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Publication Number: FHWA-HRT-12-023
Date: December 2012

 

Simplified Techniques for Evaluation and Interpretation of Pavement Deflections for Network-Level Analysis

CHAPTER 1 - Introduction

Background

The concept of a pavement management system (PMS) was developed following the American Association of State Highway Officials (AASHO) successful Road Test in the 1950s. Pavement performance was first characterized at the AASHO Road Test, providing the necessary information to compare design alternatives and expectations over the service life of flexible and rigid pavement structures. A link was established between performance and planning, designing, constructing, and maintaining pavements, and the concept of PMS was defined accordingly.

Surface distress measurements and roughness are the main components in determining a pavement's existing condition. These quantities can be used for predicting future performance and programming maintenance and construction/reconstruction activities, despite the fact that structural capacity has a major effect on how the pavement will perform in the future (i.e., rate of deterioration, types and severity of distresses, etc.). Therefore, it is important to consider the existing structural capacity of pavements and current surface distresses to predict the pavements' future condition with reasonable accuracy.

There are several techniques available to evaluate the structural capacity of pavements, most of which were developed for project-level applications (i.e., provide structural quality assessments for designing pavement rehabilitation or reinforcement). Many of these techniques are time consuming, and some require an experienced analyst. They generally provide more detail than is necessary for decision trees, making them less attractive and less cost effective for network-level applications. As a result, using pavement deflection testing for network-level analysis has been limited, even within agencies that extensively use a falling weight deflectometer (FWD) for project-level analysis.

However, some of these project-level techniques can be adapted to assist with network-level PMS applications. The key is to improve each technique in such a way that a simple parameter (or set of parameters) can be computed to describe the overall structural capacity of a uniform pavement section. Applicable techniques to assess pavement structural condition should improve the accuracy of PMS through enhanced project scoping and timing, potentially saving transportation agencies considerable funds and reducing construction delays (and therefore user costs) from poorly timed or ineffective projects. States including Texas, Kansas, New Jersey, Virginia, and Alaska have successfully incorporated structural indices in network-level applications. Such techniques are also used in countries such as South Africa, Finland, Denmark, France, and Australia.

Project Objectives

The primary objectives of this study were to identify, develop, verify, and recommend simplified deflection-based analytical techniques suitable for rapid automated screening of pavement structural capacity for inclusion in a network-level PMS. These techniques have been derived from information gathered from the Long-Term Pavement Performance (LTPP) database and from other highway agencies currently using structural information in their PMS.(1) The success of this study hinges on identifying solutions that can be implemented readily in national, State, and local municipality systems.

Another objective of the study was to develop and recommend data collection procedures that maximize testing productivity and minimize risk while still providing adequate information for use in a typical PMS. Test point spacing and frequency of data collection are the two primary parameters of interest.

It is intended that the results of this study are applicable to agencies that do not use deflection testing in their PMS but still use nondestructive deflection testing as part of their project-level analysis and design activities.

Desired Outcomes and Project Deliverables

The following list describes the project's desired outcomes and deliverables:


Report Organization

This report documents the findings from phase 1 and phase 2 of the project. The information presented in this report is organized in the following chapters:


 


The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
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