Dynamic Interpretation of Falling Weight Deflectometer Test Results: Spectral Element Method

2000 ◽  
Vol 1716 (1) ◽  
pp. 49-54 ◽  
Author(s):  
Rafid AI-Khoury ◽  
Athanassios Scarpas ◽  
Cor Kasbergen ◽  
Johan Blaauwendraad
Keyword(s):  
Iterative Algorithms ◽  
Spectral Element ◽  
Falling Weight Deflectometer ◽  
Reflection And Refraction ◽  
Element Program ◽  
Pavement Structure ◽  
Element Technique ◽  
Falling Weight ◽  
Impact Of Falling ◽  
Element Method

The use of spectral analysis as a means of analyzing the dynamic impact of falling weight deflectometer (FWD) load pulses on pavements is covered. The spectral element technique is utilized. Only forward analyses of pavement dynamics are presented, with the emphasis on the suitability of the method for solving inverse problems. LAMDA (layered media dynamic analysis), a newly developed spectral element program, is utilized for the simulation of the interaction between the FWD load pulse and the pavement structure. In LAMDA, the formulation of the wave propagation, reflection, and refraction in a layer is done in a closed form. The assembling of the elements (in the multilayer system) is carried out in a manner similar to that in the finite element method. Consequently, the size of the mesh of a pavement structure is as large as the number of the layers involved. This reduces the computational requirements substantially and hence enables utilization of LAMDA in iterative algorithms for backcalculation purposes.

Dynamic interpretation of falling weight deflectometer tests on flexible pavements using the spectral element method: backcalculation

2009 ◽  
Vol 36 (6) ◽  
pp. 957-968 ◽  
Author(s):  
Simon Grenier ◽  
Jean-Marie Konrad
Keyword(s):  
Spectral Element Method ◽  
Flexible Pavements ◽  
Spectral Element ◽  
Falling Weight Deflectometer ◽  
Dynamic Approach ◽  
Dynamic Interpretation ◽  
Minimization Technique ◽  
The Time Domain ◽  
Falling Weight ◽  
Element Method

A robust backcalculation methodology that uses the Levenberg–Marquardt iterative minimization technique is presented to identify the value of unknown layer parameters from falling weight deflectometer (FWD) tests using a dynamic approach based on the spectral element method. Backcalculation is performed in the time-domain with 20 observations on each deflection history. The efficiency of the proposed methodology is demonstrated by interpreting FWD tests on three flexible pavements that cover a variety of structures, soil, and bedrock conditions. Results indicate that the dynamic approach is capable of simulating quite well the measured deflection histories using effective backcalculated moduli. In addition, comparison of critical strains between static and dynamic interpretation of FWD tests indicates that both approaches predict similar traction strains at the bottom of the asphalt concrete layer. However, the prediction of the compression strain in the subgrade with the static approach is erratic compared with the dynamic method.

Dynamic simulation of falling weight deflectometer tests on flexible pavements using the spectral element method: forward calculations

2009 ◽  
Vol 36 (6) ◽  
pp. 944-956 ◽  
Author(s):  
Simon Grenier ◽  
Jean-Marie Konrad ◽  
Denis LeBœuf
Keyword(s):  
Dynamic Analysis ◽  
Spectral Element Method ◽  
Flexible Pavements ◽  
Computer Code ◽  
Spectral Element ◽  
Falling Weight Deflectometer ◽  
Viscous Effects ◽  
Damping Material ◽  
Falling Weight ◽  
Element Method

A dynamic analysis based on the spectral element method is described for the interpretation of falling weight deflectometer (FWD) tests on flexible pavements. This dynamic approach was implemented in the computer code Dynamic Analysis of Pavement - Université Laval (DYNAPAV-UL) that includes both frequency-independent hysteretic damping and frequency-dependent viscous damping material models. A parametric study was conducted on a four-layer flexible pavement to evaluate the influence of different layer moduli on deflection basins and deflection histories. The viscous behaviour of the asphalt concrete layer was also investigated. While the deflection basin currently used in static methods gives some details of the pavement response under transient loading, the simulations of FWD tests using the dynamic model suggest that the time histories should be included as well for the interpretation of FWD deflection measurements. In fact, important dynamic phenomena due to inertial effects and viscous effects are only revealed by deflection histories.

Pavement displacement sensitivity to layer moduli

2002 ◽  
Vol 39 (6) ◽  
pp. 1395-1398
Author(s):  
Dieter Stolle
Keyword(s):  
Finite Element ◽  
Surface Displacement ◽  
Falling Weight Deflectometer ◽  
Contribution Ratio ◽  
Displacement Sensitivity ◽  
Stiffness Characteristics ◽  
Element Technique ◽  
Falling Weight ◽  
The Relationship ◽  
Displacement Measurements

The backcalculation of layer moduli using falling weight deflectometer data has proven to be challenging owing to the insensitivity of displacement measurements to the stiffness characteristics of some layers. This note describes a rigorous, yet simple, finite element technique for identifying the relationship between surface displacement and the elastic modulus of each layer. An example is given to demonstrate the application of the procedure.Key words: pavements, subgrade, backcalculation, contribution ratio.

A New Form of Genetic Algorithm for Back-Calculating Pavement Structure Modulus Based on Database Searching Theory

2012 ◽  
Vol 193-194 ◽  
pp. 1090-1094
Author(s):  
Xin Jian Feng ◽  
Jian Fang Fu ◽  
Jian Lin Zhang
Keyword(s):  
Genetic Algorithm ◽  
Traditional Method ◽  
Measured Data ◽  
Database Searching ◽  
Falling Weight Deflectometer ◽  
Load Pulse ◽  
New Form ◽  
Pavement Structure ◽  
Falling Weight ◽  
Better Than

The Falling Weight Deflectometer (FWD) is designed to impart a load pulse to the pavement surface which simulates the load produced by a rolling vehicle wheel, wildly used in back-calculating pavement structure modulus. In this paper, a new form of Genetic Algorithm based on database searching theory is introduced. This method is not sensitive to initial values and it could identify the modulus effectively with establishing simple databases. By using a project measured data as an example, the result shows that this method is stable, convergent and practical. This method is better than the traditional method. It will be one of useful tools for the highway assessment.

scholarly journals DETERMINATION OF DEFLECTION BASIN USING PAVEMENT MODELLING COMPUTER PROGRAMS AND FINITE ELEMENT METHOD

2020 ◽  
Vol 82 (4) ◽  
Author(s):  
Sri Atmaja P. Rosyidi ◽  
Asmah Hamim ◽  
Aizat Mohd Taib ◽  
Nor Azliana Akmal Jamaludin ◽  
Zubair Ahmed Memon ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Dynamic Loading ◽  
Computer Programs ◽  
Good Potential ◽  
Pavement Structure ◽  
Pavement Structures ◽  
Falling Weight ◽  
The Comparative Study ◽  
Element Method

Several methods can be used to model pavement structures, namely multi-layered elastic theory (MET), finite element method (FEM), or finite difference method (FDM). In this study, three computer programs, KENLAYER and EVERSTRESS 5.0 which are based on MET, and ANSYS, representing the FEM, are used in Falling Weight Deflectometer (FWD) test on a pavement structure to determine deflection basin. The deflection basin was developed by using the results of vertical deflection from each sensor of an FWD test. In this study, a pavement structure was modelled for three locations of FWD tests, namely CH 200, CH 1450, and CH 2300. Based on the comparative study, all computer programs show good potential in determining deflection basin, with small percentage of Root Mean Square Error (RMSE) of between 1.00% to 4.31% for all models developed by the computer programs and field measurement. In order to obtain a higher accuracy of the FEM, the models considered the dynamic loading, increasing size of model geometry, as well as the reduction of the mesh element sizes. Moreover, changing from static to dynamic loading led to the reduction of percentage in RMSE for CH 200 from 2.41% to 0.94%.  Decreasing size of closer elements of loading region also results in lower percentages of RMSE, calculated at 4.21% to 3.63% and 1.20% to 1.18% for CH 1450 and CH 2300, respectively. FEM, therefore, is found to be the best method for determining deflection basin of FWD in comparison to other MET computer programs.

Accuracy evaluation of statically backcalculated layer properties of asphalt pavements from falling weight deflectometer data

2020 ◽  
Vol 47 (3) ◽  
pp. 317-325
Author(s):  
Guozhi Fu ◽  
Cheng Xue ◽  
Yanqing Zhao ◽  
Dandan Cao ◽  
Mohsen Alae
Keyword(s):  
Spectral Element Method ◽  
Spectral Element ◽  
Asphalt Pavements ◽  
Accuracy Evaluation ◽  
Falling Weight Deflectometer ◽  
Static Deflection ◽  
Dynamic Effects ◽  
Surface Deflection ◽  
Pavement Structures ◽  
Falling Weight

This study is to evaluate the dynamic effects of falling weight deflectometer (FWD) loading on the surface deflection of asphalt pavement and the accuracy of statically backcalculated layer moduli from FWD data. The dynamic and static deflections were computed using the spectral element method and the layer elastic theory, respectively, for various pavement structures. The static deflection is considerably larger than the dynamic deflection for typical FWD loading and the normalized difference between static and dynamic deflections increases with increasing distance from the load center and decreases with increasing loading duration. The dynamic deflections were utilized to backcalculate the layer moduli using two static backcalculation procedures, MODULUS and EVERCALC. The backcalculated moduli can be significantly different from the actual moduli. The results indicate that the static backcalculation procedure can lead to significant errors in the backcalculated layer moduli by ignoring the dynamic effects of FWD loading.

scholarly journals Interaction of Physical Parameters and The Strength of Frost Blanket Course in Road Pavement Structure

2018 ◽  
Vol 13 (4) ◽  
pp. 416-428 ◽  
Author(s):  
Lina Bertulienė ◽  
Lina Juknevičiūtė–Žilinskienė ◽  
Henrikas Sivilevičius ◽  
Alfredas Laurinavičius
Keyword(s):  
Strength Properties ◽  
Physical Parameters ◽  
Light Weight ◽  
Falling Weight Deflectometer ◽  
The Road ◽  
Road Pavement ◽  
Pavement Structure ◽  
Pavement Structures ◽  
Falling Weight ◽  
Reliable Correlation

This paper determines the interaction between the physical indicators of frost blanket course and its deflection modulus, measured by static and dynamic devices. The Pilot Road has been selected to examine the strength properties (deflection module) of frost blanket course. A Pilot Road consisting of 27 road sections, divided into 5 different road structures. A Pilot Road has been selected to examine the strength properties (deflection module) of frost blanket course. In this research was determined the strength of frost blanket course in road pavement structures of Pilot Road by four devices: Falling Weight Deflectometer Dynatest 8000, Light Weight Deflectometers Prima 100 and ZORN ZSG 02 and Static Beam Strassentest. The results showed no reliable correlation between the deflection modulus, measured by different devices, and the physical indicators of the frost blanket course of the road pavement structures in Pilot Road.

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