Load Distribution Patterns Research Articles

An analytical solution to ground stresses induced by tunneling considering ground surface boundary conditions and gravity

Accurately predicting the stress distribution around the tunnel is crucial for designing safe and economical support systems. The stress distribution is closely related to the ground stress release induced by tunneling, as well as the initial gravity stress and boundary conditions. In this study, a two-dimensional analytical model considering the ground surface boundary conditions and gravity is presented to investigate the stress field around the tunnel. Then, a numerical model was developed to validate the proposed analytical model. Finally, parametric analyses were conducted, and the limitations of the load calculation method of the code for design of shield tunnel in China were discussed. The results indicate that: (a) Tunnel excavation induces stress redistribution in the soil, resulting in a soil arching effect around the tunnel. This arching effect causes nonlinear load changes around the tunnel. (b) The soil mass around the tunnel can be divided into undisturbed and disturbed zones. Above the tunnel, the disturbance range is C-2D(C and D represent the burial depth and the tunnel diameter), while below and on both sides of the tunnel, the disturbance ranges are 4D and 1.5D, respectively. (c) Once the stress release rate reaches 0.6, a combined arching effect zone, consisting of both major and minor principal stresses, is formed in the disturbance zone above and below the tunnel. (d) The load distribution pattern calculated by the code for design of shield tunnel in China is gourd-shaped, and this calculation method is insufficient for accurately evaluating the load around the tunnel. The research results can provide a reference for the design of the shield tunnel.

Load-carrying capacity of hole threads in TOBs bolted curved T-stubs to circular steel tube connections

This study investigates the load-carrying mechanism and proposes precise strength prediction methods for hole threads in Thread-fixed One-side Bolts bolted curved T-stubs to circular steel tube connections. A series of parametric analysis was performed with an advanced 3D finite element model considering critical parameters including tube wall thickness, bolt angle and bolt size. The axial load distribution along the hole threads and the shear stress distribution at the thread root were analyzed in detail. It was found that there were three typical load distribution patterns along hole threads, which were (1) linear pattern; (2) concave parabola pattern; and (3) convex parabola pattern, and the ratio of bolt stiffness to tube wall stiffness was identified as the pivotal factor affecting the axial load distribution. Meanwhile, the analysis results indicated that the bending moment on the TOBs did not affect the load distribution along hole threads, but led to a non-uniform stress distribution along the thread in the same turn. In the end, the prediction formulas for the carrying capacity of hole threads are presented by modifying Yamamoto’s equation based on the analysis findings. The formulas are validated against the finite element analysis results and previous test results. The prediction can reach the highest accuracy when adopting the proposed failure criterion 2, with average errors of − 0.001 and − 0.002, respectively, demonstrating the accuracy and reliability.

Thermal and Mechanical Stress Analysis in Aircraft Hybrid Panels with Multi-Bolt Joints.

This study investigates the thermal stress and bolt load distribution in a hybrid panel structure of an aircraft mechanical joint under extreme temperatures. The hybrid panel structure comprises two aluminum alloy splices, six T-shaped composite stringers, and two composite skins, secured together with 96 bolts. This study analyzed the strain induced by thermal stress on composite materials and metals within the structure across temperatures, employing temperature environment tests ranging from room temperature to -54 °C, alongside a carrying capacity test at -54 °C. Furthermore, a three-dimensional simulation model of the panel structure was developed, incorporating considerations for contact, metal elastoplasticity, and the progressive damage failure of composite materials. This model facilitated the determination of thermal stress and bolt load distribution patterns. The results indicate a strong consistency between the finite element analysis outcomes and the experimental data. Temperature variations exacerbate the uneven distribution of bolt loads, concentrating the load near the edges of the hybrid structure while diminishing it in the center. The bolt load distribution parallel to the mechanical load direction forms an "M" shape, with a maximum load magnitude of approximately 31 kN. Perpendicular to the mechanical load, the bolt load undergoes significant changes, especially at the edges, reaching a maximum of about 20 kN, which warrants attention. The bolt-load distribution of the structure with the increase in mechanical load at -54 °C tends to be consistent with that at room temperature.

Design and economic implications of using steel fibers in elevated slabs of multi‐story buildings

AbstractThis paper presents a comprehensive comparison between conventional reinforced concrete (RC) and steel fiber‐reinforced concrete (SFRC) slabs. Twenty‐two‐way rectangular RC and SFRC slabs are designed with varying dimensions, aspect ratios, and boundary conditions, following verified international standards to compare the steel quantities in a unique study. SFRC slabs with larger aspect ratios and discontinuous edges required significantly higher steel percentages than square slabs, as the random three‐dimensional distribution of steel fibers suited the load distribution pattern of square slabs. To further conduct a detailed design and economic feasibility case study on a realistic building model, two 12‐story buildings are computationally designed with RC and SFRC alternatives. The results indicate that SFRC slabs required approximately 25% more steel than RC slabs due to the uniform distribution of steel fibers throughout the section. Project cost and time estimates were conducted based on standard productivity manuals and cost databases in two distinct economies, India and the USA. Despite the higher steel requirements, the 12‐story SFRC building showed time savings of 34.1 days (5.44%) and cost savings of 4.88% and 1.27% when constructed in the USA and India, respectively. The results are compared with limited available data in literature. In conclusion, the study suggests that SFRC slabs in multi‐story buildings could be more economically favorable in countries with higher labor costs.

Effects of Re on blade load temporal-spatial distribution and correlation with flow stability of transonic compressor under inlet distortion

Compressor blade operating conditions and aerodynamic load change periodically owing to inlet distortion. The effects of low Re are often unavoidable when the inlet distortion is encountered in real compressor operation. Blade load distribution and internal flow field are both affected by variations in Re. In this paper, the effects of Re on the blade load distribution patterns under 60° of total pressure distortion is investigated by numerical simulation. The distortion intensity has been set to 0.05, and four cases with Reynolds number index of 1, 0.3, 0.2 and 0.1 are chosen for further analysis. The findings demonstrate that the variation of Re affects the compressor flow field mainly by modifying the aerodynamic profile of the blade, which also results in the change of the temporal and spatial distribution of the aerodynamic load. Furthermore, the aerodynamic blade profile varies significantly by Reynolds number in different spanwise regions. The blade time constant decreases in the mid-span area, while it increases in the tip. This ultimately leads to a delay in the location of the tip maximum load, changing the starting position of the induced stall.

Analysis and optimization of rivet load distribution in multi-rivet connections of thermoplastic composite rivets

GF/PP thermoplastic composite components predominantly employ metallic fasteners, leading to corrosion and weight issues. This study utilized an extrusion process to fabricate GF/PP thermoplastic composite rivets with properties akin to laminated panel materials. Through the controlled application of heat and pressure to the rivet ends, a novel connection structure was established. The article fabricated thermoplastic composite joints with varying end configurations and compared them with metallic rivet joints. Emphasizing the convex form, diverse multi-rivet links were crafted for single-lap tensile samples. Integrating tensile tests and strain gauge measurements, this research explored load distribution patterns across diverse rivet quantities and assessed the impact of size on distribution. Furthermore, finite element software was used to dissect the load distribution patterns and failure mechanisms in the multi-riveted connection structure. Drawing from experimental findings, convex GF/PP rivets exhibited an 18% higher tensile load than metallic ones, with a simultaneous 32% weight reduction. In multi-rivet connections, end rivets demonstrated higher load-bearing capacity. Enhanced spacing and plate width improved load distribution, elevating joint load capacity by 7% (spacing 25 mm to 55 mm) and 6% (width 30 mm to 55 mm). The simulation results indicate that increasing the spacing reduces the stress concentration at the first nail location.

Early warning system for load distribution in automated warehouse based on seismic resilience evaluation

As an integral part of the storage system in an automated warehouse, the racking structure can be altered for seismic performance by adjusting the distribution of loads, which is different from other building structures with uncertain load distribution. Therefore, there are two ways to improve the seismic resilience of racks: improving structural response and optimizing load distributions. The former has been widely studied, while the latter is rarely noticed. The objective of this study is to develop a method of seismic resilience evaluation and an early warning system of over-limit load distribution for racks with spine bracing. Based on the influence of load distribution on the seismic performance of racks with spine bracing, the contribution value of load positions was calculated to make additional corrections to the maximum stress ratio in load distribution samples obtained by genetic algorithm. Then, a formula for seismic resilience evaluation for racks with spine bracing was derived and its accuracy was validated to quantify the safety level of different load distribution patterns. An early warning system for over-limit load distribution was established and codified in a software package. A traffic light system including Green, Red, and Yellow were employed in the software package as an indicator of the load distribution safety level of racks. Finally, the system developed was applied to the actual racks in an automated tobacco warehouse in Nanjing. By adjusting loads in the least number of steps and the shortest distance, the racks changed from dangerous status (red light) to safe status (green light). The early warning system allows for rapid evaluation for the seismic resilience of racks without real-time finite element analysis, and is proved to be applicable, efficient and reliable.

Influence of retainer design and number of inlay boxes on the biomechanical behavior of zirconia cantilever resin bonded fixed dental prosthesis.

The development of dental adhesives with enhanced bond strength has assisted minimally invasive dentistry. The aim of this study was to evaluate the fracture load and stress distribution pattern of two retainer designs for posterior cantilever resin bonded fixed dental protheses (RBFDPs). Forty human mandibular molars were divided into two groups according to the retainer design; lingual coverage (LC) and occlusal coverage (OC) retainers. Each main group was then divided according to the number of inlay boxes (n = 10); one inlay and two inlay boxes. High translucency (3Y) zirconia was used to manufacture all restorations, and a dual-polymerizing adhesive resin cement was used for bonding. All specimens underwent 10,000 cycles of thermocycling (5-55°C), 240,000 cycles of dynamic loading (50 N, descending speed v = 30 mm/second, frequency = 1.6 Hz), and failure load test. Both one-way and two-way ANOVA tests were used to analyze the data. The four models included in the in-vitro study are part of the finite element analysis (FEA). When the restorations failed, maximal principal stress values on restorations, enamel, dentin, and luting resin were investigated. A statistically significant (p = 0.018) higher failure load was recorded for OC1 (627.00 ± 153.4 N) than the other groups; (548.0 ± 75.6 N, 521.20 ± 11.3 N, and 509.20 ± 14.9 N for LC1, LC2, and OC2, respectively). With regard to failure mode, one inlay box designs showed more favorable failure pattern than those of two inlay boxes. FEA showed higher stress magnitude transmitted to the tooth structure in models LC2 and OC2. Lingual coverage and occlusal coverage retainers are promising designs capable to withstand the normal occlusal force for cantilever RBFDP in premolar area. The use of two inlay boxes decreased the fracture load of the two retainer designs and increased the stress transmitted to the tooth and resulted in high incidence of catastrophic failure. Monolithic high translucent zirconia RBFDP could be considered as a viable treatment option to substitute missing posterior tooth, with improved esthetics and biocompatibility.

A systematic characterization of soil/dust ingestion for typical subpopulations in China.

An accurate assessment of human exposure to pollutants through the ingestion of dust and/or soil particles depends on a thorough understanding their rate of human ingestion. To this end, we investigated the load and size distribution patterns of dust/soil particles on the hands of three typical subpopulations, including preschoolers, college students, and security guards (outdoor workers). The geometric mean diameter of dust/soil particles on hands was observed to be 38.7 ± 11.2, 40.0 ± 12.1, and 36.8 ± 10.4μm for preschoolers, college students, and security guards, respectively. The particle size distribution differed between subpopulations: Preschoolers were more exposed to fine particles, whereas security guards were exposed to more coarse particles. The geometric means of dust/soil particle loading on the hands were 0.126, 0.0163, and 0.0377mg/cm2 for preschoolers, college students, and security guards, respectively. Males had statistically higher dust/soil particle loadings on hands than females, notably for preschoolers and college students; preschoolers with frequent hand contact with the bare ground had higher dust/soil particle loadings compared to those of peers in contact with commercial and residential grounds. The mean total dust/soil particle ingestion rate was estimated to be 245, 19.7, and 33.1mg/day for preschoolers, college students, and security guards, respectively. Our estimates for college students and security guards are close to the consensus central-tendency values recommended by the U.S. EPA's Exposure Factor Handbook for American adults, whereas the estimates for children are much higher than the upper percentile values recommended for American children.

Hierarchical Collaborative Planning of County Energy Internet

Building a County Energy Internet (CEI) is crucial for achieving green and low-carbon transition and sustainable development of county energy systems. This paper proposes a bi-level collaborative planning method for CEI to configure devices’ capacities in multiple regional CEIs (RCEIs) and plan the interconnected networks simultaneously. Firstly, the models of multi-energy devices and networks are constructed. Then, an optimal partitioning method based on a clustering algorithm is proposed to divide the CEI into multiple RCEIs by considering the load distribution pattern and complementary characteristics. On top of that, a bi-level planning model for CEI is established, wherein the lower-level problem aims at configuring the capacities of devices in RCEIs through mixed-integer linear programming (MILP), while the upper-level problem is the determination of the interconnected multi-energy network topologies by searching the minimum spanning tree. This two-level planning problem is resolved iteratively, in which the network topologies of CEI and energy imbalance in each RCEI are shared information. Case studies on the modified CEI validate the effectiveness and practicality of the proposed method.

Comparing Statistics and Machine Learning to Detect Insincere Grip Force Testing Using Manugraphy.

Background Currently, there are no tests that have been proven to be capable of rating an individual's grip force measurement as sincere or insincere. However, different parameters have been found to vary in grip force testing for maximal versus submaximal effort. A novel data analysis and processing approach might be key to improving these measurements. This study explores the use of a machine learning (ML) algorithm as a means to more accurately determine the sincerity or insincerity of grip force testing. The ML algorithm compares the hand's load distribution pattern with the information generated using conventional statistical methods. Methodology This study uses manugraphy data collected as part of a previous investigation that analyzed load distribution patterns of the right and left hands of 54 healthy subjects. The subjects underwent grip force testing using maximal or submaximal effort, and the percentage contributions of each of the seven defined anatomical areas of the hand were calculated with respect to the total load applied. The predictions based on the load distribution and its use for rating individual grip force measurements as sincere or insincere were compared with the results of conventional statistical methods (thresholds for a bi-manual area-to-area comparison) and an ML algorithm. Results Based on an area-to-area comparison, our method achieved a sensitivity of 54% and a specificity of 78% to detect insincere effort. A predictive ML model developed using these data was capable of recognizing submaximal effort based on the hand's load distribution pattern, determining a sensitivity of 94% and a specificity of 99%. Conclusions Compared to conventional methods, the use of an ML algorithm considerably improved the validity of manugraphy results in discerning the sincerity or insincerity of grip effort.

Quantitative Analysis of Foot Arch Deformation and Plantar Load Distribution Pattern During Running

Quantitative Analysis of Foot Arch Deformation and Plantar Load Distribution Pattern During Running

Load Distribution Optimization of Steel Storage Rack Based on Genetic Algorithm

The distribution of load has high uncertainty, which is the main cause of a rack structure’s instabilities. The objective of this study was to identify the most unfavorable and favorable load distributions on steel storage racks with and without bracings under seismic loading through a stochastic optimization—a genetic algorithm (GA). This paper begins with optimizing the most unfavorable and favorable load distributions on the steel storage racks with and without bracings using GA. Based on the optimization results, the failure position and seismic performance influencing factors, such as the load distributions on the racks and at hazardous positions, are then identified. In addition, it is demonstrated that the maximum stress ratio of the uprights under the most unfavorable load distribution is higher than that under the full-load normal design, and it is not the case that the higher the center of gravity the more dangerous the steel storage rack is, demonstrating that the load distribution pattern has a significant impact on the structural safety of steel storage racks. The statistics of the distributions of the load generated during the optimization of the GA and the contours of the probability distributions of the load are generated. Combining the probability distribution contours and the GA’s optimization findings, the “convex” distribution hazard model and the “concave” distribution safety model for a steel storage rack with bracings are identified. In addition, the features of the distribution hazard model and the load distribution safety model are also identified for steel storage racks without bracings.

The loads developed by epicondylar and epitrochlear muscles across the elbow joint. A dynamic simulated model

The radio-humeral joint has traditionally been believed to support most of the loads transmitted through the elbow. Load transfer through the elbow has been a controversial issue since the publication of the first biomechanical studies on the subject, most of which were based on extrinsic forces acting on the extended joint. The present study analyzes load distribution across the six different compartments in the elbow while the joint is flexed, as well as the intrinsic forces generated in the epicondylar and epitrochlear muscles.Ten cadaveric elbows were positioned at 90° of flexion, forearm in a neutral position and wrist at 0°. Tekscan sensors were used for measuring intraarticular pressures.Forces generated by epitrochlear muscles results in a series of loads that affect mainly the anteromedial facet (40%), followed by the posterolateral facet (34%) of the ulnohumeral joint, with the flexor carpi ulnaris generating the heaviest loads (43% on the anteromedial and 38% on the posterolateral facets). Conversely, the forces generated by the epicondylar muscles, similar in behavior but with an opposite direction, convey heavier loads to the elbow’s anterolateral facet (45%), followed by the radiohumeral joint (26%) with the extensor carpi ulnaris generating the heaviest loads (54% on the anterolateral facet and 17% on the radiohumeral joint).Our results indicate that the elbow joint exhibits a characteristic load distribution pattern that depends on the muscles, as intrinsic forces are generated by the epicondylar and epitrochlear muscles. The anterior portion of the ulnohumeral joint is the area bearing the heaviest loads.

Quantifying the impact load of rapid dry granular flows exerted on rigid slit structures using centrifuge experiments and DEM simulation

Granular flows are typical hazard in mountainous terrains. Slit structure has been shown to be a successful mitigating strategy. However, the interaction mechanism between granular flows and slit structure has not been completely elucidated, and the impact load and impact pressure distribution pattern of granular flow on slit structures also has not been fully discussed. Therefore, a novel centrifuge flume experiment and DEM simulation were designed. The centrifugal acceleration field and Coriolis field accounting for the Coriolis effect were also implemented in the DEM model. Results reveal that, the grain size almost has no effect on normal impact forces when the granular flows act as continuous characteristic, and the initial volume and impact force do not show a simple linear relationship. Furthermore, the impact pressure profiles indicate a trapezoidal distribution with a peak impact pressure at the bottom and a decline from the bottom to the top. In addition, the impact forces also showed a decreasing trend from the slit to the flume channel sidewall, making the inner part vulnerable. This study might contribute to the study of flow-slit structure interaction and provide scientific support for slit structure engineering design.

Comparison of the debonding force of metal, glass and polyethylene Fiber reinforced composite retainers: Mechanical and finite element analyses

The studies evaluating the efficiency of fiber reinforce composite (FRC) retainers are few and contradictory. This study aimed to compare the debonding force of metal, glass FRC (GFRC) and polyethylene FRC (PFRC) retainers, assess the interactions between the materials and forces, and pattern of load distribution by finite element analysis (FEA). Forty-eight sound lower incisors were collected and randomly assigned to 3 groups (n=8; each sample included 2 teeth). Next, 15mm of the three retainers (multi-stranded metal wire, GFRC, and PFRC) were bonded to the lingual surface of the teeth and debonding force was measured by a universal testing machine. For FEA, 3D models were designed. The data related to geometrical models and material properties were transferred to ANSYS software. A 187-Newton load was applied to the incisal edge of the two centrals. Then different parameters were assessed. The three groups were compared by one-way Anova and Tukey's test. Type one error was considered to be 0.05. The debonding force decreased in the order: Metal (143.71N)≥GFRC (108.29N)>PFRC (45.08N). The difference between metal retainer and GFRC was not significant. In contrast, PFRC group showed significantly lower debonding force compared to other groups (P<0.05). FEA showed stress peak value in metal-composite interface. Maximum total deformation was noted in central, followed by lateral and canine. Glass-FRC can serve as an alternative to metal retainers as the difference in debonding force is not significant. However, the difficulty of repairing or replacing the Glass-FRC should be taken into account given the large number of failure in the interproximal dental area.

Bluetooth Load-Cell-Based Support-Monitoring System for Safety Management at a Construction Site.

At construction sites, temporary facilities have caused continuous collapse accidents, causing damage to human life. If the concrete placing height is high and the worker is pushed into one place at the time of placing, the working load may be exceeded and a collapse accident may occur. In order to solve this problem, in this research, we developed a monitoring load-measurement program based on a Bluetooth wireless load cell (load-cell sensor) so that the load can be converted to digital and the numerical value can be confirmed by the pressure sensor. The load cell using Bluetooth was designed and manufactured according to the support. Then, the performance was verified through 3D finite element analysis by modeling and experimental tests. In addition, we constructed a system to generate notifications and warnings step by step when the load is close to a dangerous load, confirmed the load distribution pattern by position, and established a method to confirm real-time data numerically and graphically. Finally, we evaluated the practical application of the load-monitoring system using field-test data using a wireless load-cell.

Estimation of design load and distribution pattern for wooden classroom chairs in use at secondary schools in Ibadan, Nigeria

ABSTRACT The absence of an established design load constitutes a challenge to the engineering design of classroom furniture. This study developed a methodology for estimating design loads for single user (SU) and multiple user (MU) wooden classroom chair and desk combinations offered to secondary school students in Ibadan, Oyo State, Nigeria. Service load distribution patterns for the chair and desk members in normal, backward and front-reclining sitting postures were determined for 15 girls and 15 boys using bathroom scales. A T-test was used to compare the significance of the means of the proportions of users’ weights transferred to the chair and the floor. Design loads were 1 kN (SU) and 2.7 kN (MU) for chair and desk configurations, respectively. Each SU and MU leg should be designed to support 35% and 40% of the service loads, respectively. Gender, sitting postures, and chair and desk designs influenced load distribution patterns significantly.

A study of vertical tie reaction forces in ballasted railroad tracks through field instrumentation and numerical modeling

This manuscript presents findings from an ongoing research study at Oklahoma State University studying different factors that affect vertical tie reaction forces in ballasted railroad tracks. A combined approach involving field instrumentation and numerical modeling has been adopted for this purpose. Measurements of tie reactions can indicate the load distribution patterns and quality of vertical support along a track. Locations where tie support conditions are not adequate can develop geometry defects, ultimately leading to component failure. Three different approaches are adopted in this study to measure the forces being transmitted through the rail-tie interface; this is equal to the tie reaction force. The field instrumentation effort validates an alternative method to measure forces at the rail-tie interface using rail-mounted strain gauges. Results from this approach are compared to two other conventional methods of force measurement, i.e. through the use of load cells (LC), and an instrumented tie plate (ITP). A validated 3-dimensional Finite Element (FE) model is used to support the field-observed trends, and explain any observed discrepancy. Parametric analyses using the FE model identify different factors that can contribute to the rail-tie interaction force, thus affecting the instrumentation results. The strain gauge-based approach, using the concept of differential shear strain measurement, has been established as a suitable method for tie reaction force measurement. Exact measurement of the tie reaction force can be ensured through proper installation of the strain gauges, away from possible boundary effects.

Research on Axial Modification of Traction Gear

When locomotive traction gear is meshed in transmission, unbalanced loading is easily formed due to various factors such as deformation and error. The research shows that axial modification can avoid this problem. In order to meet the design requirements of axial modification on different types of traction gear, the idea of parameterization can effectively reduce the development cycle. In this paper, on the premise of clarifying the structural form of locomotive driving device, the working characteristics of traction gear are introduced, the force analysis of motor shaft and axle is carried out in consideration of various aspects, the deflection deformation of each part is computed and superposed according to material mechanics, and the mathematical model of axial modification is established by combining the driving direction of motor comprehensively. The calculation model of load distribution is determined according to the actual error. Taking a certain type of locomotive traction gear as an example, the feasibility of the algorithm is verified by comparing the theoretical calculation value with the measured data and load distribution patterns before and after modification, and the results show that this method has guiding significance for axial modification.