• Title/Summary/Keyword: flexible pavement response

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Three-dimensional analysis of flexible pavement in Nepal under moving vehicular load

  • Ban, Bijay;Shrestha, Jagat K.;Pradhananga, Rojee;Shrestha, Kshitij C.
    • Advances in Computational Design
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    • v.7 no.4
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    • pp.371-393
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    • 2022
  • This paper presents a three-dimensional flexible pavement simulated in ANSYS subjected to moving vehicular load on the surface of the pavement typical for the road section in Nepal. The adopted finite element (FE) model of pavement is validated with the classical theoretical formulations for half-space pavement. The validated model is further utilized to understand the damping and dynamic response of the pavement. Transient analysis of the developed FE model is done to understand the time varying response of the pavement under a moving vehicle. The material properties of pavement considered in the analysis is taken from typical road section used in Nepal. The response quantities of pavement with nonlinear viscoelastic asphalt layer are found significantly higher compared to the elastic pavement counterpart. The structural responses of the pavement decrease with increase in the vehicle speed due to less contact time between the tires of the vehicle and the road pavement.

Finite element application of an incremental endochronic model to flexible pavement materials

  • Kerh, Tienfuan;Huang, C.Y.
    • Structural Engineering and Mechanics
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    • v.6 no.7
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    • pp.817-826
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    • 1998
  • A finite element model based on the incremental endochronic theory for flexible pavement materials was developed in this study. Three grid systems with eight-node cubic isoparametric elements, and different loading steps were used to perform the calculations for a specimen of circular cylinder. The uniaxial stress experimental results on an asphalt mixture at $60^{\circ}C$ in SHRP conducted by University of California at Berkeley were used to check the ability of the derived numerical model. Then, the numerical results showed isotropic response and deviatoric response on the specimen in a three dimensional manner, which provided a better understanding for a deformed flexible material under the specified loading conditions.

Appropriate Boundary Conditions for Three Dimensional Finite Element Implicit Dynamic Analysis of Flexible Pavement (연성포장의 3차원 유한요소해석을 위한 최적 경계조건 분석)

  • Yoo, Pyeong-Jun;Al-Qadi, Imad L.;Kim, Yeon-Bok
    • International Journal of Highway Engineering
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    • v.10 no.4
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    • pp.213-224
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    • 2008
  • Flexible pavement responses to vehicular loading, such as critical stresses and strains, in each pavement layer, could be predicted by the multilayered elastic analysis. However, multilayered elastic theory suffers from major drawbacks including spatial dimension of a numerical model, material properties considered in the analysis, boundary conditions, and ill-presentation of tire-pavement contact shape and stresses. To overcome these shortcomings, three-dimensional finite element (3D FE) models are developed and numerical analyses are conducted to calculate pavement responses to moving load in this study. This paper introduces a methodology for an effective 3D FE to simulate flexible pavement structure. It also discusses the mesh development and boundary condition analysis. Sensitivity analyses of flexible pavement response to loading are conducted. The infinite boundary conditions and time-dependent history of calculated pavement responses are considered in the analysis. This study found that the outcome of 3D FE implicit dynamic analysis of flexible pavement that utilizes appropriate boundary conditions, continuous moving load, viscoelastic hot-mix asphalt model is comparable to field measurements.

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Evaluation of extension in service life and layer thickness reduction of stabilized flexible pavement

  • Nagrale, Prashant P.;Patil, Atulya
    • Advances in Computational Design
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    • v.3 no.2
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    • pp.201-212
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    • 2018
  • Decrease in availability of suitable subbase and base course materials for highway construction leads to a search for economic method of converting locally available troublesome soil to suitable one for highway construction. Present study insights on evaluation of benefits of stabilization of subgrade soils in term of extension in service life (TBR) and layer thickness reduction (LTR). Laboratory investigation consisting of Atterberg limit, Compaction, California Bearing Ratio, unconfined compressive strength and triaxial shear strength tests were carried out on two types of soil for varying percentages of stabilizers. Vertical compressive strains at the top of unstabilized and stabilized subgrade soils were found out by elastoplastic finite element analysis using commercial software ANSYS. The values of vertical compressive strains at the top of unstabilized and stabilized subgrade, were further used to estimate layer thickness reduction or extension in service life of the pavement due to stabilization. Finite element modeling of the flexible pavement layered structure provides modern technology and sophisticated characterization of materials that can be accommodated in the analysis and enhances the reliability for the prediction of pavement response for improved design methodology. If the pavement section is kept same for unstabilized and stabilized subgrade soils, pavement resting on lime, fly ash and fiber stabilized subgrade soil B will have service life 2.84, 1.84 and 1.67 times than that of unstabilized pavement respectively. The flexible pavement resting on stabilized subgrade is beneficial in reducing the construction material. Actual savings would depend on the option exercised by the designer for reducing the thickness of an individual layer.

Pavement Response in Flexible Pavements using Nonlinear Tire Contact Pressure and Measured Tire Contact Area (타이어의 접지 면적과 비선형 접지압력을 고려한 연성포장내의 거동 분석)

  • Jo, Myoung Hwan;Kim, Nakseok;Jeong, Jin-Hoon;Seo, Youngguk
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.4D
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    • pp.601-608
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    • 2006
  • The important elements in pavement design criteria are the stress and strain distributions. To obtain reasonable stress and strain distribution, tire contact area and tire pressures are very important. In this study, finite element analysis was used to identify the three-dimension states using nonlinear tire contact pressure and measured tire contact area. Measured tire contact area was quite different from the assumed tire contact area, and it resulted in different strain states under the tire. At the surface course, considering tire rib and nonlinear tire pressure, the pavement response presented accurate data compared to the predicted one. However, at the binder course, tire effects were generally negligible and it showed that the predicted pavement response was different compared to the measured one.

Development of Falling Weight Deflectometer for Evaluation of Layer Properties of Flexible Pavement (도로포장 구조체의 물성 추정을 위한 FWD의 설계 및 제작)

  • 황성호;손웅희;최경락
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.3
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    • pp.124-130
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    • 2003
  • Many structural evaluation procedures of road and airfield pavements use the Falling Weight Deflectometer (FWD) as a critical element of non-destructive deflection testing. FWD is a trailer mounted device that provides accurate data on pavement response to dynamic wheel loads. A dynamic load is generated by dropping a mass from a variable height onto a loading plate. The magnitude of the load and the pavement deflection are measured by a load celt and geophones. And database concerning pavement damage should be enhanced to analyze loss of thickness asphalt layer caused from the plastic deformation of pavement structure, such as cracking or rutting. The prototype FWD is developed, which consists of chassis system, hydraulic loading system, data acquisition and analysis system. This system subsequently merged to from automation management system and is then validated and updated to produce a working FWD which can actually be used in the field.

Mechanistic Analysis of Geogrid Base Reinforcement in Flexible Pavements Considering Unbound Aggregate Quality

  • Kwon Jay-Hyun;Tutumluer Erol;Kim Min-Kwan
    • International Journal of Highway Engineering
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    • v.8 no.2 s.28
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    • pp.37-47
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    • 2006
  • The structural response and performance of a flexible pavement can be improved through the use of geogrids as base course reinforcement. Current ongoing research at the University of illinois has focused on the development of a geogrid base reinforcement mechanistic model for the analysis of reinforced pavements. This model is based on the finite element methodology and considers not only the nonlinear stress-dependent pavement foundation but also the isotropic and anisotropic behavior of base/subbase aggregates for predicting pavement critical responses. An axisymmetric finite element model was developed to employ a three-noded axisymmetric membrane element for modeling geogrid reinforcement. The soil/aggregate-geogrid interface was modeled by the three-noded membrane element and the neighboring six-noded no thickness interface elements. To validate the developed mechanistic model, the commercial finite element program $ABAQUS^{TM}$ was used to generate pavement responses as analysis results for simple cases with similar linear elastic material input properties. More sophisticated cases were then analyzed using the mechanistic model considering the nonlinear and anisotropic modulus property inputs in the base/subbase granular layers. This paper will describe the details of the developed mechanistic model and the effectiveness of geogrid reinforcement when used in different quality unbound aggregate base/subbase layers.

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Effects of Moving Dynamic Vehicle Loads on Flexible Pavement Response (차량의 이동하중과 하중형태가 연성 포장의 거동 특성에 미치는 영향 평가)

  • Jo, Myoung-Hwan;Kim, Nak-Seok;Nam, Young-Ho;Im, Jong-Hyuk
    • Journal of the Korean Society of Hazard Mitigation
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    • v.8 no.1
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    • pp.39-45
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    • 2008
  • The most important elements in flexible pavement design criteria are stress and strain distributions. To obtain reasonable stress and strain distributions in pavements, moving wheel loads must be applied to analyze the pavement responses. In this study, finite element analysis was used to identify the three-dimensional states using the vehicle load into a constant-position / time-variable load (25, 50 and 80km/hr). In an elastic system, the strain is the same in both longitudinal and transverse directions under a single wheel. However, the same is not necessary in a viscoelastic system. Test results showed that the maximum values between transverse and longitudinal strains the bottom of asphalt concrete base layers under 25km/hr were were about 40 percent.

The Response Prediction of Flexible Pavements Considering Nonlinear Pavement Foundation Behavior (비선형 포장 하부 거동을 고려한 연성 포장의 해석)

  • Kim, Min-Kwan
    • International Journal of Highway Engineering
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    • v.11 no.1
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    • pp.165-175
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    • 2009
  • With the current move towards adopting mechanistic-empirical concepts in the design of pavement structures, state-of-the-art mechanistic analysis methodologies are needed to determine accurate pavement responses, such as stress, strain, and deformation. Previous laboratory studies of pavement foundation geomaterials, i.e., unbound granular materials used in base/subbase layers and fine-grained soils of a prepared subgrade, have shown that the resilient responses followed by nonlinear, stress-dependent behavior under repeated wheel loading. This nonlinear behavior is commonly characterized by stress-dependent resilient modulus material models that need to be incorporated into finite element (FE) based mechanistic pavement analysis methods to predict more realistically predict pavement responses for a mechanistic pavement analysis. Developed user material subroutine using aforementioned resilient model with nonlinear solution technique and convergence scheme with proven performance were successfully employed in general-purpose FE program, ABAQUS. This numerical analysis was investigated in predicted critical responses and domain selection with specific mesh generation was implemented to evaluate better prediction of pavement responses. Results obtained from both axisymmetric and three-dimensional (3D) nonlinear FE analyses were compared and remarkable findings were described for nonlinear FE analysis. The UMAT subroutine performance was also validated with the instrumented full scale pavement test section study results from the Federal Aviation Administration's National Airport Pavement Test Facility (FAA's NAPTF).

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Evaluation of Flexible Pavement Layer Moduli Using the Depth Deflectometer and Flexible Pavement Behavior under Various Vehicle Speeds (아스팔트 콘크리트 포장구조체의 내부처짐에 의한 물성추정과 주행속도에 따른 거동분석)

  • Choi, Jun-Seong;Kin, Soo-Il;Yoo, Ji-hyung
    • International Journal of Highway Engineering
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    • v.2 no.1
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    • pp.135-145
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    • 2000
  • A new procedure needs to be developed to predict the dynamic layer properties under moving truck loads. In this study, a computer code to evaluate layer moduli of asphalt concrete pavement from measured interior deflections at various depths were developed and verified from numerical model tests. Interior deflections of the pavement are measured from Multi-Depth Deflectometer(MDD). It was found that errors between the given and backcalculated moduli in numerical analysis were less than 0.32% for several numerical models tested. When impact loads were used, a technique to determine the depth to virtual rigid base was proposed through the analysis of compressive wave velocity and impulse loading durations. It was found that errors between the given and backcalculated moduli in numerical analysis were less than 0.114% when virtual rigid base was considered in numerical analysis. The pavement behavior must be evaluated under various vehicle speeds when determining the dynamic interaction between the loading vehicle and pavement system. To evaluate the dynamic behavior on asphalt concrete pavement under various vehicle speeds, truck moving tests were carried out. From the test results with respect to vehicle speed, it was found that the vehicle speed had significant effect on actual response of the pavement system. The lower vehicle speed generates the higher interior deflections, and the lower dynamic modulus.

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