Condition Assessment of Flexible Pavements Using FWD Deflections PDF Download

Author: Yung-Chien Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 370

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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The objective of this study is to describe a mechanistic-empirical approach to developing an analysis method for assessing pavement layer conditions and estimating the remaining life of flexible pavements using multi-load level Falling Weight Deflectometer (FWD) deflections. A dynamic finite element program, incorporating a stress-dependent soil model, was developed to generate the synthetic deflection database. Based on this synthetic database, the relationships between surface deflections and critical pavement responses, such as stresses and strains in each individual layer, have been established. A condition assessment procedure for pavement layers using multi-load level FWD deflections is presented in this study. The results indicate that the proposed procedure can estimate the base and subgrade layer conditions. However, large variations were observed in the relationships between the DBCI and desg values and the subgrade CBR values for aggregate base pavements. A FWD test with a load of 53 kN or less does not result in any apparent nonlinear behavior of the subgrade in aggregate base pavements. With regard to the condition assessment of the asphalt concrete (AC) layer, the AC layer modulus and the tensile strain at the bottom of the AC layer are found to be better indicators than the deflection basin parameter. The procedures for performance prediction of fatigue cracking and rutting are developed for flexible pavements. The drastically increasing trend in fatigue cracking with time may not be predicted accurately using the proposed procedure. Such trends may be due to the environmental effects and the inconsistent distress measurements. Predicted rut depths using both single and multi-load level deflections show good agreement with measured rut depths over a wide range of rutting potential. However, the procedure using single load level deflections consistently underpredicts the rut depths. This observation demonstrates that the rutting prediction procedure usin.

Author: E. J. Yoder
Publisher: John Wiley & Sons
ISBN: 9780471977803
Category : Technology & Engineering
Languages : en
Pages : 732

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Presents a complete coverage of all aspects of the theory and practice of pavement design including the latest concepts.

Author: Y. Richard Kim
Publisher:
ISBN:
Category : Pavements
Languages : en
Pages : 208

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Book Description
The objective of this study is to develop a mechanistic-empirical method for assessing pavement layer conditions and estimating the remaining life of flexible pavements using multi-load level Falling Weight Deflectometer (FWD) deflections. A dynamic finite element program, incorporating a stress-dependent soil model, was developed to generate the synthetic deflection database. Based on this synthetic database, the relationships between surface deflections and critical pavement responses, such as stresses and strains in each individual layer, have been established. A condition assessment procedure for asphalt pavements that uses multi-load level FWD deflections has been developed using these relationships. The verification study was conducted using field data.

Author: Ranjithan, SR.
Publisher:
ISBN:
Category : Artificial neural network (ANN)
Languages : en
Pages : 17

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This paper presents a methodology based on deflection basin parameters and artificial neural networks (ANNs) for processing dynamic falling weight deflectometer (FWD) measurements to estimate layer moduli and condition. 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 all 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. Procedures in predicting layer moduli for both two- and three-layer pavement systems are presented. Field FWD measurements were analyzed both by this method and by the MODULUS program, the results of which assess the capability of the proposed method. Effects of discontinuities in the asphalt layer on the resulting FWD deflections were also studied using the finite element method. It was discovered that distresses in the asphalt layer may be detected using two deflection basin parameters, Shape Factor F2 and AREA.

Author: Daba Shabara Gedafa
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Remaining service life (RSL) has been defined as the anticipated number of years that a pavement will be functionally and structurally acceptable with only routine maintenance. The Kansas Department of Transportation (KDOT) has a comprehensive pavement management system, network optimization system (NOS), which uses the RSL concept. In support of NOS, annual condition surveys are conducted on the state highway system. Currently KDOT uses an empirical equation to compute RSL of flexible pavements based on surface condition and deflection from the last sensor of a falling-weight deflectometer (FWD). Due to limited resources and large size, annual network-level structural data collection at the same rate as the project level is impractical. A rolling-wheel deflectometer (RWD), which measures surface deflections at highway speed, is an alternate and fast method of pavement-deflection testing for network-level data collection. Thus, a model that can calculate RSL in terms of FWD first sensor/center deflection (the only deflection measured by RWD) is desired for NOS. In this study, RWD deflection data was collected under an 18-kip axle load at highway speed on non-Interstate highways in northeast Kansas in July 2006. FWD deflection data, collected with a Dynatest 8000 FWD on the KDOT network from 1998 to 2006, were reduced to mile-long data to match the condition survey data collected annually for NOS. Normalized and temperature-corrected FWD and RWD center deflections and corresponding effective structural numbers (SNeff) were compared. A nonlinear regression procedure in Statistical Analysis Software (SAS) and Solver in Microsoft Excel were used to develop the models in this study. Results showed that FWD and RWD center deflections and corresponding SNeff are statistically similar. Temperature-correction factors have significant influence on these variables. FWD data analysis on the study sections showed that average structural condition of pavements of the KDOT non-Interstate network did not change significantly over the last four years. Thus, network-level deflection data can be collected at four-year intervals when there is no major structural improvement. Results also showed that sigmoimal relationship exists between RSL and center deflection. Sigmoidal RSL models have very good fits and can be used to predict RSL based on center deflection from FWD or RWD. Sigmoidal equivalent fatigue crack-models have also shown good fits, but with some scatter that can be attributed to the nature and quality of the data used to develop these models. Predicted and observed equivalent transverse-crack values do not match very well, though the difference in magnitude is insignificant for all practical purposes.

Author:
Publisher:
ISBN:
Category : Pavements
Languages : en
Pages : 40

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The objective of this study was to develop an approach for incorporating techniques to interpret and evaluate deflection data for network-level pavement management system (PMS) applications. The first part of this research focused on identifying and evaluating existing techniques, seeking out those that were simple, reliable, and easy to incorporate into current PMS practices, as well as those that produced consistent results. The second part of the research detailed the development of guidelines for the application of recommended techniques and procedures for determining optimum falling weight deflectometer (FWD) test spacing and data collection frequency. While there are many viable techniques available for evaluating the structural capacity of pavements that use FWD for project-level analysis, many of these techniques are time consuming and require an experienced analyst. As a result, using pavement deflection testing for network-level analysis has been limited to date. This guide provides information for the assessment of pavement structural performance for PMS applications. It reflects the general findings presented in the accompanying final report, Simplified Techniques for Evaluation and Interpretation of Pavement Deflections for Network-Level Analysis (FHWA-HRT-12-023).

Author: R. J. Wedner
Publisher:
ISBN:
Category : Pavements
Languages : en
Pages : 126

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Project monitored flexible pavement dynamic deflections, roughness, and distress over a six-year period. Results show present surface condition and serve as a basis for evaluating rehabilitation needs.

Author: Kristy Lynn Wyatt Alford
Publisher:
ISBN:
Category : Nondestructive testing
Languages : en
Pages : 308

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Author: American Association of State Highway and Transportation Officials
Publisher: AASHTO
ISBN: 1560510552
Category : Pavements
Languages : en
Pages : 622

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Book Description
Design related project level pavement management - Economic evaluation of alternative pavement design strategies - Reliability / - Pavement design procedures for new construction or reconstruction : Design requirements - Highway pavement structural design - Low-volume road design / - Pavement design procedures for rehabilitation of existing pavements : Rehabilitation concepts - Guides for field data collection - Rehabilitation methods other than overlay - Rehabilitation methods with overlays / - Mechanistic-empirical design procedures.