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.

Dynamic Interpretation for Impulsive Deflection Test on Flexible Pavements

1998 ◽  
Vol 14 (2) ◽  
pp. 91-100
Author(s):  
Der-Wen Chang ◽  
Chia-Ling Chang
Keyword(s):  
Iterative Scheme ◽  
Flexible Pavements ◽  
Falling Weight Deflectometer ◽  
Correction Procedure ◽  
Subgrade Soils ◽  
Forward Analysis ◽  
Dynamic Interpretation ◽  
Equivalent Number ◽  
Deflection Test ◽  
Falling Weight

AbstractIn this study, a computer program DBFWD is developed for data analysis of Falling Weight Deflectometer (FWD) test on flexible pavements. To backcalculate the layer moduli of the pavement, a number of iterative backcalculation schemes were employed with the forward analysis of the Green's flexibility influence functions. The temperature and the moisture influences on material moduli of the asphalt surface and the subgrade soils were considered in the analysis. As the result, the iterative scheme based on the peak deflection ratios was selected to backcalculate the layer moduli of local pavements. Owing to the correction procedure used in the program, interpretations with four original deflections were found more accurate than those with equivalent number of modified deflections. Comparisons of program DBFWD with other static backcalculation programs on theoretical and experimental deflections indicated that dynamic interpretation is more effective in providing the layer modulus information. Despite of the requirements of accurate inputs of the layer thickness and the testing load for the analysis, a generalized application of the program needs to be clarified with model road test in demand.

Modelling of wave propagation in composite plates using the time domain spectral element method

2007 ◽  
Vol 302 (4-5) ◽  
pp. 728-745 ◽  
Author(s):  
Paweł Kudela ◽  
Arkadiusz Żak ◽  
Marek Krawczuk ◽  
Wiesław Ostachowicz
Keyword(s):  
Wave Propagation ◽  
Time Domain ◽  
Spectral Element Method ◽  
Composite Plates ◽  
Spectral Element ◽  
The Time Domain ◽  
Element Method

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.

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.

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