Effect of Gradation on Nonlinear Stress-Dependent Behavior of a Sandy Flexible Pavement Subgrade

2007 ◽  
Vol 133 (10) ◽  
pp. 582-589 ◽  
Author(s):  
Sung-Hee Kim ◽  
Erol Tutumluer ◽  
Dallas N. Little ◽  
Nakseok Kim
Keyword(s):  
Flexible Pavement ◽  
Dependent Behavior ◽  
Nonlinear Stress ◽  
Stress Dependent

scholarly journals Modeling Stress-Dependent Anisotropic Elastoplastic Unbound Granular Base in Flexible Pavements

2018 ◽  
Vol 2672 (52) ◽  
pp. 46-56 ◽  
Author(s):  
Yuqing Zhang ◽  
Fan Gu ◽  
Xue Luo ◽  
Bjorn Birgisson ◽  
Robert L. Lytton
Keyword(s):  
Stress Responses ◽  
Compressive Strain ◽  
Flexible Pavements ◽  
Plastic Behavior ◽  
Elastic Model ◽  
Nonlinear Stress ◽  
Anisotropic Elastic ◽  
Base Course ◽  
Granular Base ◽  
Stress Dependent

Unbound granular base (UGB) has a cross-anisotropic and nonlinear (stress-dependent) modulus with a plastic behavior. Existing UGB models address nonlinear cross-anisotropy and plasticity separately. It is unknown how the two characteristics are coupled into a finite element model (FEM) and how this will affect the pavement responses. This study presents a coupled nonlinear cross-anisotropic elastoplastic (NAEP) constitutive model for the UGB and implements it in a weak form equation-based FEM. No material subroutine is needed to address the circular dependence between the stress-dependent anisotropic modulus, structural stress responses, and elastoplastic deformation. The NAEP model was calibrated by triaxial resilient modulus and strength tests and validated using laboratory measurements in a large-scale soil-tank pavement structural test. It is found that the NAEP model is valid and effective in predicting the UGB responses in flexible pavements. The model predicted less horizontal tensile stresses at the base bottom and introduced compressive stresses in the middle and top of the base course. This is caused by an increasing confinement resulting from a horizontal plastic dilation in the base course, which cannot be modeled without considering plasticity. The stress-dependent modulus for the UGB material decreases with depth and the distance from loading centerline. Compared with a nonlinear anisotropic elastic model, the NAEP model predicted the same tensile strain at asphalt layer bottom, a higher base modulus, and a higher subgrade compressive strain. Thus, the nonlinear anisotropic elastic UGB model results in the same fatigue life as the NAEP model but may riskily under-predict rutting damage.

scholarly journals STUDY ON NONLINEAR PAVEMENT RESPONSES OF LOW VOLUME ROADWAYS SUBJECT TO MULTIPLE WHEEL LOADS / NETIESINĖS KELIO DANGOS PRIKLAUSOMYBĖS NUO MAŽO INTENSYVUMO KELIŲ, VEIKIAMŲ DAUGKARTINĖMIS RATŲ APKROVOMIS, TYRIMAS

2011 ◽  
Vol 17 (1) ◽  
pp. 45-54 ◽  
Author(s):  
Minkwan Kim ◽  
Joo Hyoung Lee
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Asphalt Pavement ◽  
Three Dimensional ◽  
Nonlinear Behavior ◽  
Element Model ◽  
Element Analysis ◽  
Nonlinear Stress ◽  
Low Volume ◽  
Stress Dependent

This paper describes numerical analyses on low volume roads (LVRs) using a nonlinear three-dimensional (3D) finite element model (FEM). Various pavement scenarios are analyzed to investigate the effects of pavement layer thicknesses, traffic loads, and material properties on pavement responses, such as surface deflection and subgrade strain. Each scenario incorporates a different combination of wheel/axle configurations and pavement geomaterial properties to analyze the nonlinear behavior of thinly surfaced asphalt pavement. In this numerical study, nonlinear stress-dependent models are employed in the base and subgrade layers to properly characterize pavement geomaterial behavior. Finite element analysis results are then described in terms of the effects of the asphalt pavement thickness, wheel/axle configurations, and geomaterial properties on critical pavement responses. Conclusions are drawn by the comparison of the nonlinear pavement responses in the base and subgrade in association with the effects of multiple wheel/axle load interactions. Santrauka Straipsnyje aprašoma skaitinė mažo intensyvumo kelių analizė, taikant netiesinį—erdvinį baigtinių elementų modelį. Skirtingi dangų paviršiaus variantai analizuojami siekiant ištirti, kokiąįtaką kelio dangos elgsenai, t. y. poslinkiams ir kelio pagrindo deformacijoms, turi dangų sluoksnių storiai, eismo apkrovos ir medžiagų savybės. Kiekvienas kelio dangos variantas turi skirtingas ratų arba ašies ir geometrinių savybių formas, kad būtų galima išanalizuoti netiesinę plonos asfalto dangos paviršiaus elgseną. Šioje skaitinėje analizėje nagrinėjami netiesiniai įtempių modeliai, kurie buvo taikomi pagrindo sluoksniams, siekiant tinkamai apibūdinti geometrinę kelio dangos elgseną. Baigtinių elementų analizės rezultatai toliau nagrinėjami atsižvelgiant į asfalto dangos storį ar ašies formą ir geometrines savybes, priklausomai nuo kritinės kelio dangos būklės. Išvados buvo gautos lyginant netiesines kelių dangos priklausomybes pagrindo sluoksnyje, atsižvelgiant į jų sąveiką su daugkartine ratų apkrova.

scholarly journals Who Says Backcalculation Is Only about Layer Moduli?

2019 ◽  
Vol 2673 (1) ◽  
pp. 317-331 ◽  
Author(s):  
Hyung Suk Lee ◽  
Douglas Steele ◽  
Harold Von Quintus
Keyword(s):  
Poisson’S Ratio ◽  
Damping Ratio ◽  
Vertical Direction ◽  
Nonlinear Behavior ◽  
Material Nonlinearity ◽  
Poisson's Ratio ◽  
Unit Weight ◽  
Nonlinear Stress ◽  
Finite Layer ◽  
Stress Dependent

In this study, an existing finite layer algorithm for dynamic analysis of pavement structure was enhanced to incorporate the nonlinear behavior of unbound pavement materials. The nonlinear (stress-dependent) modulus was approximated in the vertical direction, which is similar to the approach used with multi-layered elastic and viscoelastic analysis methods for incorporating material nonlinearity. First, the enhanced finite layer algorithm was used to backcalculate the layer thickness, unit weight, Poisson’s ratio, and damping ratio in addition to the linear (viscoelastic and elastic) modulus of all layers. Then, the parameters backcalculated from the linear analysis were used to estimate the seed values for the subsequent nonlinear analysis in which the stress-dependent moduli of the unbound layers were backcalculated. Deflection data from two field sections (with thick and thin asphalt concrete layer) were used for demonstration. The results showed excellent agreement between the measured and backcalculated deflection time histories. In addition, it was found that the use of backcalculated parameters for the thickness, unit weight, Poisson’s ratio, and damping resulted in lower errors for both the linear and nonlinear analyses. Furthermore, the results of the backcalculation indicated that the material nonlinearity was more pronounced for the thin pavement, in which case the backcalculation error may be reduced further by incorporating the stress-dependent modulus.

C-FLEX Advanced Finite Element Analysis Program for Flexible Pavement Analysis and Design

2021 ◽  
pp. 036119812110067
Author(s):  
Jiayi Luo ◽  
Haohang Huang ◽  
Issam I. A. Qamhia ◽  
Erol Tutumluer ◽  
Jeb S. Tingle
Keyword(s):  
Finite Element ◽  
Flexible Pavements ◽  
Flexible Pavement ◽  
Pavement Design ◽  
Analysis Program ◽  
Evaluation Procedures ◽  
Analysis Scheme ◽  
The Cross ◽  
Stress Dependent ◽  
The U.S

The U.S. Army Engineer Research and Development Center (ERDC) of the U.S. Army Corps of Engineers has initiated an effort to modernize the Department of Defense (DOD) pavement design and evaluation procedures initially developed in the 1950s. Flexible pavement analyses and evaluations are currently performed based on the elastic layered WESLEA and WESDEF software programs. To modernize the current pavement design and evaluation procedures used by the DOD, an advanced axisymmetric Finite Element Method (FEM) based analysis program, named C-FLEX, was developed and is introduced in this paper. The C-FLEX program is designed to feature accurate material models for all pavement layers with the capability to model the cross-anisotropic and nonlinear elastic properties of unbound base/subbase and subgrade layers, the viscoelastic behavior of the asphalt mixture, as well as mechanical reinforcement using geosynthetics in flexible pavements. The FEM formulation in C-FLEX and the program architecture and implementation details are introduced and discussed in this paper. The different analysis schemes and proper models used to characterize the cross-anisotropy and stress-dependent material nonlinearity are also described in detail. The viscoelastic analysis scheme and the geosynthetic characterization are currently under development and so are not included in this paper. Furthermore, two conventional flexible pavements with different layer properties are analyzed to verify the solutions and reliability of the C-FLEX program. Based on this development effort with ERDC, the C-FLEX program is envisioned to eventually serve as the flexible pavement analysis engine for the DOD’s new mechanistic design and evaluation platform.

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