Concern in fuel conservation and carbon foot print reduction has generated a special interest in ... more Concern in fuel conservation and carbon foot print reduction has generated a special interest in the mechanics of vehicle pneumatic tires rolling resistance. It is well known that rolling resistance between vehicle tires and pavement surface is one of the major loss mechanisms of the vehicle’s generated power. The primary aim of this paper is to evaluate the contribution of the pavement’s structural characteristics to rolling resistance. Several studies have focused on determining the vehicle rolling resistance primarily based on vehicle interaction with the pavement surface without quantifying the effect of pavement deflections on this parameter. This study focuses on isolating the pavement deflection component to quantify its influence on the rolling resistance. In order to achieve this goal, several thousand Falling Weight Deflectometer (FWD) test points were evaluated. A total of nineteen projects across the US were selected for this evaluation. Those projects included pavements...
Publication of: Svenska Vaegfoereningen Foerlags AB, 1981
The effects of natural and constructed irregularities of pavements have been simulated on a micro... more The effects of natural and constructed irregularities of pavements have been simulated on a micro computer, and in some cases the results of the computer model have been verified through full scale experiments. The main findings of the simulations were that: (1) the effect of speed reducing "bumps" is much dependent on the geometry of the bump, in some cases a bump may have the adverse effect of that intended; (2) longitudinal irregularities of pavement surfaces have a very limited effect on the energy consumption. Improving the pavement smoothness through maintenance will therefore not appreciably decrease the petrol consumption; (3) from safety point of view the minimum permissible psi (present serviceability index) for motorways should be increased to 3,0-3,5 to ensure that the vibrations do not decrease the proficiency of the driver. On some city streets it could be decreased to 1,5, and (4) the dynamic effect of a tandem axle may increase the static load by up to 40%. The use of computer simulation may quickly and cheaply provide answers to complex problems where practical testing would be expensive and time consuming. Computer simulation, however, should not be seen as a substitute for practical experiments, but rather as a means of extrapolating from the results of a limited number of practical experiments. (Author/TRRL)
... traffic loadings has been verified through full scale experiments and the allowable stresses ... more ... traffic loadings has been verified through full scale experiments and the allowable stresses and strains is based on laboratory tests and the results of the WASHO and AASHO Road Tests, modified in accordance with the experience gained from Danish road design during the ...
This paper describes the Dynatest pavement maintenance management system (DMS). The system is bas... more This paper describes the Dynatest pavement maintenance management system (DMS). The system is based on the analytical methods of pavement evaluation and overlay design that were developed in Denmark during the last two decades, and which form part of the Danish standards for pavement construction and maintenance laid down by the Danish Ministry of Transport, the Road Directorate. The DMS comprises an effect/cost analysis and an economics optimization procedure, which makes possible the determination of the optimum combination of maintenance measures for each of the coming 3-5 years within the given budget restraints. It is also possible to calculate which consequences changes to the budget will have for the maintenance standard of the road network. Results from two Danish counties are presented. (Author/TRRL)
A major research project has been conducted at the University of California Pavement Research Cen... more A major research project has been conducted at the University of California Pavement Research Center (UCPRC) to evaluate the performances of several AC overlays that contained asphalt rubber binder. This paper presents the analysis with respect to reflection cracking using a recursive mechanistic-empirical analysis procedure, known as CalME. For reflection cracking a simple model for calculating the strain in the overlay over an existing crack is presented. The fatigue properties required by the procedure for different AC mixes were determined from laboratory test data. The analysis procedure was validated by simulating full-scale pavement testing using the Heavy Vehicle Simulator (HVS). The results of the HVS tests were imported to the CalME database and the simulations were done in increments of one hour. Most HVS tests show a considerable increase in deflections during the test, due to damage of the pavement layers. This implies that other response parameters, such as stresses and strains, also change considerably during the test. As these response parameters are used in the empirical relationships to predict pavement performance, it is very important that correct values are used at any point in time during the simulation. Care was taken to ensure that the simulations with CalME would produce response values (deflections in this case) that were reasonably close to the measured responses. The predicted changes in the moduli of the overlays and the relationship between predicted damage and observed cracking indicate that recursive mechanistic-empirical approach with the reflection cracking model worked satisfactory.
The first step in structural evaluation of pavements (when using the analytical-empirical approac... more The first step in structural evaluation of pavements (when using the analytical-empirical approach) is the determination of layer thicknesses, moduli, and types of materials. Based on this the structural performance is normally predicted by calculating the number of loads to cause a certain amount and severity of cracking. Most procedures do not predict the changes in the structural condition, i.e. in the layer moduli. This paper presents two methods of calculating the damage, one based on the actual stress, i.e. the stress in the intact part of the cross sectional area, and another based on the peak internal energy. With both methods the changes in moduli and the fatigue life may be calculated for either controlled stress or controlled strain testing.
Workshop Session 10 was presented as a court case. First, two different opinions were stated by t... more Workshop Session 10 was presented as a court case. First, two different opinions were stated by the workshop coleaders: (a) user costs should be quantified in monetary value, even if they involve a number of political decisions, and (b) because uncertainties are too large and can lead to improper decisions, rather than quantifying user costs in monetary value, the impact on users should be considered, using more stable parameters. The audience was formed into juries, each electing a spokesperson, and each jury was asked to give a verdict for or against quantifying user costs in monetary terms. If consensus could not be reached, the juries were asked to cast a vote. In addition, they were asked to jot down their main arguments and present them to the other juries during the last part of the workshop. The overall conclusion of the workshop was that there is a great deal of willingness to include user costs in decision making, but current user cost models are unrealistic or incomplete.
The program described in this paper is an attempt at formulating a pavement model capable of pred... more The program described in this paper is an attempt at formulating a pavement model capable of predicting the functional as well as the structural performance of flexible pavements. The performance is described in terms of a Present Serviceability Index composed of slope variance, rutting, and cracking, and is determined as a function of loads and climatic variations. With the program, the functional and structural performance of a road structure may be followed as a function of range of parameters, such as traffic loading, climate, material characteristics, and as a function of variation of material characteristics.
At the Fifth International Conference a paper was presented by Ullidtz & Peattie, outlining how t... more At the Fifth International Conference a paper was presented by Ullidtz & Peattie, outlining how the analytical-empirical method could be used for performance prediction in a Pavement Management System (PMS). This paper presents the development that has taken place since then and that has resulted in a full PMS presently being used for more than 5,000 km of highways in Europe. An essential part of this system is still the analytical-empirical model for performance prediction. This model and some attempts at verification and improvements are described in some detail in a companion paper for this conference. This paper describes the basic elements of the PMS, consisting of: 1) Input data (functional, structural, constraints); 2) Data base ("point" and "section" data bases); 3) Data analysis (spreadsheet reports, benefit/cost, optimization); 4) Output data (predicted future condition, optimum budget); and 5) Implementation (examples of feed back). The system can be o...
In the Canadian context, climatic factors are a major cause of pavement deterioration. Temperatur... more In the Canadian context, climatic factors are a major cause of pavement deterioration. Temperature, frost and thaw action as well as moisture are factors that can cause certain types of pavement deterioration. These factors can also intensify pavement deterioration caused by heavy vehicles. Good estimates of the proportion of damage that can be attributed to climatic factors relative to those caused by heavy vehicles is required to conduct cost allocation studies. This paper describes a study done in Canada in order to assess damage ratios for different classes of road and environmental conditions prevailing in the country. Several studies were first reviewed and synthesized to obtain a preliminary set of ratios and to document methodologies used. A study was then conducted based on existing test sections available across the country. The actual condition of the section was used to compute a condition index including the combined effect of climate and traffic. Climatic effects were ...
Vehicle-pavement interaction was studied using the Mathematical Model of Pavement Performance (MM... more Vehicle-pavement interaction was studied using the Mathematical Model of Pavement Performance (MMOPP). With MMOPP a length of flexible road is first generated on the computer. Values of layer thicknesses, elastic moduli, plastic parameters, and so forth are generated at points spaced 0.3 m apart in such a way that the pattern of variation is similar to that observed on real pavements. The pavement is then loaded using a quarter car model, and the dynamic load is calculated at each point. The permanent deformation of each layer and the structural deterioration of the asphalt layer resulting from the loads are likewise calculated for each point. The next time increment is then considered, changing the materials characteristics in accordance with climatic changes, applying the loads of that increment, and so on. MMOPP was used on two sections from the AASHO Road Test. The traffic was extended to 20 years, and the effects of varying vehicle characteristics such as spring constant of the...
The maintenance costs of roads in the less developed countries are rapidly increasing, and indeed... more The maintenance costs of roads in the less developed countries are rapidly increasing, and indeed in many countries they have even surpassed the costs of new road construction. It is therefore very important that decisions on maintenance and rehabilitation measures are based on the best possible information on the condition of the pavements, so that scarce resources are not wasted. A very important aspect of pavement evaluation is the determination of its structural capacity (or bearing capacity). Objective evaluation of the structural capacity of pavements is the subject of this paper; equally important aspects, such as for example deterioration which results from the oxidation and age-hardening of bitumen, can, on the other hand, only be subjectively evaluated by an experienced engineer. This paper describes how analytically-based methods of pavement evaluation and overlay design may be used in the less developed countries, instead of the currently used empirical methods; the latt...
The analytical-empirical method of structural pavement evaluation is being more and more widely u... more The analytical-empirical method of structural pavement evaluation is being more and more widely used all over the world. The method has some important advantages over the existing, purely empirical methods. The paper describes a falling weight deflectometer equipment and the related software, which was recently introduced into Australia. With this system it is possible to non-destructively measure the elastic modulus of each layer in a pavement structure, through in situ testing, and thus to determine residual life and needed overlay thickness through the analytical- empirical method. The system has been used on a number of projects in New South Wales and some interesting results from an experimental road section are presented. The results show how insufficient layer thicknesses influence the moduli of both asphalt and fine crushed rock and also show a very pronounced variation in subgrade modulus within a rather short length of test pavements. Residual lives are calculated for the ...
Concern in fuel conservation and carbon foot print reduction has generated a special interest in ... more Concern in fuel conservation and carbon foot print reduction has generated a special interest in the mechanics of vehicle pneumatic tires rolling resistance. It is well known that rolling resistance between vehicle tires and pavement surface is one of the major loss mechanisms of the vehicle’s generated power. The primary aim of this paper is to evaluate the contribution of the pavement’s structural characteristics to rolling resistance. Several studies have focused on determining the vehicle rolling resistance primarily based on vehicle interaction with the pavement surface without quantifying the effect of pavement deflections on this parameter. This study focuses on isolating the pavement deflection component to quantify its influence on the rolling resistance. In order to achieve this goal, several thousand Falling Weight Deflectometer (FWD) test points were evaluated. A total of nineteen projects across the US were selected for this evaluation. Those projects included pavements...
Publication of: Svenska Vaegfoereningen Foerlags AB, 1981
The effects of natural and constructed irregularities of pavements have been simulated on a micro... more The effects of natural and constructed irregularities of pavements have been simulated on a micro computer, and in some cases the results of the computer model have been verified through full scale experiments. The main findings of the simulations were that: (1) the effect of speed reducing "bumps" is much dependent on the geometry of the bump, in some cases a bump may have the adverse effect of that intended; (2) longitudinal irregularities of pavement surfaces have a very limited effect on the energy consumption. Improving the pavement smoothness through maintenance will therefore not appreciably decrease the petrol consumption; (3) from safety point of view the minimum permissible psi (present serviceability index) for motorways should be increased to 3,0-3,5 to ensure that the vibrations do not decrease the proficiency of the driver. On some city streets it could be decreased to 1,5, and (4) the dynamic effect of a tandem axle may increase the static load by up to 40%. The use of computer simulation may quickly and cheaply provide answers to complex problems where practical testing would be expensive and time consuming. Computer simulation, however, should not be seen as a substitute for practical experiments, but rather as a means of extrapolating from the results of a limited number of practical experiments. (Author/TRRL)
... traffic loadings has been verified through full scale experiments and the allowable stresses ... more ... traffic loadings has been verified through full scale experiments and the allowable stresses and strains is based on laboratory tests and the results of the WASHO and AASHO Road Tests, modified in accordance with the experience gained from Danish road design during the ...
This paper describes the Dynatest pavement maintenance management system (DMS). The system is bas... more This paper describes the Dynatest pavement maintenance management system (DMS). The system is based on the analytical methods of pavement evaluation and overlay design that were developed in Denmark during the last two decades, and which form part of the Danish standards for pavement construction and maintenance laid down by the Danish Ministry of Transport, the Road Directorate. The DMS comprises an effect/cost analysis and an economics optimization procedure, which makes possible the determination of the optimum combination of maintenance measures for each of the coming 3-5 years within the given budget restraints. It is also possible to calculate which consequences changes to the budget will have for the maintenance standard of the road network. Results from two Danish counties are presented. (Author/TRRL)
A major research project has been conducted at the University of California Pavement Research Cen... more A major research project has been conducted at the University of California Pavement Research Center (UCPRC) to evaluate the performances of several AC overlays that contained asphalt rubber binder. This paper presents the analysis with respect to reflection cracking using a recursive mechanistic-empirical analysis procedure, known as CalME. For reflection cracking a simple model for calculating the strain in the overlay over an existing crack is presented. The fatigue properties required by the procedure for different AC mixes were determined from laboratory test data. The analysis procedure was validated by simulating full-scale pavement testing using the Heavy Vehicle Simulator (HVS). The results of the HVS tests were imported to the CalME database and the simulations were done in increments of one hour. Most HVS tests show a considerable increase in deflections during the test, due to damage of the pavement layers. This implies that other response parameters, such as stresses and strains, also change considerably during the test. As these response parameters are used in the empirical relationships to predict pavement performance, it is very important that correct values are used at any point in time during the simulation. Care was taken to ensure that the simulations with CalME would produce response values (deflections in this case) that were reasonably close to the measured responses. The predicted changes in the moduli of the overlays and the relationship between predicted damage and observed cracking indicate that recursive mechanistic-empirical approach with the reflection cracking model worked satisfactory.
The first step in structural evaluation of pavements (when using the analytical-empirical approac... more The first step in structural evaluation of pavements (when using the analytical-empirical approach) is the determination of layer thicknesses, moduli, and types of materials. Based on this the structural performance is normally predicted by calculating the number of loads to cause a certain amount and severity of cracking. Most procedures do not predict the changes in the structural condition, i.e. in the layer moduli. This paper presents two methods of calculating the damage, one based on the actual stress, i.e. the stress in the intact part of the cross sectional area, and another based on the peak internal energy. With both methods the changes in moduli and the fatigue life may be calculated for either controlled stress or controlled strain testing.
Workshop Session 10 was presented as a court case. First, two different opinions were stated by t... more Workshop Session 10 was presented as a court case. First, two different opinions were stated by the workshop coleaders: (a) user costs should be quantified in monetary value, even if they involve a number of political decisions, and (b) because uncertainties are too large and can lead to improper decisions, rather than quantifying user costs in monetary value, the impact on users should be considered, using more stable parameters. The audience was formed into juries, each electing a spokesperson, and each jury was asked to give a verdict for or against quantifying user costs in monetary terms. If consensus could not be reached, the juries were asked to cast a vote. In addition, they were asked to jot down their main arguments and present them to the other juries during the last part of the workshop. The overall conclusion of the workshop was that there is a great deal of willingness to include user costs in decision making, but current user cost models are unrealistic or incomplete.
The program described in this paper is an attempt at formulating a pavement model capable of pred... more The program described in this paper is an attempt at formulating a pavement model capable of predicting the functional as well as the structural performance of flexible pavements. The performance is described in terms of a Present Serviceability Index composed of slope variance, rutting, and cracking, and is determined as a function of loads and climatic variations. With the program, the functional and structural performance of a road structure may be followed as a function of range of parameters, such as traffic loading, climate, material characteristics, and as a function of variation of material characteristics.
At the Fifth International Conference a paper was presented by Ullidtz & Peattie, outlining how t... more At the Fifth International Conference a paper was presented by Ullidtz & Peattie, outlining how the analytical-empirical method could be used for performance prediction in a Pavement Management System (PMS). This paper presents the development that has taken place since then and that has resulted in a full PMS presently being used for more than 5,000 km of highways in Europe. An essential part of this system is still the analytical-empirical model for performance prediction. This model and some attempts at verification and improvements are described in some detail in a companion paper for this conference. This paper describes the basic elements of the PMS, consisting of: 1) Input data (functional, structural, constraints); 2) Data base ("point" and "section" data bases); 3) Data analysis (spreadsheet reports, benefit/cost, optimization); 4) Output data (predicted future condition, optimum budget); and 5) Implementation (examples of feed back). The system can be o...
In the Canadian context, climatic factors are a major cause of pavement deterioration. Temperatur... more In the Canadian context, climatic factors are a major cause of pavement deterioration. Temperature, frost and thaw action as well as moisture are factors that can cause certain types of pavement deterioration. These factors can also intensify pavement deterioration caused by heavy vehicles. Good estimates of the proportion of damage that can be attributed to climatic factors relative to those caused by heavy vehicles is required to conduct cost allocation studies. This paper describes a study done in Canada in order to assess damage ratios for different classes of road and environmental conditions prevailing in the country. Several studies were first reviewed and synthesized to obtain a preliminary set of ratios and to document methodologies used. A study was then conducted based on existing test sections available across the country. The actual condition of the section was used to compute a condition index including the combined effect of climate and traffic. Climatic effects were ...
Vehicle-pavement interaction was studied using the Mathematical Model of Pavement Performance (MM... more Vehicle-pavement interaction was studied using the Mathematical Model of Pavement Performance (MMOPP). With MMOPP a length of flexible road is first generated on the computer. Values of layer thicknesses, elastic moduli, plastic parameters, and so forth are generated at points spaced 0.3 m apart in such a way that the pattern of variation is similar to that observed on real pavements. The pavement is then loaded using a quarter car model, and the dynamic load is calculated at each point. The permanent deformation of each layer and the structural deterioration of the asphalt layer resulting from the loads are likewise calculated for each point. The next time increment is then considered, changing the materials characteristics in accordance with climatic changes, applying the loads of that increment, and so on. MMOPP was used on two sections from the AASHO Road Test. The traffic was extended to 20 years, and the effects of varying vehicle characteristics such as spring constant of the...
The maintenance costs of roads in the less developed countries are rapidly increasing, and indeed... more The maintenance costs of roads in the less developed countries are rapidly increasing, and indeed in many countries they have even surpassed the costs of new road construction. It is therefore very important that decisions on maintenance and rehabilitation measures are based on the best possible information on the condition of the pavements, so that scarce resources are not wasted. A very important aspect of pavement evaluation is the determination of its structural capacity (or bearing capacity). Objective evaluation of the structural capacity of pavements is the subject of this paper; equally important aspects, such as for example deterioration which results from the oxidation and age-hardening of bitumen, can, on the other hand, only be subjectively evaluated by an experienced engineer. This paper describes how analytically-based methods of pavement evaluation and overlay design may be used in the less developed countries, instead of the currently used empirical methods; the latt...
The analytical-empirical method of structural pavement evaluation is being more and more widely u... more The analytical-empirical method of structural pavement evaluation is being more and more widely used all over the world. The method has some important advantages over the existing, purely empirical methods. The paper describes a falling weight deflectometer equipment and the related software, which was recently introduced into Australia. With this system it is possible to non-destructively measure the elastic modulus of each layer in a pavement structure, through in situ testing, and thus to determine residual life and needed overlay thickness through the analytical- empirical method. The system has been used on a number of projects in New South Wales and some interesting results from an experimental road section are presented. The results show how insufficient layer thicknesses influence the moduli of both asphalt and fine crushed rock and also show a very pronounced variation in subgrade modulus within a rather short length of test pavements. Residual lives are calculated for the ...
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