components to the specific soil conditions in Xinjiang, this study conducted Discrete Element Method (DEM)-based calibration of soil mechanical parameters using field soil samples with 1–20% moisture content from typical peanut cultivation areas in southern Xinjiang. Through the EDEM simulation platform, a comprehensive approach integrating the Hertz–Mindlin with the JKR adhesion model and Hertz–Mindlin with the Bonding model was employed to systematically calibrate nine key parameters: coefficient of restitution, static friction coefficient, rolling friction coefficient, JKR surface energy, normal/tangential stiffness per unit area, critical normal/tangential force, and soil bonding disk radius. Adopting static angle of repose (SAOR) and unconfined compressive force (UCF) as dual-response indicators, a hybrid experimental design strategy combining Central Composite Design (CCD), Plackett–Burman (PB) screening, and Box–Behnken Design (BBD) optimization was implemented. Regression models for SAOR and UCS were established, yielding six sets of soil parameters optimized for different moisture conditions through parameter optimization. Field validation demonstrated the following: ≤3.27% error in SAOR, ≤1.46% error in UCF, and ≤5.05% error in drawbar resistance validation for field digging shanks. Experimental results confirm that the model demonstrates strong prediction accuracy for soils in typical peanut harvesting regions of southern Xinjiang, thereby providing key parameter references for the future self-developed, highly adaptive soil-engaging components with drag reduction optimization in peanut harvesters for the Xinjiang region. Full article

Aiming at the characteristics of limited actuation capability of the semi-active control system and strong nonlinearity of the hydro-pneumatic suspension, a constrained nonlinear control strategy of a semi-active hydro-pneumatic suspension system is proposed. According to the mathematical model of nonlinear hydro-pneumatic suspension, the static stiffness and linear damping coefficient based on the equivalent energy are calculated, and then the control-oriented dynamic equation whose expression minimizes the nonlinear term is constructed. Combined with actuation capacity constraints, an optimization model with constraints is established to minimize the deviation between the actual overall control force and the expected optimal control force, and the optimal approximation from nonlinear control to linear quadratic optimal control is realized. The control simulation results of various methods show that the nonlinear control with constraints of the semi-active hydro-pneumatic suspension system, which effectively combines the actuation capacity constraints and nonlinear characteristics of the system, achieves a good comprehensive control effect for the nonlinear suspension control with constraints. Full article

The application of precast assembled pier systems in high-seismicity regions is often constrained by their seismic performance limitations. To validate the optimization effect of GFRP confinement on the hysteretic performance of bridge piers, this study first conducted axial compression tests on 54 glass fiber-reinforced polymer (GFRP)-confined concrete cylindrical specimens. The investigation focused on the effects of fiber layers (6 and 10), orientation angles ($\pm 45°$, $\pm 60°$, $\pm 80°$), slenderness ratios (2 and 4), and compression section configurations (fully loaded vs. core concrete loading only) on confinement efficacy. The experimental results demonstrate that specimens with $\pm 60°$ fiber angles achieved an optimal balance between strength and ductility, exhibiting an average strength enhancement of 298.0% and a maximum axial strain of 2.7% compared to unconfined concrete. Subsequently, two GFRP tube-confined concrete bridge piers with varying fiber layers (PRCG1: 6 layers; PRCG2: 10 layers) and one unconfined reference pier (PRC) were designed and fabricated. All specimens employed grout-filled sleeves to connect caps and piers. Pseudo-static tests revealed that GFRP confinement effectively mitigated damage in plastic hinge zones and enhanced seismic performance. Compared to the PRC, PRCG1 and PRCG2 exhibited increases in ultimate displacement by 19.50% and 28.57%, in ductility coefficients by 18.56% and 27.84%, and in cumulative hysteretic energy dissipation by 13.90% and 26.43%, respectively. At the 5% drift ratio, their load capacities increased by 26.74% and 23.25%, stiffnesses improved by 28.91% and 25.51%, and residual displacements decreased by 20.89% and 11.17%. The accuracy and applicability of the GFRP tube-confined bridge pier model, developed based on the Lam–Teng model, were validated through numerical simulations using the OpenSees fiber element approach. Full article

Static stretching (SS) is commonly used in athletic programs, and the intensity of SS has recently been examined for its effects on range of motion (ROM), strength and passive stiffness. However, the reliability of high-intensity SS across multiple testing sessions has not been investigated. The purpose of this investigation was to examine the reliability of high-intensity SS of the hamstrings across five laboratory visits on ROM, strength, power and passive stiffness. Thirteen physically active males (age: 26 ± 4 years, height: 180 ± 8 cm, body mass: 81 ± 10 Kg) underwent five repeated measures of laboratory SS on an isokinetic dynamometer where point of discomfort (POD) was measured, followed by a 30 s stretch at 120% POD. Across the visits, the pooled intraclass correlation coefficient was good for knee extension ROM (0.82), knee flexion strength (0.81) and passive stiffness (0.81). The ROM achieved to determine the POD before the SS was not different for the five visits (p = 0.370). These findings suggest high-intensity SS to 120% POD on an isokinetic dynamometer is reliable across multiple testing sessions. It is not clear if high-intensity static stretching is also reliable within applied scenarios and warrants further investigation. Full article

This study introduces an analytical framework that integrates the state-space method with generalized thermoelasticity theory to obtain exact solutions for the static and dynamic behaviors of laminated plates featuring imperfect interfaces and resting on a Winkler foundation. The model comprehensively accounts for the foundation-structure interaction, interfacial imperfection, and the coupling between the thermal and mechanical fields. A parametric analysis explores the impact of the dimensionless foundation coefficient, interface flexibility coefficient, and thermal conductivity on the static and dynamic behaviors of the laminated plates. The results indicate that a lower foundation stiffness results in higher sensitivity of structural deformation with respect to the foundation parameter. Furthermore, an increase in interfacial flexibility significantly reduces the global stiffness and induces discontinuities in the distribution of stress and temperature. Additionally, thermal conductivity governs the continuity of interfacial heat flux, while thermo-mechanical coupling amplifies the variations in specific field variables. The findings offer valuable insights into the design and reliability evaluation of composite structures operating in thermally coupled environments. Full article

To investigate the interaction mechanism between agricultural tillage machinery and soil, this study established a precise simulation model by integrating physical and numerical experiments using typical yellow cinnamon soil collected from western Henan Province, China. The discrete element parameters for soils with varying moisture contents were calibrated based on the Hertz–Mindlin (no slip) contact model. Through Plackett–Burman screening, steepest ascent optimization, and Box–Behnken response surface methodology, a predictive model correlating moisture content, parameters, and repose angle was developed, yielding the optimal contact parameter combination: interparticle static friction coefficient (0.6), soil–65Mn static friction coefficient (0.69), and interparticle rolling friction coefficient (0.358). For the Bonding model, orthogonal experiments coupled with NSGA-II multi-objective optimization determined the optimal cohesive parameters targeting maximum load (673.845 N) and displacement (9.765 mm): normal stiffness per unit area (8.8 × 10⁷ N/m³), tangential stiffness per unit area (6.85 × 10⁷ N/m³), critical normal stress (6 × 10⁴ Pa), critical tangential stress (3.15 × 10⁴ Pa), and bonding radius (5.2 mm). Field validation using rotary tillers and power harrows demonstrated less than 6% deviation in soil fragmentation rates between simulations and actual operations, confirming parameter reliability and providing theoretical foundations for constructing soil-tillage machinery interaction models. Full article

Stiffness parameters are very important and effective in the constitutive models used in finite element analysis. It is not easy or common to obtain these parameters in the laboratory. However, even if the modulus is determined in the small and medium deformation range, there is a need to make transitions in both static and dynamic parameters. In almost all studies, the Alpan approach is used for the relationship between static and dynamic moduli of elasticity. Therefore, a better understanding of this approach is required. In this study, the relationship between static and dynamic stiffness was determined by monotonic triaxial and resonant column tests on five different sand samples with different relative stiffness and grain distributions, and the results were compared with Alpan’s approach. It is not clear which of the initial or maximum modulus of elasticity (E₀), unloading-reloading modulus (E_ur) or secant modulus of elasticity (E₅₀) are used by Alpan for static modulus of elasticity (E_stat). Therefore, the coefficient R_sec = E_stat/E₅₀ was introduced and queried to indicate which E_stat is a multiple of E₅₀. In connection with this, the dynamic modulus of elasticity (E_dyn) was calculated using the small deformation shear modulus (G₀) obtained from resonant column experiments and assuming Poisson’s ratios (ν = 0.2, 0.3, 0.4). It was found that Alpan’s empirical approach achieved a significant degree of agreement for the sands in this study and the studies of other researchers. It was observed that the best agreement between dynamic and static stiffness ratio (E_dyn/E_stat) and static modulus of elasticity (E_stat) for sand specimens in this study was obtained with υ = 0.2 and R_sec = 2. According to the experimental results, it is safe to say that Alpan’s empirical approach is still valid when the values of Poisson’s ratio and E_stat in the very small deformation region are used. Since there are limited studies on E_dyn/E_stat ratio in the literature, it is thought that the findings in this paper will assist engineers and researchers. However, this work would also assist engineers in selecting appropriate stiffness parameters for calibrating constitutive models. Full article

Steel slag aggregate (SSA), as a high-performance and sustainable material, has demonstrated significant potential in enhancing the mechanical properties of concrete and improving the bond behavior between reinforcement and the concrete matrix, thereby contributing to the seismic resilience of steel slag concrete columns (SSCCs). Nevertheless, the underlying mechanism through which SSA influences the seismic performance of SSCCs remains insufficiently understood, and current analytical models fail to accurately capture the effects of bond strength on structural behavior. In this study, a comprehensive experimental program comprising central pull-out tests and quasi-static cyclic loading tests was conducted to investigate the influence of SSA on bond strength and the seismic response of SSCCs. Key seismic performance indicators, including the hysteresis curve, equivalent viscous damping ratio, and ductility coefficient, were evaluated. The role of bond strength in governing energy dissipation and ductility characteristics was elucidated in detail. The results indicate that bond strength significantly affects the seismic performance of SSCC components. At an SSA replacement ratio of 40%, the specimens show optimal performance: energy dissipation capacity increases by 11.3%, bond–slip deformation in the plastic hinge region decreases by 10%, and flexural deformation capacity improves by 9% compared to the control group. However, when the SSA replacement exceeds 60%, the performance metrics are similar to those of ordinary concrete, showing no significant advantages. Based on the experimental findings, a modified bond–slip constitutive model for the steel slag concrete–reinforcement interface is proposed. Furthermore, a finite element model incorporating bond–slip effects is developed, and its numerical predictions exhibit strong agreement with the experimental results, effectively capturing the lateral load-carrying capacity and stiffness degradation behavior of SSCCs. Full article

To enhance the seismic performance of existing reinforced concrete (RC) columns, this study proposes a novel strengthening method that combines steel strips with ultra–high–performance concrete (UHPC). The seismic behavior of the proposed method is investigated through quasi–static cyclic tests conducted on four strengthened columns and one control column. The experimental parameters include the type of reinforcement (UHPC–only and UHPC combined with steel strips) and the thickness of the UHPC strengthening layer. The failure modes, hysteretic behavior, energy dissipation capacity, and stiffness degradation of the specimens are systematically analyzed. The results show that, compared to the unstrengthened column, the UHPC–strengthened columns achieved maximum increases of 73.73% in peak load and 23.68% in ductility coefficient, while the columns strengthened with composite steel strips achieved further improvements of up to 84.79% and 50.23%, respectively. The composite strengthening method significantly improved the failure mode, with crack distribution changing from localized crushing to multiple fine cracks. The displacement ductility coefficient reached as high as 6.28, and the hysteretic curve fullness and cumulative energy dissipation increased by a factor of two to three. Finally, based on moment equilibrium theory, a theoretical formula is proposed to calculate the lateral ultimate flexural capacity of RC columns strengthened with steel strip–UHPC composites, which shows good agreement with the experimental results. Full article