Evaluation of Equipment, Methods, and Pavement Design Implications of the AASHTO 2002 Axle ...

94 Pages·2006·1.94 MB·English

Technical Report Documentation Page
1. Report No. 2. Government 3. Recipient’s Catalog No.
FHWA/TX-06/0-4510-1 Accession No.

4. Title and Subtitle 5. Report Date
Evaluation of Equipment, Methods, and Pavement Design February 2004, Rev. July 2006, 2nd Rev.
Implications of the AASHTO 2002 Axle Load Spectra August 2006
Traffic Methodology 6. Performing Organization Code
7. Author(s) 8. Performing Organization Report No.
Feng Hong, Jorge A. Prozzi 0-4510-1

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)
Center for Transportation Research 11. Contract or Grant No.
The University of Texas at Austin 0-4510
3208 Red River, Suite 200
Austin, TX 78705-2650
12. Sponsoring Agency Name and Address 13. Type of Report and Period
Texas Department of Transportation Technical (Interim) Report 4510-1
Research and Technology Implementation Office September 2002-August 2003
P.O. Box 5080
Austin, TX 78763-5080 14. Sponsoring Agency Code
15. Supplementary Notes
Project performed in cooperation with the Texas Department of Transportation and the Federal Highway
Administration.

16. Abstract
Traffic volume influences the geometric requirements of a highway; however, it is only the axle loads of
heavy commercial traffic that affect the structural design of pavements. Mechanistic-based pavement design
approaches, coupled with faster computers, are changing the way in which traffic loads are accounted for in
pavement design. In the M-E Design Guide for the Design of New and Rehabilitated Pavement Structures, traffic
loading will be accounted for by using axle load spectra. Axle load spectra consist of the histograms of axle load
distribution for each of four axle types: single, tandem, tridem, and quad.
Currently, the Texas Department of Transportation (TxDOT) does not have adequate regional
representation of weigh data and uses a statewide average to generate load data for most highways, a practice that is
inconsistent with the proposed M-E design approach. This research project will assess and evaluate the implications
of the axle load spectra approach proposed by the M-E Design Guide and develop guidelines and recommendations
that will facilitate the transition from current practice to the application of the new proposed methodology.
The evaluation of current equipment and methodology for traffic data collection and data management will
be addressed during the first part of the research project. With these findings in hand, guidelines and
recommendations for the implementation of the M-E Design Guide will be developed. Finally, implications for the
structural design of pavement will be determined.
This interim report presents the findings of the initial literature review, a description of traffic data
requirements for the M-E Design Guide for the Design of New and Rehabilitated Pavement Structures, and a
preliminary sensitivity analysis conducted under typical Texas environmental conditions.
17. Key Words 18. Distribution Statement
Traffic characterization, axle load spectra, traffic No restrictions. This document is available to the
classification, WIM, M-E Design Guide, public through the National Technical Information
mechanistic design Service, Springfield, Virginia 22161. www.ntis.gov
19. Security Classif. (of report) 20. Security Classif. (of this page) 21. No. of pages 22. Price
Unclassified Unclassified 94
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

Evaluation of Equipment, Methods, and Pavement Design
Implications of the AASHTO 2002 Axle Load Spectra
Traffic Methodology

Feng Hong
Jorge A. Prozzi

CTR Technical Report: 0-4510-1
Report Date: February 2004, Rev. August 2006
Research Project: 0-4510
Research Project Title: Evaluate Equipment, Methods, and Pavement Design Implications for Texas
Conditions of the AASHTO 2002 Axle Load Spectra Methodology
Sponsoring Agency: Texas Department of Transportation
Performing Agency: Center for Transportation Research at The University of Texas at Austin

Project performed in cooperation with the Texas Department of Transportation and the Federal Highway
Administration.
Center for Transportation Research
The University of Texas at Austin
3208 Red River
Austin, TX 78705

www.utexas.edu/research/ctr

Copyright © 2006
Center for Transportation Research
The University of Texas at Austin

All rights reserved
Printed in the United States of America

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Disclaimers
Authors’ Disclaimer: The contents of this report reflect the views of the authors, who are
responsible for the facts and the accuracy of the data presented herein. The contents do not
necessarily reflect the official view or policies of the Federal Highway Administration or the
Texas Department of Transportation. This report does not constitute a standard, specification, or
regulation.
Patent Disclaimer: There was no invention or discovery conceived or first actually
reduced to practice in the course of or under this contract, including any art, method, process,
machine manufacture, design or composition of matter, or any new useful improvement thereof,
or any variety of plant, which is or may be patentable under the patent laws of the United States
of America or any foreign country.
Notice: The United States Government and the State of Texas do not endorse products or
manufacturers. If trade or manufacturers’ names appear herein, it is solely because they are
considered essential to the object of this report.

Engineering Disclaimer
NOT INTENDED FOR CONSTRUCTION, BIDDING, OR PERMIT PURPOSES.

Project Engineer: Randy Machemehl
Professional Engineer License State and Number: 41921

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Acknowledgments
The authors want to thank German Claros, PC, Research and Technology Implementation
Office; Joseph Leidy, PD, Construction Division; and Richard Rogers, PA, Construction
Division for their assistance during the development of this project. Likewise, gratitude is
expressed to all the personnel from TxDOT that were involved in the development of field tasks
conducted for this project.
Research performed in cooperation with the Texas Department of Transportation.

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Table of Contents

1. Introduction.................................................................................................................................1
1.1 Problem Statement.................................................................................................................1
1.2 Research Goals and Principles...............................................................................................1
1.3 Current Practice of Traffic Data Collection at TxDOT.........................................................3
1.4 Future Development in Truck Weight, Size, and Allowable Axle Loads.............................4
1.5 Research Approach................................................................................................................5
2. Traffic Characterization..............................................................................................................7
2.1 Introduction............................................................................................................................7
2.2 Traffic Load Forecast (ESAL)...............................................................................................7
2.3 Load Spectra........................................................................................................................13
2.4 Traffic Classifications..........................................................................................................18
2.5 Traffic Load Forecasting.....................................................................................................28
2.6 Economic Effects on Traffic Development—NAFTA........................................................33
3. The M-E Design Guide.............................................................................................................35
3.1 Background..........................................................................................................................35
3.2 The M-E Design Guide........................................................................................................37
3.3 Mechanistic-Empirical Design Approach............................................................................38
3.4 Traffic inputs in the M-E Design Guide..............................................................................41
4. Mechanistic Analysis................................................................................................................53
4.1 Sensitivity Analysis.............................................................................................................53
4.2 Results of the Sensitivity Analysis......................................................................................65
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5. Preliminary Conclusions and Future Work...............................................................................67
5.1 Preliminary Conclusions......................................................................................................67
5.2 Work to be Performed..........................................................................................................69
References.....................................................................................................................................71
Appendix A...................................................................................................................................73

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List of Figures

Figure 2.1 SDHPT’s Traffic Load Forecasting Procedure........................................................9
Figure 2.2 Tandem Load Spectra Histogram (Expressed in Relative Frequency)..................14
Figure 2.3 Dimensions of Tandem-Axle-Trailer Normally in Operation...............................14
Figure 2.4 Dimensions of Tridem-axle-trailer Normally in Operation...................................15
Figure 2.5 General Tandem Axle Load Spectra across All Dates and Locations
according to the California Study (Lu and Harvey, 2002).....................................16
Figure 2.6 Tandem Load Spectra in Three Regions of California..........................................17
Figure 2.7 Typical Truck Profiles for FHWA Classification..................................................21
Figure 2.8 Illustrative Truck Configurations of the U.S. Fleet...............................................22
Figure 2.9 Typical Truck Profiles for TxDOT Traffic Types.................................................28
Figure 2.10 Impact from Differences in AADT and Truck Growth Rates...............................31
Figure 2.11 Typical Monthly Volume Patterns (TMG, 2001)..................................................31
Figure 2.12 Typical Monthly Volume Patterns by WSDOT.....................................................32
Figure 2.13 Projected Volumes for Two-Axle NAFTA Trucks along I-35..............................34
Figure 3.1 Screen for Main Input Variables Required by M-E Design Guide........................42
Figure 3.2 Screen for General Traffic Input Variables...........................................................43
Figure 3.3 Monthly Adjustment Factors Screen.....................................................................44
Figure 3.4 Vehicle Class Distribution Screen.........................................................................45
Figure 3.5 Hourly Distribution Screen....................................................................................46
Figure 3.6 Screen Showing Traffic Forecasting Models.........................................................47
Figure 3.7 Axle Load Distribution per Traffic Class and per Axle Type...............................48
Figure 3.8 Single-Axle Load Distribution...............................................................................48
Figure 3.9 Tandem-Axle Load Distribution............................................................................49
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Figure 3.10 Tridem-Axle Load Distribution.............................................................................49
Figure 3.11 Screen Showing Expected Number of Axles per Truck........................................50
Figure 3.12 Mean Axle Configuration Parameters...................................................................51
Figure 3.13 Mean Wheelbase Dimensions for Short, Medium, and Long Units.....................52
Figure 3.14 Flow Chart of Traffic Input to Obtain Axle Load Spectra.....................................52

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