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Publication Number:  FHWA-HRT-16-011    Date:  December 2017
Publication Number: FHWA-HRT-16-011
Date: December 2017


Using Falling Weight Deflectometer Data With Mechanistic-Empirical Design and Analysis, Volume III: Guidelines for Deflection Testing, Analysis, and Interpretation

CHAPTER 5. Summary

This report presents guidelines for users who want to perform deflection testing, analysis, and interpretation. Deflection testing is recognized as an effective method for determining the material parameters of in-place pavement layers, the structural condition of existing pavements, LTE of PCC pavement joints and cracks, and the presence of voids beneath PCC pavements. The major factors affecting pavement deflections are discussed, including the pavement structure (type and thickness), pavement loading conditions (load magnitude and type of loading), and climatic forces (temperature and moisture effects).

FWD testing guidelines are provided and include recommendations for sensor configuration, number of drops and load levels, testing location, testing increments, deflection testing data checks, and safety procedures for use during FWD testing. Backcalculation guidelines include an overview of the backcalculation process, data inputs and suggested default values, measures of convergence, and a summary of various studies that have verified backcalculation results and evaluated backcalculated versus laboratory determined moduli. Finally, a summary of mechanistic-empirical pavement design principles, an overview of the MEPDG, a summary of inputs (including deflection data) for use in the MEPDG for rehabilitation design, and a summary of how deflection basins can be used in rehabilitation strategy selection and design are provided.

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