Axle Load Distribution Research Articles

Research on Regenerative Braking of Pure Electric Mining Dump Truck

When the pure electric mining dump truck is working, it mainly ascends the slope at full load and descends the slope at no load. The loading state of the vehicle and the slope of the road will directly affect its axle load distribution and braking force distribution. In this paper, the slope dynamics analysis of the pure electric double-axle four-wheel drive mining dump truck was carried out. Based on the regenerative braking priority strategy, four regenerative braking control methods were developed based on the Matlab/Simulink platform and ADVISOR 2002 vehicle simulation software to study the ability of regenerative braking energy recovery and its impact on vehicle economic performance. The simulation results show that the regenerative braking priority control strategy used can maximize the regenerative braking force of the vehicle; the regenerative energy recovery capability of pure electric mining dump truck is proportional to the regenerative braking force that can be provided during braking; the two-axis braking strategy based on the I curve and the β line can make full use of the front and rear axle regenerative braking force when the braking intensity is large, and recover more braking energy; under road drive cycle, the single-axis braking force required to the braking strategy based on the maximized front axle braking force is the largest among all strategies, the motor braking efficiency is the highest, and the recovered braking energy is the most. For the studied drive cycle, the regenerative braking technology can reduce the vehicle energy consumption by 1.06%–1.56%. If appropriate measures are taken to improve the road surface condition and reduce the rolling resistance coefficient from f = 0.04 to f = 0.02, the regenerative braking technology can further reduce the vehicle energy consumption to 4.76%–5.73%. The economic performance of the vehicle is improved compared to no regenerative braking. In addition, the vehicle loading state and the driving motor working efficiency also directly affect the regenerative braking energy recovery capability of the pure electric mining truck.

Updating Traffic Inputs for Use in the Pavement Mechanistic-Empirical Design in Michigan

A study, completed in 2009, characterized traffic inputs in support of implementing the new Mechanistic-Empirical Pavement Design Guide for the state of Michigan. The inputs included monthly adjustment factors, hourly distribution factors, vehicle class distributions, axle groups per vehicle, and axle load distributions for different axle configurations. During the last 7 years, new traffic data were collected that reflect recent economic growth, and additional and downgraded weigh-in-motion (WIM) sites. Performance models for the Pavement mechanistic-empirical (ME) design were recently calibrated to local conditions in Michigan. Hence it was appropriate to incorporate these changes in the re-evaluation of traffic inputs. Weight and classification data were obtained from 41 WIM sites throughout the Michigan to develop Level 1 (site-specific) traffic inputs. Cluster analyses were conducted to develop Level 2A inputs. Classification models (decision trees, random forests) were developed to assign a new site to these clusters; however, this proved difficult, hence, an alternative, simplified method to develop Level 2B inputs by grouping sites with similar attributes was also adopted. The optimal set of attributes for developing Level 2B inputs was identified by using an algorithm developed in this study. The effects of the developed hierarchical traffic inputs on the predicted performance of rigid and flexible pavements were investigated using Pavement-ME. Based on the statistical and practical significance of the life differences, appropriate levels were established for each traffic input. The methodology for developing traffic inputs is intuitive and could easily be adopted by Michigan Department of Transportation for future updates.

Distribution of Masses and Presses on Axles and Wheels and Vehicles' Properties

Abstract One of the most important parameters affecting traction properties as well as driving safety, especially with regard to vehicles with special purpose, is the distribution of wheel and axle loads on the ground. This issue should be taken into account during the process of creating new vehicles as well as during the modernization process. In the first case, it is quite simple because the mass distribution is shaped already in the design phase. In the second case, the problem is more complex, because with modernization solutions we enter an already existing structure. Modernization basically assumes improving the performance and capabilities of the vehicle with possibly small changes in its base structure. Thus, it imposes important boundary conditions. The article presents the methodology of measurement and selected results of measurements of mass distribution as well as wheel and axle loads of selected motor vehicles during their advanced modernization (STAR 266 cars to the version STAR 266M2 and Honker 2000 to the version Honker M-AX). Modernizations carried out by Autobox Innovations Ltd. Lim. Par are mainly focused on increasing the traction of vehicles, traffic safety, and driving comfort. Measurements were made at the above-mentioned company.

Enhancing the Passing Ability of Unmanned Vehicles Using a Variable-Wheelbase Driving System

A six-wheel driving system with a variable wheelbase is proposed to improve the passing ability of unmanned vehicles. As the first step, the effect of the wheelbase variation on the axle load distribution is analyzed. Next, the relationship between the wheelbase variation and rolling resistance is obtained by numerical calculation combined with the theory of terramechanics, and it shows that the traction performance of the vehicle can be optimized by adjusting the wheelbase. Considering the deformation of tires and soil, the mechanism of the effect of the change in wheelbase on the ability of the vehicle to overcome an obstacle and cross a trench is studied, and a variable-wheelbase strategy for a vehicle overcoming an obstacle and crossing a trench is then proposed on the basis of theoretical calculations. Finally, the rationality of the variable-wheelbase strategy is verified in simulation experiments.

Performance Assessment of a Newly Constructed Skewed Half-Through Railway Bridge Using Integrated Sensing

© 2018 American Society of Civil Engineers. Half-through steel plate girder bridges are widely used across the United Kingdom's railway network. However, few studies have investigated their real in-service behavior. Concurrently, the use of advanced sensor systems, such as those utilizing fiber-optic sensors, have begun to find widespread use in structural health monitoring due to their high accuracy and long-term stability and durability. In this paper, the real performance of a newly constructed skewed half-through plate girder railway bridge was assessed using an integrated fiber optic monitoring system installed during the bridge's construction. Monitoring data recorded during the passage of 12 separate trains consisted of strains measured along the length of the main steel plate girders and crossbeams. Based on available design and construction information, a three-dimensional finite-element model capable of simulating the railway bridge's response was constructed and used to investigate and provide comparisons with monitoring results of the performance of such bridges under passing trains. The influence of track cant on load distribution between the two main girders was discussed, and the live load utilization percentage of the main girders was estimated to be approximately 37% of its design capacity. In addition, the effect of different transverse crossbeam end-connection details (pinned or moment connected) and the influence of axle load distribution through track ballast on the overall response of the bridge structure were evaluated. The results obtained in this study have not only led to the establishment of a comprehensive performance baseline for the newly constructed bridge for long-term condition monitoring but may also be used for improving the design and in-service structural evaluation of such bridges.

Evaluation of Pavement Performance due to Overload Single-Trip Permit Truck Traffic in Wisconsin

This study investigated the impacts of overweight (OW) permit truck traffic on flexible pavement performance in Wisconsin using field investigation and analysis utilizing the AASHTOWare Pavement ME Design software. A database of overweight single-trip permit truck records was analysed to produce a network of Wisconsin corridors heavily travelled by OW trucks. Four Wisconsin highways were selected for investigation due to high levels of OW truck traffic. The research included field work (traffic counts and visual pavement surface distress surveys) and AASHTOWare Pavement ME Design. Comprehensive analyses were conducted to evaluate pavement performance due to normal traffic loads as well as normal traffic loads plus the OW truck traffic loads. The use of mechanistic-empirical (ME) pavement analyses provided a methodology for estimating the proportion of pavement deterioration attributable to OW truck traffic. OW axle load distributions were developed and integrated with baseline truck traffic levels to develop axle load spectra and other traffic input parameters for the ME pavement analysis. The predicted total pavement deterioration levels from the AASHTOWare Pavement ME Design software were generally consistent with the levels of deterioration observed. The proportion of pavement damage and deterioration attributable to OW truck traffic was predicted to constitute a relatively minor proportion of total deterioration, with most distress indices showing relative increases of approximately 0.5% to 4%, with a few outliers. However, due to the small proportion of OW vehicles relative to the overall traffic levels, the OW vehicles were generally predicted to cause up to ten times the per-truck damage as compared with a typical legal-weight truck, depending on the distress mode and the test site.

Finite Element Analysis and Experimental Simulation of Chassis Mounted Platform for Off-Road Wheeled Combat and Transport Utility Vehicles

Chassis mounted platform is an intermediate component between vehicle chassis and chassis mounted shelter, and is intended to act as a levelled base for shelters. Shelters in combat vehicles provide a closed stipulated environment to computerized tracking systems, sophisticated defense combat equipments to suit the operational and environmental requirements during warhead situations. Platform carries transfers and sustains unevenness in load arising from the road or soil irregularities during off-road vehicle travel. Present work deals with development, evaluation and improvement of one such platform for 8x8 vehicles. In this work, the platform under consideration is designed to accommodate two shelters, each being secured to the platform using standard twist locking arrangements. Securing locations are dependent on the size and weight of the commodity to be placed inside shelter. Major design ruminations of the platform include nature and pattern of load, flange orientations of channel sections, span between webs of consecutive channels, axle load distribution and vehicle geometry constraints as ground clearance and departure angle. Finite element analysis is carried out in to order evaluate stress and deflection in the present platform configuration. Experimental strain measurement at critical locations on the platform is carried at Automotive Research Association of India (ARAI) to evaluate the performance of the platform under specified load-speed conditions. Relation between experimental stress values and strain gauge locations on the platform is assessed for different load magnitudes.

The Influence of Axle Load Distribution of Machine-Tractor Aggregates on the Dip of the Wheel-Track

It is defined that while doing some agricultural operations the area covered by the machine-tractor aggregates wheels exceeds the area of the field. (Purpose of research) The regularity of repeated accumulation of the soil puddling and the influence of the specifity of axle load distribution of machine-tractor aggregates on the dip of the wheel-track is justified. (Materials and methods) The mathematical apparatus to describe the influence of the effects connected with the soil particles reposition while the repeated loading is developed. The over consolidated soil creates some raised resistance while the following tillage which results in increased fuel consumption and lost productivity of machine-tractor aggregates. The modified soil structure is difficult to be restored entirely. As a result the intensive worked tilth top soil degrades with time which creates the ecosystem disbalance of cultivated land. The laboratory experiments of the soil features influence and the specifity of wheel loading on the dip of the wheel-track are performed. The regularity of repeated puddling accumulation being subject to Bolstman correlation which links the process entropy and the probability of this state (statistical interpretation of the principle of entropy increase) is set. (Results and discussion) The dependences to determine the deformation of soil with various physical and mechanical properties under different drive system loading conditions of machine-tractor aggregates are obtained. The influence of axle load distribution on the dip of the wheel-track is established. The dependence to describe the process of wheel track formation on the sod-podzolic sandy loam soil of low moisture level which corresponds to the empirical data is obtained. The calculations from the dependence obtained are performed. While doing repeated passes the wheel sinkage is provided only by the increase of contact stresses. (Conclusions) The regularity of the soil puddling rise from the deformer while the repeated loading is set. The regularity obtained makes possible to define the soil deformation depending on the different operating conditions and the drive system parameters of machine-tractor aggregates on different types of soil.

Reduction of Vehicle‐Induced Vibration of Railway Bridges due to Distribution of Axle Loads through Track

Short span railway bridges are prone to resonate caused by dynamic train axle loads, which were usually modeled as moving point loads on the bridge in many numerical studies. In reality, the axle weight of the train is a spread load for the bridge deck because of the transfer of the track structure. Previous numerical studies indicated that the spread axle load distributed through the track structure significantly reduces bridge responses compared to the point load model. In this study, the reduction effect is investigated analytically by solving the moving load problem for both the point load and the spread load cases. The analytical solution reveals that bridge responses from the spread load model can be obtained by filtering bridge responses from the point load model. The filter function is exactly the Fourier transform (FT) of the load spreading function. Based on this relationship, a reduction coefficient reflecting the load spreading effect on bridge responses is derived. Through numerical examples, the accuracy of this proposed reduction coefficient is validated not only for the moving load models but also for vehicle‐bridge interaction (VBI) problems.

Determination of load equivalency factors by statistical analysis of weigh-in-motion data

The load equivalency factors for pavement design currently in use by the Hungarian standard have been developed using Weigh-in-Motion data obtained during the first few years of operations after installing some 30 measuring sites in Hungary in 1996. In the past years, and currently, data is collected mainly at the border crossings of the country, however the data is used only for law enforcement purposes, and no comprehensive statistical analyses have been done. To develop actual load equivalency factors for the use in pavement design, data of one year was collected and statistical methods were applied. An algorithm was used to help managing the multimodal distribution of axle loads in mathematical perspectives. Monte-Carlo methods were applied to determine the factors for each heavy vehicle type and eventually for each vehicle class used by the current Hungarian pavement design manual. The calculated factors are considerably different from the current ones, indicating that the pavement design may lead to a false result. Furthermore, there are three vehicle types suggested to be incorporated into the standard due to their high occurrence.

The effect of traffic data source on deterioration rates of heavy-duty flexible pavements

The purpose of this study is to assess the effect of traffic data source (estimated vs. actual) on predicted progression rates of roughness and rutting for heavy-duty flexible pavements of rural freeways. Progression rates are predicted using calibrated HDM-4 models. The assessment is performed in terms of variations in maintenance intervention timing associated with the variations in progression rates. Time series pavement condition data (covering 3–5 years) have been collected for 7 sections of rural freeways for use in calibrating HDM-4 deterioration models. They range in length from 10 to 60.8 km and cover different traffic volumes, climate zones and subgrade soil types. For these sections, estimated annual average daily traffic (AADT), growth factors and assumed loading have been extracted from relevant database. Only six segments of these sections have Weigh-in-Motion (WIM) sites so relevant actual AADT, growth factors and axle load distributions have been extracted from WIM reports. The results of running the calibrated HDM-4 deterioration models using different traffic data show that actual traffic data from WIM sites result in higher rates of deterioration to that of estimated data for four sites, resulting in earlier intervention timing and higher present value agency cost. The other two sites have lower rates with actual data due to lower traffic loading than estimated.

Measurement of the Moment of Inertia for a Zero Turning Radius Mower

<abstract> The moment of inertia (MI) is one of the important factors that affect the continuous roll behavior of a zero turning radius (ZTR) mower, and therefore, an accurate measurement or calculation of the MI is required. Previous research focused on the estimation techniques for vehicle MIs, and the measurements included a car, pickup truck, sport utility vehicle, and van, all of which have a small front/rear axle load distribution difference (i.e., the front/rear axle load distribution ratio ranges from 0.67 to 1). However, little research has investigated the MI of a ZTR mower, which has a large front/rear axle load distribution difference (i.e., the front/rear axle load distribution ratio is approximately 0.33); thus, the load distribution of a ZTR mower is more nonhomogeneous than that of the other vehicles. The primary objectives of this research were to investigate a mathematical model and a suitable MI measurement method for the ZTR mower, which is a difference in front/rear axle load distribution. A mathematical model was developed based on the principle of the pendulum method for measuring the MI in the x-, y-, and z-axes. Three ZTR mowers were used as test vehicles: a mower without a deck, a 1.2 m swath mower, and a 1.8 m swath mower. The test results were compared with the results obtained using the empirical formulas. Based on the comparison of the MIs, the results of the tests were within the range of 6.7% to 16.5% of the relative error from the values calculated using the empirical formulas. The test results indicated that the relative errors increased for mowers with a large difference in the front/rear axle load distribution.

Investigation of Truck Weights and Dimensions Using WIM Data

This paper presents a study carried out with extensive weigh-in-motion (WIM) data collected on the French main road network, involving 3 millions of trucks. The data were collected by three WIM stations located on highly trafficked highways and motorways, continuously over a whole year. The data were analyzed using statistical software developed by the US National Science Foundation.The trucks of the traffic flow were classified into almost 20 categories, depending on the silhouette, number and spacing of axles, body configuration (trailer/semi-trailer), type of axles (steering, driving or standard axle) and wheel or tire (single, twin, wide). The data were analyzed by category.The location of the centre of gravity of the payload was calculated and the variability of its abscissa along the vehicle was analyzed in each category. The loading patterns and behavior were analyzed and the results reported here for 5-axle articulated trucks and 2-axle rigid truck with 2-axle trailer.Then, the axle load distributions were analyzed by axle rank and truck category, and modeled with multimodal Gaussian probability distribution functions. The modes have been determined using a maximum of likelihood method. These modes are useful to design endurance tests of truck tires.These investigations provide a better knowledge about truck loading, overloads and truck aggressiveness on infrastructure, and may lead to optimization policies. In this case, the results are used directly in the domain of tyre optimization.

Design Evaluation of Chassis Mounted Platform for Off-Road Wheeled Heavy Vehicles

Chassis mounted platform is an intermediate component between vehicle chassis and shelter,and acts as a levelled base for shelters. Platform transfers and sustains unevenness in load arising from the road or soil irregularities during vehicle travel in rough terrains. Present work deals with development, evaluation and improvement of one such platform. In this work, the platform under consideration is designed to accommodate two shelters, each being secured to the platform using standard twist locking arrangements. Securing locations are dependent on the size and weight of the commodity to be placed inside the shelter. Major design modifications of the platform include nature and pattern of load, flange orientations of channel sections, span between webs of adjacent channels, axle load distribution and vehicle geometry constraints as ground clearance and departure angle. Hand calculations, computer aided design and finite element analysis are carried to evaluate the stress and deflection for different platform configurations. Road profiles for platform analysis include rough road and cross-country terrains. Experimental strain measurement at critical locations on the platform is carried out to evaluate the performance of the platform under specified load-speed conditions. Mathematical relation between experimental stress values and strain gauge locations on the platform is developed for different load magnitudes and loading patterns.

Analysis of effect of overloaded vehicles on fatigue life of flexible pavements based on weigh in motion (WIM) data

Overloaded vehicles have a significant impact on pavement fatigue life and distress. As the studies show, the phenomena intensify when the control of traffic is poor. The paper presents the results of the research including analysis of weigh in motion data from eight stations and analysis of asphalt pavement fatigue caused by mixed traffic. Distributions of vehicles axles load including the multiple axles effects are presented. Mixed axle loads were transformed into equivalent number of standard 100 kN axle loads. The regression model of load equivalency factor depending on the axle load distribution and the percentage of overloaded vehicles is presented. The analysis of the effect of overloaded vehicles on decrease of fatigue life of a pavement structure is presented. The analysis has shown that the increase of percentage of overloaded vehicles from 0% to 20% can reduce the fatigue life of asphalt pavement upto 50%.

Effect of Axle Load Spreading and Support Stiffness on the Dynamic Response of Short Span Railway Bridges

In dynamic analyses of railway bridges, the train axle loads are often modeled as moving point forces. However, these point forces are further distributed to the bridge structures through the ballast, which can lead to large reductions in the bridge response, especially for short span bridges. For this reason, the Eurocode prescribes distribution of the axle loads over three adjacent sleepers. In this paper, the axle load distribution is first studied using a plane finite element analysis, and based on this, a triangular load distribution is proposed. Then, numerical simulations are performed to compare the effect of this load distribution with the one prescribed by the Eurocode. Both simply supported bridges and bridges with integrated backwalls, all with span lengths less than 10 m, are studied. For the latter bridges, the effect of the stiffness of the foundation has been studied by adding springs at the supports.

Influence of Atypical Vehicle Types on Girder Distribution Factors of Secondary Road Steel-Concrete Composite Bridges

This paper investigated the influence of atypical agricultural vehicle parameters on girder distribution factors (GDFs) for two simply supported steel-concrete composite bridges located on secondary roads in the United States. As part of the parametric investigation, field measurements were performed on the bridges under the passage of full-scale agricultural vehicles along each bridge centerline. Strain data obtained from field tests were used to determine field GDFs. Both field data and GDFs were used to calibrate a finite element model of the bridge. Data from over in-use one hundred agricultural vehicles were collected, and then each vehicle was applied to the model to compute analytical GDFs. These vehicles were analytically and statistically investigated to determine the sensitivity of GDFs to vehicle parameters, including maximum vehicle axle load, gage width, and spacing distributions. Based upon field strain investigation for the two bridges, the responses of the central girders were greater than those of the exterior girders, resulting in greater field GDFs for central girders than those of the exterior girders. Results also indicated from the sensitivity study that each girder had different levels of correlation between GDFs and single vehicle parameters.

Estimating vehicle speed with embedded inertial sensors

Pavements were instrumented with inertial sensors, and the possibility of estimating the speed of a passing vehicle was investigated numerically and experimentally from the measurements of two embedded accelerometers. The sensors were spaced apart in the travel direction, and subsequently the speed was directly related to the time delay between the received signals. No assumption was made regarding the vehicle and pavement properties. Model accelerations were presented, studied, and contrasted against field measurements; the latter were shown to be dominated by random vibration sources. Two calculation techniques were offered and applied to handle the noisy data. The first was based on time-centroids, and the second was based on cross-correlation with kernel presmoothing. The overall concept is deemed promising not only for inferring speeds but also for extracting additional traffic characteristics such as axle spacing and relative axle load distributions.

Comparison between Alternative Methods for Estimating Vehicle Class Distribution Input to Pavement Design

The recently developed mechanistic-empirical pavement design guide (M-E PDG) represents a significant improvement over the AASHTO design guide. One of the major improvements to the M-E PDG is traffic characterization. The M-E PDG does not use the equivalent single axle load (ESAL) approach that is employed in the AASHTO design guide. Instead, it follows a more rational approach that is based on describing traffic in terms of number of axles by axle type and axle load distributions. In recent years, several research studies have been conducted to evaluate the sensitivity of the M-E PDG to the required traffic inputs. It was determined that vehicle class distribution (VCD) has a significant influence on the design of pavement structures. This study investigated various methods for estimating the VCD factors based on functional classification (FC), truck traffic classification (TTC), cluster analysis, and short-term counts. An extensive traffic monitoring data set that included information from 143 permanent traffic monitoring sites, composed of 93 automated vehicle classifier (AVC) and 50 weigh-in-motion (WIM) sites distributed throughout the state of Ohio, was used to evaluate these methods. A sensitivity analysis was also conducted to determine the effect of these methods on the predicted pavement service life. It was found that the functional classification, M-E PDG TTC grouping system and cluster analysis methods may significantly underestimate or overestimate the predicted pavement service life, whereas the short-term count method produces small variations in the predicted pavement service life. This suggests that the short-term count method is the most accurate method for estimating the VCD factors to be used in pavement design.

Influence of Heavy Axle Load on Dynamic Response of Semi-Rigid Base of Asphalt Pavement

In order to study the dynamic response law of semi-rigid base of asphalt pavement under heavy load traffic, the viscoelastic system model under heavy load was established based on measured loading pattern and axle load distribution with the finite element software ANSYS12.0. Heavy load traffic effect on the dynamic response of semi-rigid base of asphalt pavement was discussed . The results show that semi-rigid asphalt pavement structure dynamic response value changed with the increase of axle load; time varying regularity of stress and strain was not the same in different directions.