Estimation of tensile strains at the bottom of asphalt concrete layers under wheel loading using deflection basins from falling weight deflectometer tests

2012 ◽  
Vol 39 (7) ◽  
pp. 771-778 ◽  
Author(s):  
Jean-Pascal Bilodeau ◽  
Guy Doré
Keyword(s):  
Asphalt Concrete ◽  
Tensile Strain ◽  
Analysis Tool ◽  
Falling Weight Deflectometer ◽  
Proposed Model ◽  
Mechanistic Analysis ◽  
Pavement Engineering ◽  
Wheel Loading ◽  
Using Data ◽  
Falling Weight

The falling weight deflectometer is a pavement analysis tool that is now widely used in the pavement engineering field. Using the backcalculation process and the measured deflection basin, the layers moduli can be determined and a mechanistic analysis of the pavement can be made. A new approach is proposed to bypass the necessity of the backcalculation by allowing a direct estimation of the tensile strain at the bottom of asphalt concrete using the deflection basin. A model based on a finite element theoretical pavement analysis is proposed for this purpose. Complementary models have been developed to use the proposed models without having to determine the layers moduli. The proposed model to estimate the tensile strain at the bottom of the asphalt concrete layers is validated and calibrated using data obtained on an instrumented experimental site.

Direct estimation of vertical strain at the top of the subgrade soil from interpretation of falling weight deflectometer deflection basins

2014 ◽  
Vol 41 (5) ◽  
pp. 403-408 ◽  
Author(s):  
Jean-Pascal Bilodeau ◽  
Guy Doré
Keyword(s):  
Analysis Tool ◽  
Falling Weight Deflectometer ◽  
Estimation Model ◽  
Vertical Strain ◽  
Direct Estimation ◽  
Subgrade Soil ◽  
Pavement Engineering ◽  
Pavement Structures ◽  
Using Data ◽  
Falling Weight

The falling weight deflectometer is a pavement analysis tool that is now widely used in the pavement engineering field. Using the backcalculation process and the measured deflection basin, the layer modulus can be determined and a mechanistic analysis of the pavement can be made. A new approach proposes to bypass the necessity of the backcalculation by allowing a direct estimation of the vertical strain at the top of the subgrade using the deflection basin. A model based on a finite element theoretical pavement analysis is proposed for this purpose. The estimation model revisited existing deflection based index and adapted modifications were proposed to consider thicker pavement structures. The proposed model to estimate the vertical strain at the top of the subgrade is validated and calibrated using data obtained on two instrumented experimental sites.

Multiscale Modeling of Asphalt Concrete and Validation through Instrumented Pavement Section

2021 ◽  
pp. 036119812198972
Author(s):  
Zafrul H. Khan ◽  
Rafiqul A. Tarefder ◽  
Hasan M. Faisal
Keyword(s):  
Asphalt Concrete ◽  
Tensile Strain ◽  
Nanoindentation Test ◽  
Falling Weight Deflectometer ◽  
Vehicle Model ◽  
Dynamic Analyses ◽  
Morphological Image Analysis ◽  
Maximum Tensile Strain ◽  
Falling Weight ◽  
Morphological Image

In this study, macroscale responses of asphalt concrete (AC) are predicted from the responses of its corresponding microscale representative volume element (RVE) within a finite element framework using quasi-static and dynamic analyses. Nanoindentation test was performed on the mastic and aggregate phase of an AC sample to determine the viscoelastic and elastic properties of RVE elements. Aggregate-mastic proportions in the RVE were obtained from the morphological image analysis. Macroscale model responses were compared with the AC pavement responses obtained from an instrumented pavement section subjected to falling weight deflectometer loading and a class 9 vehicle. Model responses are very close to the actual responses. The multiscale analyses show that tensile strain in microscale RVE is 5–10 times higher than that in a macroscale element. Furthermore, multiscale analyses also show that variations in the microscale RVE, such as the reduction in the aggregate-mastic ratio or increment in the voids, can increase the maximum tensile strain at the bottom of the AC in macroscale model by around 25%.

scholarly journals Backcalculated Modulus of Asphalt Concrete

2019 ◽  
Vol 8 (4) ◽  
pp. 127-136
Author(s):  
Md Rashadul Islam ◽  
Rafiqul Tarefder ◽  
Mesbah U. Ahmed
Keyword(s):  
New Mexico ◽  
Asphalt Concrete ◽  
Dynamic Modulus ◽  
Asphalt Pavement ◽  
Homogeneous Material ◽  
Loading Frequency ◽  
Falling Weight Deflectometer ◽  
Different Temperatures ◽  
Wheel Loading ◽  
Falling Weight

Asphalt Concrete (AC) is considered a spatially homogeneous material when analyzing and designing asphalt pavement. However, the modulus of AC along the wheel path and the middle of the wheel path may not be the same considering the continuous compaction by wheel loading. This study conducted monthly Falling Weight Deflectometer (FWD) tests to determine the AC modulus of a pavement section on Interstate 40 (I-40) in the state of New Mexico, USA from 2013 to 2015. The AC moduli on the wheel path, on the middle of the wheel path, on the shoulder with friction course, and on the shoulder without friction course are determined. It is mentionable that the driving lane and the shoulder have the same geometry, materials, and compaction effort. Results show that the modulus along the wheel path is almost the same as that of along the middle of the wheel path. The shoulder without friction course has a modulus greater than that of the lane AC modulus and the shoulder with the friction course. In addition, FWD backcalculated moduli at different temperatures are compared with the dynamic modulus values of the AC layer. It is found that the dynamic modulus at a loading frequency of 5 Hz is 1.7 to 1.9 times the backcalculated AC modulus.

Rutting Development in Linear Tracking Test Pavements To Evaluate Shell Subgrade Strain Criterion

1997 ◽  
Vol 1570 (1) ◽  
pp. 23-29 ◽  
Author(s):  
J. Groenendijk ◽  
C. H. Vogelzang ◽  
A. Miradi ◽  
A. A. A. Molenaar ◽  
L. J. M. Dohmen
Keyword(s):  
Data Analysis ◽  
Shear Deformation ◽  
Asphalt Concrete ◽  
Heavy Traffic ◽  
Falling Weight Deflectometer ◽  
Wheel Load ◽  
Strain Criterion ◽  
Average Criterion ◽  
Tracking Device ◽  
Falling Weight

Two full-depth gravel asphalt concrete (AC) pavements of 0.15- and 0.08-m thickness on a sand subgrade were loaded with 4 million and 0.65 million repetitions of a 75-kN super-single wheel load using the linear tracking device (LINTRACK), a heavy-traffic simulator. Frequent measurements of asphalt strains, temperatures, rutting, cracking, and falling weight deflectometer (FWD) were made. The data analysis of the rutting measurements indicates that all rutting could be ascribed to subgrade deformation (secondary rutting). No evidence was found of shear deformation within the asphalt layer (primary rutting). The data analysis also indicates that the observed rutting performance of the LINTRACK test sections (to a maximum rut depth of 18 mm) coincides closely with the average criterion from the Shell Pavement Design Manual, which relates subgrade strain to allowable number of strain repetitions.

Effectiveness of static and dynamic backcalculation approaches for asphalt pavement

2020 ◽  
Vol 47 (7) ◽  
pp. 846-855
Author(s):  
Dandan Cao ◽  
Changjun Zhou ◽  
Yanqing Zhao ◽  
Guozhi Fu ◽  
Wanqiu Liu
Keyword(s):  
Asphalt Concrete ◽  
Elastic Moduli ◽  
Complex Modulus ◽  
Asphalt Pavement ◽  
Falling Weight Deflectometer ◽  
Fixed Frequency ◽  
Dynamic Approach ◽  
Layer Effect ◽  
Static Approach ◽  
Falling Weight

In this study, the field falling weight deflectometer (FWD) data for asphalt pavement with various base types were backcalculated through dynamic and static backcalculation approaches, and the effectiveness of backcalculation approaches was studied. Asphalt concrete (AC) was treated as a viscoelastic material and the complex modulus was obtained using the dynamic approach. The dynamic modulus at a fixed frequency was computed for comparison purposes. The coefficient of variance and the compensating layer effect were assumed as two characteristics for the effectiveness of backcalculation approaches. The results show that the layer property from the dynamic backcalculation approach for different stations were more consistent and showed smaller coefficient of variance, which were more appropriate for the characterization pavement behavior. The elastic moduli from the static approach were more variable and exhibited a compensating layer effect in which a portion of the modulus of one layer was backcalculated into other layers. The dynamic approach is more effective than static approaches in backcalculation of layer properties.

scholarly journals Comparing Traffic Speed Deflectometer and Falling Weight Deflectometer Data

2018 ◽  
Vol 2672 (40) ◽  
pp. 22-31 ◽  
Author(s):  
Eyal Levenberg ◽  
Matteo Pettinari ◽  
Susanne Baltzer ◽  
Britt Marie Lekven Christensen
Keyword(s):  
Experimental Data ◽  
Loading Conditions ◽  
Falling Weight Deflectometer ◽  
Engineering Community ◽  
Taylor Diagram ◽  
Comparison Results ◽  
Pavement Engineering ◽  
Traffic Speed ◽  
Falling Weight

In recent years the pavement engineering community has shown increasing interest in shifting from a stationary falling weight deflectometer (FWD) to moving testing platforms such as the traffic speed deflectometer (TSD). This paper dealt with comparing TSD measurements against FWD measurements; it focused on the comparison methodology, utilizing experimental data for demonstration. To better account for differences in loading conditions between the two devices a new FWD deflection index was formulated first. This index served as reference/benchmark for assessing the corresponding TSD measurements. Next, a Taylor diagram was proposed for visualizing several comparison statistics. Finally, a modern agreement metric was identified and applied for ranking comparison results across different datasets. Overall, the suggested methodology is deemed generic and highly applicable to future situations, especially for assessing the worth of emerging device upgrades or improved interpretation schemes (or both).

Mechanistic-Based Approach to Utilize Traffic Speed Deflectometer Measurements in Backcalculation Analysis

2020 ◽  
Vol 2674 (5) ◽  
pp. 208-222
Author(s):  
Zia U. A. Zihan ◽  
Mostafa A. Elseifi ◽  
Patrick Icenogle ◽  
Kevin Gaspard ◽  
Zhongjie Zhang
Keyword(s):  
Asphalt Concrete ◽  
Traffic Control ◽  
Parametric Study ◽  
Complex Modulus ◽  
Falling Weight Deflectometer ◽  
Software Application ◽  
Traffic Speed ◽  
Definition Of ◽  
Falling Weight ◽  
Surface Deflections

Backcalculation analysis of pavement layer moduli is typically conducted based on falling weight deflectometer (FWD) deflection measurements; however, the stationary nature of the FWD requires lane closure and traffic control. In recent years, traffic speed deflection devices such as the traffic speed deflectometer (TSD), which can continuously measure pavement surface deflections at traffic speed, have been introduced. In this study, a mechanistic-based approach was developed to convert TSD deflection measurements into the equivalent FWD deflections. The proposed approach uses 3D-Move software to calculate the theoretical deflection bowls corresponding to FWD and TSD loading configurations. Since 3D-Move requires the definition of the constitutive behaviors of the pavement layers, cores were extracted from 13 sections in Louisiana and were tested in the laboratory to estimate the dynamic complex modulus of asphalt concrete. The 3D-Move generated deflection bowls were validated with field TSD and FWD data with acceptable accuracy. A parametric study was then conducted using the validated 3D-Move model; the parametric study consisted of simulating pavement designs with varying thicknesses and material properties and their corresponding FWD and TSD surface deflections were calculated. The results obtained from the parametric study were then incorporated into a Windows-based software application, which uses artificial neural network as the regression algorithm to convert TSD deflections to their corresponding FWD deflections. This conversion would allow backcalculation of layer moduli using TSD-measured deflections, as equivalent FWD deflections can be used with readily available tools to backcalculate the layer moduli.

Pavement Rehabilitation Selection Based on Mechanistic Analysis and Field Diagnosis of Falling Weight Deflectometer Data: Virginia Experience

2000 ◽  
Vol 1730 (1) ◽  
pp. 177-186 ◽  
Author(s):  
Sameh Zaghloul ◽  
Mohamed Elfino
Keyword(s):  
Life Cycle Cost ◽  
Visual Inspection ◽  
Cost Savings ◽  
Cost Effective ◽  
Construction Cost ◽  
Rehabilitation Program ◽  
Falling Weight Deflectometer ◽  
Mechanistic Analysis ◽  
The Difference ◽  
Falling Weight

The effectiveness of using the field diagnosis and falling weight deflectometer (FWD) mechanistic analysis in reducing a 65-km (40-mi) segment of asphalt pavement to project level segments is discussed, along with selecting a cost-effective rehabilitation strategy. A mechanistic-based analysis was performed on the deflection basins measured from I-85 in Virginia to backcalculate the layer moduli. The 65-km segment was divided into structurally homogeneous sections based on the back-calculated layer moduli. The data of each homogeneous section were analyzed further to assess the in situ structural capacity, to identify weak layers, to estimate the remaining structural life, and to determine the current and future rehabilitation needs. It was found that some sections have almost no remaining structural life, and others have remaining structural life of more than 10 years. A comparison was made between the FWD–field diagnosis rehabilitation program and a visual inspection rehabilitation program. Results of the comparison indicated that the visual inspection rehabilitation program resulted in selecting thicker overlays for some of the project sections (overdesigned) and thinner overlays for the other sections (underdesigned). It is estimated that the difference between the FWD–field diagnosis rehabilitation program and the visual inspection rehabilitation program for the overdesigned sections is in the range of 45 percent of the construction cost (savings). Life-cycle cost analysis (LCCA) was performed to quantify the difference between the two rehabilitation programs for the underdesigned sections. Results of the LCCA indicated that the FWD–field diagnosis rehabilitation program would result in 26 percent and 42 percent reduction in the construction cost and user delay cost, respectively.

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