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    <title>Transport Research International Documentation (TRID)</title>
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    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>PROJECT-LEVEL STRUCTURAL EVALUATION OF PAVEMENTS BASED ON DYNAMIC DEFLECTIONS</title>
      <link>https://trid.trb.org/View/270800</link>
      <description><![CDATA[The framework of a structural evaluation system for pavements, which is based on the mechanistic evaluation of dynamic deflection data, is described. The computer program RPEDD1 has been developed for the evaluation of dynamic deflection basins measured on rigid pavements by nondestructive testing devices (a falling weight deflectometer and a Dynaflect). The analysis models presented in this paper include (a) a self-iterative procedure to determine in situ moduli of pavement layers, assuming a layered linearly elastic medium; (b) a selfiterative procedure for determining nonlinear strain-dependent moduli of granular layers and subgrade; and (c) a procedure for predicting fatigue life and existing structural capacity. A methodology has been developed to eliminate any need for assuming initial values of moduli. This has also improved efficiency of the self-iterative basin matching procedure and ensured unique values of the in situ moduli. Implementation of the proposed computerized evaluation procedures also provides a rational way to delineate sections for rehabilitation design.]]></description>
      <pubDate>Fri, 27 Aug 2004 21:59:36 GMT</pubDate>
      <guid>https://trid.trb.org/View/270800</guid>
    </item>
    <item>
      <title>A STRUCTURAL EVALUATION METHODOLOGY FOR PAVEMENTS BASED ON DYNAMIC DEFLECTIONS. INTERIM REPORT</title>
      <link>https://trid.trb.org/View/268682</link>
      <description><![CDATA[A framework for structural evaluation of pavements based on dynamic deflections is presented.  A self-iterative procedure has been developed to estimate insitu Young's moduli of pavement layers by using the approach of inverse application of layered elastic theory (ELSYM5) to obtain the best fit of a measured deflection basin.  For asphalt pavements, a temperature correction procedure is presented for the asphaltic concrete moduli.  Nonlinear strain-softening models are introduced and discussed to take into account nonlinear behavior of granular layers and subgrade.  A self-iterative procedure has been developed to estimate nonlinear strain-softening moduli of these layers from Dynaflect deflection basins based on the concepts of equivalent linear analysis.  An indication of the structural capacity of existing pavement is obtained from the remaining life analysis.  Computer programs RPEDD1 (for rigid pavement) and FPEDD1 (for flexible pavements) are developed to evaluate dynamic deflection basins measured by the Falling Weight Deflectometer and Dynaflect.  Guidelines are presented for applications and implementation of these computer programs, especially in rehabilitation design.]]></description>
      <pubDate>Fri, 27 Aug 2004 21:44:08 GMT</pubDate>
      <guid>https://trid.trb.org/View/268682</guid>
    </item>
    <item>
      <title>DYNAMIC SURFACE DEFLECTION MEASUREMENTS ON RIGID PAVEMENTS COMPARED WITH THE MODEL OF AN INFINITE PLATE ON AN ELASTIC FOUNDATION</title>
      <link>https://trid.trb.org/View/165798</link>
      <description><![CDATA[The purpose of this study was to develop relations by using the Hertz theory of an infinite plate on a dense fluid subgrade between deflections measured at the point of and away from an applied load and the strength parameters of the pavement.  An evaluation procedure was to be developed based on these relations, known pavement characteristics, and dynamic response data collected with the U.S. Army Engineer Waterways Experiment Station (WES) 16-kip vibrator. Deflection relations were established by using a computer program (PCADL) developed by the Portland Cement Association.  The deflections were related to the radius of relative stiffness (l), which is a characteristic length dependent on the rigidity of the plate.  Maximum stresses were predicted by using the General Dynamics Corporation's H-51 program.  From these stresses, a relation was developed between the dynamic stiffness modulus, l, and the allowable single-wheel aircraft load (ASWL).  Both destructive and nondestructive vibratory data were collectd on 28 different pavements.  Destructive data were used to characterize the pavement material properties and then, by using conventional procedures, to predict the ASWL.  Deflection basin data from the WES 16-kip vibrator were used to measure l by using the relations developed from the PCADL program.  The study concluded that non-destructive test data can be used with more confidence than previously developed procedures to predict l and ASWL as a function of l.]]></description>
      <pubDate>Sun, 21 May 2000 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/165798</guid>
    </item>
    <item>
      <title>DEFLECTION RESPONSE MODELS FOR CRACKED RIGID PAVEMENTS</title>
      <link>https://trid.trb.org/View/475386</link>
      <description><![CDATA[The static elastic layer model is customarily used for analyzing deflection measurements and back-calculating pavement layer moduli.  Estimation of in-situ layer moduli by means of a mechanistically based iterative technique is known as back-calculation.  Despite the fact that the falling weight deflectometer (FWD) load induces a dynamic load, dynamic/impact analysis routines are seldom, because of the mathematical complexity.  Dynamic deflection prediction models are developed in this study, which can be used in back-calculation routines. The first step in accomplishing this is to select an appropriate analysis model for which ABAQUS, a general purpose finite-element program, is used.  Static and dynamic deflection responses from the ABAQUS model of an uncracked pavement are validated. Following this first step, cracks and joints along with other features of the pavement are modeled in addition to nonlinear behavior of pavement materials.  Deflection responses of cracked pavement under a series of increasing loads, assuming linear and nonlinear behavior of base, subbase, and subgrade materials, are computed and compared.  After finalizing the model, a synthetic deflection database, specifically with FWD load, is developed relying on a fractional factorial design layout in which thicknesses, layer moduli, and cracks are allowed to vary over a range.  Making use of this database, regression equations that predict surface deflection bowls in terms of layer moduli and thicknesses are developed.  Deflection equations are validated using field data from two in-service pavements.]]></description>
      <pubDate>Sat, 03 Jan 1998 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/475386</guid>
    </item>
    <item>
      <title>CORRELATION BETWEEN THE DYNAMIC (FWD) AND TRADITIONAL DEFLECTION MEASUREMENT METHODS</title>
      <link>https://trid.trb.org/View/469204</link>
      <description><![CDATA[Deflection measurements in Hungary are carried out regularly using Benkelman beams for 40 years and Lacroix deflectographs for 20 years.  The strengthening and the design of pavement structures are based on the deflection values, and the bearing capacity is one of the characteristic properties of the behaviour of road structures.  Since 1991, measurements are carried out by KUAB falling weight deflectometer.  The connection between the dynamic deflection and quasi static deflection, as the evaluation of the bearing capacity of the road network was based on the deflection measurements and the data are stored in the databank, had to be determined.  Every databank stored deflection value refers the deflection determined by hand operated Benkelman beams at 20 degrees celsius asphalt temperature.  In this report the first results of this work are presented.]]></description>
      <pubDate>Thu, 27 Nov 1997 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/469204</guid>
    </item>
    <item>
      <title>SEASONAL VARIATIONS IN PAVEMENT STRENGTH</title>
      <link>https://trid.trb.org/View/469230</link>
      <description><![CDATA[In regions subjected to severe frost, spring thaw and the corresponding reduction in subgrade strength can pose significant problems for pavement structural capacity.  A large portion of the annual pavement fatigue occurs during the spring thaw when the pavement is in its weakest state from a support perspective. The magnitude of pavement damage varies with the amount of thawing, type of subgrade, and loads applied.  An investigation into the effects of seasonal variations in pavement response to loading has been completed for a series of test sections in southern Ontario, Canada, by monitoring variations in the pavement deflection and subgrade modulus values from Falling Weight Deflectometer (DFW) tests.  The key pavement layer response indicators such as normalized dynamic deflection, subgrade modulus, subgrade deflection, and vertical compressive strain were calculated using the MTO PROBE pavement layer analysis program.  By charting the variations in these key pavement response indicators throughout the traditional spring thaw period, and comparing them to the measurements taken during the previous fall, a series of environmental factors affecting pavement performance and response has been developed.]]></description>
      <pubDate>Thu, 27 Nov 1997 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/469230</guid>
    </item>
    <item>
      <title>VIBRATIONAL BEHAVIOR OF CONTINUOUS SPAN HIGHWAY BRIDGE--INFLUENCING VARIABLES</title>
      <link>https://trid.trb.org/View/482335</link>
      <description><![CDATA[The authors use an approach based on the finite-element method for three-dimensional dynamic bridge analysis to explain how different factors influence bridge behavior.  A continuous nonprismatic four-span bridge was monitored in the field by the authors and is used as an example here.  The influence of the dynamic behavior is illustrated using plots of the dynamic deflections at various locations.  The factors that influence the dynamic behavior of bridges are the dimensions; the material properties; the section properties; the damping characteristics; the surface roughness; and vehicular weights, speeds, and locations.  Comparisons are made for each factor.]]></description>
      <pubDate>Sun, 20 Apr 1997 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/482335</guid>
    </item>
    <item>
      <title>TEMPERATURE ADJUSTMENT OF DYNAMIC DEFLECTION MEASUREMENTS ON ASPHALT CONCRETE PAVEMENTS. FINAL REPORT</title>
      <link>https://trid.trb.org/View/369253</link>
      <description><![CDATA[The application of elastic theory to the design of overlays on existing pavement requires that a modulus of elasticity be assigned to the existing structural system.  Estimates of elastic modulus are obtained from dynamic deflection readings in the field; but asphalt is a highly temperature-sensitive visco-elastic material and deflections not corrected to a standard temperature can produce misleading results.  It is therefore the objective of the present study to develop a procedure for which some temperature gradient exists because of the combined influences of solar radiation, wind, air temperature, cloud cover and other variables specific to time and location which cause temperature variations within the pavement layer.  Two models are presented for the achievement of that objective.  The first of the two models has been designed to utilize site-specific conditions for calculating a temperature profile at a given time within an asphaltic layer. The second model relates an equivalent elastic modulus to the calculated temperature profile.]]></description>
      <pubDate>Mon, 29 Apr 1996 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/369253</guid>
    </item>
    <item>
      <title>RESPONSE OF PAVEMENT SYSTEMS TO DYNAMIC LOADS IMPOSED BY NONDESTRUCTIVE TESTS</title>
      <link>https://trid.trb.org/View/453025</link>
      <description><![CDATA[Dynamic nondestructive testing of pavements can be grouped into two categories:  (a) deflection basin tests and (b) wave propagation tests.  Among the deflection basin tests, the Falling Weight Deflectometer (FWD) test has seen the most widespread use.  Of the wave propagation tests, the Spectral Analysis of Surface Waves (SASW) test can be used with or serve as an alternative to deflection basin tests.  The theoretical formulation used to analyze the dynamic response of pavement systems to dynamic loads imposed by such nondestructive testing techniques is presented.  Analytical studies of the dynamic response of two generalized pavement systems (a flexible one and a rigid one) to the FWD and SASW tests were carried out.  The results indicate that dynamic deflection basins due to the FWD load can be substantially different from those obtained under static conditions.  The study shows that when complete time histories of FWD deflections are stored, the additional information can provide substantial insight into the properties of the pavement system and can significantly facilitate the inversion process.  The dispersion curves obtained with the SASW test are very sensitive to the stiffness of the surface and subgrade layers but, unfortunately, are relatively insensitive to the properties of the base layer.  These results are true even when bedrock is present at shallow depths.]]></description>
      <pubDate>Tue, 02 Jan 1996 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/453025</guid>
    </item>
    <item>
      <title>PAVEMENT-FALLING WEIGHT DEFLECTOMETER INTERACTION USING DYNAMIC FINITE-ELEMENT ANALYSIS</title>
      <link>https://trid.trb.org/View/451802</link>
      <description><![CDATA[In almost all linear elastostatic programs used in backcalculation procedures, a uniform pressure distribution is assumed for the applied load.  As such, the loading system of any falling weight deflectometer (FWD) should be designed so that the load transferred to the pavement is uniform.  This is difficult because the pressure distribution under the FWD is also affected by the pavement profile being tested.  The other aspect of the FWD testing that is typically ignored is the dynamic nature of the load.  The dynamic effects are related to the pulse width as well as the variation in the stiffness of the subgrade.  A finite-element study has been carried out to investigate the significance of these parameters on the determination of the remaining lives of pavements.  Cases where the imparted load would or would not yield a uniform pressure distribution under the FWD plate are identified.  An investigation of the effects of the plate-pavement interaction on the static interpretation of the dynamic deflections is presented.  The results indicate that the dynamic nature of the load may more significantly affect the deflections measured away from the load, whereas the plate-pavement interaction may affect the deflection of the first sensor.  The errors in the estimation of the layer moduli that would be obtained from the standard backcalculation procedures are also determined.  The results of this study confirm that the plate-pavement interaction and the dynamic effects are important for the FWD test on flexible pavements.]]></description>
      <pubDate>Tue, 07 Nov 1995 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/451802</guid>
    </item>
    <item>
      <title>ERROR ANALYSIS FOR A PROPOSED MOVING DYNAMIC DEFLECTION SYSTEM FOR HIGHWAY PAVEMENTS. FINAL REPORT</title>
      <link>https://trid.trb.org/View/448198</link>
      <description><![CDATA[This report presents the results of a study in which an error analysis of a system for dynamically measuring road deflection was conducted.  The system configuration has been proposed by Surface Dynamics, Inc., and consists of an instrumented tractor-trailer truck configuration that will permit road deflection measurements to be made at highway speeds.  The proposed system utilizes a beam that is configured to carry laser distance measuring sensors.  The sensors are positioned to make reference measurements of undeflected surface as well as the deflected surface.  Signal processing algorithms are proposed that give the system the potential to compensate for beam movement as well as the random surface texture features. This study included a complete error analysis of the system beginning with suitable mathematical models for all components as well as all signal processing steps.  A random and systematic error analysis was conducted of all components and of the complete system.  This study was conducted analytically as well as in computer simulation.  The error analysis has shown that the system total errors are within the allowed error bands for practical application provided all components function in accordance with manufacturers stated performance capability.]]></description>
      <pubDate>Thu, 26 Oct 1995 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/448198</guid>
    </item>
    <item>
      <title>DEVELOPMENT AND PRELIMINARY INVESTIGATION OF ROLLING DYNAMIC DEFLECTOMETER</title>
      <link>https://trid.trb.org/View/427203</link>
      <description><![CDATA[Nondestructive testing (NDT) is an important part of optimizing any pavement management system.  At this time in the United States NDT is performed at discrete points on the pavement to evaluate the properties of the pavement layers.  Techniques such as the falling weight deflectometer (FWD), Dynaflect, and spectral-analysis-of-surface-waves are used.  A new technique is described.  It is called the rolling dynamic deflectometer (RDD) and is a large truck on which a servo-hydraulic vibrator is mounted.  The vibrator is used to apply large vertical dynamic loads [up to a total load of 147 kN (33,000 lb)] to rolling wheels that come into contact with the pavement.  A receiver wheel located midway between the loading wheels is used to monitor the dynamic deflections.  The truck is driven at a slow speed [about 5 km/hr (3 mph)], and continuous profiles of pavement flexibility are measured under heavy traffic conditions.  Descriptions of the equipment, calibration results, and test procedures are presented.  Several examples involving tests of flexible pavements and comparisons with FWD results are included.  The results show that the RDD can be used to (a) determine uniformity along pavement sections, (b) measure differences in average flexibility between different sections, and (c) observe nonlinearities in a given pavement section.]]></description>
      <pubDate>Thu, 24 Aug 1995 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/427203</guid>
    </item>
    <item>
      <title>BACKCALCULATION OF FLEXIBLE PAVEMENT MODULI FROM DYNAMIC DEFLECTION BASINS USING ARTIFICIAL NEURAL NETWORKS</title>
      <link>https://trid.trb.org/View/427206</link>
      <description><![CDATA[The falling weight deflectometer (FWD) test measures the response of a pavement system to a transient load applied at the pavement surface.  A limitation of existing, widely used techniques for backcalculating pavement layer moduli from FWD results is that they are based on a static analysis of pavement response.  Previous studies have shown that significant errors in moduli can accrue from the discrepancy between this static assumption and the dynamic nature of the FWD test.  Dynamic solutions for pavement response are available, but their computational complexity makes them impractical for use in conventional backcalculation programs that use gradient search or data base techniques.  This limitation has been overcome by applying artificial neural network technologies to the backcalculation problem.  An artificial neural network has been trained to backcalculate pavement layer moduli for three-layer flexible pavement systems with synthetic dynamic deflection basins.  The dynamic pavement response was calculated by using an elastodynamic Green function solution based on a stiffness matrix formulation of the pavement system.  The computational efficiency of the trained neural network means that moduli can be backcalculated with a speed that is several orders of magnitude greater than that which can be achieved by conventional gradient search and data base approaches.  This is significant because it demonstrates the feasibility of backcalculating pavement layer moduli from dynamic deflection basins in real time.]]></description>
      <pubDate>Thu, 24 Aug 1995 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/427206</guid>
    </item>
    <item>
      <title>EVALUATION OF FRONT SEAT BACK FORCE/DEFLECTION CHARACTERISTICS. FINAL REPORT</title>
      <link>https://trid.trb.org/View/405859</link>
      <description><![CDATA[A test program was designed and conducted to determine the dynamic force/deflection characteristics of passenger vehicle front seat backs.  Seat backs from nine different passenger vehicles were tested using a modified six-year-old headform. The headform was impacted at two different locations on each seat back and the results of these tests are presented. Stiffness corridors were created for each impact location based on the results.  A single corridor was then created to represent a stiffness range over the entire seat back region.  The criteria used to develop the corridor boundaries are discussed and presented as well.]]></description>
      <pubDate>Sun, 11 Sep 1994 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/405859</guid>
    </item>
    <item>
      <title>EFFECT OF DEPTH TO BEDROCK ON DEFLECTION BASINS OBTAINED WITH DYNAFLECT AND FALLING WEIGHT DEFLECTOMETER TESTS</title>
      <link>https://trid.trb.org/View/370866</link>
      <description><![CDATA[The dynaflect and falling weight deflectometer (FWD) are commonly used for nondestructive testing of pavements.  In both cases a dynamic load is imparted on the surface of the pavement, and deflections are measured at various points along the surface.  Evaluation of the moduli of the surface layer, base, and subgrade is normally performed by comparing the experimental deflections with the results of static analyses.  The moduli of the layers in the static model are then varied in an iterative procedure until a reasonable match between experimental and theoretical deflections is obtained.  This solution ignores the dynamic nature of these nondestructive tests.  In this paper the effect of depth to bedrock on the amplitude of the deflections and the shape of the deflection basins obtained with the dynaflect and the FWD tests is investigated analytically. Dynamic and static deflections at four different pavement profiles are compared.  The results show that the range of bedrock depths over which dynamic effects are important differs between the two nondestructive tests because of the excitation frequencies and depends mainly on the stiffness of the subgrade. The results also show that, when dynamic effects occur in the measurements but are not taken into account in the analysis, the modulus of the subgrade is generally underestimated, sometimes by 50% or more, and the moduli of the base and surface layer are overestimated.  Finally, a simple method is suggested for the FWD that makes it possible to estimate the depth to bedrock by recording the free vibration of the pavement system.]]></description>
      <pubDate>Thu, 16 Dec 1993 00:00:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/370866</guid>
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