Search Results (379)

Sometimes only a portion of the surface of a concrete element is loaded, which causes stress concentration in that region. To safely transfer concentric loads to concrete components such as column bases, short cantilevers, superstructure piers, post-tensioned elements, and support anchors, it is imperative to investigate the local compressive characteristics of concrete. To learn more about this subject, further research is required, as there are currently insufficient studies in this field. Therefore, the local compressive behavior of concrete under concentric stresses is the main focus of this work. Concrete is represented as block samples with dimensions of 200 × 200 × 250 mm. A stiff steel plate is used to apply concentric loading on the surface of the samples. The primary parameters are the bearing plate dimensions, shape (square, rectangle, and circular with varying areas), and rectangularity. Additionally, the bearing plate’s movement is examined. The stress-slip curves, ultimate bearing strengths, failures, and related slippages of the tested samples are discussed. The findings revealed that the upper surface of the concrete samples exhibited localized deterioration beneath the bearing plate. Additionally, the ultimate bearing strength of the sample loaded with the 6 × 6 cm square plate was 163% greater than that of the sample loaded with the 10 × 10 cm square plate. Furthermore, the sample loaded with the circular plate with a diameter of 4 cm had an ultimate bearing strength that was 181% greater than the sample loaded with the circular plate with a diameter of 11 cm. It is clear that the samples loaded with a circular plate of varying diameters had an ultimate bearing strength that was 8.5–11% higher than the samples loaded with a square plate of varying lengths. Full article

The palmaris longus (PL) remains insufficiently quantified in cercopithecoids (Cercopithecoidea), despite growing comparative data across primates. We examined adult archival material of the Anubis baboon (Papio anubis) to document PL presence, tendon configuration and topography, describe muscle–tendon morphometrics, and test for side-, sex- and size-related effects. A PL was present in all limbs. Two tendon configurations were observed: a single tendon inserting into the palmar aponeurosis (Type I, 87.0%) and a bifurcated tendon with both medial and lateral slips inserting into the palmar aponeurosis (Type II, 13.0%). No side- or sex-related differences were found in variant distribution. Males showed larger absolute values for selected measurements, but these differences were not independent of antebrachial size. PL lengths and interstyloid distances were strongly correlated with antebrachial size, indicating overall scaling with limb dimensions. These findings identify a species-level pattern in which PL is consistently present and predominantly unbranched, with only occasional distal bifurcation. The data establish a comparative anatomical baseline for Papio and broaden the available evidence on PL morphology in non-human primates. Full article

To further improve the seismic behavior of high-strength foam concrete filled cold-formed checkered steel composite wall structures, it is crucial to investigate the bond–slip behavior between the cold-formed checkered steel (CFCS) and foam concrete (FC) within the wall. Hence, six CFCSFC specimens were designed and subjected to monotonic and cyclic loading tests to study the influence of anchorage lengths on failure modes, bond strength-slip displacement curves, and characteristic bond strength. Results indicated that with the anchorage length increases, the ultimate bond strength of the specimens continuously decreases, and the specimens exhibit more severe failure under cyclic loading than monotonic loading. Compared to the specimens with a 400 mm anchorage length, the ultimate bond strength decreased by 4.8–9.6% for those with a 500 mm length, and by 10.7–16.0% for those with a 600 mm length. Strain along the inner flange of the steel section generally decreased with increasing anchorage length, with loading end strain significantly exceeding free-end strain. Finite element simulations revealed that specimen failure primarily manifested as steel section yielding when anchorage lengths ranged from 1400 mm to 1800 mm. Furthermore, a calculation formula for characteristic bond strength as a function of anchorage length was proposed. Full article

This study numerically examined the anchorage mechanism of rebar hooks under varying straight development lengths, including high stress levels. A three-dimensional rigid body spring model (3D RBSM) was used for the investigation and successfully reproduced the experimental pullout test stress–slip relationships and inner–outer strain distributions for the rebar hook with and without a straight development length. A validated numerical model was used to assess local concrete stresses and internal crack propagation, enabling a clear interpretation of how straight development length influences the anchorage mechanism. The results revealed that increasing straight development length increases stiffness, reduces rebar strains and concrete stresses in the hook region, promotes crack formation around the rebar surface, and forms maximum tensile stresses closer to the top surface, ultimately resulting in earlier splitting failure at high rebar stress levels. A comparison of cases with and without hooks shows that combining the hook with straight development length improves stress distribution, delays crack propagation, and increases anchorage by reducing tensile stress concentrations near the top surface and side faces. These findings provide valuable insights into the role of straight development length in the anchorage performance of 180-degree rebar hooks. Full article

Efficient and clean separation of residual plastic mulch film is the primary bottleneck hindering its resource-oriented reutilization. Currently, the field faces critical technical challenges, most notably the elusive motion mechanisms of flexible materials and the inherent difficulty of film–impurity separation. To address these issues, this study investigates a drum-type mulch-film impurity-removal unit by modeling the throw-off motion mechanism of the material stream, followed by comprehensive multiphysics simulation and optimization. First, to overcome the simulation hurdles typical of flexible materials, “Meta-particles” and the “Bonding V2” contact model were implemented on the EDEM platform to establish a discrete element method (DEM) framework. The resulting analysis revealed a non-linear transport trajectory and morphological evolution within the drum flow field, characterized by a “wall-adhering–slipping–throwing” sequence. These findings were further quantified through MATLAB-based numerical calculations to determine collision frequency and axial residence behavior. Second, ANSYS modal analysis verified the dynamic stability of the frame structure, confirming that the operating frequency (2.37 Hz) remains well below the first natural frequency (6.77 Hz). Furthermore, Box–Behnken response surface methodology (RSM) was employed to elucidate the coupled effects of key process parameters. The results demonstrated that separation efficiency and impurity-removal mass are predominantly governed by the quadratic terms of the inclination angle and rotational speed, respectively. After multi-objective optimization and engineering refinement, the optimal operating parameters were established: a film length of 220 mm, an inclination angle of 3°, and a drum rotational speed of 25 r/min. Bench tests indicated that, under these optimal conditions, the impurity-removal rate stabilized between 71.5% and 72.4%, satisfying the design requirement (≥70%). By elucidating the drum’s throw-off screening mechanism, this study achieves a coordinated improvement in both impurity-removal mass and separation efficiency, resolving long-standing engineering uncertainties regarding film–impurity trajectories and providing a theoretical foundation for the clean treatment of waste mulch film. Full article

This study investigates the bond–slip behavior of glass fiber-reinforced polymer (GFRP) bars embedded in concrete and exposed to alkaline environments at different temperatures. Although GFRP reinforcement is increasingly adopted for its corrosion resistance, the long-term bond performance of the bar–concrete interface in high-pH conditions is still not fully understood. To help close this gap, a comprehensive database of 84 pull-out tests from the literature was assembled, focusing on three key parameters: bar surface configuration, exposure duration, and conditioning temperature. The comparative analysis highlights the dominant role of surface treatment in bond degradation and reveals substantial variability across existing results. To complement the literature review, additional pull-out tests were carried out on sand-coated GFRP bars conditioned in an alkaline solution (pH = 12) for 1.5 months at ambient temperature and at 60 °C. These tests showed average reductions in bond strength of approximately 28% and 32%, respectively, compared with unconditioned specimens, together with marked changes in the post-peak portion of the bond–slip response. An analytical formulation was also applied, not as a novel bond–slip law but as a consistent mechanical framework to interpret durability-induced degradation effects, to describe the local interface shear stress–slip law, and to assess the resulting stress and slip distributions along the bonded length. Overall, the combined experimental and analytical findings emphasize the need to account for environmentally induced degradation when evaluating durability and defining design criteria for GFRP-reinforced concrete structures. Full article

This paper addresses global path planning for a wheeled mobile robot with two different kinematic structures, considering both shortest path and minimum energy consumption criteria. The main research question concerns how the robot’s kinematic structure and the selected planning algorithm influence the resulting path with respect to these criteria. Our review of the state of the art discusses selected path planning methods, including model-based approaches. To determine the energy optimal path, a simplified model of the PIAP GRANITE robot was developed. The robot can be configured as either differentially driven or skid-steered. In the differentially driven configuration, the robot has two driven wheels and two caster wheels, whereas in the skid-steered configuration all wheels are independently driven. The robot’s models are based on previous theoretical and experimental studies and include kinematics, dynamics, drive units, and wheel slip phenomena. For path planning, it was assumed that the robot can move straight or turn. A flat terrain representative of typical urban environments was modeled as a grid of square cells, each characterized by friction and rolling resistance coefficients. Path planning was performed using A*, Theta*, and RRT* algorithms. In order to quantitatively evaluate the results, quality indexes were defined, including path length, energy consumption, computation time, and the number of analyzed nodes. Simulation results are presented for selected terrain maps, both robot configurations, all algorithms, and both optimization criteria. The results show that the differentially driven configuration is consistently more energy-efficient. For the skid-steered robot, minimizing the number of turns is crucial due to high turning energy costs. The A* algorithm consistently finds optimal paths, whereas RRT* is faster but produces non-optimal and non-repeatable results. Theta* does not always achieve optimality due to limitations imposed by the line-of-sight function. Full article

The preparation of the core–shell-like structured before hot working can significantly enhance the hot workability of the alloy. In order to research the properties of the alloy, the finite element method combined with the crystal plasticity constitutive theory was used to establish the finite element model of the core–shell-like structured TiAl alloy with (α₂ + γ) lamellae colonies as the core and α₂ matrix as the shell. The research focuses on the influence of the length and number of γ lamellae on the stress–strain distribution and the contribution of slip systems in each phase to the plasticity of the alloy. The results show that when the γ lamella length increases from 12 μm to 16 μm, the overall stress decreases by 12.0%; when the number increases from 6 to 10, the stress decreases by 7.7%. The stress reduction is primarily influenced by the α₂ phase. Increasing the volume fraction of γ lamellae facilitates stress distribution within the α₂ phase and enhances the plasticity of the material. In the γ phase O4, S1 and S7 slip systems contribute the most to the plastic deformation of the γ phase. In the α₂ phase, the B1 slip system is the main contributor to the plasticity of the α₂ phase. And the B1 slip system contributes more significantly to the plastic deformation of the entire model. Full article

The laterite formations consist of top layers that are highly porous, followed by a lithomargic soil layer over the weathered residual soil and parent rock. The excavated slopes are stable during summer, but the slopes with exposed lithomargic soils have failed during rainy season even when safety factor was more than one. The present study considers the effect of erosion in the lithomargic layer of soil while analyzing the stability of slopes. Janbu’s GPS (Generalized Procedure of Slices) method in conjunction with a genetic algorithm is used to analyse the slope stability and to locate the noncircular critical slip surface. A failed slope from the Yekkur site was considered for the study considering three possible failure mechanisms (Mechanism I, II and III) of slopes due to progressive erosion of fines in the lithomargic soil layer. It is observed that the lithomargic soil’s vulnerability to erosion depends on a critical combination of sand content and hydraulic gradient causing piping. Mechanism III is more critical as compared to other mechanisms and a similar observation was made from failed slopes in the field. The failure in lateritic soil slopes is mainly due to piping of lithomargic soil, which reduces the length of the critical slip surface, and failure due to erosion is progressive. Full article

Glass fibre-reinforced polymer (GFRP) offers a durable, high-tensile strength alternative to steel rebar in reinforced concrete (RC). However, the inherent lack of ductility in GFRP limits its structural applications, which has led to the development of hybrid GFRP–steel RC systems. The composite nature of these systems requires an accurate understanding of the bond interaction between GFRP rebar and concrete. Existing bond models often fall short of accurately representing the distinct mechanical properties and surface characteristics of GFRP bars, particularly within finite element (FE) analysis environments. To address this gap, the present study proposes a computational method that employs a feedforward neural network (FFNN) trained on experimental data encompassing a specific range of parameters (bar diameters 8–16 mm, concrete strengths 18–50 MPa), including bar diameter, bond length, concrete strength, and cover thickness. Unlike conventional models that typically focus on peak bond strength, the developed FFNN accurately predicts the complete bond–slip relationship. The developed bond model is then integrated into the FE analysis. The simulation results demonstrate strong agreement with experimental data (average R² = 0.93) and effectively capture key behavioral aspects such as crack initiation and propagation. Full article

Given an ellipse rolling along a straight line without slipping and a point P on the ellipse, we will determine the shape of the elliptic cycloid traced by P as the ellipse rolls and compute the area under one arch of the elliptic cycloid. We also investigate the arc length, though we are only able to express it as an integral. Full article

Carbon fibre-reinforced polymer (CFRP) bonded steel structures are increasingly adopted in offshore floating structures, yet their interfacial performance is highly susceptible to corrosion in marine environments. Corrosion-induced degradation of the CFRP–steel interface can significantly affect load transfer mechanisms and long-term structural reliability. This paper reports an experimental study on corrosion-induced degradation mechanisms and bond–slip behaviour of CFRP–steel double-strap joints. Controlled corrosion damage was generated using an accelerated electrochemical technique calibrated to ISO 9223 corrosivity categories. Tension tests were performed to examine the effects of corrosion degree, CFRP bond length, and the inclusion of glass fibre sheets (GFS) in the adhesive layer on failure modes, ultimate load capacity, and effective bond length. Digital image correlation (DIC) was employed to obtain strain distributions along the CFRP plates and to establish a bond–slip model for corroded interfaces. The results indicate that corrosion promotes a transition from CFRP delamination to steel–adhesive interface debonding, reduces interfacial shear strength to 17.52 MPa and fracture energy to 5.49 N/mm, and increases the effective bond length to 130 mm. Incorporating GFS mitigates corrosion-induced bond degradation and enhances joint performance. The proposed bond–slip model provides a basis for more reliable durability assessment and design of bonded joints in corrosive environments. Full article

This paper presents a pressure-driven liquid transfer system for laboratory automation, along with a physics-based model and calibration method. The device maintains near-isothermal transport by storing reagents at a prescribed temperature and routing the flow through a single PTFE tube enclosed within a heated jacket. The pressure-drop model accounts for temperature-dependent viscosity and the thermal expansion of PTFE. Residual deviations from the no-slip prediction in submillimeter tubing are represented by an effective slip length, which is identified through linear regression. This parameter is subsequently used to calculate the pressure required to achieve a target flow rate. Experimental results compare unheated and heated operating conditions and characterize the dependence of slip length on temperature and flow rate. Under heated operation with slip-compensated pressure commands, the system achieved dispensing accuracy within $\pm 4\%$ over the tested range, whereas unheated operation exhibited larger errors due to axial temperature gradients. These results demonstrate that effective thermal management and slip compensation are critical for accurate pressure-based metering under temperature-sensitive conditions, as validated using water-based tests. Full article

Grouted sleeves are commonly used to connect prefabricated structural components, but construction defects can easily occur after installation, posing potential risks to the structure. This study conducts comparative uniaxial tensile tests on 39 grouted-sleeve specimens in 13 groups—including standard specimens, defective specimens, and specimens repaired with supplementary grouting. The strain distribution patterns under different grouting lengths and loading levels are analyzed to investigate the load-transfer mechanism between reinforcement bars and grouted sleeves, as well as the influence of various supplementary grouting amounts and material strengths on the mechanical performance of defective sleeves. In the uniaxial tensile test of grouted sleeves, with grout strengths of 85 MPa and 100 MPa and HRB400-grade steel bars, when the grouted anchorage length was 4 d, insufficient anchorage length resulted in low bond strength between the grout and the steel bar, leading to bond–slip failure. When the grouted anchorage length reached 6 d, steel bar fracture occurred inside the sleeve. When the total anchorage length formed by two grouting sessions reached 8 d, specimen slippage decreased, showing a trend where the strain growth rate of the sleeve gradually decreased from the grouted end to the anchored end, while the strain growth rate of the steel bar gradually increased. The longer the total anchorage length in the sleeve after grout repair, the stronger its anti-slip capability. The bearing capacity and failure mode of the specimens depend on the strength of the steel bars connected to the grouted sleeves and the strength of the threaded connection ends at the top. Experimental results show that the anchorage length and strength of high-strength grout materials have a significant reinforcing effect on defective sleeves. The ultimate bearing capacity of specimens with anchorage length of 6 d or more is basically the same as that of steel bars. Specimens with a total anchorage length of 8 d show approximately 10~20% less slippage than those with 6 d. The safe anchorage length for HRB400-grade steel bars in sleeve-grouted connections is 8 d, even though the bearing capacity of grouted sleeves with a 6 d anchorage length already meets the requirements. Bond strength analysis confirms that the critical anchorage length is 4.49 d. When the grouted anchorage length exceeds the critical length, the failure mode of the specimen is steel bar fracture. When the grouted anchorage length is less than the critical length, the failure mode is steel bar slippage. This conclusion aligns closely with experimental results. In engineering practice, the critical anchorage length can be used to predict the failure mode of grouted sleeve specimens. Based on experimental research and theoretical analysis, it is clear that using grout repair to reinforce defective grouted sleeve joints with a safe anchorage length of 8 d is a secure and straightforward strengthening method. Full article

This study evaluated the effects of nitrogen fertilization and different types of planting material on the yield and fruit quality of pineapple (Ananas comosus var. comosus) cv. Smooth Cayenne under the edaphoclimatic conditions of the Northern region of Rio de Janeiro State, Brazil. The experiment was conducted in a randomized block design, arranged in a factorial scheme with four nitrogen rates, six types of planting material, and two harvest seasons (winter and summer). Based on the results, it can be inferred that slips provided higher yields and heavier fruits, whereas plants derived from crowns and suckers showed lower productivity. Increasing nitrogen rates promoted greater fruit mass and length, higher pulp percentage, and increased production of vegetative propagules. Fruits harvested in the summer showed higher soluble solids content (15.5 °Brix), greater pulp and juice percentages, and lower titratable acidity, which are desirable characteristics for fresh consumption. Despite the seasonal differences, fruit mass ranging from 1.5 to 2.0 kg met commercial standards for both processing and domestic markets. The soluble solids/titratable acidity ratio (15.8) was below the ideal range for fresh consumption. The combination of appropriate planting material and nitrogen fertilization contributes to higher production efficiency, cost reduction, and improved fruit quality. Full article