Showing papers on "Axle load published in 1988"

System for measuring air pressure on drive axles of road tractor trailers and load distribution

Abstract: A system for measuring the load on drive axles of tractors of over the road semitrailers and for determining load distribution on the front and drive axles of the tractor and the rear axles of the trailer. A calibratable air pressure gauge, placed in the cab of the tractor or truck, senses the pressure exerted by the trailer load on conventional air bags used to cushion the load on the drive axles. Approximate weight load may be determined by reading the pressure gauge. The gauge may be variably calibrated to accommodate the progression of settings for the fifth wheel assembly placement on an adjustment rack. Besides use on semitrailers, the system may be employed on straight or box trucks and trailers provided with air bags to cushion the axle load.

Road damaging effects of dynamic axle loads

Abstract: The paper proposes several criteria and associated statistical analysis procedures for relating the dynamic wheel forces generated by heavy vehicles to road surface damage. The criteria are evaluated in the time domain, which requires both time histories of the dynamic forces generated by vehicle axles as well as the calculation of transient stresses and strains in road structure during the passage of a vehicle. The paper presents simulated wheel forces generated by the linked tandem axles of a semitrailer and provides an examination of the effects of vehicle speed and road roughness on road damage.

Analyses of moving dynamic loads on highway pavements: part i - vehicle responses

Abstract: The influence of heavy vehicle dynamics on flexible pavement response is investigated in this paper. Full non-linear models were used to describe the dynamic behavior of articulated vehicles traversing random flexible pavements in order to predict the forces at the road/tire interface. Both leaf spring and air bag suspensions are modeled. The paper provides a description of the mathematical representation of the dynamic vehicle-pavement interaction. Also discussed are the effects of varying various vehicle parameters on road damage calculated VESYS and using the modified Road Stress Factor. The parameters examined are suspension type, friction parameters, shock absorber damping, tire pressure, axle load sharing coefficients and suspension spring constants.

Low grade material axle shaft

Abstract: A new SAE 1541M alloy steel composition consisting essentially of 0.40-0.48% carbon, 1.35-1.61% maganese, 0.16-0.30% silicon, 0-0.23% chromium and the balance iron and other materials not affecting hardenability of the steel, especially adapted for forming axle shafts in the 1.70-2.05" diameter range to be used as drive axles with an axle load carrying capacity between 30,000 and 44,000 pounds.

The new zealand road charging system

Abstract: This paper discusses the road user charges act 1977, which became effective on 1 April 1978 and introduced a major reform of New Zealand road taxation. The scheme was set up to ensure that the operators of heavy vehicles paid for road infrastructure and maintenance costs and compete with rail on a realistic basis. As a result, most heavy vehicles, weighing over 3.5 tonnes gross and including passenger vehicles, have been required to pay licence fees rising sharply with the weight per axle and directly proportional to the distance travelled. Vehicles in the scheme have to be fitted with a 'hubodometer' to measure this distance. The author concludes that the charging procedure is sophisticated in design and application and that, although it has the potential to reflect accurately the economic cost of road use by different vehicle types, this potential has not been fully realised. A working party, set up in 1983 to consider possible improvements, failed to reach agreement on suitable draft recommendations. "however, the scheme is one method of approaching the problem of the taxation of heavy vehicles".

Load factor method for dynamic track loadings

Abstract: Design of track structural components and foundations is based upon design loads higher than the nominal static values. These design loads generally have been determined using dynamic impact factor...

Air suspension for vehicle with tandem axle

Abstract: A device is proposed for the pneumatically assisted suspension of a vehicle with a plurality of rear axles, of which at least one rear axle serves as drive axle and at least one further rear axle as non-driven axle, for example a lifting axle. In order to improve the traction in difficult driving situations, the bellows (1) of the drive axle in each load condition are subjected to the maximum possible load not exceeding the admissible load. Should the vehicle load exceed the maximum admissible axle load of the drive axle, the bellows (1) of the drive axle assume their maximum admissible load and the bellows (2) of the lifting axle assume the excess proportion of the vehicle load. According to the invention the control valves (14, 16), which undertake the axle load distribution, are connected so that they have to be actuated only in the event of a variation of the vehicle loading.

Trends in axle loading and their effect on design of road pavements

Abstract: The results of the continuing programme of monitoring using the TRRL weighscale, and the results of static axle weighing surveys, have been used to study trends in axle loading and their effect on the design of road pavements. The results have been analysed to show how the effect of commercial vehicles has changed with time and how it is related to vehicle type. There is particular emphasis on recent changes in regulations that have allowed higher gross weight vehicles and led to the appearance of considerable numbers of five axle articulated vehicles of 38 tonne gvw, and some six axle vehicles. The results of the analysis have been used to provide procedures for the estimation of the effect of commercial vehicles on the design and performance of road pavements for past, present and future years.

Rail testing: strategies for safe and economical rail quality assurance

Abstract: Current trends toward increased mainline traffic density, greater average axle load, and extension of wear life are expected to increase the rate at which metal fatigue defects form in rails. A decade of research on rail integrity has led to better understanding of how rail defects form and propagate. The research is discussed and examples are presented to show how the results can be used to provide guidelines for improving in-service inspection methods and schedules.

Slow speed "dynamic" axle weighers: effects of surface irregularities

Abstract: Enforcement officers check-weigh goods vehicles using slow speed ("dynamic") axle weighers. Each weigher consists of a weighbeam which is installed in a length of concrete (the "apron") laid to a precision of + or -3 mm and which measures the loads imposed by axles as they pass over it axle by axle at a speed of not more than 2.5 mile/h. TRRL has test-weighed goods vehicles on three axle weighers to determine how the precision of each apron's construction influenced the accuracy of weighing vehicles. This report describes the test results and their implications on the accuracy with which vehicles can be weighed. The verification procedure that is used to check a weigher's accuracy is discussed. (TRRL)

Vehicle brake installation.

Abstract: of EP02562831. Motor vehicle brake system having an antilocking device with electronic control unit (3) for monitoring the grip on the carriageway of the motor vehicle wheels and having a yawing moment reduction device (8) which, in the case of widely differing coefficients of friction, prevents too large a difference in braking pressure on the two sides of the motor vehicle, characterized in that the motor vehicle is provided with an axle load sensor (7) known per se, and in that the measure of the axle load can be evaluated in the electronic control unit (3) and fed to the yawing moment reduction device (8) as control variable.

Road loading as a function of vehicle characteristics

Abstract: The justification of recently legislated permissable European weight increases and tendencies is argued from the aspects of optimisation in benefits to the overall economy by reduction in cost, and optimisation in road loading effects through compensation by improved vehicle design. The assessment of the prevailing type of road loading by either effective or maximum value dynamic load amplitude is discussed, based on results of recent research. From examples of test results, the beneficial effects of damping of axle motion are demonstrated (a).

Axle weight measuring instrument

Abstract: PURPOSE:To measure the weight of each axle weight of a vehicle and also measure the weight of the vehicle by calculating the means value of axle loads of the same axle among respective axle load signals obtained when the vehicle is placed on a platform and removed. CONSTITUTION:Plural load detectors 14 are provided on the reverse surface of the platform 12 and the outputs of those load detectors 1 are summed up and supplied to an A/D converter 22. This A/D converter 22 receives a conversion command signal generated by a conversion command signal generator 23 at specific intervals of time, and digitizes and supplies the output signals of the respective load detectors 14 which are supplied currently to a CPU 24. The CPU 24 calculates the mean value of plural axle loads of the same axle obtained when the vehicle 2 is mounted on the platform and removed at least once and handles the mean value as each axle load signal. Consequently, not only the weight values of respective axles 3, 4, and 5 of the vehicle, but also the weight of the vehicle 2 itself can be measured.

Evaluation of flexible pavement performance from pavement structural response

Abstract: A model for predicting flexible pavement performance was developed from AASHO Road Test data. The pavement condition indicator selected for quantifying performance is pavement surface roughness, which correlated highly with pavement serviceability as perceived by the road user. In the development of the model, pavement performance was initially defined as the history of a pavement condition indicator(s) over time or with increasing axle load applications. Consequently, the performance model developed predicts the trend in pavement surface roughness with cumulative axle load applications. Since strain basins provide more information on the pavement response under load than just the maximum pavement response, indices determined from an evaluation of subgrade compressive and asphalt tensile strain basins were evaluated for their utility as performance predictors. The results obtained strongly indicate that strain basin indices are important predictors of the performance of AASHO flexible pavement sections.

Problems and effects of overloading on jordanian roads

Abstract: This article describes and discusses the results of studies on axle load and the Jordanian road system, and includes recommendations related to the overloading problem. Criteria for the choice of axle load limit are discussed. It is noted that ecoomic and political requirements encourage the use of higher loads; however, this would result in rapid pavement deterioration and early destruction of the road network. It is suggested that a solution could be the building of special road links that are adequately designed to carry the heavy traffic, thus relieving the remainder of the network of unnecessary loading. The road links would be paid for through a toll system. Regarding the existing network, a rigid weight control and law enforcement system must be applied, especially on busy truck routes.

Weight measuring method

Abstract: PURPOSE:To quickly execute the measurement with saving labor and time, by allowing a flange part of a wheel to run on a charge receiving part of a load cell provided on the side part of a running rail. CONSTITUTION:A flange part of a wheel is allowed to run on a charge receiving part 3 of load cells 1a-1d provided on the side part of a running rail 2. As a result, the wheel floats a little from the running rail 2, the wheel load is all applied to the charge receiving part 3 of the load cells 1a-1d, and the output signal of a level corresponding to the wheel load is generated from the load cells 1a-1d. Accordingly, the wheel load of the wheel which has run on its charge receiving part 3 is obtained directly from the output signal of the load cells 1a-1d. Subsequently, when the wheel load is obtained with regard to each wheel in the same way, the axle load and the total weight can be obtained by adding them.

Heavy vehicle suspension variations affecting road life --truck designers sprung? symposium on heavy vehicle suspension characterisitcs, proceedings, canberra, australia, march 23-25, 1987

Abstract: The Canadian weights and dimensions study has examined practical vehicle parameter variations with regard to their contribution to vehicle stability and control and road life. This paper presents one facet of the study that concentrated on an experimental study of the effects of suspension parameter variations on dynamic wheel loads. A prime mover and semi trailer were modified to form a representative test vehicle for the study. All load carrying axles were instrumented to provide continuous road loading data. Two prime mover tandem drive suspensions and three semi trailer tandem axle suspensions were studied. Variations in axle load, axle spacing and suspension pitch attitude were examined. Input variables included road roughness, speed and discrete bumps associated with grade level railway crossings and bridge approach irregularities. The influence of dynamic axle loads on flexible pavement deformation was also studied. The findings of this research will be presented in a manner so as to show the range of performance characteristics of the suspensions and will discuss suspension parameter variations with respect to improving road distress (a). For the abstract of the covering record of the symposium, see IRRD no 808884.

Flexible pavement design - the french practice

Abstract: French methods, using pavement courses stabilised with hydraulic binders, have been devised by experience and extensive research. Specifications are comprehensive and are stringent for aggregate materials to cater for an axle load of 130 kn. The choice of a continuous grading of sizes, generally less than 20 mm, is to obtain easily used materials to support the traffic without segregation. Strong and stable subbases are made from binding inert aggregate materials with cement, flyash or blast furnace slag. Examples are given of typical designs for different traffic loadings and subgrades. France has a large programme of road strengthening to meet the demands of high axle loadings. The structure will normally be made up of a base course of 250 mm to 280 mm of hydraulically bound materials with surfacing of 60 mm bituminous concrete. Guidelines have been produced based on four different levels of loading and the subgrade strength for new roads. Lime stabilisation of the subgrade is commonly used. Subgrade soils are classified into six classes based on grain size. (TRRL)

Method and device for measuring wheel load of running vehicle

Abstract: PURPOSE:To improve the measurement accuracy of weight of a vehicle by constituting the titled device so that the wheel load can be measured exactly, irrespective of the grounding width of a tire of a vehicle to be measured even when ground pressure of the tire is not distributed uniformly. CONSTITUTION:The vehicle weight is the total of each axle load, and this axle load can be derived by the total of each wheel load of right and left wheels. Therefore, a detector for detecting the distribution ground pressure of a tire of a vehicle to be measured is installed in a running path, and also, a speed measuring means for measuring a running speed of the wheel to be measured is installed in the vicinity of the detector. In such a state, extending from the time point when the tire of the vehicle to be measured has started to load on the detector for the most part, to the time point when it ends to descend for the most part, the linear component force in the width direction of the tire is measured by a time division at a prescribed time interval by the detector. Also, by adding and calculating each measured data thereof, a measured wheel load value is derived. On the other hand, the running speed of the vehicle to be measured is measured by the speed measuring means. By such a measured wheel load value by the measured data of the running speed, a true wheel load value is derived.

Procedures for controlling the effect of increased tire pressure on asphalt concrete pavement damage. final report

Abstract: As the axle load increases, higher tire pressures become more popular for long-haul truck operators. To collect data on tire pressures and the types of tires in use, a survey was carried out at a weigh station located on Interstate 5 in Oregon during the summer of 1986. Of the tires surveyed, 87% were of radial construction. The average measured pressures (hot) of the radial and bias tires were 102 psi and 82 psi, respectively. This study investigates the influence of increased tire pressures on the fatigue and rutting performance (in terms of vertical compressive stress, tensile strain, and compressive strain) of asphalt-surfaced pavements, through use of elastic layer analysis (ELSYM5), for two typical state highways in Oregon. This theoretical analysis shows that the effect of increased tire pressure on vertical compressive stress is significant in the asphalt wearing layer. As tire pressure increases, the maximum tensile strain at the bottom of the asphalt layer increases. Theoretical equivalency factors for the two asphalt pavements (SN=3.0 and 3.4) were developed using ELSYM5 to take into account tire pressures (80, 100, 125, and 150 psi) and number of tires per axle (2, 4, and 8 tires). A single axle with an 18-kip load, dual tires, and a tire pressure of 80 psi was used as a standard axle load and tire pressure. The results indicate that a 25% increase in tire pressure could result in a 40 to 60% increase in the equivalency factor for a dual-tired single axle with an 18-kip load or a tandem axle with a 34-kip load. In order to evaluate current asphalt concrete specifications and mix design criteria, aggregates from four different sources were tested. Two of the aggregates were treated with 1% lime slurry prior to testing. Six different aggregate gradations were tested. In general, the creep stiffness decreased proportionally to the percentage of fines passing the #200 sieve. Results show that treating the aggregates with 1% lime slurry improves the resistance to deformation of the asphalt concrete mixes.

Applications of state-of-the-art technology in vehicle data collection

Abstract: This paper discusses recent developments in the technology of vehicle load and traffic volume data collection and proposes methods for their application. Applications focus on innovative methods for calculating equivalent axle load (EAL) data. The first part of the study contains an example output of the state-of-the-art vehicle monitoring equipment. Typical output of weigh-in-motion scales (WIM), vehicle classifiers, and vehicle monitors are presented to demonstrate the potential of the new technology. In the second part of the study, WIM scale data covering a period of 1 year is analyzed to explore new methods for collecting EAL data. It is shown that, in terms of daily data, EAL repetitions correlate better with the volume of large vehicles (e.g., 5-axle semitrailer trucks) than with the total number of axle counts traditionally collected. Furthermore, the notion of using vehicle length to index broad vehicle classes is explored as a means of obtaining volume counts of the large vehicles. It is conclud...

Evaluation of increased pavement loading, volume I: research results and findings

Abstract: The effects of increased truck loads and higher tire pressures on performance of flexible pavements were investigated in this project. This Volume 1 report presents the research performed and the useful results obtained. Tire pressure studies were performed using both in field measurements and theoretical simulations of the effects of tire pressures on pavements. Higher tire pressures were found, in general, to reduce pavement life. A new mechanistic damage model was developed to allow the evaluation of the effects of loads and tire pressures on pavements. A new set of equivalence factors were developed using the damage models. The resulting equivalence factors were incorporated into a computer program to calculate 18 kip equivalent single axle loads. The programs also have the capability to use the AASHTO equivalence factors for the calculation as a basis for comparison. These programs were developed for both static truck weight measurements and weigh in motion measurements. A mechanistic pavement design program was also developed using the damage models in order to generate pavement designs that are compatible with the new mechanistic load equivalence factors. This volume is the first in a two volume set. Volume 2, provides documentation for all of the computer programs developed on the project (A).

The effect of the design of goods vehicle suspensions on loads on roads and bridges

Abstract: This paper examines the ways in which heavy goods vehicle suspensions apply unexpectedly large loads to road pavements. Roadside surveys show that for many multi axle bogies the axle loads are not equal, and tests with an instrumented semi trailer show that these inequalities persist with the vehicle in motion. Air suspensions show good equalisation. Goods vehicles in motion bounce continuously on the tyres and suspension; this can increase the loads applied to the road. Tests have shown that the pattern of loads along a length of the road during repeated runs at the same speed is rather consistent for a particular vehicle. Instruments in the road have shown that at a given speed the strains in the road structure are approximately proportional to the instantaneous load applied to the road by an axle. Tests of a semi trailer on alternate air and steel suspensions running over the same road profile have shown that on some parts of the road the air suspension produced smaller dynamic loads, but on other parts of the road the air suspension produced higher dynamic loads. The TRRL suspension research programme is described. It is seeking to identify what characteristics of goods vehicle suspensions minimise road loading (a).