Feasibility of Backcalculation of Nonlinear Flexible Pavement Layer Parameters from Nondestructive Testing

2003 ◽  
Vol 1860 (1) ◽  
pp. 16-25 ◽  
Author(s):  
Amitis Meshkani ◽  
Imad N. Abdallah ◽  
Soheil Nazarian
Keyword(s):  
Nondestructive Testing ◽  
Laboratory Testing ◽  
Nonlinear Behavior ◽  
Falling Weight Deflectometer ◽  
Nonlinear Parameters ◽  
Pavement Materials ◽  
Linear Elastic ◽  
Texas Department ◽  
Pavement Structures ◽  
Falling Weight

Nondestructive testing (NDT) methods are typically used to measure the variations in the modulus of different pavement layers. The falling-weight deflectometer (FWD) and the seismic pavement analyzer (SPA) are two of the NDT devices used for this purpose by the Texas Department of Transportation. Since the loads applied by the FWD to the pavement are similar to those exerted by traffic, the FWD moduli are used in pavement design and analysis without adjusting them for the nonlinear behavior of the materials. Seismic moduli are similar to linear elastic moduli since they correspond to small external loads. A constitutive model that considers nonlinear behavior of pavement materials is essential in order to convert seismic moduli to those appropriate for the state of stress applied by a truck. Nonlinear parameters needed for these models can normally be obtained from laboratory testing. A study was carried out to determine whether these nonlinear parameters can be estimated from the FWD deflection basin alone or from integration of the seismic and FWD data. FWD deflection alone in most cases does not seem to contain enough information to reliably provide the nonlinear parameters of the layers. Combining the seismic and deflection data would allow the estimation of some of the nonlinear parameters for weaker pavement structures. In the authors’ experience, the most reliable way to estimate the nonlinear parameters of base and subgrade is still laboratory testing.

Influence of Cracking Damage on Deflection Basin Test Data of FWD

2014 ◽  
Vol 620 ◽  
pp. 55-60 ◽  
Author(s):  
Xin Qiu ◽  
Xiao Hua Luo ◽  
Qing Yang
Keyword(s):  
Probabilistic Approach ◽  
Asphalt Pavements ◽  
Falling Weight Deflectometer ◽  
Layer System ◽  
Linear Elastic ◽  
Distribution Features ◽  
Pavement Structures ◽  
And Performance ◽  
Falling Weight ◽  
Non Destructive

With the popularization of falling weight deflectometer (FWD) to calculate the stiffness related parameters of the pavement structures, non-destructive evaluation of physical properties and performance of pavements has taken a new direction. FWD backcalculation is mathematically an inverse problem that could be solved either by deterministic or by probabilistic approach. A review of the currently used backcalculation procedures indicates that the calculation is generally based on a homogeneous, continuous, and linear elastic multi-layer system. Identifying effective data of dynamic deflection basins seems to be an important task for performing modulus backcalculation. Therefore, the main objective of this paper was to discuss the distribution features of dynamic deflection basins of asphalt pavements with crack distresses, and present the reasonable criteria to filter the testing data of FWD deflection basins. Finally, the study aims to validate the established criteria by conducting in-situ case study.

Use of falling weight deflectometer time history data for the analysis of seasonal variation in pavement response

2010 ◽  
Vol 37 (9) ◽  
pp. 1224-1231 ◽  
Author(s):  
Kate Deblois ◽  
Jean-Pascal Bilodeau ◽  
Guy Doré
Keyword(s):  
Phase Angle ◽  
Time History ◽  
Test Site ◽  
Flexible Pavement ◽  
Dissipated Energy ◽  
Falling Weight Deflectometer ◽  
History Data ◽  
The Road ◽  
Pavement Structures ◽  
Falling Weight

This paper presents the results of an exploratory analysis of falling weight deflectometer (FWD) data collected on a large project about the spring thaw behaviour of pavements. The test site includes four test sections, two of which are conventional flexible pavement structures, whereas the other two are built with a cement-treated base. The aim of this study is to verify the applicability of using FWD time history data to evaluate damage to a road during the thawing period. The applicability of the analysis techniques is verified through the phase angle and dissipated energy. The data analyzed were obtained from tests conducted with an FWD on one flexible pavement test section. The results obtained showed a clear difference between the winter, thawing, and summer periods. It was found that the phase angle and dissipated energy can be used to evaluate the road damage during the thawing period through quantification of the phase angle and dissipated energy. These factors can also be used to describe the pavement behaviour in terms of elasticity and viscoelasticity.

Estimated remaining fatigue life of flexible pavements based on the normalized comprehensive area ratio deflection parameter

2020 ◽  
Vol 47 (5) ◽  
pp. 546-555
Author(s):  
Karthikeyan Loganathan ◽  
Mayzan M. Isied ◽  
Ana Maria Coca ◽  
Mena I. Souliman ◽  
Stefan Romanoschi ◽  
...  
Keyword(s):  
Simulation Analysis ◽  
Area Ratio ◽  
Pavement Management ◽  
Falling Weight Deflectometer ◽  
Structural Capacity ◽  
Pavement Management Systems ◽  
Pavement Structures ◽  
Traffic Disturbance ◽  
Falling Weight

A lot of pavement deflection data are available that may be utilized as a tool to evaluate the structural capacity of pavement structures at network and project levels. Falling weight deflectometer (FWD) is one of the most widely utilized devices in pavement deflection testing. Under FWD testing, deflections generated at several lateral locations as a result of surface loading application are recorded. One of the major downsides of the static FWD testing is the traffic disturbance due to the required lane closures during testing. As an effort to reduce the amount of the required FWD testing on the network level, this study aims to run an advanced computer simulation analysis to mimic the FWD deflection bowl obtained from the field. The entire simulated FWD deflection bowl was utilized in the development of the new comprehensive pavement deflection bowl area parameters. The tensile strain at the bottom of the asphalt layer was successfully related to the developed normalized comprehensive area ratio parameter ([Formula: see text]) and to the number of load repetitions to fatigue failure. The newly developed parameter was evaluated utilizing data for 35 long term pavement performance sections in Texas. The newly developed [Formula: see text] can be easily implemented and utilized as a tool in any pavement management systems.

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.

Moving Wheel versus Impact Deflections and Their Use in Pavement Evaluation

2021 ◽  
pp. 036119812110288
Author(s):  
Douglas Steele ◽  
Hyung Suk Lee ◽  
Curt Beckemeyer ◽  
Thomas Van
Keyword(s):  
Moving Load ◽  
Field Tests ◽  
Falling Weight Deflectometer ◽  
Structural Evaluation ◽  
Pavement Evaluation ◽  
Advanced Analysis ◽  
Finite Layer ◽  
Pavement Structures ◽  
Rolling Wheel ◽  
Falling Weight

Traffic speed deflection devices (TSDDs) have been developed since around 2000 to allow for safe and efficient structural evaluation of highway networks. One barrier to TSDD implementation is the inherent differences in deflections produced by moving truck loads and by falling weight deflectometer (FWD), the current deflection testing standard. To better understand the differences in data produced by the two devices, FHWA sponsored research into one particular TSDD, the rolling wheel deflectometer (RWD). The study utilized the finite layer program ViscoWave to model both FWD and RWD loads to demonstrate the effect of their inherent differences on pavement deflections and other simulated parameters. In addition, ViscoWave was used to generate theoretical FWD and RWD deflections for a diverse set of pavement structures and subgrade conditions. The resulting deflections were used to develop correlations between the two devices, which were validated with side-by-side FWD and RWD field tests performed on 23 sites. The research determined that the differences between FWD and RWD deflections vary depending on pavement factors and loading characteristics. The two devices produced similar deflections on thicker, stiffer, lower-deflection pavements, while the FWD produced relatively higher deflections on thinner, weaker, higher-deflection pavements. Therefore, use of common FWD data analysis programs will produce different results, such as layer moduli, for TSDD devices. Advanced analysis routines capable of modeling the TSDD’s moving load and loading configurations are needed.

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