Non-linear finite element analysis of flexible pavements (original) (raw)
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Assessment of Linear and Non-Linear Analyses of Flexible Pavement
International Conference on Aerospace Sciences and Aviation Technology, 1999
Two computer programs were reviewed and evaluated, one for linear an alysis (LA) and the other for non-linear analysis (NLA), to identify the most appropOate analysis type for flexible pavement structural analysis. The programs were three-dimensional (3-D) finite element (FE) programs called SAP90 and ANSYS5.3. The comparison items were the maximum surface deflection, the maximum' vertical compressive strain at the top of the subgrade and the maximum horizontal tensile strain at the bottom of the asphalt concrete (AC)'lkOr, which are the most commonly used criteria for pavement design. In addition to these items, maximum tensile stress in AC layer and vertical stress distribution alort the pavement depth were used as the basis for comparison. Three load conditions include horizontal forces (HF) were applied to the flexible pavement models. Non-linear analysis was found to be more realistic for flexible pavement analysis. It satisfied the surface boundary condition and gave more acceptable results when studying shoving and vertical stress distribution under loading center.
Analysis of Response of Flexible Pavements Using Finite Element Method
2005
The characteristic response of flexible pavements under traffic load depict a delayed lateral strain relaxation (Viscoelasticity), a phenomenon that may be more accurately and expeditiously analysed using finite element (FE) viscoelastic response models. In this study a flexible pavement was modelled using ANSYS/ED finite element software suite. The pavement model was subjected to cyclic loading that simulated three levels of truck loads on 10R20 tyres at four tyre inflation pressures (viz. 350,490,630 and 770 kPa). The modelled results were in good agreement with the measured in-situ full-scale test data. Therefore, for known pavement material characteristics and tyre-pavement contact regime, finite element method could be used to efficiently estimate the fatigue life of flexible pavement with thin bituminous surfacing layers. * Corresponding author. Tel: +35318851194; Fax: +353-1-8851001 Email address: rachel.mulungye@itb.ie Introduction Characteristic response of in-situ bitumino...
Determination of permanent deformation of flexible pavements using finite element model
Determination of permanent deformation of flexible pavements using finite element model The unbound granular material used in flexible road pavements exhibits an elastoplastic behaviour under repetitive traffic loads. Permanent deformation occurring on pavement surface under traffic load is one of the main road pavement problems affecting road performance. Therefore, many permanent deformation models for calculating road pavement rutting have recently been developed by researchers. Most of these studies involve performance of dynamic triaxial tests. In this study, deformation characteristics of unbound granular materials are determined using the resonant column test. Then, instead of determining the total permanent deformation by summing up the calculated permanent deformations obtained in each pavement layer, dynamic 2D axisymmetric finite element analyses are performed for four different pavement cross sections to predict the total permanent deformation occurring on pavement surface under certain load cycles. The first modelled cross section of unbound granular material consists of natural aggregate. The base and/or subbase of remaining three cross sections consists of steel slag waste material. The permanent deformation versus load cycle is presented for four multi-layer road cross sections using semi logarithmic graphs. Finally, the permanent deformation model equation is developed for each pavement cross section using their fitting curves.
BEHAVIOUR OF DIFFERENT PAVEMENT TYPES UNDER TRAFFIC LOADS USING FINITE ELEMENT MODELLING
IAEME PUBLICATION, 2020
Finite Element Modelling (FEM) has become an increasingly popular method to help researchers find solutions to complex problems of structural mechanics in engineering. Pavement is a complex structure which consists of multiple layers of different materials that influence its behaviour under stress. Rutting behaviour can be predicted by 3D model analysis using the ABAQUS program. The modelling process assumes that the performance of all materials is one of linear elastic behaviour. The main inputs in the modelling process are the material elastic modulus, Poisson’s ratio and layer thickness. Models consist of surface, base, subbase and subgrade layers. Subgrade layers are assumed to have infinite depth in all pavement models. This study employed a simulation process of rigid, semi-rigid and flexible pavements using a standard axle load of 80 kN, which represents a single two-wheeled axle. FEM analysis showed that instantaneous vertical displacement along the Z-axis reached 0.105 mm, 0.32 mm and 0.66 mm for rigid, semi-rigid and flexible pavements respectively. Increasing the subgrade elastic modulus from 10 MPa to 200 MPa decreased the vertical displacement by seven, six and a half, and three and a half times for rigid, semirigid and flexible pavement respectively. KENLAYER results refer to the maximum vertical displacements as being 0.1, 0.28 and 0.60 mm for rigid, semi-rigid and flexible pavement respectively. The subgrade elastic modulus is key to improving the resistance to failure of all pavement types. Incremental increase to the subgrade elastic modulus is a potential engineering solution to reducing vertical displacement.
In the past few years, LCPC has been implementing in its finite element code CESAR-LCPC a module for pavement modelling, including non-linear models for asphalt materials and unbound granular materials. This program has been used to model results of a full scale experiment on a flexible pavement, with a granular base, performed on the LCPC accelerated pavement testing facility. The experimental results indicated that the response of the pavement depends strongly on the level of load and on the water content of the unbound granular layers. The modelling of the pavement was performed in 3D, and several modelling hypotheses were successively tested : linear elasticity, a non-linear elastic model for the unbound layers (Boyce model) and a visco-elastic model for the asphalt concrete (Huet-Sayegh model). The most complete model, coupling non-linear elasticity for the unbound materials and visco-elasticity for the asphalt concrete, led to realistic predictions of the pavement response for different levels of load and different loading speeds.
Use of a Three-Dimensional, Dynamic Finite Element Program for Analysis of Flexible Pavement
Pred?minantly ~exible pavement structural response to loads is pred1c~e? by using an elastic multilayer analysis. This type of analys~s 1s based on the assumption that pavements are subjected to static loads and that paving and subgrade materials are linear elastic materials. In this paper, ABAQUS, a three-dimensional dynamic finite element program (3D-DFEM), was used to ana~ lyze flexible pavements subjected to moving loads at various speeds. A number of material models were used to represent actual material c~a:acteristics such as viscoelasticity and elastoplasticity. The vahd1ty and then the application of 3D-DFEM to flexible pavement. analysis were. examined. Validation was accomplished by analysis of both static and dynamic cases. The static and dynamic verification studies indicated that 3D-DFEM can be used with confidence to predict actual pavement response from moving loads.
An improved dynamic model for the study of a flexible pavement
Advances in Engineering Software, 2012
This paper introduces the semi-analytical and finite element models implemented to study a Falling Weight Deflectometer test conducted on a flexible pavement. These dynamic models take into account the effects of both Rayleigh damping in soil and viscous damping in bituminous materials, with respect to temperature, on structural deflection. Moreover, numerical results have been compared with in situ measurements recorded on an instrumented pavement. Results from numerical models showed the importance of taking into account the effect of damping (hysteretic or viscoelastic) of all layers of the pavement against temperature, loading and mechanical parameters. The parametric analysis introduced as a basis for future development of a dynamic backcalculation program.
Stress-Strain Characteristics of Flexible Pavement by Finite Element Method
International Journal For Computational Civil and Structural Engineering, 2011
Design of flexible pavement is largely based on empirical methods using layered elastic and twodimensional finite element (FE) analysis. Currently a shift underway towards more mechanistic design techniques to minimize the limitations in determining stress, strain and displacement in pavement analysis. This research documents the use of 3D finite element application for predicting mechanical behavior and pavement performance subjected to various traffic factors. Different axle configuration, tire imprint areas and inflation pressure are investigated here to analyze the considerable impact on pavement damage initiation from fatigue and permanent deformation point of view. In this study, flexible pavement modeling is done using ABAQUS software in which model dimensions, element types and meshing strategies are taken by successive trial and error to achieve desired accuracy and convergence of the study. Thus proper tire imprint area is determined to apply in economical design of pavement for various axle configurations.