Three-dimensional Loading Research Articles

Dynamic response analysis of a floating bridge structure under combined actions from seismic loading and waves at different incident angles

Abstract This paper investigates the complex coupled response of a cross-sea floating bridge under the combined actions of seismic loading and wave at different incident angles. The bridge structure is modeled using the finite element method, considering the interaction between the girder, pier, pontoon, and mooring chains. Wave forces are calculated based on potential theory, and an added mass approach is applied to simulate the hydrodynamic forces induced by the earthquake. Simulations were conducted using a one-year random wave at three different incident angles of 0o, 45o, and 90o, combined with three-dimensional seismic loading of varying magnitudes: 0.3 g, 0.5 g, and 1 g. The simulation results indicate that the direction of the incident wave significantly influences the bridge's response. The coupling effect between wave and seismic forces on the floating bridge's response is not simply additive. Generally, when the earthquake magnitude is low, the wave loading significantly impacts the bridge's dynamics. However, as the earthquake magnitude increases, the bridge's response becomes dominated by the seismic forces, rendering the influence of wave forces negligible.

Optimization of Truck–Cargo Matching for the LTL Logistics Hub Based on Three-Dimensional Pallet Loading

This study investigates the truck–cargo matching problem in less-than-truckload (LTL) logistics hubs, focusing on optimizing the three-dimensional loading of goods onto standardized pallets and assigning these loaded pallets to a fleet of heterogeneous vehicles. A two-stage hybrid heuristic algorithm is proposed to solve this complex logistics challenge. In the first stage, a tree search algorithm based on residual space is developed to determine the optimal layout for the 3D loading of cargo onto pallets. In the second stage, a heuristic online truck–cargo matching algorithm is introduced to allocate loaded pallets to trucks while optimizing the number of trucks used and minimizing transportation costs. The algorithm operates within a rolling time horizon, allowing it to dynamically handle real-time order arrivals and time window constraints. Numerical experiments demonstrate that the proposed method achieves high pallet loading efficiency (close to 90%), near-optimal truck utilization (nearly 95%), and significant cost reductions, making it a practical solution for real-world LTL logistics operations.

Post-Earthquake Emergency Logistics Location-Routing Optimization Considering Vehicle Three-Dimensional Loading Constraints

Post-Earthquake Emergency Logistics Location-Routing Optimization Considering Vehicle Three-Dimensional Loading Constraints

Three-Dimensional Mechanical Microenvironment Rescued the Decline of Osteogenic Differentiation of Old Human Jaw Bone Marrow Mesenchymal Stem Cells.

Resorption and atrophy of the alveolar bone, as two consequences of osteoporosis that remarkably complicate the orthodontic and prosthodontic treatments, contribute to the differentiated biological features and force-induced response of jaw bone marrow-derived mesenchymal stem cells (JBMSCs) in elderly patients. We isolated and cultured JBMSCs from adolescent and adult patients and then simulated the loading of orthodontic tension stress by constructing an in vitro three-dimensional (3D) stress loading model. The decline in osteogenic differentiation of aged JBMSCs was reversed by tensile stress stimulation. It is interesting to note that tension stimulation had a stronger effect on the osteogenic differentiation of elderly JBMSCs compared to the young ones, indicating a possible mechanism of aging rescue. High-throughput sequencing of microRNA (miRNAs) was subsequently performed before and after tension stimulation in all JBMSCs, followed by the comprehensive comparison of mechanically responsive miRNAs in the 3D strain microenvironment. The results suggested a significant reduction in the expression of miR-210-3p and miR-214-3p triggered by the 3D strain microenvironment in old-JBMSCs. Bioinformatic analysis indicated that both miRNAs participate in the regulation of critical pathways of aging and cellular senescence. Taken together, this study demonstrated that the 3D strain microenvironment efficiently rescued the cellular senescence of old-JBMSCs via modulating specific miRNAs, which provides a novel strategy for coordinating periodontal bone loss and regeneration of the elderly.

Dynamic mechanical response and crack evolution law of raw coal loaded by dynamic-static coupling under three-dimensional constraints

This paper presents the investigation of the dynamic mechanical properties of coal rock under complex stress conditions at depth, based on the improved Separate Hopkinson Pressure Bar Test System. A total of 15 groups of coal samples were used to perform dynamic impact tests under different conditions. The changing rules of dynamic strength, crushing, fractal dimension and damage modes of coal under different stress conditions were analyzed. A total of nine groups of coal samples were selected for numerical simulation using ANSYS/LS-DYNA. The results show that: (1) The stress–strain curves of coal specimens under different strain rates, different confining pressures and axial pressures have basically the same trend and the curves show a certain jump forward. (2) The peak dynamic stress of the coal specimens increased linearly with the increase of strain rate and confining pressure, and the ambient pressure limited the expansion of internal cracks of the coal specimens under impact loading. Based on the experimental and simulated data, the maximum relative errors between the experimental and simulated data were determined to be 2.9578% for Group A, 6.177% for Group B, and 6.382% for Group C, respectively. (3) The damage modes of the coal samples under the three-dimensional dynamic-static combined loading were mainly “X” type and “conical” shear damage. The fractal dimension increases with the increase of strain rate, decreases with the increase of confining pressure, and first decreases and then increases with the increase of axial pressure. This research achievement can provide theoretical support for the prevention of dynamic disasters in deep coal mine engineering.

Research on Genetic Algorithm Optimization with Fusion Tabu Search Strategy and Its Application in Solving Three-Dimensional Packing Problems

Symmetry is an important principle and characteristic that is prevalent in nature and artificial environments. In the three-dimensional packing problem, leveraging the inherent symmetry of goods and the symmetry of the packing space can enhance packing efficiency and utilization.The three-dimensional packing problem is an NP-hard combinatorial optimization problem in the field of modern logistics, with high computational complexity. This paper proposes an improved genetic algorithm by incorporating a fusion tabu search strategy to address this problem. The algorithm employs a three-dimensional loading mathematical model and utilizes a wall-building method under residual space constraints for stacking goods. Furthermore, adaptation of fitness variation strategy, chromosome adjustment, and tabu search algorithm are introduced to balance the algorithm’s global and local search capabilities, as well as to enhance population diversity and convergence speed. Through testing on benchmark cases such as Bischoff and Ratcliff, the improved algorithm demonstrates an average increase of over 3% in packing space utilization compared to traditional genetic algorithms and other heuristic algorithms, validating its feasibility and effectiveness. The proposed improved genetic algorithm provides new insights for solving three-dimensional packing problems and optimizing logistics loading schedules, offering promising prospects for various applications.

生鲜农产品冷链集货车辆路径与货物配载联合优化研究

As a bridge connecting agricultural production and consumption, the circulation of agricultural products has the function of connecting supply and demand, guiding production and promoting consumption. However, the development of rural logistics in China is slow, and most logistics centers still rely on experience to plan the pick-up vehicle routings, resulting in long transport time and high cost. In order to improve the efficiency of pick-up and reduce transportation costs, a joint optimization model of cold-chain pick-up vehicle routing and cargo allocation for fresh agricultural products was proposed in this study. Soft time window constraint and three-dimensional loading constraints were considered, and the lowest pick-up cost was used as optimization goals in this model. In addition, adaptive large neighborhood search algorithm (ALNS) and heuristic depth-first search algorithm (HDFS) were combined to solve the model. A case study of Kunming International Flower Auction Center was conducted to compare the schemes of pick-up vehicle routing before and after optimization. Results demonstrate that the pick-up cost after optimization decreases by 9.6 %, the number of vehicles decreases by one, the total volume utilization rate of vehicles increases by 23 %, and the total load utilization rate of vehicles increases by 15 %. This study provides a model reference and solution method for enterprise operators to formulate schemes of pick-up vehicle routing quickly and reasonably.

Engineering Tendon Assembloids to Probe Cellular Crosstalk in Disease and Repair.

Tendons enable locomotion by transferring muscle forces to bones. They rely on a tough tendon core comprising collagen fibers and stromal cell populations. This load-bearing core is encompassed, nourished, and repaired by a synovial-like tissue layer comprising the extrinsic tendon compartment. Despite this sophisticated design, tendon injuries are common, and clinical treatment still relies on physiotherapy and surgery. The limitations of available experimental model systems have slowed the development of novel disease-modifying treatments and relapse-preventing clinical regimes. In vivo human studies are limited to comparing healthy tendons to end-stage diseased or ruptured tissues sampled during repair surgery and do not allow the longitudinal study of the underlying tendon disease. In vivo animal models also present important limits regarding opaque physiological complexity, the ethical burden on the animals, and large economic costs associated with their use. Further, in vivo animal models are poorly suited to systematic probing of drugs and multicellular, multi-tissue interaction pathways. Simpler in vitro model systems have also fallen short. One major reason is a failure to adequately replicate the three-dimensional mechanical loading necessary to meaningfully study tendon cells and their function. The new 3D model system presented here alleviates some of these issues by exploiting murine tail tendon core explants. Importantly, these explants are easily accessible in large numbers from a single mouse, retain 3D in situ loading patterns at the cellular level, and feature an in vivo-like extracellular matrix. In this protocol, step-by-step instructions are given on how to augment tendon core explants with collagen hydrogels laden with muscle-derived endothelial cells, tendon-derived fibroblasts, and bone marrow-derived macrophages to substitute disease- and injury-activated cell populations within the extrinsic tendon compartment. It is demonstrated how the resulting tendon assembloids can be challenged mechanically or through defined microenvironmental stimuli to investigate emerging multicellular crosstalk during disease and injury.

Interface and Morphology Engineered Amorphous Si for Ultrafast Electrochemical Lithium Storage.

Ultrafast high-capacity lithium-ion batteries are extremely desirable for portable electronic devices, where Si is the most promising alternative to the conventional graphite anode due to its very high theoretical capacity. However, the low electronic conductivity and poor Li-diffusivity limit its rate capability. Moreover, high volume expansion/contraction upon Li-intake/uptake causes severe pulverization of the electrode, leading to drastic capacity fading. Here, interface and morphology-engineered amorphous Si matrix is being reported utilizing a few-layer vertical graphene (VG) buffer layer to retain high capacity at both slow and fast (dis)charging rates. The flexible mechanical support of VG due to the van-der-Waalsinteraction between the graphene layers, the weak adhesion between Si and graphene, and the highly porous geometry mitigated stress, while the three-dimensional mass loading enhanced specific capacity. Additionally, the high electronic conductivity of VG boosted rate-capability, resulting in a reversible gravimetric capacity of ≈1270mAhg-1 (areal capacity of ≈37µAhcm-2) even after 100 cycles at an ultrafast cycling rate of 20C, which provides a fascinating way for conductivity and stress management to obtain high-performance storage devices.

MOEA/D with customized replacement neighborhood and dynamic resource allocation for solving 3L-SDHVRP

Split delivery heterogeneous vehicle routing problem with three-dimensional loading (3L-SDHVRP) is a critical issue in manufacturing logistics. Current mainstream research formulates this problem as a single objective optimization problem, which fails to reveal the relationship among multiple conflicting objectives and cannot provide various trade-off solutions for decision-makers in real-world logistics scenarios. This paper concentrates on a multi-objective 3L-SDHVRP and proposes a multi-objective evolutionary algorithm based on decomposition with customized replacement neighborhood and dynamic resource allocation (called MOEA/D-RD) to deal with it. The numerical experiments on the dataset from the 11th International Conference on Evolutionary Multi-Criterion Optimization (EMO 2021) show the superior performance of the proposed method over some state-of-the-art ones. The source code of MOEA/D-RD is available at https://github.com/CIAM-Group/EvolutionaryAlgorithm_Codes/tree/main/MOEAD-RD.

The split delivery vehicle routing problem with time windows and three-dimensional loading constraints

The split delivery vehicle routing problem with time windows and three-dimensional loading constraints

Non-coaxiality behaviours and unified flow rule of soil–structure interfaces

Non-coaxiality is one of the key characteristics of soil–structure interfaces that broadly occur in geotechnical engineering. A series of interface tests between gravel and a structure was performed to address and model the non-coaxiality behaviours of interfaces subjected to various three-dimensional (3D) loadings. Non-coaxiality of the interface was identified during the yielding phase when subjected to 3D cycling of shear stress and could be captured by the non-coaxiality angle. The non-coaxiality angle does not evolve as a result of 3D cyclic shearing but depends primarily on the magnitude and direction of the current shear stress and the direction of the shear stress increment. The shear stress amplitude ratio, shear stress amplitude, shear stress rotation and initial shear stress significantly affect the magnitude and change pattern of the non-coaxiality angle, attributed to varied shear stress and shear stress increment vectors. A unified flow rule for interfaces was established based on 3D interface test analysis. The flow rule perfectly determines the flow direction of different kinds of interfaces prior to and at the mobilisation of shear strength under diverse two-dimensional and 3D loading conditions, such as arbitrary shear paths and differing shear stress amplitudes, shear stress amplitude ratios, initial shear stresses, normal stresses, shear strengths and anisotropy characteristics.

Dynamic response of a low plasticity silt deposit: comparison of in-situ and laboratory responses

This study compares the in-situ dynamic response of a low plasticity silt deposit subjected to multidirectional loading from vibroseis shaking and controlled blasting to a suite of element-scale, cyclic laboratory test specimens. The agreement between excess pore pressures and simple shear strain relationships over a wide range in strains is remarkable. Slightly larger excess pore pressures observed in-situ are attributed to three-dimensional loading and pore pressure migration/redistribution in the shallower portions of the deposit. Noted differences in shear modulus, G, are attributed to strain rate effects, spatial variability in the in-situ stiffness, and hydraulic boundary conditions. The variation in in-situ G/Gmax follows the trend from torsional shear specimens up to 0.4% shear strain; larger strains in the silt deposit imposed by controlled blasting yielded a stiffer response than that from cyclic torsional shear and direct simple shear specimens due in part to field drainage for deeper portions of the deposit. The in-situ cyclic resistance ratio for the deeper portion of the deposit in which plane body waves could be assumed and for the selected excess pore pressure ratio criterion was larger than that of stress-controlled cyclic direct simple shear (CDSS) test specimens, despite the detrimental effect of multidirectional shaking in the field. The effect of strain history, spatial variability, and drainage boundary conditions to drive differences between the in-situ and laboratory test specimens is identified.

Nonlocal Theory for Submerged Cantilever Beams Undergoing Torsional Vibrations

Abstract We propose a new theory for fluid–structure interactions of cantilever microbeams undergoing small amplitude vibrations in viscous fluids. The method is based on the concept of nonlocal modal hydrodynamic functions that accurately capture three-dimensional (3D) fluid loading on the structure. For short beams for which 3D effects become prominent, existing local theories based on two-dimensional (2D) fluid approximations are inadequate to predict the dynamic response. We discuss and compare model predictions in terms of frequency response functions, modal shapes, quality factors, and added mass ratios with the predictions of the local theory, and we validate our new model with experimental results.

Value of Cargo Pooling in On-Demand Intra-City Freight Logistics

On-demand intra-city freight logistics (ICFL) has recently emerged as a new freight service, where shippers can submit their shipping requests using smartphones and be matched to drivers in real time based on their locations and drivers’ availability. A major challenge faced by on-demand ICFL platforms is the shortage of vehicles during peak demand periods. Cargo pooling, the cargo version of carpooling, offers as a promising way to increase supply: cargoes heading in the same direction would share the cargo compartment of the same vehicle and be serviced simultaneously, which is achieved by careful sequencing of the pickup and delivery locations of the cargoes. We investigate models for cargo pooling for on-demand ICFL and quantify its benefit, which is new to the literature. The major difference between existing studies on ICFL and ours is that we no longer assume that demands are known beforehand. Instead, the demands arrive gradually throughout the day and we need to periodically match requests to drivers and re-optimize vehicle routes. We formulate the matching problem as a dynamic pickup and delivery problem with three-dimensional loading and time window constraints. To solve this model, we develop an algorithm based on large neighborhood search and tree search. The algorithm is tested with real freight data in a city in the Yangtze River Delta. Results show that the algorithm can reduce the total cost by 21.4% and reduce the total vehicle miles traveled by 36.0%.

Research on Active Disturbance Rejection Algorithm for Loading Control of 3-DOF Parallel Robot

A three-dimensional (3D) loading device based on a pneumatic 3-universal-prismatic-universal (UPU) parallel manipulator (three chains with UPU joint each) is designed to apply time-varying multi-dimensional loads to a target. First, according to the principle of vector superposition and Newton–Raphson method, the inverse and forward kinematics of the loading device are analyzed. Second, based on the screw theory, the static mapping between the dynamic platform and actuations is derived. Third, a second-order mathematical model is established for pneumatic 3-UPU parallel mechanism based on proportional flow valve and a metal seal pneumatic cylinder. A referential inaccurate model is provided for the control algorithm during modeling. Fourth, based on active disturbance rejection control (ADRC) technique, a 3D loading control algorithm is proposed and dynamic loading control is realized. Experimental results show that the ADRC algorithm has good robustness against disturbances, the steady-state control accuracy is less than 2 N, and the mean square error in dynamic tracking (sinusoidal tracking at 0.2 Hz) is less than 10.5 N.

Research on a permeability model of coal damaged under triaxial loading and unloading

It is important to research permeability models to clarify the evolution of methane seepage from coal seams and to reduce the occurrence of gas accidents. However, existing permeability models do not fully account for the influences of effective stress and adsorption/desorption on the permeability of coal rocks damaged during the three-dimensional stress loading and unloading process in coal mining. This study proposed a novel coal permeability model by more robustly considering the effects of stress and gas adsorption/desorption based on the generalized Hooke's law and Gibbs' equation. Then, a series of triaxial stress loading–unloading seepage experiments for coal rock were performed to validate the proposed model. The experimental research shows that triaxial stress loading and unloading have a significant effect on coal rock permeability. Before coal rock failure, the gas permeability shows a “V”-shaped development trend. After the deviatoric stress exceeds the compressive strength of the coal, the coal permeability increases sharply. Theoretical verification shows that the established exponential permeability model can effectively reflect not only the dynamic increase in the permeability of damaged coal under triaxial stress loading–unloading conditions but also the decrease in coal rock permeability during the increase in gas pressure with a constant effective stress. Moreover, the influence factors introduced in the permeability model can effectively reflect the influences of effective stress and gas adsorption/desorption on coal permeability under triaxial stress loading–unloading with different gas pressure conditions. These findings elucidate the variation in methane permeability of damaged coal rock under triaxial stress loading and unloading. The established permeability model can be used to carry out other numerical simulation studies to provide theoretical support for the prediction of gas permeability and efficient recovery of coalbed methane for coal mining working faces.

Pickup capacitated vehicle routing problem with three-dimensional loading constraints: Model and algorithms

This study addresses the pickup capacitated vehicle routing problem with three-dimensional loading constraints (3L-PCVRP), which combined the container loading problem (CLP) and the capacitated vehicle routing problem (CVRP). A mixed-integer linear programming model for 3L-PCVRP is designed with the objective of minimizing the total transportation cost. The basic constraints of CLP and CVRP as well as the practical constraints imposed by the pickup operations are incorporated in 3L-PCVRP. An improved branch-and-price-based (B&P) algorithm is proposed to solve 3L-PCVRP. The 3L-PCVRP model is decomposed into the restricted master problem (RMP) for selecting routes and the subproblem (SP) for generating routes that satisfy the loading and routing constraints. A label-correcting-based algorithm (LCA) is presented to solve the SP, which employs a two-stage method and two enhanced loading algorithms to ensure the loading feasibility of the routes. The two loading algorithms (tree search and greedy heuristic algorithms) are improved by a new evaluation function and an improved space-merging method. The two-stage method is designed to call the two loading algorithms at different frequencies to investigate the route feasibility accurately and efficiently. Numerical experiments are designed to test the performance of the proposed algorithms. The efficiency and effectiveness of the improved loading algorithms are demonstrated in hundreds randomly generated instances. For small-scale 3L-PCVRP instances, the B&P algorithm can generate solutions that are not worse than those of the solver within 0.14% of the solver’s running time. The efficiency and effectiveness of the improved B&P algorithm are also validated in large-scale benchmark instances.

Multi-category Fresh Agricultural Products Are Matched Joint Optimization of Load and Distribution

The core of the VRP problem is the process of distribution from the distribution center through multi-demand points under the condition of considering a variety of factors, and the VFP problem, as the precursor to the VRP problem, is that the distribution center carries out reasonable loading and loading according to the needs of multiple demand points. Both are important research topics in the logistics industry. The two influence and restrict each other in the distribution link, and are an indispensable part of the distribution link. This paper combines the two to study the joint optimization problem of VRP problem and VFP problem of urban logistics distribution, which is conducive to the effective integration of logistics and transportation resources. In this study, multi-category fresh agricultural products are taken as the research object, and the joint optimization of three-dimensional loading and distribution routes of multi-category fresh agricultural products at multiple task demand points in a distribution center is studied. In the process of joint optimization, the fragile characteristics of some products and the different sizes of each product feature are considered, and a three-dimensional loading-distribution route joint optimization model is established. In the process of joint optimization of stowage and distribution, the fragile characteristics of some products and the different sizes of each product feature are considered, and a three-dimensional joint optimization model of stowage and distribution route is established. The multi-objective problem with the largest load rate and the smallest mileage is converted into a single-objective function with the lowest cost; Secondly, the application of GA-TS hybrid algorithm to joint optimization is proposed. Finally, a study simulation is performed. The distribution scheme and loading scheme affect the size of the loading rate and the number of miles delivered. Distribution centers have found that proper stacking can effectively ensure vehicle load rates while reducing operating costs.

Synchronous dynamic calibration of triaxial high-g accelerometers using a modified Hopkinson bar method: Theory, principle and experiment

Because the inter-axis coupling effect and nonlinearity of triaxial high-g accelerometers (3-Axis-Gs) are significant under high-g and high-frequency loads, calibrating the sensitivity characteristics using a triaxial synchronous method is necessary but experimentally difficult. This study focused on the physics-based sensitivity model of 3-Axis-Gs, as well as the principle and experimental method of triaxial synchronous calibration. First, a sensitivity model of 3-Axis-Gs was established based on the physical source of cross-sensitivity. Then, a new triaxial synchronous calibration method was proposed using the modified Hopkinson pressure bar, which can simultaneously apply excitation accelerations with amplitudes greater than 100,000 g and frequencies greater than 50 kHz along the three axes of 3-Axis-Gs. Finally, a 3-Axis-G was calibrated using both triaxial synchronous and uniaxial calibration methods. Compared with uniaxial calibration, triaxial synchronous calibration can cover the entire test range, whose results can reflect the actual cross-sensitivity characteristics of 3-Axis-Gs in a three-dimensional loading environment.