Backcalculation of pavement layer parameters using artificial. Incremental layerwise finite element formulation for viscoelastic. Implementation of the bitumen performance grading system in estonia pouya teymourpour hussain u. In most existing pavement design methods, pavements are analyzed using linear elastic multilayer theory, with the assumption that isotropic conditions are present in the structural layers of the pavement section. Pdf a computational framework for viscoelastic analysis of flexible. Base on visco elastoplastic theory, using laplace transformation the asphalt pavement parameters of viscoelasticity model and visco elastoplastic model are converted into parameters of prony series, the rutting deformations of asphalt pavement are analyzed by using ansys, the influence of load, material temperature and loading cycles are considered. Influence of asphalt viscoelastic properties on flexible pavement performance. Calculation of the elastic moduli of a two layer pavement system from measured surface deflections by frank h. Implementation of the aashto pavement design procedures into. This report presents the results of a literature survey into design methods for asphaltic pavements, discussing.
So, it is very difficult to model the complete flexible pavement using traditional methods. Major impetus to more fundamentally based pavement design was provided by the heavy. The asphalt layer is considered either elastic or viscoelastic in each analysis. Visco elastic modelling for asphalt pavements software viscoroute. With these assumptions, only two material properties. There are various methods of flexible pavement design such as empirical and semiempirical methods. Viscoelastic approach enhanced analysis of falling.
In the rigid pavement design, thickness of the concrete slab is calculated for the various types of rigid pavements. On account of the viscoelastic ac, the theory of linear viscoelasticity is reformulated briefly from a. For example, the poissons ratio of viscoelastic materials is not constant. Hotmix asphalt is a viscoelastic material that is characterized by. Mechanisticempirical pavement design procedure for geosynthetically stabilized flexible pavements salman ahmed bhutta department of civil engineering virginia polytechnic institute and state university blacksburg, va 24060, 1998 abstract in june 1994, a 150mlong secondary road pavement section was built as part of the. Huetsayegh model 1963 gives a set of constitutive equations of a visco elastic material which accounts well for the behaviour of asphalt pavement layers, especially regarding thermal effects. For example, determination of elastic modulus e3 for asphalt base course at. In addition to providing an analytical approach to structural pavement design, chapter 54 presents an analytical method for selecting the most economical pavement design that can be expected to meet structural design requirements. The designer should take into account not only the cost of materials but also the. Therefore the complete viscoelastic behaviour of each asphalt pavement layers has to be taken into account. Rutting deformations analysis for asphalt pavement base on.
In that model, the huetsayegh behaviour is taken into account with its equivalent elastic modulus at the 15c french average temperature and a 10 hz frequency. Bahia tallinn, estonia university of wisconsinmadison feb 19, 2015. Pavement design tries to prevent the major distress such as permanent deformation. The french pavement design method consists in a pavement mechanistic analysis based on the burmister multilayer elastic model 1943 lcpc software alize 1982. Elastic theory methods assume that the pavement has adequate strength for the wheel load to be carried, and that the pavement surface after deflecting as a wheel of a vehicle moves over it, rebounds immediately. Mar 29, 20 in this study, predictions of fullscale micromechanical mm finite element fe models, developed from xray computed tomography images of asphalt concrete samples that were sawn from the accelerated pavement test sections, were used to evaluate the accuracy of layered elastic theory let models that are used in pavement design today. Hot mix asphalt is a viscoelastic material that is characterized by. Moore research report number 1236 a system analysis of pavement design and research implementation research study number 1869123 conducted in cooperation with the. Pdf influence of asphalt viscoelastic properties on. An empirical analysis of flexible pavement design can be done with or with out a soil strength test. Knowledge of the e master curve of an inservice pavement using fwd data can lead to a more accurate estimation of its remaining life and rehabilitation design. Burmister extended boussinesqs theory from a single layer to a multilayer elastic model 4. All this explains why the current design methods are classified as mechanistic empirical.
This modulus is a complex quantity and the absolute value of the. Layered elastic theory has been systemized and widely used for. Constitutive models of pavement asphaltic layers based on. It will be assumed that the materials are isotropic, homogeneous and linear elastic. Flexible pavement design by semiempirical method is discussed in this article. Thus based on correspondence principle in the theory of linear viscoelaticity we can replace e by. Investigation of layered elastic theory prediction accuracy. There are three mathematical processes hoffman and thompson, 1986 that have been adopted. I ran kenpave software for the linear elastic behavior no visco elastic and nonlinear case. The visco 1 introduction elastic properties of asphalt play a crucial role in pavement. Therefore, the elasticity assumption is valid only when the. Analytical modelling of visco elastic behaviour of hotmix asphalt j komba, j w maina, j k anochieboateng, and j oconnell csir built environment, building 2c, p o box 395, pretoria, 0001, south africa tel.
The mechanistic design of flexible pavement is usually done with linear elastic theory let. In this research, the linear visco elastic lve behavior of the existing asphalt mixes is analyzed. For example, incremental constitutive equations in conjunction. His research interests primarily concern mechanistic based pavement design. Design pamphlet for the backcalculation of insupport of the. Results of this analysis indicated that the elastic theory grossly underpredicts pavement responses to vehicular loading at intermediate and high temperatures. But to carry large loads multiple axles are provided. Some applications of the elastic theory approach to the.
A sensitivity analysis performed on various design parameters indicated that. Since the design of flexible pavements is by layered theory, only the wheels on one side needed to be considered. To illustrate an example, the viscoelastic surface deflections of the threelayer. Calculation of the elastic moduli by research report number 1236. The use of elasticity theory to model pavement structures is very common. Guide for mechanisticempirical design of new and rehabilitated pavement. In this paper, a step in this direction is taken by considering the asphalt concrete surface course as a viscoelastic plate on an elastic foundation. Finally, a new mechanisticempirical flexible pavement design method for pavements with and without geosynthetics has been developed. In addition, the elastic fe model could not simulate permanent deformation or delayed recovery. Therefore, the assumption of elasticity is valid only when the asphalt mixture. The 1993 version of aashto guide for design of pavement structures is the basis for developing the modules.
A sensitivity analysis performed on various design parameters indicated. Westergaard s theory and assumptions, stresses due to curling, stresses. Comparison of elastic and viscoelastic analysis of asphalt. It is shown that the stateof on classical layered elastic theory cf. The multilayered elastic theory is widely used to determine the tensile strain. Modulus of elasticity for existing pavement structures. Pavement analysis and design teaching and examination.
Mechanistic pavement design t u b r a u n s c h w e i g multilayer elastic theory layered elastic model elastic model boussinesq, 1885 layers extend infinitely in the horizontal direction. Department of transportation federal highway administration. Vehiclepavement interaction, visco elastic theory and assumptions, layered systems concepts, stress solutions for one, two and three layered systems, fundamental design concepts. The fundamental basis for me pavement design could arguably go all the way back to boussinesq elastic theory, but the more modern basis could well be attributed to burmisters solutions for two and three layer elastic systems responses to loads 3.
Viscoelastic modeling and field validation of flexible pavements. Burmister introduced the use of the multilayer elastic theory to analyse pavement structures. This is one of the way of explaining the stressstrain relationship of viscoelastic materials. Results of this analysis indicated that the elastic theory grossly.
Usually, however, linear elastic is the theory of choice in practice, with some exceptions. After that, the boussinesq model has been improved by the work of burmister 1945. But the design methodology has taken rapid strides towards rationality in the past few decades based on an understanding of the stresses and strains in the layers constituting the pavement and application of the concept of reliability in achieving the desired level of service during the pavements design life. Bitumen properties, as well as asphalt mixture properties, vary depending on temperature and loading conditions. Even though every layer of pavement structure is important and affects pavement performance, the asphalt layers viscoelasticity plays significant role. This modulus is a complex quantity and the absolute value of the complex modulus is called the dynamic modulus. When the loading wave form is sinusoidal and if there is no rest period, then, the modulus obtained is called dynamic complex modulus. First, mm fe and let models were both calibrated using. Theoretical models of road meshes and their use in. Since the early 1960s, pavement engineers have gone from empirical to mechanistic. Rep resentations of the flexible pavement structure, im. Influence of asphalt visco elastic properties on flexible pavement performance article pdf available in the baltic journal of road and bridge engineering 114. Design of pavements has been based on experience and judgment in the past. Nevertheless, asphalt mixes are not simple materials.
Stresses and displacements in viscoelastic pavement. Pdf analysis and design of flexible pavement using. Implementation of the bitumen performance grading system. Although engineers realize that a highway pavement is subject to moving loads as well as stationary ones, most current methods of pavement design are based on the assumptions that the pavement materials are time independent and linearly elastic, and that the design wheel load is stationary. Visco elastic theory considers flow characteristics in asphalt. Lecture notes ct 4860 structural pavement design design of. Viscoelastic analysis of flexible pavements and its. Viscoelastic modelling for asphalt pavements software. Pdf viscoelastic modeling and field validation of flexible.
In these lecture notes we will concentrate on the use of linear elastic multi layer theory for the calculation of stresses and strains in pavement structures. Viscoelastic modeling and field validation of flexible pavements article pdf available in journal of engineering mechanics 22 february 2006 with 850 reads how we measure reads. Linear elastic layer theory as a model of displacements. According to the authors simplified assumption, temperature is independent of the depth. Flexible pavement design by semiempirical method is discussed. Small trailer dropping weight geophones deflection basin uses elastic theory to predict the deflection basin for the given load. He also has an interest in constitutive modelling of viscoelasticplastic materials. While the standards contained in this manual provide a basis for uniform design practice for typical pavement design situations, precise rules which would apply to all possible situations are impossible to give. For example, a dashpot and a spring in series constitute the maxwell model.
Pdf evaluation of representative loading frequency for. Multilayer elastic theory finite element methods viscoelastic theory dynamic analysis inertial effects thermal models temperature change falling weight deflectometer. The increased rutting or decreased fatigue life of the flexible pavements may be attributed to the shortcomings of the application. Grids approximation models can be used in any standard road pavement design software where the model of layered elastic or viscoelastic half space is on a theoretical basis.
Further analysis of the field data showed that geotextilestabilization may increase the service life of flexible secondary road pavements by 1. Using schaperys quasielastic theory, the viscoelastic response at time t to a. Request pdf viscoelastic analysis of flexible pavements and its effects on. Pavement design is primarily a matter of sound application of acceptable engineering criteria and standards. Mechanisticempirical pavement design procedure for.
In these methods, especially in layered elastic theory and fem, the mathematical formulations are complex configuration and based on nonrealistic assumptions as being in elt method. Pavement design tries to prevent the major distress such as permanent deformation rutting and fatigue cracking. To fully utilize each pavement material in an economic design, a pavement should generally have reasonably balanced design between the rutting and fatigue modes of distress. Their mechanical properties are the principal cause of its visco elastic behavior. Comparison of isotropic and crossanisotropic analysis of. Each layer continuous linearly material is finite thickness except last layer topic 3 flexible pavement stress analysis 2.
1121 83 723 105 239 1395 1002 1465 45 1605 1194 1478 192 124 410 646 487 891 950 333 662 1477 225 248 1182 1078 819 304 1556 204 149 654 427 30 1060 660 225 114 297 421 1232 60 1332