Axle Configurations Research Articles

Use of Finite Element Analysis and Fatigue Failure Model to Estimate Costs of Pavement Damage Caused by Heavy Vehicles

The transportation of heavy loads potentially causes more damage to pavements than regular vehicle traffic. This study investigated the impact of heavy vehicles on asphalt pavement to optimize axle configurations, select routes, and estimate permit costs. Finite element analysis, validated by field measurement, was used to evaluate pavement responses under various heavy load scenarios. From the results, the remaining pavement service life was predicted with the use of pavement distress models. The permit cost for a single pass of a heavy vehicle was estimated from the reduction of pavement fatigue life and associated pavement maintenance cost. Sensitivity analyses were conducted to determine factors affecting pavement fatigue damage and permit costs. Field measurement indicated that a significant longitudinal pavement defection occurred under the heavy vehicle. The results from finite element analysis showed a significant overlapping effect between multiple axles over the depth. Pavement defection was caused mainly by the deformation within subgrade soil. Generally, pavements with high thickness and stiffness would incur less damage and lower permit cost. A pavement structure with deep bedrock would incur more damage and higher cost. Because of the temperature dependency of asphalt mixtures, the damage cost in winter was much less than that in summer, even considering the potential weak subgrade during the spring thaw. It was also found that newly constructed pavements would incur higher permit cost than relatively older pavements. To reduce potential pavement damage and the associated cost effectively, the number of dollies and axle distance should be increased to spread the load to a larger area.

Fatigue life prediction of an asphalt pavement subjected to multiple axle loadings with viscoelastic FEM

A model for determining bituminous pavement degradation due to multiple-axle moving traffic loads is presented. The developmental work has been based on a viscoelastic finite element method (FEM) dedicated to bituminous pavements subjected to multiple-axle traffic loads, through reliance on the following variables: pavement structure, load speed, load configuration, and bituminous material temperature. The Load Equivalent Factor (LEF) relative to various axle configurations is approximately proportional to the number of axles within a given axle group. For flexible pavements, the fatigue life predictions using the Homsi model exceed the other two models (i.e. the French standard fatigue law, developed by LCPC–SETRA [7], and the interface fatigue law developed by Diakhaté et al. [31]). Results obtained indicate that the design concept based on bending fatigue in bituminous layers is insufficient to realistically predict the degradation of a bituminous pavement structure. The phenomenon of shear at bituminous interfaces must also be taken into account, as revealed by simulation results for the degradation of two pavement structures from the French design code [8] (i.e. flexible pavement and thick asphalt pavement). For the thick asphalt pavement structure, the main damage mode is of the “bottom-up cracking” type, whereas “interface cracking” damage is typically displayed for flexible pavements. Even before determining life expectancy by means of fatigue models, the LEF clearly indicates in every pavement structure the spot where degradation was most severe (at either the interface or bottom of asphalt layers).

Framework for Determining Load Equivalencies with DARWin-ME

This paper presents a methodology for use of mechanistic–empirical design procedures to determine load equivalencies for various axle configurations and loads with a focus on oversize and overweight vehicles. The study uses the DARWin-ME system for pavement analysis and computation of equivalent damage factors (EDFs). In the context of the study, the EDFs for a given axle load and configuration consist of two partial factors: the axle load factor and the group equivalency factor. The framework adopted in this study defines a given axle load and configuration equivalent to a reference axle load based on equivalent pavement responses that results in the same distress level. The EDFs for single, tandem, tridem, and quad axles were evaluated for a wide spectrum of varying loads, and three failure criteria were applied: rutting, fatigue cracking, and roughness. Except in the case of rutting, there was no evidence that EDFs are affected by the structural capacity of the pavement sections. For single axles, it was found that thicker pavement structures are less sensitive to traffic loads. For tandem, tridem, and quad axles, the relationship was nonmonotonic. For fatigue cracking, a linear relationship between the axle load factor and the number of axles per axle group was observed. Finally, for roughness, the EDFs showed no systematic trend for the different structural numbers.

Kinematic model of three wheeled mobile robot

In this paper, the behavior of wheeled mobile robots (WMR) has been analyzed. These robots ride on a system of wheels and axles, some of which may be steerable or driven. For WMRs, there are many wheels and axle configuration that have been used. The present work outlined for five categories of WMRs. The ultimate objective of this paper is to investigate the complete description of the control theory of such robots and its maneuverability. Equations are modeled to describe the rigid body motions that arise from rolling trajectories based on the geometrical constraints of these wheels. Finally this analysis is applied to various three wheeled mobile robots. Key words: Wheeled mobile robot, kinematic analysis, degree of maneuverability.

Study of Load Spectra of the Jaozhou Bay Expressway Based on MEPDG

To study the traffic characteristic and axles load spectra of Jaozhou bay expressway, WIM data was collected, axle configuration and vehicles classification was determined. The characteristic of truck traffic monthly distribution and the truck hourly distribution was studied and axle load spectra for major tuck class groups were developed. The results show that there were more than 22 truck types running on the expressway, the peaks of truck traffic monthly distribution was in December and the rush hour of the hourly distribution was at noon. All major axles had a bimodal pattern of load spectra.

On the equivalent wheelbase of a three-axle vehicle

The steady-state handling properties of a rigid vehicle with a tandem rear axle configuration are developed. This work uses conventions resulting in a parsimonious characterisation of steady-state handling of such three-axle vehicles that is shown to be a simple extension of the well-known two-axle bicycle model. Specifically the concepts of understeer and wheelbase are developed for a three-axle vehicle, and shown to play the same role in characterising vehicle handling as they do in the well-known two-axle vehicle model. An equivalent wheelbase of a three-axle vehicle is expressed in terms of vehicle geometry and cornering stiffness of each axle. The model developed in this work is reconciled with previous models that make use of simplifying assumptions found in the literature.

Load Spectra Development for a Heavy Traffic Expressway

To study the traffic characteristic and axles load spectra of a heavy load expressway, WIM data was collected, axle configuration and vehicles classification was determined. The characteristic of truck traffic monthly distribution and the truck hourly distribution was studied and axle load spectra for major tuck types were developed. The results show that there were more than 30 truck types running on the expressway, the peaks of truck traffic monthly distribution was in April, September and December and the rush hour of the hourly distribution was at midnight. All major axles had a bimodal pattern of load spectra. The second peak of single axle was about 12 to 13 ton, tandem axle 14 to 22 ton and the tridem axle 28 to 32 ton. More than 50% of axles were overloading.

Evaluation of fatigue and rut damage prediction methods for asphalt concrete pavements subjected to multiple axle loads

The new Mechanistic–Empirical Pavement Design Guide (MEPDG) developed under NCHRP 1-37A does away with the American Association of State Highway and Transportation Officials-derived equivalent single axle load concept and calculates damage caused by various axle configurations directly. However, the calculation of pavement damage caused by multiple axles (tandem, tridem, etc.) is significantly affected by the summation method used to describe the response of the pavement due to the passage of a given axle type or truck configuration. In this paper, the results from different methods of accounting for the passage of a given axle group are compared using laboratory fatigue and rut data from repeated cyclic load tests. The evaluation criterion for these different summation methods was the degree of agreement with the measured laboratory performance. The results show that for fatigue damage, dissipated energy and strain area methods have an excellent agreement with the laboratory values, whereas peak and peak mid-way methods have poor agreement. This implies that it is important to consider the entire strain pulse when calculating fatigue damage under multiple axles. For rutting damage, the peak strain method has the best agreement with the laboratory values, whereas dissipated energy and peak mid-way methods underestimate the rutting damage. Finally, the MEPDG procedure for calculating the strain under multiple axles considerably underestimates the damage for both fatigue and rutting. However, model calibration in the MEPDG does improve the prediction of the damage due to multiple axles for fatigue and to a lesser extent for rutting.

Evaluation of Nonintrusive Technologies for Traffic Detection, Phase 3

The third phase of the project on evaluation of nonintrusive technologies for traffic detection is a pooled-fund study in which field tests of selected nonintrusive sensors were conducted to determine their accuracy for volume, speed, and classification by length and by axle configuration. Sensors were evaluated in a variety of traffic and environmental conditions at two freeway test sites, with additional tests performed at both signalized and unsignalized intersections. Emphasis was placed on urban traffic conditions, such as heavy congestion, and varying weather and lighting conditions. Although previous tests evaluated sensors’ volume and speed accuracy, the current generation of nonintrusive sensors introduces robust classification capabilities. New technologies, such as ground-mounted laser sensors and improved radar, contribute to this improved performance. Overall, the sensors performed better than their counterparts in previous phases of research for volume and speed accuracy. However, the additional classification capabilities had mixed results. The length-based sensors were generally able to report vehicle lengths within their tolerances, and the axle-based sensors provided accurate interaxle measurements, but significant errors were found in relating these data with a standardized classification scheme, such as FHWA's 13-class scheme. Agencies must perform independent analysis of their classification schemes to determine whether nonintrusive sensors will provide acceptable results.

Development of Traffic Inputs for Mechanistic–Empirical Pavement Design Guide in Michigan

Characterizing traffic and developing accurate and desirable traffic inputs for the new Mechanistic–Empirical Pavement Design Guide (MEPDG) are critical but challenging activities. The purpose of this study was to develop a process for characterizing traffic inputs in support of the new MEPDG for the state of Michigan. These traffic characteristics include monthly distribution factors, hourly distribution factors, truck traffic classifications, axle groups per vehicle, and axle load distributions for different axle configurations. Axle weight and vehicle classification data were obtained from 44 weigh-in-motion and classification stations located throughout the state of Michigan to develop Level 1 (site-specific) traffic inputs. Cluster analyses were conducted to group sites with similar characteristics for development of Level 2 (regional) inputs. Finally, data from all sites were averaged to establish the statewide Level 3 inputs. The effects of the developed hierarchical traffic inputs on the predicted performance of rigid pavements were investigated with the MEPDG models. An algorithm based on discriminant analysis was developed to acquire the appropriate Level 2 traffic characteristic inputs for pavement design. For pavement analysis and design, it is recognized that site-specific data should be used wherever available. For projects in which site-specific data are not available, it is necessary to know whether Level 2 or Level 3 data are acceptable at a minimum for design. The MEPDG was used to investigate the impact of traffic input levels on predicted pavement performance for rigid pavements. The results of the analysis showed that for pavement design in Michigan, statewide averages should be used instead of MEPDG Level 3 data.

Data Collection Methodology for Container Truck Traffic in Inland Port Cities

This paper describes a data collection methodology to address insufficient data sources for estimation of urban container truck traffic (drayage) volumes. The methodology is sensitive to the characteristics of drayage and offers a systematic approach for acquiring container truck traffic data for constructing models to estimate drayage volumes. The methodology consists of (a) acquiring urban truck traffic estimates and national and provincial- or state-level container traffic databases, (b) characterizing shippers and carriers through field investigations and surveys, and (c) designing a container truck data collection program. Short-term manual truck classification intersection turning movement counts were conducted to obtain body style and axle configuration data for articulated trucks. Temporal expansion factors were developed and applied to short-term count data to produce average daily container truck traffic volume estimates and reveal temporal, physical, and spatial distribution differences between container trucks and other articulated trucks. The paper provides a rationale for selecting count station locations and their temporal characteristics, choosing the number of counts and their duration, determining the types of data to collect, and identifying container generators. The methodology is generally applicable to North American inland port cities. The data feed a model that is intended to assist transportation engineers in understanding urban drayage operations and quantifying the exposure of these trucks.

Direct Measurement of the Impact of Heavy Loads on Thin Membrane Pavements

This paper presents the results of a field study of the loads imposed by heavy oilfield cranes (with hydraulic suspensions and super single tires) on thin membrane asphalt pavements in Alberta, Canada. Three 150-m test road sections (thin asphalt wearing course, bituminous surface treatment, and granular surface) were built and instrumented for strain at the bottom of the asphalt layer, surface deflection, and subgrade pressures. Temperature and moisture profiles were also measured. Field testing involved controlled speed experiments of standard axle configurations and heavy-axle (12,000-kg) vehicles with and without hydraulic suspensions. Focusing on the hot-mix asphalt section, this paper presents a description of the test road design, instrumentation, and testing plan, followed by some results and findings from two seasons (spring and fall 2005) of testing. Vertical stress in the subgrade, longitudinal interfacial strain, and surface deflection are compared for three vehicle types used in the test. Results from tests show that subgrade stress and interfacial strain are very similar for the standard axle configuration during spring compared with those of the cranes without the dolly during the fall season. It could be argued that on the basis of the pavement response, the cranes could operate during the winter season without the dolly (and thereby increase road safety by removing a long combination vehicle from the traffic stream) without causing substantial long-term deterioration.

Process to Estimate Permit Costs for Movement of Heavy Trucks on Flexible Pavements

A process based on a mechanistic–empirical (ME) analysis was developed to estimate permit fees on the basis of truck-axle loading and configuration as well as the predicted pavement deterioration that they cause. The process was implemented in a software package, Integrated Pavement Damage Analyzer (IntPave). IntPave is a finite element–based program that calculates pavement responses, uses ME distress models to predict performance under any type of traffic load, is capable of comparing the level of distress caused by a heavy truck relative to a standard truck, and accordingly provides a permit fee. On the basis of a parametric study, it was found that, aside from the truck gross vehicle weight and axle configuration, pavement structure and the damage threshold to rehabilitation also heavily affect the permit fee.

Characterization and Development of Truck Axle Load Spectra for Implementation of New Pavement Design Practices in Louisiana

This study addresses the traffic data needs and requirements associated with the adoption of the Mechanistic–Empirical Pavement Design Guide in Louisiana. The objective of the study is to develop the truck axle load spectra from existing data and to identify possible improvements in data collection techniques. Data collected from portable weigh in motion (WIM) sites were screened by using data validation tests and were used to develop axle load spectra for different axle configurations (single, tandem, and tridem) of the primary vehicle class. A significant variation in vehicle class distributions was observed for the same roadway functional classification, and therefore an alternative grouping method based on the truck traffic classification (TTC) procedure was recommended. The results showed that Class 9 was the dominant vehicle class for single axle loads at most of the portable WIM sites located on Interstates and principal arterials. The majority of tandem axles in TTC groups appeared to belong to Class 9, whereas the majority of tridem axles in TTC groups appeared to belong to Class 10. For single axle load spectra, the developed spectra were very similar to the default values, except for TTC 5. For both tandem and tridem axle load spectra, the developed spectra appeared to differ significantly from the default values. It was strongly recommended that traffic data from portable WIM stations be collected for a longer monitoring period and that calibration be done more frequently. Another strong recommendation was to develop a strategic plan for installing permanent WIM sites and tap into axle load data from existing weight enforcement sites to supplement the data collected by portable WIM sites.

Lessons learned about the impacts of size and weight regulations on the articulated truck fleet in the Canadian prairie region

Three highway engineering policies directed at improving truck productivity by increasing size and weight limits have been implemented in the Canadian prairie region within the last 35 years: the 1974 Western Canada Highway Strengthening Program, the 1988 Roads and Transportation Association of Canada Memorandum of Understanding on Heavy Vehicle Weights and Dimensions, and special permitting of longer combination vehicles. As policies change, the trucking industry adjusts its fleets to take advantage of available efficiencies. Evidence of these changes and the lessons learned from the adoption of these policies are provided. Ultimately, as a result of these policies, articulated trucks now carry heavier and larger payloads, have different axle configurations, and have higher axle weight limits than they did 35 years ago. The threefold to fivefold increase in articulated truck volumes that occurred during this period would have been more dramatic had these policies not been implemented. Further research is necessary to understand the interactions among policies, vehicles, and infrastructure.

Analysis of Load Pulse Durations for Marquette Interchange Instrumentation Project

The loading frequency is an important input for determining the stiffness of asphalt materials on the basis of their dynamic modulus data. This stiffness relationship is used in the Mechanistic–Empirical Pavement Design Guide (MEPDG) to calculate a pavement's structural response to loading. This response—typically maximum horizontal strain and vertical pressure—is then used to estimate the number of load repetitions to failure. The Marquette Interchange Perpetual Pavement Instrumentation Project is a research effort carried out by the Transportation Research Center at Marquette University. The project implemented different pavement sensors to provide researchers with a complete set of pavement response data for calibration of local design variables and to provide insight into the structural behavior of a perpetual pavement opened to live urban freeway traffic. An analysis of the strain and pressure data recorded from the project was conducted to measure the length of strain and pressure pulse durations. The load pulse durations for each axle were then analyzed and compared with models contained in the MEPDG software. The analysis showed that the models may broadly fit actual load durations, but the surrounding assumptions may not be adequate for all axle and load configurations.

A Laboratory Investigation of the Effect of Multiple Axle and Truck Configurations on HMA Mixture Rutting

ABSTRACT Few studies have investigated pavement damage resulting from different axle and truck configurations, and they were generally limited to single and tandem axles. The unconfined compression cyclic load test with loading cycles that simulate different axle and truck configurations was used to examine their relative effect on permanent deformation of an asphalt mixture. The laboratory investigation indicates that the rutting damage due to different axle configurations is approximately proportional to the number of axles. However, the effect of rest period between axles groups within a truck configuration is significant. Calculating truck rutting damage by simply summing the vertical permanent deformation corresponding to its constituent axle groups results in erroneous predictions. The application of Miner's rule results in improved truck rutting damage predictions for a wider range of truck configurations, although it does not account for the effect of rest periods within a truck configuration. Fin...

A Laboratory Investigation of the Effect of Multiple Axle and Truck Configurations on HMA Mixture Rutting

ABSTRACT Few studies have investigated pavement damage resulting from different axle and truck configurations, and they were generally limited to single and tandem axles. The unconfined compression cyclic load test with loading cycles that simulate different axle and truck configurations was used to examine their relative effect on permanent deformation of an asphalt mixture. The laboratory investigation indicates that the rutting damage due to different axle configurations is approximately proportional to the number of axles. However, the effect of rest period between axles groups within a truck configuration is significant. Calculating truck rutting damage by simply summing the vertical permanent deformation corresponding to its constituent axle groups results in erroneous predictions. The application of Miner's rule results in improved truck rutting damage predictions for a wider range of truck configurations, although it does not account for the effect of rest periods within a truck configuration. Finally, unique HMA rutting damage curves, which can be used for any axle or truck configuration, were developed using strain and energy response parameters.

Relating Axle Load Spectra to Truck Gross Vehicle Weights and Volumes

Axle load spectra have been used to develop the mechanistic-empirical pavement design guide (M-E PDG). Use of these load spectra provides a more direct and rational approach for the analysis and design of pavement structures to estimate the effects of actual traffic on pavement response and distress. However, the demand for specific truck- and axle load-related data makes the collection of axle load spectra a very complicated, costly, and labor-intensive operation. Due to limited resources available in state and local highway agencies for traffic data collection, the M-E PDG allows for various levels of traffic data collection and analysis. These levels vary from site-specific (Level 1) to regional average (Level 3) traffic load and volume data. This paper explores the possibility of extracting axle loads from truck weight and volume data and presents a practical method of modeling axle load spectra. Axle load-related data used in the analyses cover diversified geographical locations in the United States. The results show that truck weights and proportions on a highway can be used to estimate individual axle load spectra for various axle configurations. The practical implication of these results is that truck weights, which can be measured easily or estimated from existing data, can be related to the axle loads if accurate and rational models are developed for a region based on the local truck traffic characteristics and weights. Such estimates will be superior to assuming a Level 3 input for axle load spectra in the new M-E PDG.

Impact of tridem and trunnion axle groups on premature damage of pavement infrastructure

To make appropriate decisions on overload limits of various axle configurations that can be endorsed for routine permitting, highway agencies need to understand the impact of these axle groups in terms of pavement infrastructure damage. This paper examines the relative damage to pavements induced by tridem and trunnion axle groups. The analysis was conducted with typical structures of both flexible and rigid pavements by first analyzing the mechanistic responses of pavements to tridem and trunnion axle groups. Then the mechanistic responses were used as the input to performance-based fatigue models to quantify the relative accumulative damage to the pavements. The use of the performance-based fatigue models ensured that all types of damage (such as rutting and cracking) induced by the axle groups were taken into consideration. Based on the analysis results, it was found that for flexible pavements, tridem axle groups are more damaging than trunnion axle groups, whereas for rigid pavements, trunnion axle groups are more damaging than tridem axle groups.Key words: trunnion, tridem, load equivalency, pavement damage.