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.

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.

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.

scholarly journals Propagation of Surface Waves in Asphalt Pavements Generated by Different Load Impulse of Falling Weight Deflectometer

2019 ◽  
Vol 15 (1) ◽  
pp. 29-35
Author(s):  
Jozef Komačka ◽  
IIja Březina
Keyword(s):  
Surface Waves ◽  
Travel Time ◽  
Time History ◽  
Asphalt Pavements ◽  
Load Force ◽  
Falling Weight Deflectometer ◽  
Waves Propagation ◽  
Propagation Of Waves ◽  
Falling Weight ◽  
The Waves

Abstract The propagation of waves generated by load impulse of two FWD types was assessed using test outputs in the form of time history data. The calculated travel time of wave between the receiver in the centre of load and others receivers showed the contradiction with the theory as for the receivers up to 600 (900) mm from the centre of load. Therefore, data collected by the sensors positioned at the distance of 1200 and 1500 mm were used. The influence of load magnitude on the waves propagation was investigated via the different load force with approximately the same load time and vice versa. Expectations relating to the travel time of waves, depending on the differences of load impulse, were not met. The shorter travel time of waves was detected in the case of the lower frequencies. The use of load impulse magnitude as a possible explanation was not successful because opposite tendencies in travel time were noticed.

Normal Stresses in a Granular Material under Falling Weight Deflectometer Loading

1996 ◽  
Vol 1540 (1) ◽  
pp. 24-28 ◽  
Author(s):  
P. Ullidtz ◽  
V. Askegaard ◽  
F. O. Sjølin
Keyword(s):  
Elastic Half Space ◽  
Vertical Force ◽  
Falling Weight Deflectometer ◽  
Normal Stresses ◽  
Dynamic Effects ◽  
Sand Fraction ◽  
Measured Stress ◽  
Actual Force ◽  
Boussinesq’S Equation ◽  
Falling Weight

The vertical normal stress under a falling weight deflectometer (FWD) was measured in a sand. The material had more than 90 percent falling within the sand fraction from 60 μm to 2 mm. The stress was measured with three different transducers. All transducers were installed at a depth of 280 mm. The sand was uniform to a depth of 700 mm and at a distance of 600 mm to either side of the centerline. An FWD was used to exert a known vertical force on the surface of the sand, using a loading plate 300 mm in diameter. The average stress under the plate was about 300 kPa. All the loads were imposed in the centerline of the three gauges, but at different horizontal distances from FWD to transducers. An integration of the measured stress on the plane of the transducers results in a force 10 to 14 percent larger than the peak force exerted by the FWD. The measured force is thus reasonably close to the actual force. When the measured stress is compared with the stress predicted using Boussinesq's equation for an elastic half-space, a very large difference is observed. At the centerline of the load, the measured stress is about twice the theoretical value. This difference cannot be explained by variation in material characteristics, including nonlinearity, or by dynamic effects.

scholarly journals Application of FWD data in developing dynamic modulus master curves of in-service asphalt layers

2017 ◽  
Vol 23 (5) ◽  
pp. 661-671 ◽  
Author(s):  
Nader SOLATIFAR ◽  
Amir KAVUSSI ◽  
Mojtaba ABBASGHORBANI ◽  
Henrikas SIVILEVIČIUS
Keyword(s):  
Dynamic Modulus ◽  
Master Curve ◽  
Asphalt Pavements ◽  
Falling Weight Deflectometer ◽  
Master Curves ◽  
Simple Method ◽  
High Frequencies ◽  
Design Guide ◽  
Falling Weight

This paper presents a simple method to determine dynamic modulus master curve of asphalt layers by con­ducting Falling Weight Deflectometer (FWD) for use in mechanistic-empirical rehabilitation. Ten new and rehabilitated in-service asphalt pavements with different physical characteristics were selected in Khuzestan and Kerman provinces in south of Iran. FWD testing was conducted on these pavements and core samples were taken. Witczak prediction model was used to predict dynamic modulus master curves from mix volumetric properties as well as the bitumen viscosity characteristics. Adjustments were made using FWD results and the in-situ dynamic modulus master curves were ob­tained. In order to evaluate the efficiency of the proposed method, the results were compared with those obtained by us­ing the developed procedure of the state-of-the-practice, Mechanistic-Empirical Pavement Design Guide (MEPDG). Re­sults showed the proposed method has several advantages over MEPDG including: (1) simplicity in directly constructing in-situ dynamic modulus master curve; (2) developing in-situ master curve in the same trend with the main predicted one; (3) covering the large differences between in-situ and predicted master curve in high frequencies; and (4) the value obtained for the in-situ dynamic modulus is the same as the value measured by the FWD for a corresponding frequency.

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.

scholarly journals Temperature Correction of Deflections and Backcalculated Elasticity Moduli Determined from Falling Weight Deflectometer Measurements on Asphalt Pavements

2022 ◽  
Vol 24 (1) ◽  
pp. D1-D8
Author(s):  
Ilja Březina ◽  
Ondřej Machel ◽  
Tomáš Zavřel
Keyword(s):  
Bearing Capacity ◽  
Thermal Gradient ◽  
Temperature Correction ◽  
Asphalt Pavements ◽  
Falling Weight Deflectometer ◽  
Elasticity Moduli ◽  
Similar Comparison ◽  
Pavement Temperature ◽  
Falling Weight

The evaluation of the bearing capacity of asphalt pavements is usually performed by analysing the deflections measured by a Falling Weight Deflectometer (FWD). The deflection changes with the pavement temperature. In evaluation is necessary to consider the thermal gradient of pavement and perform the temperature correction. The article contains an analysis of effects of the pavement temperature on FWD results on the long-term monitored sections. The temperature correction was performed on measured deflections or back-calculated elasticity moduli. The moduli recalculated to the temperature of 20 °C according to both procedures were similar. Comparison of moduli determined by recalculation to moduli backcalculated from the deflection bowls measured at the temperature of 20 °C, has proven smaller differences for the moduli determined from the deflection bowl corrected to the temperature of 20 °C.

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.

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