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1
Chen, Dar-Hao, Emmanuel Fernando, and Michael Murphy. "Application of Falling Weight Deflectometer Data for Analysis of Superheavy Loads." Transportation Research Record: Journal of the Transportation Research Board 1540, no. 1 (1996): 83–90. http://dx.doi.org/10.1177/0361198196154000112.
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Permitting superheavy loads may increase the rate of pavement damage and the cost of maintenance. An analysis of a proposed superheavy load route (FM519) to evaluate the potential pavement damage caused by a planned superheavy load move is presented. Falling weight deflection (FWD) tests and backcalculations of layer moduli were performed on the FM519. FWD tests and backcalculation of layer moduli were performed on the pavement before and after the superheavy load was moved. ELSYM5 and BISAR were used to evaluate the pavement responses using the backcalculated layer moduli from FWD data. The predictions of surface deflections from ELSYM5 and BISAR were close to (within 10 percent of) the measured deflections from FWD tests. The FWD data and analyses show that the existing pavement structure is adequate for the planned superheavy load move. Finally, the permit was issued with the condition that the transport vehicle should be kept within the travel lanes and away from the shoulder whenever possible. FWD tests were conducted after the superheavy load move and comparisons with before superheavy load move were made. T-tests were performed to check for significant difference at the 95 percent confidence level. T-tests showed that there is no significant difference between before and after superheavy load move. Also, no significant distresses due to this superheavy load were observed after the move, and the pavement condition is consistent with the analysis performed to issue the permit.
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Domitrović, Josipa, and Tatjana Rukavina. "Application of GPR and FWD in Assessing Pavement Bearing Capacity." Romanian Journal of Transport Infrastructure 2, no. 2 (2013): 11–21. http://dx.doi.org/10.1515/rjti-2015-0015.
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Abstract The process of pavement maintenance and rehabilitation starts by collecting the data which will form the base for evaluation of pavement functional and structural condition. Collection of data can be performed by destructive and non-destructive testing. Usually preferred are the non-destructive methods, that do not damage the pavement, and the process of pavement evaluation is objective and repeatable. Non-destructive testing methods are becoming more and more popular, especially for assessing the structural condition of the pavement. Non-destructive testing by a Falling Weight Deflectometer (FWD) and the analysis of so collected data by the process of backcalculations is today the usual tool for assessing pavement bearing capacity. One of the basic input parameters for analysis of the data collected by FWD is pavement layers thickness. The practice in Croatia is to determine pavement layers thickness by coring. This destructive method affects pavement integrity, so the number of such tests should be kept to the minimum. By coring the accurate thickness of all pavement layers is obtained on specific point locations. Thus, numerous deviations in layer thickness remain unnoticed, and in the end, use of such data for the process of backcalculations does not provide ac urate values of layer moduli. Coring can be replaced with non-destructive method of testing by Ground Penetrating Radar (GPR), which provides continuous information on thickness of all pavement layers. The paper shows the method for assessing the bearing capacity of the pavement based on the data collected by FWD, GPR and coring. The calculation for layer moduli was performed by the ELMOD software, separately for the layers thickness data obtained by coring, and separately for the thickness obtained by GPR tests. Analysis and comparison of the results of calculated elasticity moduli obtained by using various methods for collecting layer thickness data were performed in the paper.
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Tutka, Paweł, Roman Nagórski, Magdalena Złotowska, and Marek Rudnicki. "Sensitivity Analysis of Determining the Material Parameters of an Asphalt Pavement to Measurement Errors in Backcalculations." Materials 14, no. 4 (2021): 873. http://dx.doi.org/10.3390/ma14040873.
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Nondestructive tests of road pavements are among the most widely used methods of pavement condition diagnostics. Deflections of road pavement under a known load are most commonly measured in such tests, e.g., with the use of falling weight deflectometer (FWD). Measured values allow to determine the material parameters of the road structure, corresponding to the obtained results, by means of backcalculations. Among the factors that impact on the quality of results is the accuracy of deflection measurement. Deflection basins with small differences of displacement values may correspond to significantly different combinations of material parameters. Taking advantage of them for mechanistic calculations of road pavement may eventually lead to incorrect estimation of the remaining fatigue life and then inadequate selection of pavement reinforcement. This study investigated the impact of measurement errors on the change of the obtained values of stiffness moduli of flexible road pavement layers. Additionally, the influence of obtained material parameters on the values of key pavement strain, and consequently on its design fatigue life was presented.
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Le, Minh-Tu, Quang-Huy Nguyen, and Mai Lan Nguyen. "Numerical and Experimental Investigations of Asphalt Pavement Behaviour, Taking into Account Interface Bonding Conditions." Infrastructures 5, no. 2 (2020): 21. http://dx.doi.org/10.3390/infrastructures5020021.
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The interface bond between layers plays an important role in the behavior of pavement structure. However, this aspect has not yet been adequately considered in the pavement analysis process due to the lack of advanced characterizations of actual condition. In many pavement design procedures, only completely bonded or unbounded interfaces between the layers are considered. For the purpose of the better evaluation of the asphalt pavement behavior, this work focused on its investigation taking into account the actual interface bonding condition between the asphalt layers. Based on the layered theory developed by Burmister (1943), the actual interaction between pavement layers was taken into account by introducing a horizontal shear reaction modulus which represents the interface bonding condition for a given state. The analytical solution was then implemented in a numerical program before doing forward calculations for sensitivity analysis which highlights the influence of the interface bonding conditions on the structural behaviors of asphalt pavement under a static load. Furthermore, the numerical program was applied through an original experimental case study where falling weight deflectometer (FWD) tests were carried out on two full-scale pavement structures with or without a geogrid at the interface between the asphalt layers. Backcalculations of the FWD measurements allowed determining field condition of the interface bond between the asphalt layers. The obtained values of the interface shear modulus in pavement structure with a geogrid are smaller than the ones in pavement structure without geogrid. Moreover, all of these values representing field performance are at the same order of magnitude as those from dynamic interlayer shear testing.
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Sharma, Sunil, and Animesh Das. "Backcalculation of pavement layer moduli from falling weight deflectometer data using an artificial neural network." Canadian Journal of Civil Engineering 35, no. 1 (2008): 57–66. http://dx.doi.org/10.1139/l07-083.
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Efforts have been made in this paper to backcalculate the in situ elastic moduli of asphalt pavement from synthetically derived falling weight deflectometer (FWD) deflections at seven equidistant points. An artificial neural network (ANN) is used as a tool for backcalculation in this work. The ANN is observed to backcalculate layer moduli, both from normal as well as noisy deflection basins, with better accuracy compared with other software, namely, EVERCALC and ExPaS. EVERCALC is a backcalculation software downloaded from the Internet and ExPaS is a backcalculation algorithm developed in-house, based on a “search and expand” approach. Work have been extended further to develop ANN models that can predict a possible rigid layer at the bottom of the pavement and can directly predict the remaining life of the pavement without backcalculating the layer moduli. Finally, a reliability analysis is performed to quantify the performance of backcalculation using an ANN.
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Livneh, Moshe. "Single-Measurement Estimation of In Situ Asphalt-Layer Moduli with Portable Falling Weight Deflectometer." Transportation Research Record: Journal of the Transportation Research Board 1570, no. 1 (1997): 118–25. http://dx.doi.org/10.3141/1570-14.
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The portable falling weight deflectometer (FWD) was introduced some time ago. The use of this measuring device in Israel was stimulated by the contradictory results of various studies described in the technical literature. These studies indicated that significant deviations may exist between the in situ FWD-backcalculated asphalt-layer moduli and the expected true moduli values from laboratory testing. In addition to these deviations, it is known that uncertainties associated with the backcalculation procedure do not allow the backcalculation of moduli for thin asphalt layers less than 75 to 100 mm thick. Therefore, the need for an additional in situ testing device that would produce reasonable results for the in situ asphalt-layer moduli became obvious. In Israel, the portable FWD was considered to be a promising testing device to serve this need. In situ tests showed that the new device required additional testing on the asphalt surface after coring the asphalt layers to their bottom. This type of double-testing enabled the derivation of the in situ asphalt-layer modulus using a straightforward backcalculating technique. It was also thought, however, that the double-testing procedure may be sometimes too clumsy and costly. Therefore, it was decided to examine the possibility of conducting a single measurement to obtain a good estimate of the asphalt-layer modulus. The current study led to a proposed procedure for estimating the in situ asphalt-layer modulus after only one run.
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Qiu, Xin, Xiao Hua Luo, and Qing Yang. "Influence of Cracking Damage on Deflection Basin Test Data of FWD." Key Engineering Materials 620 (August 2014): 55–60. http://dx.doi.org/10.4028/www.scientific.net/kem.620.55.
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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.
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Tutka, Paweł, Roman Nagórski, and Magdalena Złotowska. "The Impact of Dynamic Effects on the Results of Non-Destructive Falling Weight Deflectometer Testing." Materials 17, no. 17 (2024): 4412. http://dx.doi.org/10.3390/ma17174412.
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The article investigates the impact of applying a dynamic computational model that considers inertia forces on pavement deflections under rapidly changing loads over time. This study is particularly relevant to the modelling of falling weight deflectometer (FWD) testing. Initially, the article examines the deflection values obtained from computational models under loads with varying frequencies. In this context, considering inertia forces was significant for load durations shorter than 0.04 s. In such cases, the results of static and dynamic analyses differed considerably. One application of FWD measurement results is determining the stiffness moduli of pavement layers using backcalculation. The study explored the impact of incorporating inertia forces into the pavement model on the estimated values of stiffness moduli obtained via backcalculation. The results revealed differences of several percent between the stiffness moduli calculated using dynamic and static numerical models. Subsequently, the key pavement deformations and fatigue life were determined using the obtained moduli. Again, significantly different results were observed between dynamic and static cases. Based on these findings, it can be concluded that dynamic effects should not be ignored when using FWD testing for backcalculation. Additionally, the article addresses the sensitivity of backcalculation results, which is crucial for the accurate interpretation of the obtained data.
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Cao, Dandan, Changjun Zhou, Yanqing Zhao, Guozhi Fu, and Wanqiu Liu. "Effectiveness of static and dynamic backcalculation approaches for asphalt pavement." Canadian Journal of Civil Engineering 47, no. 7 (2020): 846–55. http://dx.doi.org/10.1139/cjce-2019-0052.
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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.
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Elbagalati, Omar, Momen Mousa, Mostafa A. Elseifi, Kevin Gaspard, and Zhongjie Zhang. "Development of a methodology to backcalculate pavement layer moduli using the traffic speed deflectometer." Canadian Journal of Civil Engineering 45, no. 5 (2018): 377–85. http://dx.doi.org/10.1139/cjce-2017-0570.
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Backcalculation analysis of pavement layer moduli is typically conducted based on falling weight deflectometer (FWD) measurements; however, the stationary nature of FWD requires lane closure and traffic control. To overcome these limitations, a number of continuous deflection devices were introduced in recent years. The objective of this study was to develop a methodology to incorporate traffic speed deflectometer (TSD) measurements in the backcalculation analysis. To achieve this objective, TSD and FWD measurements were used to train and to validate an artificial neural network (ANN) model that would convert TSD deflection measurements to FWD deflection measurements. The ANN model showed acceptable accuracy with a coefficient of determination of 0.81 and a good agreement between the backcalculated moduli from FWD and TSD measurements. Evaluation of the model showed that the backcalculated layer moduli from TSD could be used in pavement analysis and in structural health monitoring with a reasonable level of accuracy.
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Fu, Guozhi, Cheng Xue, Yanqing Zhao, Dandan Cao, and Mohsen Alae. "Accuracy evaluation of statically backcalculated layer properties of asphalt pavements from falling weight deflectometer data." Canadian Journal of Civil Engineering 47, no. 3 (2020): 317–25. http://dx.doi.org/10.1139/cjce-2019-0152.
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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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Shoukry, Samir N. "Backcalculation of Thermally Deformed Concrete Pavements." Transportation Research Record: Journal of the Transportation Research Board 1716, no. 1 (2000): 64–72. http://dx.doi.org/10.3141/1716-08.
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Nonlinear explicit three-dimensional finite element (3-D FE) modeling is used to investigate the performance of the falling weight deflectometer (FWD) test in the evaluation of layer moduli of jointed plain concrete pavements (JPCP) subjected to nonlinear thermal gradient through the slab thickness. Concrete slab separation from the base, in-plane friction at the concrete-base interface, the gravitational forces, and the interface characteristics between dowel bars and surrounding concrete are all represented in the 3-D FE model. Experimental verification of the model is obtained through comparison of the 3-D FE generated response to ( a) the FWD measured deflection basin and ( b) the measured response of an instrumented rigid pavement section located in Ohio to a loaded truck moving at 21.8 m/s (48 mph). Several cases of linear and nonlinear thermal gradients are applied to the model, and deflection basins are obtained. Two backcalculation programs, MODULUS 5.0 and EVERCALC 4.0, are used for prediction of the layer moduli in each case, and the values are compared. The results indicate that thermal curling of the slab due to negative thermal gradient has little effect on the accuracy of backcalculated moduli. Warping of the slab due to positive thermal gradient greatly influences the measured FWD deflection basin and leads to significant errors in the backcalculated moduli. These errors may be minimized if the time an FWD test is conducted falls between the late afternoon and midmorning (from 5:30 p.m. to 9:30 a.m. during summer in West Virginia).
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Grenier, Simon, and Jean-Marie Konrad. "Dynamic interpretation of falling weight deflectometer tests on flexible pavements using the spectral element method: backcalculation." Canadian Journal of Civil Engineering 36, no. 6 (2009): 957–68. http://dx.doi.org/10.1139/l09-010.
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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.
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Meier, Roger W., Don R. Alexander, and Reed B. Freeman. "Using Artificial Neural Networks as a Forward Approach to Backcalculation." Transportation Research Record: Journal of the Transportation Research Board 1570, no. 1 (1997): 126–33. http://dx.doi.org/10.3141/1570-15.
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In recent years, artificial neural networks have successfully been trained to backcalculate pavement layer moduli from the results of falling weight deflectometer (FWD) tests. These neural networks provide the same solutions as existing programs, only thousands of times faster. Unfortunately, their use is constrained to the test conditions assumed during network training. These limitations arise from practical aspects of neural network training and cannot be circumvented easily. The goal of this research was to develop a backcalculation program combining the speed of neural networks and the flexibility of conventional programs to produce the same solutions as existing programs. This was accomplished by forgoing neural network backcalculation in favor of neural network forward-calculation, that is, using neural networks in place of complex numerical models for computing the forward-problem solutions used by the conventional backcalculation programs. A suite of neural networks, covering a range of flexible pavement structures, was trained using data generated by WESLEA, the forward-problem solver used in the WESDEF backcalculation program. When tested on 110 experimental FWD results, a version of WESDEF augmented by the neural networks provided statistically identical answers 42 times faster, on average, than the original. Provisions have been made for periodic upgrades as additional networks are trained for other pavement types and test conditions. Meanwhile, the original WESLEA can still be used when an appropriate network is unavailable. This preserves the flexibility of the original program while taking maximum advantage of the speed gains afforded by the neural networks.
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Zihan, Zia U. A., Mostafa A. Elseifi, Patrick Icenogle, Kevin Gaspard, and Zhongjie Zhang. "Mechanistic-Based Approach to Utilize Traffic Speed Deflectometer Measurements in Backcalculation Analysis." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 5 (2020): 208–22. http://dx.doi.org/10.1177/0361198120914296.
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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.
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Meshkani, Amitis, Imad N. Abdallah, and Soheil Nazarian. "Feasibility of Backcalculation of Nonlinear Flexible Pavement Layer Parameters from Nondestructive Testing." Transportation Research Record: Journal of the Transportation Research Board 1860, no. 1 (2003): 16–25. http://dx.doi.org/10.3141/1860-02.
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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.
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Stubstad, Richard N., Lynne H. Irwin, Erland O. Lukanen, and M. Lawrence Clevenson. "It’s 10 o’Clock: Do You Know Where Your Sensors Are?" Transportation Research Record: Journal of the Transportation Research Board 1716, no. 1 (2000): 10–19. http://dx.doi.org/10.3141/1716-02.
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More than 400 falling weight deflectometer (FWD) devices are presently in use throughout the world, and deflection reading accuracy is very important. Deflections are measured in microns, or hundredths of a mil, and even very small errors in the deflection readings can have a profound effect on the results of backcalculation. One question that has somehow escaped scrutiny is the one alluded to in the title to this paper—exactly where along the deflection basin are the FWD deflection sensors positioned? This is an extremely important issue for proper definition of the deflection basin as a function of distance from the center of the loading plate. A review of the FWD load-deflection data in the Long Term Pavement Performance (LTPP) study found that in at least 7 percent of some 4 million lines of FWD deflection data in the National Information Management System (NIMS) database, the sensors were not positioned as reported. This problem is not limited to LTPP and NIMS, and it occurs all too frequently on FWDs everywhere. How sensor positioning errors influence backcalculated moduli, even if all other facets of the FWD data are 100 percent correct, is described. Examples of the errors found in NIMS are also presented—real-life illustrations of what can go wrong and how much influence these errors can have on pavement analysis. A method of scanning for sensor positioning errors without carrying out backcalculation is presented. By use of the suggested transform, sensor positioning errors are clearly evident when suspect data are compared with correct data along the same, or other, pavement sections.
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Zhang, Yating, and Jeffery Roesler. "Improved Backcalculation Procedure for Continuously Reinforced Concrete Pavement." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 40 (2018): 336–47. http://dx.doi.org/10.1177/0361198118758010.
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Falling weight deflectometer (FWD) testing is effective in evaluating the structural response of in-situ concrete pavements through the backcalculated pavement layer parameters. Specifically, the FWD data can be used to backcalculate the foundation layer and concrete stiffness or the soil layer stiffness, effective slab thickness, and slab–base interface condition. Since continuously reinforced concrete pavement (CRCP) has closely spaced transverse cracks, the traditional backcalculation assumption of an infinite slab can lead to significant errors in the backcalculated results. In this paper, solutions for backcalculated modulus of subgrade reaction ( k-value), elastic modulus of concrete ( E), and effective thickness ( heff) for different crack spacing have been derived from 2-D finite element analysis. AASHTO sensor configuration (0, 12, 24, 36 in.) was recommended for CRCP with crack spacing ≥6 ft, and an alternative solution for crack spacing of 4 and 5 ft was proposed with AREA24. Crack load transfer efficiency (LTE) across transverse cracks had limited impact on backcalculated results if the LTE was >80%. As expected, the backcalulation values were sensitive to the load plate’s longitudinal position relative to the transverse crack especially for crack spacings smaller than 8 ft. The proposed backcalculation method was applied to a field CRCP test section with different crack spacing, reinforcement ratio, and base types.
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Appea, Alexander K., and Imad L. Al-Qadi. "Assessment of Falling Weight Deflectometer Data for Stabilized Flexible Pavements." Transportation Research Record: Journal of the Transportation Research Board 1709, no. 1 (2000): 19–25. http://dx.doi.org/10.3141/1709-03.
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Backcalculation of pavement moduli through the utilization of the falling weight deflectometer (FWD) is used for pavement monitoring and evaluation. The performance and structural condition of nine flexible pavement test sections built in Bedford County, Virginia, have been monitored over the past 5 years using FWD. The nine sections include three groups with aggregate base layer thicknesses of 100, 150, and 200 mm, respectively. Sections 1, 4, and 7 are control, whereas Sections 2, 5, 8 and 3, 6, 9 are stabilized with geotextiles and geogrids, respectively. The FWD testing used five double-load drops ranging from 26.5 to 58.9 kN. The deflection basins obtained from the testing have been analyzed using the ELMOD backcalculation program to find the pavement structural capacity and to detect changes in the aggregate resilient modulus. The analysis shows a reduction in the backcalculated resilient modulus of the 100-mmthick base layer. The reduction was 33 percent over 5 years for the nonstabilized section compared with the geosynthetically stabilized section. The reduction in base layer resilient modulus may have resulted from subgrade fine migration into this layer as confirmed by excavation. The study confirms the effectiveness of using woven geotextile as a separator in a pavement system built over weak subgrade. This supports the continuous rutting measurements and ground truth excavation conducted in late 1997.
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Parvini, Mehdi, and Dieter FE Stolle. "Interpretation of pavement deflection measurement data using an elastodynamic stochastic approach." Canadian Journal of Civil Engineering 25, no. 1 (1998): 151–60. http://dx.doi.org/10.1139/l97-074.
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Pavement deflection measurements, together with backcalculation procedures, are widely used to estimate the layer moduli of pavement-subgrade systems. Sensitivity analysis of a sample problem indicates that conclusions drawn from static analyses with regards to deflection sensitivity to variation in layer moduli may apply when characterizing uncertainty associated with the interpretation of the falling weight deflectometer (FWD) data. The uncertainty associated with the values of the backcalculated parameters from deflection data is investigated in this paper using an elastodynamic, stochastic finite element approach. The results of the simulations indicate that, in order to properly estimate surface layer moduli, loading frequencies higher than that of excitation by typical FWD loading are required. The low sensitivity of deflection uncertainty to random variations in surface modulus, when compared with that associated with subgrade modulus, is demonstrated to contribute to high variations in backcalculated surface modulus from measured surface deflections. Although focus is placed on uncertainties in elastic modulus and deflection, the methodology presented in the paper can be used to quantify uncertainties associated with other layer properties and pavement responses.Key words: stochastic, finite element, pavement deflection, elastodynamic, backcalculation, layer moduli, falling weight deflectometer test.
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Maitra, Swati Roy, K. S. Reddy, and L. S. Ramachandra. "Estimation of Joint and Interface Parameters for the Finite Element Analysis of Jointed Concrete Pavement Using Structural Evaluation Results." International Journal on Pavement Engineering & Asphalt Technology 16, no. 2 (2015): 21–38. http://dx.doi.org/10.1515/ijpeat-2015-0007.
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Abstract In the analysis of jointed concrete pavement, it is necessary to appropriately model certain aspects of the pavement for accurate estimation of its structural responses. These include load transfer at joints (doweled and aggregate interlocked) and interface condition between slab and foundation. This paper presents a backcalculation method for estimating the joint parameters, both transverse and longitudinal, and the interface parameter along with the pavement layer moduli by using the results of structural evaluation of an in-service concrete pavement. The details of the structural evaluation using Falling Weight Deflectometer (FWD) and the two-stage backcalculation procedure using a three-dimensional finite element (FE) model for jointed concrete pavement are discussed. Modulus of dowel support and modulus of interlocking joints are the transverse and longitudinal joint parameters respectively and the coefficient of friction between concrete slab and foundation is the interface parameter considered for the analysis. These parameters are the useful inputs in modeling jointed concrete pavement using finite element method.
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Khogali, Walaa E. I., and Kenneth O. Anderson. "Evaluation of Seasonal Variability in Cohesive Subgrades Using Backcalculation." Transportation Research Record: Journal of the Transportation Research Board 1546, no. 1 (1996): 140–50. http://dx.doi.org/10.1177/0361198196154600116.
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Seasonal variation in pavement strength is an important concern for engineers and transportation authorities. In 1990, an investigation was initiated that aimed at quantifying seasonal variations within a typical cohesive subgrade soil in Alberta. The study consisted of two phases: a field investigation phase and a laboratory testing program. The field phase involved instrumenting a pavement section that is representative of the primary highway system in Alberta with thermal conductivity suction sensors. Falling weight deflectometer (FWD) deflection tests were conducted at regular time intervals over a period of 2 years and at various locations within this section. Effective pavement layer moduli were backcalculated using measured deflections, and the results were plotted versus time to quantify seasonal changes occurring in pavement structural strength. Only the research findings obtained from the FWD deflection tests that deal primarily with subgrade moduli are discussed. Remaining field data represent a valuable resource to researchers investigating other pavement structural factors. Use of the backcalculation approach for quantifying seasonal variations in subgrade stiffness seems promising. Following a significant reduction in subgrade stiffness upon thawing, a long period of relatively constant strength prevails. After that a period of gradual recovery and subsequent increase in strength is experienced as freezing approaches. Backcalculated subgrade fill moduli were found to be 65 percent greater than their counterparts in cut areas. Furthermore, the subgrade fill moduli were observed to experience less seasonal fluctuation than the cut moduli. Finally, the backcalculated subgrade moduli were found to be insensitive to asphalt concrete surface temperature influences.
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Long, Bing, Mustaque Hossain, and Andrew J. Gisi. "Seasonal Variation of Backcalculated Subgrade Moduli." Transportation Research Record: Journal of the Transportation Research Board 1577, no. 1 (1997): 70–80. http://dx.doi.org/10.3141/1577-09.
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Seasonal variations in pavement material properties and behavior due to variations in temperature and moisture conditions are known to affect the structural performance of pavement. Temperature, subgrade moisture content, and falling weight deflectometer (FWD) deflection data were collected monthly on four asphalt pavement test sections for a year. Subgrade moduli were backcalculated using the elastic layer theory with two calculation schemes and pavement models. Backcalculation of subgrade moduli by subdividing the subgrade into a compacted subgrade layer and a natural soil subgrade layer resulted in compacted subgrade moduli that are more sensitive to the seasonal variation for all sites. It was found that for almost all sites, the patterns of subgrade response, in terms of subgrade moduli versus subgrade moisture content, simulated sine-shaped forms signifying a temperature effect. The temperature effect was confirmed by the strong correlation between backcalculated subgrade moduli and pavement surface temperature during FWD tests. The lowest backcalculated subgrade moduli were obtained for two sections during months when asphalt surface temperatures were excessively high (greater than 40°C). Both backcalculation schemes showed similar trends in variation of subgrade moduli over seasons. When the AASHTO relative damage concept was used to compute the effective roadbed soil resilient modulus for design, similar values were found for both schemes for most of the sites. The minimum frequency of FWD testing to capture the seasonal variation of subgrade was found to be three tests per year, or testing every fourth month, assuming that unusually high temperature regimes could be avoided.
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Khan, Zafrul H., Rafiqul A. Tarefder, and Md Amanul Hasan. "Field Characterization of Pavement Materials using Falling Weight Deflectometer and Sensor Data from an Instrumented Pavement Section." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 4 (2020): 205–21. http://dx.doi.org/10.1177/0361198120911926.
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This study deals with the backcalculation of the mechanical properties of pavement layers using not only the falling weight deflectometer (FWD) sensor data but also pavement response under that FWD load from the embedded sensors in an instrumentation section. To perform the backcalculation, a layered viscoelastic pavement model incorporating asphalt concrete (AC) cross-anisotropy is developed as the forward model. Field degree of cross-anisotropy in AC is determined at the maximum magnitude frequency obtained through continuous wavelet transform of the material response signal. The material response signal is obtained from the deconvolution between the loading signal and the signal registered at the embedded sensors. An inverse analysis methodology is also developed to calculate the gross vehicle weight (GVW) of any vehicle passing through the instrumentation section using only the backcalculated material properties and pavement responses. From the results, it is observed that inclusion of the AC cross-anisotropy reduces the error norm, and a good agreement is observed with the laboratory dynamic modulus in both horizontal and vertical directions. It is also observed that the maximum magnitude frequency of material response and degree of cross-anisotropy in AC both decrease with an increase in average AC temperature. Furthermore, using the backcalculated material properties and pavement responses, it is possible to determine the GVW with 95% accuracy.
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SONE, Akihito, Kiyoshi FUJINAMI, Kunihito MATSUI, and Yukio KIKUTA. "DEVELOPMENT OF DYNAMIC BACKCALCULATION SOFTWARE“Easy DBALM for Windows” FOR FWD TESTS." JOURNAL OF PAVEMENT ENGINEERING, JSCE 12 (2007): 25–30. http://dx.doi.org/10.2208/journalpe.12.25.
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Mun, Sungho, and Y. Richard Kim. "Backcalculation of subgrade stiffness under rubblised PCC slabs using multilevel FWD loads." International Journal of Pavement Engineering 10, no. 1 (2009): 9–18. http://dx.doi.org/10.1080/10298430701827650.
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Chang, Der-Wen, and Chia-Ling Chang. "Dynamic Interpretation for Impulsive Deflection Test on Flexible Pavements." Journal of Mechanics 14, no. 2 (1998): 91–100. http://dx.doi.org/10.1017/s1727719100000113.
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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.
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Stolle, Dieter F. E., and Gabriel Sedran. "Influence of inertia on falling weight deflectometer (FWD) test response." Canadian Geotechnical Journal 32, no. 6 (1995): 1044–48. http://dx.doi.org/10.1139/t95-101.
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This note addresses the appropriateness of adopting an elastostatic model for backcalculating in situ layer moduli from falling weight deflectometer (FWD) data. By approximating the elastodynamic displacement field using an elastostatic solution for a given load distribution, it is shown via Ritz vector analyses that elastostatic fields do not accurately represent the displacements associated with pavements subjected to FWD-type loading. Some improvement is, however, possible by including first-order corrections for inertial forces. The main conclusion stemming from the analyses is that elastostatic models should not be used to estimate in situ moduli. Key words : pavement, elastodynamic analysis, Ritz vectors, back-calculation, structural integrity.
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Yue, Z. Q., and Jian-hua Yin. "Backcalculation of Moduli in FWD Evaluation of Pavements: A Solution of Global Minimum." HKIE Transactions 5, no. 2 (1998): 37–44. http://dx.doi.org/10.1080/1023697x.1998.10667750.
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Bech, Nathan D., and Julie M. Vandenbossche. "Relationship between Backcalculated and Estimated Asphalt Concrete Dynamic Modulus with Respect to Falling Weight Deflectometer Load and Temperature." Transportation Research Record: Journal of the Transportation Research Board 2674, no. 9 (2020): 887–97. http://dx.doi.org/10.1177/0361198120932560.
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There are several methods for determining the stiffness of asphalt concrete in an existing pavement. The three primary methods are: dynamic modulus testing in the laboratory, predictive equations, and falling weight deflectometer (FWD) testing. Asphalt over asphalt (AC/AC) overlay design procedures allow the use of multiple methods to characterize fatigue damage in the existing asphalt concrete. Therefore, understanding the difference between these methods is critical for AC/AC overlay design. The differences between the methods for determining asphalt concrete stiffness and how these differences are related to FWD load magnitude and asphalt temperature are examined. Data from the Federal Highway Administration’s Long-Term Pavement Performance Program (LTPP) are used in this investigation. It is found that the stiffness determined through FWD testing and backcalculation is generally less than that estimated using the Witczak predictive equation and binder aging models. Furthermore, it is found that both FWD load magnitude and asphalt temperature have a significant effect on the difference between backcalculated and estimated stiffness of asphalt concrete. Backcalculated stiffness increases relative to estimated stiffness as FWD load and temperature increase. These effects must be considered when multiple methods of determining asphalt concrete stiffness are used interchangeably for overlay design.
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Maina, James, Wynand JvdM Steyn, Emile B. van Wyk, and Frans le Roux. "Static and Dynamic Backcalculation Analyses of an Inverted Pavement Structure." Advanced Materials Research 723 (August 2013): 196–203. http://dx.doi.org/10.4028/www.scientific.net/amr.723.196.
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A crucial part of any maintenance strategy is an intricate understanding of the material characteristics of the pavement, so that the current level of damage may be accurately assessed and an appropriate plan implemented. Advances in the precision to which these parameters can be determined, as well as improvements in how these results are interpreted under varying conditions of measurement and analysis, are essential in the effective execution of a maintenance strategy. Results from Falling Weight Deflectometer (FWD), which is a Non-Destructive Testing (NDT) device, can be used to predict elastic modulus of any layer by comparing measured deflection data to calculated values through an iterative process referred to as back-calculation. This paper presents a comparison between static and dynamic back-calculation procedures, specifically with regard to typical South African inverted pavements. The analysis indicates a dynamic analysis provides results of greater accuracy than a static analysis, although the effect of the difference requires further investigation.
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KAWANA, Futoshi, Hiroyasu NAKAMURA, Shigeki TAKAHASH, Yasushi TAKEUCHI, and Kunihito MATSUI. "DYNAMIC BACKCALCULATION OF PHAVEMENT LAYER PROPERTIES USING FWD TEST DATA CONSIDERING CONTACT PRESSURE DISTRIBUTION." Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 71, no. 3 (2015): I_145—I_152. http://dx.doi.org/10.2208/jscejpe.71.i_145.
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Ahmed, Namir G. "INFLUENCE OF VARIABILITY IN FLEXIBLE PAVEMENT PARAMETERS ON BACKCALCULATED MODULI." Journal of Engineering 12, no. 02 (2006): 445–57. http://dx.doi.org/10.31026/j.eng.2006.02.20.
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Many researchers recommended Falling Weight Deflectometer (FWD) to be use for the purpose ofstiffness profile determination of existing pavement. Several sources of uncertainties contribute tothe inaccuracies in moduli obtained in this manner. these include: 1) the measured parameters(deflection basin and FWD load), 2) the back calculation model, and 3) the pavement parameters, such as Poisson's ratio and thickness of each pavement layer . In the present study the influence of the variation in the thickness and other pavement parameters on the backcalcuted moduli are investigated .Theoretical deflection basins were generated for different pavement structure using program Mich-pave. Mich-back program was then utilized to backcalculate the moduli from these theoretical basins. To assess the influence of the variability in thickness, Poisson's ratio, FWD load and deflection, a Monte Carlo simulation process was employed. Results show that the backcalculation of the layer moduli is greatly influence by the variability of the combined pavement. A sensitivity analysis showed that the uncertainties in thicknesses are the major contributor to variations of the backcalculated Moduli.
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AI-Khoury, Rafid, Athanassios Scarpas, Cor Kasbergen, and Johan Blaauwendraad. "Dynamic Interpretation of Falling Weight Deflectometer Test Results: Spectral Element Method." Transportation Research Record: Journal of the Transportation Research Board 1716, no. 1 (2000): 49–54. http://dx.doi.org/10.3141/1716-06.
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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.
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Ksaibati, Khaled, Jamshid Armaghani, and Jason Fisher. "Effect of Moisture on Modulus Values of Base and Subgrade Materials." Transportation Research Record: Journal of the Transportation Research Board 1716, no. 1 (2000): 20–29. http://dx.doi.org/10.3141/1716-03.
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Moisture in the base and subgrade layers of pavement can significantly decrease the modulus values of these layers. Recently, a study was performed on several Florida state roads for the purpose of evaluating the decrease in moduli of bases and subgrades due to the proximity of the water table. Dynaflect and falling weight deflectometer (FWD) tests were performed on pavement test sections throughout Florida for the purpose of backcalculation of the modulus values of the different layers. Testing was performed at different times of the year, and the water table fluctuations were recorded throughout the study. The Dynaflect and FWD deflections, water contents, depths to water table, layer thicknesses, pavement temperatures, and air temperatures were recorded on all test sections over a 5-year period. EVERCALC was used for back-calculation of modulus values on the basis of FWD tests. The Dynaflect data were also used for calculation of layer properties on the basis of a procedure developed by the Florida Department of Transportation. Both Dynaflect and FWD showed that the water table had a significant negative impact on the modulus values of the base and subgrade materials. Such results are extremely beneficial aids for establishing acceptable embankment depths so that the effects of moisture on the modulus values of pavements may be reduced.
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NISHIZAWA, Tatsuo, Kenji TAKAI, Naofumi NORO, Nobuhiro KURATO, and Yasuhiro NAKAMURA. "STRUCTURAL EVALUATION OF TRANSVERSE JOINT OF 30 YEARS CONCRETE PAVEMENT ON EXPRESSWAY WITH FWD BACKCALCULATION." Journal of Japan Society of Civil Engineers, Ser. E1 (Pavement Engineering) 76, no. 1 (2020): 1–11. http://dx.doi.org/10.2208/jscejpe.76.1_1.
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Tarefder, R. A., and M. U. Ahmed. "Consistency and accuracy of selected FWD backcalculation software for computing layer modulus of airport pavements." International Journal of Geotechnical Engineering 7, no. 1 (2013): 21–35. http://dx.doi.org/10.1179/1938636212z.0000000009.
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Dai, Shongtao, and Dave Van Deusen. "Field Study of In Situ Subgrade Soil Response Under Flexible Pavements." Transportation Research Record: Journal of the Transportation Research Board 1639, no. 1 (1998): 23–35. http://dx.doi.org/10.3141/1639-03.
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Falling weight deflectometer (FWD) and truck tests were performed on three instrumented flexible pavement sections at the Minnesota Road Research project. The purposes of the study were (1) to investigate sub-grade soil response under FWD and moving truck loads and (2) to estimate in situ resilient modulus of the subgrade soil. The truck tests were performed at various speeds ranging from 16 to 78 km/h. The subgrade deformations and the vertical pressures on the top of the subgrade soils were measured from in situ displacement and soil pressure gauges. The experimental results showed that the deformations and the vertical pressures, in general, did not show significant dependency of truck speed within the above speed range. However, a slight decrease of the vertical pressure with increase of speed was observed for a thin conventional pavement section, while the vertical pressure in a relatively thick pavement section appeared to be less sensitive to speed. The results from FWD tests indicated that the subgrade deformation was linearly related to the FWD loads up to approximately 40 kN. Furthermore, a method is presented to estimate in situ subgrade modulus using the linear elastic theory and the measurements from the in situ sensors. The estimated modulus is comparable with the laboratory results at a low deviator stress level and is lower than modulus obtained from the backcalculation using FWD deflection basins.
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ABE, Ryuji, Jun TAKO, Kunihito MATSUI, and Yuichi KUBO. "STUDY ON STRUCTURAL EVALUATION OF PAVEMENT LAYER MODULI OBTAINED BY BACKCALCULATING FWD DEFLECTION DATA." JOURNAL OF PAVEMENT ENGINEERING, JSCE 12 (2007): 31–38. http://dx.doi.org/10.2208/journalpe.12.31.
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Gopalakrishnan, Kasthurirangan, and Siddhartha Kumar Khaitan. "FINITE ELEMENT BASED ADAPTIVE NEURO‐FUZZY INFERENCE TECHNIQUE FOR PARAMETER IDENTIFICATION OF MULTI‐LAYERED TRANSPORTATION STRUCTURES." TRANSPORT 25, no. 1 (2010): 58–65. http://dx.doi.org/10.3846/transport.2010.08.
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During the service life of a pavement, it is often required to conduct Non-destructive tests (NDTs) to evaluate its structural condition and bearing capacity and to detect damage resulting from the repeated traffic and environmental loading. Among several currently used NDT methods, the Falling Weight Deflectometer (FWD) is the most commonly used pavement NDT method applied by many transportation agencies all over the world. Non-destructive testing of pavements using FWD is typically accompanied by the prediction of the Young’s modulus of each layer of the pavement structure through an inverse analysis of the acquired FWD deflection data. The predicted pavement layer modulus is both an indicator of the structural condition of the layer as well as a required input for conducting mechanistic-based pavement structural analysis and design. Numerous methodologies have been proposed for backcalculating the mechanical properties of pavement structures from NDT data. This paper discusses the development of an Adaptive-Network-based Fuzzy Inference System (ANFIS) combined with Finite Element Modeling (FEM) for the inverse analysis of the multi-layered flexible pavement structures subjected to dynamic loading.
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Taranovs, Andrejs. "Falling Weight Deflectometre And Plate Load Test: Direct And Indirect Comparative Testing." IOP Conference Series: Materials Science and Engineering 1202, no. 1 (2021): 012021. http://dx.doi.org/10.1088/1757-899x/1202/1/012021.
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Abstract Plate load test is a widely used method in Latvia both in quality control and in road design process. This test is performed according to the standard DIN 18134. Such test usually takes at least 30 minutes and requires certain load weight. Considering the relatively long time needed for this test, alternatives were sought and a potential alternative was defined to perform testing with Falling Weight Deflectometre (FWD). In order to check this assumption both direct and indirect testing was performed and correlation between the results of both tests was defined. In the first case the test was performed in the same location with both pieces of equipment on a surface of unbound pavement. In the second case the test with Falling Weight Deflectometre was performed on the surface of bituminous pavement but plate load test was performed in the same location on the surface of base course with prior demolition of bituminous layers. In order to compare the results of indirect comparative testing, the backcalculation for the data acquired with Falling Weight Deflectometre was performed according to German calculation method. Results acquired with direct testing showed that the testing with Falling Weight Deflectometre and plate load test are interchangeable if no characterization of the layer compaction is required. The German method of backcalculation (FGSV, 2014) is very simple. Despite positive references from other specialists this method in comparative testing did not show sufficiently good correlation with the results acquired in plate load test.
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Salles, L. S., and J. T. Balbo. "Experimental continuously reinforced concrete pavement parameterization using nondestructive methods." Revista IBRACON de Estruturas e Materiais 9, no. 2 (2016): 263–74. http://dx.doi.org/10.1590/s1983-41952016000200007.
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ABSTRACT Four continuously reinforced concrete pavement (CRCP) sections were built at the University of São Paulo campus in order to analyze the pavement performance in a tropical environment. The sections short length coupled with particular project aspects made the experimental CRCP cracking be different from the traditional CRCP one. After three years of construction, a series of nondestructive testing were performed - Falling Weight Deflectometer (FWD) loadings - to verify and to parameterize the pavement structural condition based on two main properties: the elasticity modulus of concrete (E) and the modulus of subgrade reaction (k). These properties estimation was obtained through the matching process between real and EverFE simulated basins with the load at the slab center, between two consecutive cracks. The backcalculation results show that the lack of anchorage at the sections end decreases the E and k values and that the longitudinal reinforcement percentage provides additional stiffness to the pavement. Additionally, FWD loadings tangential to the cracks allowed the load transfer efficiency (LTE) estimation determination across cracks. The LTE resulted in values above 90 % for all cracks.
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Oktavia Tanjung, Fitri, Bambang Sugeng Subagio, and Harmein Rahman. "Analisis Kondisi Jalan Perkerasan Lentur Berdasarkan Prediksi Umur Sisa Menggunakan Metode AASHTO 1993 serta Analisis Kerusakan Lapis Perkerasan Lentur Menggunakan Metode Horack (Studi Kasus: Ruas Jalan Bypass Kota Pariaman STA 52+100 s/d 57+100)." Jurnal Teknik Sipil 30, no. 2 (2023): 255–62. http://dx.doi.org/10.5614/jts.2023.30.2.13.
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Abstrak Jalan yang dibebani oleh lalu lintas kendaraan yang tinggi dan terus menerus dapat menyebabkan terjadinya kerusakan jalan baik secara fungsional maupun struktural. Ruas jalan Bypass Kota Pariaman merupakan ruas jalan nasional yang diperuntukan bagi kendaraan-kendaraan berat yang akan melintasi Kota Pariaman menuju ke arah Kota Padang dan sebaliknya ke arah Kabupaten Agam. Dalam beberapa tahun terakhir ruas jalan ini telah mengalami kerusakan yang cukup parah sehingga dapat mengganggu kenyamanan serta keamanan dalam berkendara. Prediksi umur sisa perkerasan jalan penting dilakukan untuk mengetahui apakah ruas jalan ini masih mampu menanggung beban lalu lintas atau tidak. Prediksi umur sisa dilakukan menggunakan metode AASHTO 1993 berdasarkan data lendutan jalan tahun 2020 yang di uji menggunakan alat FWD dengan analisis perhitungan Backcalculation untuk mendapatkan nilai CESAL pada saat kondisi failure. Hasil analisis menunjukan, jumlah repetisi beban yang masih mampu ditanggung oleh ruas jalan ini sebesar 2.337.881 ESAL ditahun 2023 dengan umur sisa = 0 tahun lagi. selanjutnya dilakukan analisis untuk mengetahui kondisi kerusakan tiap lapisan perkerasan menggunakan metode Horack dengan data lendutan sebagai parameter penilaian. Hasil analisis menunjukan rata-rata kondisi tiap lapis perkerasan jalan telah berada dalam kategori rusak berat dengan lapisan yang mengalami kerusakan paling parah yaitu di lapisan subbase. Kata-kata Kunci: AASHTO 1993, CESAL, FWD, horack, umur sisa perkerasan jalan, Abstract Roads loaded with high vehicle traffic can cause road damage both functionally and structurally. The Pariaman City Bypass Road is a national road section intended for heavy vehicles that will cross Pariaman City to Padang City and vice versa to Agam Regency. In recent years, this road has been damaged quite severely which can interfere with driving comfort and safety. Prediction of the remaining life is important to know whether the road section is still able to carry the traffic load or not. Prediction of remaining life is by using the 1993 AASHTO method based on 2020 road deflection data tested using the FWD tool with Backcalculation analysis to obtain the CESAL value at the time of failure. The analysis results show that the number of load repetitions that can still be borne by this road section is 2,337,881 ESAL in 2023 with a remaining life of 0 year. Furthermore, an analysis is carried out to determine the damage condition of each pavement layer using the Horack method with deflection data as an assessment parameter. The analysis results show that the average condition of each pavement layer has been in the category of severe damage with the most severely damaged layer being the subbase layer. Keywords: AASHTO 1993, CESAL, FWD, horack, pavement remaining life
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Lee, Yung-Chien, Y. Richard Kim, and S. Ranji Ranjithan. "Dynamic Analysis-Based Approach To Determine Flexible Pavement Layer Moduli Using Deflection Basin Parameters." Transportation Research Record: Journal of the Transportation Research Board 1639, no. 1 (1998): 36–42. http://dx.doi.org/10.3141/1639-04.
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Most of the deflection analysis programs used today to analyze falling weight deflectometer (FWD) data are based on static analysis, which often underestimates the subgrade strength. Unfortunately, dynamic analysis usually involves complex calculations and requires significant computation time, thus making it impractical for routine applications. A methodology based on deflection basin parameters and artificial neural networks (ANN) for processing dynamic FWD measurements to estimate layer strengths is presented in this paper. Two-dimensional, dynamic finite element analysis using the ABAQUS program was employed to develop the deflection information for this study. Unlike the majority of the existing backcalculation programs that iteratively adjust the layer moduli to match the measured deflections, the proposed method first determines the subgrade modulus by means of two deflection basin parameters—Base Damage Index and Shape Factor F2—and then applies the estimated subgrade modulus and other parameters as input variables to a trained ANN to estimate the upper layers’ moduli. In contrast to other programs that require the input of seed values for layer moduli, this method does not require initial estimates as input. A set of field FWD measurements were analyzed both by this method and by the MODULUS program. Results reveal that the proposed method is able to better predict the asphalt concrete layer modulus while taking into account the dynamic effects of the FWD test. This method is also shown to be computationally efficient, which makes it applicable for routine tasks and field use.
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Elshamy, M. M. M., and A. N. Tiraturyan. "USING APPLICATION OF AN ARTIFICIAL NEURAL NETWORK SYSTEM TO BACKCALCULATE PAVEMENT ELASTIC MODULUS." Russian Journal of Building Construction and Architecture, no. 2(46) (October 30, 2020): 84–93. http://dx.doi.org/10.36622/vstu.2020.2.46.006.
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Statement of the problem. The article is devoted to the use of artificial neural networks in solving the problems of processing the results of instrumental recording of bowls of flexible pavement deflections using FWD shock loading settings. Results. The analysis was carried out, the shortcomings of the existing processing methods were noted, in particular the “backcalculation” method, which consists of a long calculation time, and the instability of the results obtained. The structure of the artificial neural network was built to determine the elastic moduli of the pavement layers. Training of an artificial neural network was carried out using the method of back propagation of error. Conclusions. The developed neural network has shown good results in training on the test data set, as well as high accuracy of prediction of the elastic moduli of the pavement.
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Pożarycki, Andrzej, Przemysław Górnaś, and Paweł Zalewski. "The influence of cracks on changes in stiffness moduli of asphalt mixtures based on in situ tests." Roads and Bridges - Drogi i Mosty 14, no. 4 (2016): 257–70. http://dx.doi.org/10.7409/rabdim.015.017.
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The role of diagnosis in predicting changes in the technical condition of pavement within the scope of potential repair needs and their costs is decisive. One of its aims it to detect certain factors, e.g. cracks which can considerably accelerate the degradation of pavement. Whereas the identification of cracks visible on the surface of wearing courses is possible at a visual inventory or photo-based pavement condition survey, revealing cracks in bituminous courses located below the wearing course requires the application of different methods. The present article introduces the effectiveness of identifying in a controlled way damaged bituminous courses of the pavement test section by means of the backcalculation technique. Basing on measurement results with the use of FWD (Falling Weight Deflectometer) device and pseudo-static values, the stiffness analysis of courses in the three-course pavement enabled to indicate the correct location of constrained damage.
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Shao, Lisheng, Sun Woo Park, and Y. Richard Kim. "Simplified Procedure for Prediction of Asphalt Pavement Subsurface Temperatures Based on Heat Transfer Theories." Transportation Research Record: Journal of the Transportation Research Board 1568, no. 1 (1997): 114–23. http://dx.doi.org/10.3141/1568-14.
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Surface deflection measurements and backcalculation of layer moduli in flexible pavements are significantly affected by the temperature of the asphalt concrete (AC) layer. Correction of deflections or backcalculated moduli to a reference temperature requires determination of an effective temperature of the AC layer. For routine deflection testing and analysis in state highway agencies, it is preferable, from a practical point of view, to use a nondestructive prediction method for determining the effective AC layer temperature instead of measuring the temperature directly from a small hole drilled into the AC layer. A simplified procedure to predict asphalt pavement subsurface temperatures is presented. The procedure is based on fundamental principles of heat transfer and uses the surface temperature history since yesterday morning to predict the AC layer mid-depth temperature at the time of falling weight deflectometer (FWD) testing today. The surface temperature history is determined using yesterday’s maximum air temperature and cloud condition, the minimum air temperature of today’s morning, and surface temperatures measured during FWD tests. FWD tests and temperature measurements have been conducted on seven pavement sections with varying structural designs located in three different climatic regions of North Carolina. The field temperature records from these pavements have provided values of pavement thermal parameters and coefficients in temperature functions that are needed in the prediction procedure. A set of verification results are presented using examples with different climatic regions, changing AC layer thicknesses, and varying weather patterns in different seasons.
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Habbouche, Jhony, Elie Y. Hajj, Peter E. Sebaaly, and Nathan E. Morian. "Damage Assessment for ME Rehabilitation Design of Modified Asphalt Pavements: Challenges and Findings." Transportation Research Record: Journal of the Transportation Research Board 2672, no. 40 (2018): 228–41. http://dx.doi.org/10.1177/0361198118777090.
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The overall objective of this study was to assess the use of Level 1 analysis for mechanistic-empirical (ME) rehabilitation designs of deteriorated polymer-modified asphalt concrete (AC) pavements in Nevada using the AASHTOWare® Pavement ME software. This research also explored the possible implementation of a hybrid approach for AC damage characterization to overcome the challenges associated with the use of the Witczak model for estimating the undamaged dynamic modulus master curve of the existing AC layer. Two rehabilitation field projects were used as part of this study. The experimental plan involved falling weight deflectometer (FWD) testing in the right wheelpath before rehabilitation, analysis of core samples, estimation of an equivalent undamaged dynamic modulus, and estimation of equivalent damaged dynamic modulus from FWD backcalculation. The proposed hybrid approach consisted of conducting laboratory dynamic modulus testing on the collected core samples and estimating an equivalent undamaged dynamic modulus at the same FWD testing temperature and loading frequency. The pre-overlay damage, characterized based on the approach in Pavement ME Design software (i.e., using a Witczak prediction model and backcalculated modulus), showed overly high values that did not match with the collected pre-overlay distress data on either of the rehabilitation projects. Based on the findings from this study, the hybrid approach was recommended for implementation by Nevada Department of Transportation (NDOT) when designing AC overlay over polymer-modified asphalt pavements in Nevada. Recommendations for user inputs were also provided for future consideration in Pavement ME Design software.
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Li, Maoyun, and Hao Wang. "Development of ANN-GA program for backcalculation of pavement moduli under FWD testing with viscoelastic and nonlinear parameters." International Journal of Pavement Engineering 20, no. 4 (2017): 490–98. http://dx.doi.org/10.1080/10298436.2017.1309197.
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Georgouli, Konstantina, Christina Plati, and Andreas Loizos. "Evaluation of a Comprehensive Approach for the Development of the Field E* Master Curve Using NDT Data." NDT 2, no. 4 (2024): 474–86. http://dx.doi.org/10.3390/ndt2040029.
Full textAbstract:
Non-destructive testing (NDT) systems are essential tools and are widely used for assessing the condition and structural integrity of pavement structures without causing any damage. They are cost-effective, provide comprehensive data, and are time efficient. The bearing capacity and structural condition of a flexible pavement depends on several interrelated factors, with asphalt layers stiffness being dominant. Since asphalt mix is a viscoelastic material, its performance can be fully captured by the dynamic modulus master curve. However, in terms of evaluating an in-service pavement, although a dynamic load is applied and the time history of deflections is recorded during testing of FWD, only the peak deflection is considered in the analysis. Therefore, the modulus of stiffness estimated by backcalculation is the modulus of elasticity. While several methods have been introduced for the determination of the field dynamic modulus master curve, the MEPDG approach provides significant advantages in terms of transparency and robustness. This study focuses on evaluating the methodology’s accuracy through an experimental study. The data analysis and validation process showed that routine measurements with the FWD and GPR, within the framework of a pavement monitoring system, can provide valuable input parameters for the evaluation of in-service pavements.