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PennDOT Pavement ME Design Preliminary User Input Guide
[Areas colored in YELLOW indicate areas that inputs are required from PennDOT. Areas colored in BLUE indicate areas that will be updated once lab test results
become available and local calibration is performed.]
Submitted to:
Pennsylvania Department of Transportation
Highway Design and Technology Section 400 North Street-7th Floor
Harrisburg, Pennsylvania 17120
Submitted by: Biplab B. Bhattacharya, P.E. Michael I. Darter, Ph.D., P.E.
Olga Selezneva, Ph.D. Deepak Raghunathan
Harold L. Von Quintus, P.E. Paul Wilke, P.E.
Applied Research Associates, Inc. 100 Trade Center Drive, Suite 200
Champaign, IL 61820
November 30, 2015
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DISCLAIMER STATEMENT This document is disseminated under the sponsorship of the Pennsylvania Department of Transportation and the United States Department of Transportation in the interest of information exchange. The State of Pennsylvania and the United States Government assume no liability of its contents or use thereof. The contents of this report reflect the views of the authors, who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official policies of the Pennsylvania Department of Transportation or the United States Department of Transportation. The State of Pennsylvania and the United States Government do not endorse products of manufacturers. Trademarks or manufacturers’ names appear herein only because they are considered essential to the object of this document.
ACKNOWLEDGEMENTS This report was prepared under sponsorship of the Pennsylvania Department of Transportation. The project team recognizes and appreciates the services provided by the Pennsylvania Department of Transportation. Specific individuals involved in the work and in providing data for developing the Pavement ME user input guide include Lydia Peddicord, Andrew O’Neill, Timothy Ramirez, Patricia Miller, and Bob Horwhat. Mohammad Dehghani from GHD assisted in project management.
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Technical Report Documentation Page
1. Report No. FHWA/PA-DOT-RD-xxx-xxx
2. Government Accession No.
3. Recipient's Catalog No.
4. Title and Subtitle PennDOT Pavement ME Design Preliminary User Input Guide
5. Report Date November 30, 2015 6. Performing Organization Code
7. Author(s) Biplab B. Bhattacharya, Michael I. Darter, Olga Selezneva, Deepak Raghunathan, Harold L. Von Quintus, and Paul Wilke
8. Performing Organization Report No. PA-DOT-RD-XXX-XXXX
9. Performing Organization Name and Address Applied Research Associates, Inc. 100 Trade Centre Drive, Suite #200 Champaign, IL 61820
10. Work Unit No. (TRAIS) 11. Contract or Grant No. E02978
12. Sponsoring Agency Name and Address Pennsylvania Department of Transportation Highway Design and Technology Section 400 North Street-7th Floor Harrisburg, PA 17120
13. Type of Report and Period Covered Draft Report June 2015 to November 2015 14. Sponsoring Agency Code Task Orders # 2.1
15. Supplementary Notes Research performed in cooperation with the Pennsylvania Department of Transportation and the United States Department of Transportation, Federal Highway Administration. This document is an initial draft report submitted to the sponsoring agency to facilitate use of the MEPDG procedure in AASHTOWare Pavement ME Design software. Contracting Officer’s Technical Representative (COTR): Lydia Peddicord. 16. Abstract The objective of this study was to develop a detailed and comprehensive Pavement ME Design user input guide for PennDOT. This guide provides useful information on design inputs, software usage, local calibrations, and outputs to implement and use the AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG) software that was developed under NCHRP Projects 1-37A and 1-40D. This guide includes design inputs for flexible pavement, jointed plain rigid pavement, and the rehabilitation of both types of pavement. This report provides detailed guidance and recommendations for determining the Pennsylvania-specific inputs to the AASHTO Pavement ME Design software. It also overviews and presents the information necessary for pavement design engineers in PennDOT to begin to use the Pavement ME design and analysis method. 17. Key Words Pavement Design, Pavement ME Design, Mechanistic-Empirical, Fatigue Cracking, Rutting, Thermal Cracking, Transverse Cracking, Joint Faulting, IRI, Smoothness, Calibration, Transfer Functions, Distress Prediction Models.
18. Distribution Statement Unrestricted. This document is available through the National Technical Information Service, Springfield, VA 21161.
19. Security Classification of this Report: Unclassified.
20. Security Classification of this Page: Unclassified.
21. No. of Pages 136
22. Price
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SI* (MODERN METRIC) CONVERSION FACTORS APPROXIMATE CONVERSIONS TO SI UNITS
Symbol When You Know Multiply By To Find Symbol LENGTH
in inches 25.4 millimeters mm ft feet 0.305 meters m yd yards 0.914 meters m mi miles 1.61 kilometers km
AREA in2 square inches 645.2 square millimeters mm2
ft2 square feet 0.093 square meters m2
yd2 square yard 0.836 square meters m2
ac acres 0.405 hectares ha mi2 square miles 2.59 square kilometers km2
VOLUME fl oz fluid ounces 29.57 milliliters mL gal gallons 3.785 liters L ft3 cubic feet 0.028 cubic meters m3
yd3 cubic yards 0.765 cubic meters m3
NOTE: volumes greater than 1000 L shall be shown in m3
MASS oz ounces 28.35 grams glb pounds 0.454 kilograms kgT short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t")
TEMPERATURE (exact degrees) oF Fahrenheit 5 (F-32)/9 Celsius oC
or (F-32)/1.8 ILLUMINATION
fc foot-candles 10.76 lux lx fl foot-Lamberts 3.426 candela/m2 cd/m2
FORCE and PRESSURE or STRESS lbf poundforce 4.45 newtons N lbf/in2 poundforce per square inch 6.89 kilopascals kPa
APPROXIMATE CONVERSIONS FROM SI UNITS Symbol When You Know Multiply By To Find Symbol
LENGTHmm millimeters 0.039 inches in m meters 3.28 feet ft m meters 1.09 yards yd km kilometers 0.621 miles mi
AREA mm2 square millimeters 0.0016 square inches in2
m2 square meters 10.764 square feet ft2
m2 square meters 1.195 square yards yd2
ha hectares 2.47 acres ac km2 square kilometers 0.386 square miles mi2
VOLUME mL milliliters 0.034 fluid ounces fl oz L liters 0.264 gallons gal m3 cubic meters 35.314 cubic feet ft3
m3 cubic meters 1.307 cubic yards yd3
MASS g grams 0.035 ounces ozkg kilograms 2.202 pounds lbMg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T
TEMPERATURE (exact degrees) oC Celsius 1.8C+32 Fahrenheit oF
ILLUMINATION lx lux 0.0929 foot-candles fc cd/m2 candela/m2 0.2919 foot-Lamberts fl
FORCE and PRESSURE or STRESS N newtons 0.225 poundforce lbf kPa kilopascals 0.145 poundforce per square inch lbf/in2
*SI is the symbol for th International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. e(Revised March 2003)
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TABLE OF CONTENTS
CHAPTER 1—INTRODUCTION ............................................................................................................... 1
CHAPTER 2—OVERVIEW OF THE PAVEMENT ME DESIGN METHODOLOGY ............................ 2 2.1 PERFORMANCE CRITERIA INPUTS CONSIDERED IN PAVEMENT ME
SOFTWARE ................................................................................................................................ 3 2.2 DISTRESS TRANSFER FUNCTIONS INCLUDED IN PAVEMENT ME
SOFTWARE ................................................................................................................................ 6 2.3 PAVEMENT DESIGN STEPS USING PAVEMENT ME SOFTWARE .................................. 6 2.4 INPUT CATEGORIES .............................................................................................................. 11 2.4 HIERARCHICAL APPROACH FOR DETERMINING INPUTS ........................................... 14
CHAPTER 3—GENERAL PROJECT INFORMATION .......................................................................... 16 3.1 DESIGN AND PAVEMENT TYPE STRATEGIES ................................................................ 16
3.1.1 New/Reconstructed Flexible Pavements and AC Overlays ................................................ 16 3.1.2 New/Reconstructed Rigid Pavements and PCC Overlays .................................................. 17 3.1.3 Pavement Preservation and Preventive Maintenance.......................................................... 18
3.2 PROJECT FILE/NAME ............................................................................................................ 18 3.3 DESIGN LIFE ........................................................................................................................... 18 3.4 BASE AND PAVEMENT CONSTRUCTION & TRAFFIC OPENING DATES ................... 19
3.4.1 New Construction ............................................................................................................... 19 3.4.2 Rehabilitation ...................................................................................................................... 20
3.5 SCREEN SHOTS FOR GENERAL INFORMATION ............................................................. 20
CHAPTER 4—PERFORMANCE CRITERIA .......................................................................................... 21 4.1 INITIAL INTERNATIONAL ROUGHNESS INDEX (IRI) .................................................... 21 4.2 DISTRESS CRITERIA OR THRESHOLD VALUES ............................................................. 21
4.2.1 Terminal IRI Criterion ........................................................................................................ 23 4.2.2 Fatigue (Load-Related) Cracking Criterion—Flexible Pavements ..................................... 24 4.2.3 Permanent Deformation (Rut Depth) Criterion—Flexible Pavements ............................... 24
4.3 DESIGN RELIABILITY ........................................................................................................... 25 4.3 SCREEN SHOTS FOR THE PERFORMANCE CRITERIA ................................................... 25
CHAPTER 5—TRAFFIC INPUTS ............................................................................................................ 30 5.1 AVERAGE ANNUAL DAILY TRUCK TRAFFIC (TRAFFIC VOLUME INPUTS) ............ 30 5.2 TRAFFIC CAPACITY .............................................................................................................. 31 5.3 AXLE CONFIGURATION ....................................................................................................... 31 5.4 LATERAL WANDER .............................................................................................................. 32 5.5 WHEEL BASE .......................................................................................................................... 32 5.6 VEHICLE CLASS DISTRIBUTION AND GROWTH ............................................................ 33 5.7 MONTHLY ADJUSTMENT .................................................................................................... 37 5.8 HOURLY ADJUSTMENT ....................................................................................................... 37 5.9 AXLES PER TRUCK CLASS .................................................................................................. 39 5.10 AXLE LOAD DISTRIBUTION FACTORS ............................................................................. 40 5.11 SCREEN SHOTS FOR THE TRAFFIC INPUTS .................................................................... 45
CHAPTER 6—CLIMATE INPUTS ........................................................................................................... 49 6.1 PROJECT LOCATION INFORMATION ................................................................................ 49 6.2 DEPTH TO WATER TABLE ................................................................................................... 49 6.3 CLIMATE STATIONS ............................................................................................................. 50 6.4 CREATION OF SIMULATED CLIMATE STATION ............................................................ 52 6.5 SCREEN SHOTS FOR THE CLIMATE INPUTS ................................................................... 52
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CHAPTER 7—DESIGN FEATURES AND LAYER PROPERTY INPUTS ........................................... 55 7.1 AC (HMA) LAYER PROPERTIES: NEW AND EXISTING LAYERS ................................ 55
7.1.1 Multi-Layer Rutting Calibration Parameters ...................................................................... 55 7.1.2 AC Surface Shortwave Absorptivity ................................................................................... 55 7.1.3 Endurance Limit .................................................................................................................. 55 7.1.4 Layer Interface Friction ...................................................................................................... 55 7.1.5 Rehabilitation: Condition of Existing Flexible Pavement................................................... 56 7.1.6 Milled Thickness of Existing AC Layers ............................................................................ 58 7.1.7 Screen Shots for the AC Layer Properties: New and Existing Layers ................................ 58
7.2 JPCP: NEW AND EXISTING LAYERS ................................................................................. 60 7.2.1 PCC Surface Shortwave Absorptivity ................................................................................. 60 7.2.2 Joint Spacing ....................................................................................................................... 60 7.2.3 Sealant Type ........................................................................................................................ 60 7.2.4 Dowels ................................................................................................................................ 60 7.2.5 Widened Slab ...................................................................................................................... 60 7.2.6 Tied Shoulders .................................................................................................................... 61 7.2.7 Erodibility Index of Base Course ........................................................................................ 61 7.2.8 PCC-Base Contact or Interface Friction for JPCP .............................................................. 61 7.2.9 Pavement Curl/Warp Effective Temperature Difference .................................................... 61 7.2.10 Foundation Support for Rehabilitation of Rigid Pavements ............................................... 62 7.2.11 Condition of Existing PCC Surface for JPCP Rehabilitation Design ................................. 62 7.2.12 Screen Shots for the JPCP Layer Properties: New and Existing Layers ............................. 63
7.3 CRCP: NEW AND EXISTING LAYERS ............................................................................... 66 7.3.1 Inputs ................................................................................................................................... 66
7.4 INVERTED PAVEMENTS: NEW CONSTRUCTION .......................................................... 66
CHAPTER 8—LAYER/MATERIAL PROPERTY INPUTS .................................................................... 68 8.1 PAVEMENT LAYERS FOR FLEXIBLE PAVEMENT DESIGN .......................................... 68 8.2 PAVEMENT LAYERS FOR RIGID PAVEMENT DESIGN .................................................. 72 8.3 ASPHALT CONCRETE (AC) .................................................................................................. 73
8.3.1 Mixture Volumetric Properties ........................................................................................... 73 8.3.2 Mechanical Properties ......................................................................................................... 74 8.3.3 Thermal Properties .............................................................................................................. 80 8.3.4 Screen Shots for the AC Properties: New and Existing Layers .......................................... 80
8.4 PORTLAND CEMENT CONCRETE (PCC) – NEW MIXES ................................................. 83 8.4.1 General Properties ............................................................................................................... 83 8.4.2 Thermal Properties .............................................................................................................. 83 8.4.3 Mix Physical Properties: New and Intact Existing PCC Slabs .......................................... 84 8.4.4 Strength Properties .............................................................................................................. 85 8.4.5 Screen Shots for the PCC Properties: New Layers ............................................................. 86
8.5 PORTLAND CEMENT CONCRETE (PCC) – EXISTING FOR REHABILITATION DESIGNS .................................................................................................................................. 89
8.5.1 AC or PCC Overlay of Existing Intact PCC Slabs ............................................................. 89 8.5.2 Fractured PCC Slabs ........................................................................................................... 90 8.5.3 Restoration of JPCP ............................................................................................................ 91 8.5.4 PCC Overlay of Existing Flexible AC Pavement ............................................................... 92 8.5.3 Screen Shots for the Fractured PCC Properties .................................................................. 92
8.6 UNBOUND AGGREGATE BASE MATERIALS AND SOILS ............................................. 94 8.6.1 General Physical and Volumetric Properties ...................................................................... 94 8.6.2 Resilient Modulus ............................................................................................................... 94 8.6.3 Poisson’s Ratio .................................................................................................................. 102
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8.6.4 Hydraulic Properties ......................................................................................................... 102 8.6.5 Screen Shots for the Unbound Base and Subgrade Layer Properties................................ 102
8.7 CEMENT AGGREGATE BASE MIXTURES ....................................................................... 104 8.8 STABILIZED SUBGRADE FOR STRUCTURAL LAYERS ............................................... 104
8.8.1 Screen Shots for the Stabilized Base Layer Properties ..................................................... 104 8.9 BEDROCK .............................................................................................................................. 106
8.9.1 Screen Shots for the Bedrock Properties ........................................................................... 106
CHAPTER 9—PENNSYLVANIA CALIBRATION FACTORS ............................................................ 108 9.1 BASELINE FILES FOR THE CALIBRATION FACTORS .................................................. 108 9.2 TRANSFER FUNCTION CALIBRATION COEFFICIENTS ............................................... 109 9.4 SCREEN SHOTS FOR THE CALIBRATION COEFFICIENTS .......................................... 113
CHAPTER 10—INPUT WORKSHEET .................................................................................................. 119
REFERENCES 135
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LIST OF TABLES Table 2.1—Stages of Pavement ME Iterative Design Procedure ................................................................. 2 Table 2.2—Definitions of Distress Types and Smoothness for Asphalt Concrete (AC) and Jointed Plain
Concrete Pavement (JPCP) Surfaced Pavement Design ................................................................. 4 Table 2.3—Performance Indicators Predicted by Pavement ME ................................................................. 8 Table 2.4—Example Design Features to Revise for Flexible Pavement and AC Overlay Designs Not
Meeting the Design Criteria or Target Reliability ........................................................................ 12 Table 2.5—Example Design Features to Revise for JPCP and Overlay Designs Not Meeting the Design
Criteria or Target Reliability ......................................................................................................... 13 Table 2.6—Example Design Features to Revise for CRCP and Overlay Designs Not Meeting the Design
Criteria or Target Reliability ......................................................................................................... 14 Table 2.7—Hierarchical Input Levels ......................................................................................................... 15 Table 3.1—Design Life for Flexible and Rigid Pavement and Rehabilitation ........................................... 19 Table 3.2—Construction and Traffic Opening Dates (General Suggestions) ............................................. 19 Table 4.1—Initial IRI Values...................................................................................................................... 21 Table 4.2—Flexible Pavement Design Criteria or Threshold Values ......................................................... 22 Table 4.3—AC Overlay of Existing Flexible Pavement Design Criteria or Threshold Values .................. 22 Table 4.4— JPCP Design Criteria or Threshold Values ............................................................................. 22 Table 4.5— CRCP Design Criteria or Threshold Values ........................................................................... 23 Table 4.6—Semi-Rigid Pavement Design Criteria or Threshold Values ................................................... 23 Table 4.7—Composite Pavement Design Criteria or Threshold Values .................................................... 23 Table 4.8—Terminal IRI and Corresponding PennDOT Half-Car Roughness Index (HRI) Ratings or
Values............................................................................................................................................ 24 Table 4.9—Reliability Level Recommended for Use with Pavement ME Design ..................................... 25 Table 5.1—Lane Distribution Factor Recommended for Use with Pavement ME .................................... 31 Table 5.2—Axle Configuration for Pennsylvania (see Figure 5.1b) .......................................................... 32 Table 5.3—Wheelbase for Pennsylvania (see Figure 5.1c) ........................................................................ 32 Table 5.4—Traffic Pattern Group (TPG) in Pennsylvania ......................................................................... 35 Table 5.5—Recommended Vehicle Class Distribution Inputs for Level 2 Design for Pennsylvania
Roadways ...................................................................................................................................... 35 Table 5.6—Truck Traffic Classification Groups Common to Pennsylvania Roadways for Level 3 Design
....................................................................................................................................................... 36 Table 5.7—Recommended Monthly Adjustment Factor Inputs for Level 2 Design for Pennsylvania
Roadways ...................................................................................................................................... 37 Table 5.8—Recommended Hourly Distribution Factor Inputs for Level 2 Design for Pennsylvania
Roadways ...................................................................................................................................... 39 Table 5.9—Recommended Number of Axles per Truck Class Inputs for Level 2 Design for Pennsylvania
Roadways ...................................................................................................................................... 40 Table 5.10—Normalized Axle Load Distribution Files included in the PennDOT Database Library ....... 44 Table 5.11—Normalized Axle Load Distribution Factors for Vehicle Class 9 Tandem Axles (values in
percentages) .................................................................................................................................. 44 Table 6.1—Annual Depth to Water Table Recommended for Use ............................................................ 50 Table 7.1—Ratios to Distribute Total Rut Depth to Individual Layers ...................................................... 56 Table 7.2—Pavement ME Level 3 Condition Ratings Related to Existing Alligator Cracking in Percent
Lane Area ...................................................................................................................................... 57 Table 7.3— Pavement ME Level 3 Condition Ratings Related to Existing Transverse Cracking in Feet
per Mile ......................................................................................................................................... 57 Table 7.4—Recommended Dowel Diameter .............................................................................................. 60
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Table 7.5—Erodibility Category Index Recommended for Different Base Materials................................ 61 Table 7.6—Base/Slab Friction Coefficient Recommended for Different Layers below CRCP ................. 66 Table 8.1—Minimum and Maximum Layer Thicknesses .......................................................................... 70 Table 8.2—AC Layer Thickness Ratios (R) to be Used in Combining Thin Layers with Lower Dense-
Graded AC Layers......................................................................................................................... 70 Table 8.3—Volumetric Properties for Pennsylvania’s Dense-Graded Mixtures ........................................ 74 Table 8.4—Binder Grades Typically Used in Pennsylvania’s Dense-Graded Mixtures ............................ 75 Table 8.5—Dynamic Modulus Values of Typical PennDOT Dense-Graded Mixtures.............................. 76 Table 8.6—Gradation for Pennsylvania’s Dense-Graded Mixtures ........................................................... 77 Table 8.7—Complex Shear Modulus (G*) and phase angle (δ) Values of Typical PennDOT Dense-
Graded Mixtures ........................................................................................................................... 78 Table 8.8—Creep Compliance Values of Typical PennDOT Dense-Graded Mixtures .............................. 79 Table 8.9—Indirect Tensile Strength Values of Typical PennDOT Dense-Graded Mixtures .................... 80 Table 8.10—Recommended CTE Values for PCC Mixtures in Pennsylvania that Contain Type I Portland
Cement and Natural Sand (Based on PennDOT and LTPP data) ................................................. 83 Table 8.11—28-Day Compressive Strength Values of Typical PennDOT PCC Mixtures ........................ 85 Table 8.12—28-Day Elastic Modulus Values of Typical PennDOT PCC Mixtures .................................. 85 Table 8.13—Recommended Effective Modulus Values for Existing Intact PCC Slabs............................. 89 Table 8.14—Recommended Inputs for Crack and Seat Fractured Slab and Rubblized PCC Slabs ........... 90 Table 8.15—Resilient Modulus Level 3 Values for Granular Aggregate Base Materials in Pennsylvania 95 Table 8.16—Resilient Modulus Values Derived for Selected Subgrade Soils in Pennsylvania ................. 96 Table 8.17—Summary of the Adjustment Factors Recommended for Use in Pennsylvania to Convert
Back-Calculated Layer Modulus Values to Laboratory Equivalent Modulus Values .................. 97 Table 8.18—Resilient Modulus Values Derived for Subgrade Soil from DCP Tests for Use in
Pennsylvania ................................................................................................................................. 99 Table 8.19—Poisson’s Ratio Suggested for Use for Unbound Layers ..................................................... 102 Table 8.20—Resilient Modulus and Poisson’s Ratio Values Suggested for Use for Stabilized Subgrade
Layers .......................................................................................................................................... 104 Table 8.21—Layer Properties for Bedrock ............................................................................................... 106 Table 9.1—AC Rutting: PennDOT Calibration Factors ........................................................................... 109 Table 9.2—Unbound Layer Rutting: PennDOT Calibration Factors ....................................................... 109 Table 9.3—AC Bottom-Up Alligator Cracking: PennDOT Calibration Factors ...................................... 110 Table 9.4—AC Thermal Transverse Cracking: PennDOT Calibration Factors ....................................... 110 Table 9.5—AC Reflective Fatigue Cracking: PennDOT Calibration Factors (AC over AC only) .......... 110 Table 9.6—AC Reflective Transverse Cracking: PennDOT Calibration Factors (AC over AC only) ..... 111 Table 9.7—AC IRI: PennDOT Calibration Factors .................................................................................. 111 Table 9.8—JPCP Mid-Slab Cracking: PennDOT Calibration Factors (Use for all JPCP Applications:
Overlays and Restoration) ........................................................................................................... 111 Table 9.9—JPCP Faulting: PennDOT Calibration Factors (Use for all JPCP Applications: Overlays and
Restoration) ................................................................................................................................. 112 Table 9.10—JPCP IRI: PennDOT Calibration Factors (Use for all JPCP Applications: Overlays and
Restoration) ................................................................................................................................. 112 Table 9.11—CRCP Punchout: PennDOT Calibration Factors (All CRCP Applications) ........................ 112 Table 9.12—CRCP IRI: PennDOT Calibration Factors (All CRCP Applications) .................................. 113
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LIST OF FIGURES Figure 2.1—Conceptual Flow Chart for the Pavement ME Three-Stage Design-Analysis Process
(NCHRP, 2008) ............................................................................................................................... 7 Figure 2.2—Pavement ME Output Summary Sheet ................................................................................... 10 Figure 5.1—Schematic Illustration of Mean Wheel Location .................................................................... 33 Figure 5.2—Illustration of FHWA/AASHTO vehicle class type description ............................................ 34 Figure 5.3—Default Vehicle Class Distributions for Pennsylvania by FC and TPG ................................. 36 Figure 5.4—Default Vehicle Class Distributions for Pennsylvania by FC and TPG ................................. 38 Figure 5.5—Comparison of the Four NALS Defaults for Vehicle Class 9 Tandem Axles – Entire Range
of Axle Loads ................................................................................................................................ 41 Figure 5.6—Comparison of the Four NALS Defaults for Vehicle Class 9 Tandem Axles – Axle Loads
between 24,000 and 54,000 lbs (heavy loads and overloads) ....................................................... 42 Figure 6.1—Pennsylvania and Neighboring States Default Weather Stations in Pavement ME Software 51 Figure 8.1—New Pavement Structures Typically Required by PennDOT ................................................. 69 Figure 8.2—Limiting Layer Modulus Criterion of Unbound Aggregate Base Layers ............................. 101
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LIST OF ABBREVIATIONS AADTT Average annual daily truck traffic AASHTO American Association of State Highway and Transportation Officials AC Asphalt concrete ALD Axle load distribution ATB Asphalt treated base ATLAS Advanced Traffic Loading Analysis System ATR Automated traffic recorder BPR Bureau of Planning and Research CBR California bearing ratio CCC Cubic clustering criterion CPR Concrete pavement restoration CRCP Continuously reinforced concrete pavement CTB Cement treated base CTE Coefficient of thermal expansion DGAB Dense graded asphalt base ESAL Equivalent single axle load FHWA Federal Highway Administration FWD Falling Weight Deflectometer HMA Hot-mix asphalt IDT Indirect tensile IRI International Roughness Index JPCP Jointed plain concrete pavement JTCP Joint Technical Committee on Pavements LCB Lean concrete base LTE Load transfer efficiency LTPP Long Term Pavement Performance MAF Monthly adjustment factor MEPDG Mechanistic-Empirical Pavement Design Guide NCDC National Climatic Data Center NCHRP National Cooperative Highway Research Program NRCS National Resources Conservation Service NWS National Weather Service PATB Permeable asphalt treated base PCC Portland cement concrete PennDOT Pennsylvania Department of Transportation PMA Polymer modified asphalt PSI Present serviceability index QA Quality assurance QC Quality control R2 Coefficient of determination RLPD Repeated load permanent deformation SEE Standard error of estimate VAR Variance Vbeff Volumetric moisture content VFA Voids filled with asphalt VMA Voids in mineral aggregate WIM Weigh-in-motion
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PREFACE TO THE PENNSYLVANIA DEPARTMENT OF TRANSPORTATION PAVEMENT ME DESIGN USER INPUT GUIDE
From the early 1960s through 1993, all versions of the American Association of State Highway and Transportation Officials (AASHTO) Design Guide for pavements were based on the empirical performance equations developed from the American Association of State Highway Officials (AASHO) Road Test (AASHTO, 1993). The need for and benefits of a mechanistic-based pavement design procedure were recognized at the time the 1986 Design Guide was adopted (AASHTO, 1986). To meet that need, the AASHTO Joint Task Force on Pavements — in cooperation with the National Cooperative Highway Research Program (NCHRP) and the Federal Highway Administration (FHWA) — sponsored the development of an AASHTO Mechanistic-Empirical (ME) pavement design procedure. NCHRP project 1-37A (ARA, 2004a,b,c,d) produced rudimentary software that used existing ME-based models and databases reflecting current state-of-the-art ME pavement design procedures. The Mechanistic-Empirical Pavement Design Guide (MEPDG) was completed in 2004 and released to the public for review and evaluation. A formal review was completed by an independent set of consultants under NCHRP Project 1-40A, and version 1.0 of the MEPDG was submitted in 2007 to NCHRP, FHWA, and AASHTO for further consideration as an AASHTO Standard Practice. The MEPDG was formally adopted by AASHTO as an Interim Guide in 2008 (AASHTO, 2008). Pavement ME Design is a software upgrade to version 1.0 that became available in 2011. AASHTO distributes and manages the software as an AASHTOWare product. This User Input Guide is an engineering manual for determining the inputs needed for pavement design engineers in Pennsylvania to begin using Pavement ME Design. Many State Highway Agencies (SHAs) implementing Pavement ME Design conduct a local calibration or verification effort to establish local design inputs and determine the calibration factors that result in unbiased predictions. Forensic investigations, including materials testing and pavement performance data, are needed to establish the accuracy and bias of the distress transfer functions and International Roughness Index (IRI) prediction models. The Pennsylvania Department of Transportation (PennDOT) also sponsored a local calibration effort, the results from which were used in preparing this User Input Guide.
GENERAL NOTE The final report for this project presents the local calibration of the Pavement ME transfer functions
and the recommended default values to be used in design for the primary pavement design and rehabilitation strategies used in Pennsylvania.
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CHAPTER 1—INTRODUCTION The Pennsylvania Department of Transportation (PennDOT) currently uses the 1993 American Association of State Highway and Transportation Officials (AASHTO) Interim Design Guide for design of new and rehabilitated pavements. Since 2008, however, AASHTO has discontinued its support to this empirical-based pavement design procedure and adopted a mechanistic-empirical (ME) based procedure for design of both new and rehabilitated flexible and rigid pavements. An ME-based design method represents a rational engineering approach that has been used by some agencies to replace the empirical AASHTO design procedure (AASHTO, 1993). Illinois, Kentucky, Texas, and Washington (State) already use an ME-based approach for pavement design. The primary advantage of an ME-based design system is that it is based on pavement fracture and deformation characteristics of all layers and the prediction of several key distress types, rather than solely on the pavement’s surface ride condition. The AASHTOWare Pavement ME Design procedure (referred to as Pavement ME Design in the subsequent sections of this report) was developed based on the results and findings from a series of National Cooperative Highway Research Program (NCHRP) research studies, namely, NCHRP 1-37A, 1-40B, and 1-40D, conducted from 1998 through 2008. The Pavement ME Design procedure accounts for changes in traffic, material, and environmental conditions and incorporates mechanistic-based algorithms, computations, and transfer functions to simulate the impact of these changes on the long-term performance of the pavements. This design procedure computes pavement responses such as stresses, strains, truck axle load deflections, and accumulated pavement damage over the pavement design/analysis period. The accumulated pavement damage is then used to determine pavement distresses that are indicative of the performance of pavements over the analysis period. Such a rational engineering design approach provides a reliable and cost-effective method of diagnosing pavement problems, as well as forecasting maintenance and rehabilitation needs. AASHTO adopted this procedure in 2008 and published a Manual of Practice for its use (AASHTO, 2008). This Input Guide provides an overview of the Pavement ME procedure and has been prepared for PennDOT’s interim use to:
• Determine the inputs of the Pavement ME software • Provide guidance on the use of the Pavement ME software to perform pavement design for most
of the new and rehabilitated pavement types, specifically for Pennsylvania conditions. This manual is divided into 10 chapters on topics that include an overview of the Pavement ME methodology, materials and traffic inputs and characterization, flexible and rigid pavement designs, rehabilitation with asphalt concrete or Portland cement concrete (PCC), and calibration factors.
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CHAPTER 2—OVERVIEW OF THE PAVEMENT ME DESIGN METHODOLOGY
The Pavement ME procedure is based on ME design concepts, which means that the design procedure calculates pavement responses such as stresses, strains, and deflections, and accumulates the incremental damage from these responses over time. The procedure then empirically relates accumulated damage calculated from the responses to pavement distresses observed on roadway segments over time. This field calibration and validation is essential to a reliable design procedure. The Pavement ME procedure utilizes several mechanistic-based algorithms to (i) characterize new or existing pavement foundation, structure, layer materials, traffic, and climate, (ii) simulate stress/strains/deflection due to the interactions between applied traffic load and climate, and (iii) calculate the resulting damage manifested as distress and smoothness loss over the “Design Life” of a pavement. This Pavement ME Iterative Design Procedure is shown in flowchart form in Figure 2.1, and the stages are described in Table 2.1.
Table 2.1—Stages of Pavement ME Iterative Design Procedure Pavement ME Design Stage Design Steps
Evaluation stage
a) Characterize proposed pavement site conditions, paving materials properties, and existing pavement condition/properties (only for rehabilitation/reconstruction of existing pavements).
b) Assemble information in a project database for use in trial design development and evaluation.
Analysis stage
a) Select a trial design strategy (new pavement or rehabilitation type) using the Pavement ME software tool.
b) Define a trial pavement structure to analyze (pavement layer types, material properties, design features, construction practices etc.) for given site conditions (climatic, traffic, and subgrade/foundation properties).
c) Populate the trial design in Pavement ME software with materials, design, construction, climate, traffic, and other inputs.
d) Select appropriate failure or performance criteria that the trial design must satisfy at the end of the design life at a given level of reliability.
e) Run the trial design using the Pavement ME software. f) Obtain analysis outputs and (1) evaluate the outputs for accuracy and
reasonableness and (2) examine predicted distress/smoothness to determine if the trial design satisfies the predefined failure criteria and reliability at the end of the evaluation period.
g) If the trial design passes the performance criteria, proceed to next stage. If otherwise, revise the trial design.
Strategy selection stage
a) Assemble key design, structure, maintenance and rehabilitation (M&R), and cost information on viable design alternatives.
b) Perform engineering and cost analysis. c) Evaluate other design/construction considerations. d) Select preferred design strategy.
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A more in-depth understanding of the ME-based concepts, procedure, algorithms, models, and transfer functions used to predict distress and smoothness can be obtained through a wide range of references, including the MEPDG Manual of Practice (AASHTO, 2015), NCHRP project 1-37A research reports (ARA, 2004 a,b,c,d), and the “HELP” manual that is included in the Pavement ME software. This chapter of the Input Guide provides an overview of the transfer functions, design steps, input categories, and hierarchical input approach included in the Pavement ME design procedure. The remaining chapters are focused on determining the Pennsylvania-specific inputs to the software for predicting distress and smoothness over the design life of the pavement structure.
2.1 PERFORMANCE CRITERIA INPUTS CONSIDERED IN PAVEMENT ME SOFTWARE
Performance criteria are used to ensure satisfactory pavement performance over its design life/analysis period. The pavement performance is primarily influenced by factors such as traffic loading, materials aging, and environment. For design, inputs for both initial and terminal pavement conditions are required. The overall performance of the trial design is determined based on a mix of distresses and smoothness measured as International Roughness Index (IRI). The designer selects and uses performance criteria limits to evaluate the design adequacy at a given reliability level. Guidelines to the performance criteria specific to Pennsylvania conditions are presented in Chapter 4 of this guide. The distresses used to characterize performance are specific to the pavement type (flexible, rigid, and composite) considered for design. The definitions of distresses and IRI that were adopted from the Long-Term Pavement Performance (LTPP) program Distress Identification Manual for the Pavement ME software are presented in Table 2.2.
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Table 2.2—Definitions of Distress Types and Smoothness for Asphalt Concrete (AC) and Jointed Plain Concrete Pavement (JPCP) Surfaced Pavement Design
Performance Measure Pavement Type Description Photo
Alligator (bottom-up
fatigue) cracking,
percent lane area
New AC or replacement with AC
Occurs in areas subjected to repeated traffic loadings (wheel paths). Typically initiates as longitudinal cracks in the wheel paths and progresses to a series of interconnected many-sided, sharp-angled pieces, characteristically with a chicken wire/alligator pattern, in later stages. All levels of severity are included.
Resurfacing with AC
This form of distress is only applicable to existing AC pavement resurfaced with AC. The AC total fatigue cracking is the sum of bottom-up fatigue (alligator) cracking and fatigue (alligator) reflective cracking that reflects from the existing layer through the AC layer to the surface.
Transverse cracking, ft/mi
New AC or replacement with AC
Non-wheel load related cracks predominately perpendicular to the pavement centerline caused by low temperatures or thermal-induced stresses. The Pavement ME computes AC transverse cracking for the surface layer only.
Resurfacing with AC
This form of distress is applicable to existing AC pavement resurfaced with AC as well as existing JCP resurfaced with AC. For existing AC resurfaced with AC, the AC total transverse cracking is the sum of transverse cracking (thermal cracking) and reflective cracking that reflects from the existing layer through the AC layer to the surface. For existing JCP resurfaced with AC, total transverse cracking is the total of (1) low temperature cracks and (2) reflection transverse cracks originating from existing (pre-overlay cracks and joints) and future fatigue transverse cracks developed post overlay placement (i.e., cracks predominantly perpendicular to pavement centerline originating from the underlying rigid or semi rigid layers and AC overlay).
Total rutting, in
New AC or replacement with AC
Longitudinal surface depression in the wheel path due to permanent strain in the hot-mix asphalt (HMA), unbound aggregate base and subbase, and subgrade. The Pavement ME also computes the rutting in the AC, unbound aggregate base/subbase layers, and subgrade/foundation separately and sums them up to estimate total rutting.
Resurfacing with AC
For AC pavement resurfaced with AC, total rutting is the additional rutting occurring post AC overlay placement in the existing pavement plus the rutting in the AC overlay itself. Typically, post overlay rutting in the existing pavement is minimal.
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Table 2.2—Definitions of Distress Types and Smoothness for AC and JPCP Surfaced Pavement Design, continued Performance
Measure Pavement
Type Description Photo
Longitudinal (top-down
fatigue) cracking, ft/mi
New AC or replacement with AC Cracks predominantly parallel to pavement centerline and located in the wheel paths:
These cracks are initiated from the top of the AC surface downward through the layer. This distress is not recommended for use in design in Pennsylvania due to prediction model deficiencies.
Resurfacing with AC
Transverse (fatigue) cracking,
percent slabs cracked
New JPCP or replacement with JPCP Repeated loading by heavy truck results in fatigue damage of the top or bottom of the
slab, which eventually results in a transverse crack. Cracks are predominantly perpendicular to the pavement centerline.
Resurfacing with JPCP
Transverse joint faulting,
in
New JPCP or replacement with JPCP Transverse joint faulting is the differential elevation across the joint measured
approximately 1 foot from the slab edge. Since joint faulting varies significantly from joint to joint, the mean faulting of all transverse joints in a pavement section is the parameter predicted by the Pavement ME.
Resurfacing with JPCP
Smoothness (IRI), in/mi All Generally defined as an expression of irregularities in the pavement surface that
adversely affects the ride quality of a vehicle (and thus the user).
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2.2 DISTRESS TRANSFER FUNCTIONS INCLUDED IN PAVEMENT ME SOFTWARE
Chapter 5 in AASHTOWare Pavement ME Design —A Manual of Practice includes a summary of the transfer functions for all types of pavements that are included in the Pavement ME design and analysis methodology (AASHTO, 2015). Table 2.3 lists the performance indicators and the type of model or equation used to predict performance for use in design for each family of pavements included in the Pavement ME Design software. Table 2.3 also lists the transfer functions and regression equations that are recommended for use in Pennsylvania and whether or not they were locally calibrated. The different types of pavements are defined in Chapter 3.
2.3 PAVEMENT DESIGN STEPS USING PAVEMENT ME SOFTWARE
Pavement design using the Pavement ME software is an iterative process that can result in multiple acceptable designs. The specific design strategy for a project is selected external to the Pavement ME and is based on other factors, such as constructability, life cycle costs, and other policies established by PennDOT. The software, however, does include an optimization tool that defines the minimum thickness of an identified layer that satisfies all of the design criteria or threshold values entered by the user. The design-analysis process includes the following six steps, which are listed and discussed after Table 2.3.
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Figure 2.1—Conceptual Flow Chart for the Pavement ME Three-Stage Design-Analysis Process (NCHRP, 2008)
Foundation Analysis
REHABILITATIONEvaluate Existing
Pavement
DrainageVolume Changes
Frost Heave
NEW PAVEMENTSSubgrade Analysis
ENVIRONMENTTemperature
Moisture
PAVEMENT MATERIALSProperties as functions of loading
rate, temperature, & moisture
TRAFFICAxle Loads
ClassificationForecasting
RELIABILITY
Modify Strategy Select TrialPavement Strategies
Pavement Response Models
Pavement PerformanceModels
Doesperformance
meetcriteria?
EngineeringAnalysis
ViableAlternatives
Life CycleCost Analysis
SelectStrategy
STAGE 1 -- EVALUATION
STAGE 2 -- ANALYSIS
STAGE 3 – STRATEGY SELECTION
No
Yes
Other Considerations
Foundation Analysis
REHABILITATIONEvaluate Existing
Pavement
DrainageVolume Changes
Frost Heave
NEW PAVEMENTSSubgrade Analysis
ENVIRONMENTTemperature
Moisture
PAVEMENT MATERIALSProperties as functions of loading
rate, temperature, & moisture
TRAFFICAxle Loads
ClassificationForecasting
RELIABILITY
Modify Strategy Select TrialPavement Strategies
Pavement Response Models
Pavement PerformanceModels
Doesperformance
meetcriteria?
EngineeringAnalysis
ViableAlternatives
Life CycleCost Analysis
SelectStrategy
STAGE 1 -- EVALUATION
STAGE 2 -- ANALYSIS
STAGE 3 – STRATEGY SELECTION
No
Yes
Other Considerations
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Table 2.3—Performance Indicators Predicted by Pavement ME
Type of Pavement Performance Indicator Type of Model Recommended
for Use in Pennsylvania
Flexible Pavement and AC Overlays
AC Rutting ME Transfer Function Yes, locally calibrated
Unbound Aggregate Base and Subgrade Rutting ME Transfer Function Yes, locally
calibrated
Fatigue Cracking
Alligator Area Cracking; Bottom-Up Cracking ME Transfer Function Yes, locally
calibrated Longitudinal Cracking; Top-Down Cracking ME Transfer Function No (see notes
included in table) Thermal, Low-Temperature Cracking (Transverse) ME Transfer Function Yes, locally
calibrated
International Roughness Index Regression Equation Yes, locally calibrated
Reflection Cracking; confined to AC overlays ME Transfer Function Yes, locally
calibrated
Inverted Pavements
Alligator Fatigue Cracking ME Transfer Function No, not locally calibrated
AC Rutting ME Transfer Function No, not locally calibrated
Unbound Aggregate Base and Subgrade Rutting ME Transfer Function No, not locally
calibrated Thermal, Low-Temperature Cracking (Transverse) ME Transfer Function No, not locally
calibrated
International Roughness Index Regression Equation No, not locally calibrated
Semi-Rigid Pavement
Fatigue Cracking of Cementitious Layer ME Transfer Function No (see notes
included in table) AC Rutting, Fatigue Cracking, and Low-Temperature Cracking; same as for flexible pavements
ME Transfer Functions
Yes, not locally calibrated
International Roughness Index Regression Equation No (see notes included in table)
Rigid Pavements
JPCP & JPCP Overlays
Faulting ME Transfer Function Yes, locally calibrated
Fatigue Mid-Slab Cracking ME Transfer Function Yes, locally calibrated
International Roughness Index Regression Equation Yes, locally calibrated
Continuously Reinforced Concrete Pavement (CRCP) & CRCP Overlays
Punchouts ME Transfer Function Yes, not locally calibrated
International Roughness Index Regression Equation Yes, not locally calibrated
NOTES: The predicted distress or performance indicator should not be used to make design decisions or change the design until that transfer function has been locally or globally calibrated.
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Step 1: Select a trial design strategy (new pavement or rehabilitation design). The pavement designer can use PennDOT’s current design procedure (guidelines and catalog) to develop a trial design cross section as a starting point. Establishing the layer structure for all pavements is discussed in Chapters 7 and 8 of this User Input Guide.
For ease of use within the initial implementation of the Pavement ME software, a set of baseline files will be established and will be included in the PennDOT Pavement ME database library. These files are listed and defined in Chapter 9 of this User Input Guide, because they are specific to the transfer function calibration coefficients to be used in Pennsylvania. One of the appropriate files should be selected in setting up the trial design strategy. Step 2: Select the appropriate performance indicators or distress criteria and design reliability level for the project. Performance criteria can include bottom-up fatigue (alligator) cracking, total rut depth, thermal transverse cracking, and roughness (as estimated using the IRI) for flexible pavement design. Transverse fatigue (mid-slab) cracking, joint faulting, and IRI are the performance criteria for jointed plain concrete pavements (JPCP). Punchouts, crack width, crack load transfer, and IRI are the criteria for continuously reinforced concrete pavement (CRCP) design. The performance indicator criteria were obtained from PennDOT policies for triggering major rehabilitation or reconstruction and are included in Chapter 4 of this User Input Guide. Step 3: Obtain all inputs for the trial design under consideration. This step can be a time consuming effort, but sets apart the Pavement ME from most other procedures. The Pavement ME software allows the designer to determine the inputs based on their importance to pavement performance. The inputs required to run the software can be obtained using one of three levels of effort (and accuracy). The hierarchical input levels are defined in Section 2.3 of this chapter. The input categories include general project information, design criteria, traffic, climate, structure layering, design features, and material properties. The latter chapters of this User Input Guide are focused on determining values for the inputs to the Pavement ME software. Worksheets are included in Chapter 10 for documenting the inputs for a specific design problem. These worksheets are intended to facilitate use of the Pavement ME software. Step 4: Run Pavement ME Design software and examine the inputs for engineering reasonableness. The pavement design engineer should examine the input summary to ensure the inputs and calibration factors are correct and what the designer intended. This step should be completed before or after each run, until the designer becomes more familiar with the program and its inputs.
Step 5: Review and interpret the outputs in terms of the predicted distresses and IRI over the design life of the pavement both at the mean (50th percentile) and design reliability levels. Pavement ME software provides a summary of the predicted distresses and IRI of the pavement design strategy and the reliability of the design strategy for each distress. The user should assess if the trial design has met each of the performance indicator criteria at the design reliability level chosen for the project.
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Figure 2.2 shows an example of the summary output for a new AC pavement design. The target distress (performance criteria) and predicted distress at the specified reliability level are listed followed by the target reliability level and achieved reliability level for the target distress. If the “Achieved” reliability is equal to or greater than the “Target” reliability, the pavement structure passes. If the reverse is true, however, the pavement structure fails. If any key distress fails, the designer must alter the trial design to correct the problem, with the following exceptions.
o Rutting in flexible pavements and AC overlays can be milled and overlaid at the time the rut
depth criterion is exceeded to establish the preventive maintenance schedule. However, a minimum time period before this occurs is often considered.
o Faulting in rigid pavements can be diamond ground at the time the faulting criterion is exceeded to establish the preventive maintenance schedule. However, a minimum time period before this occurs is often considered.
o Thermal or low temperature and reflective cracks in flexible pavements and AC overlays can be sealed during the design period in establishing the preventive maintenance schedule.
o IRI in flexible and rigid pavements and overlays can be restored through milling and overlay or diamond grinding, respectively, at the time the IRI criterion is exceeded to establish the preventive maintenance schedule.
Figure 2.2—Pavement ME Output Summary Sheet
The distresses and IRI are output by graphs and tables at the end of each month over the design period, so the designer knows the time at which any of the design criteria are exceeded. In addition, materials properties and other factors are output on a month-by-month basis over the design period. The designer should examine the output material properties, climate summaries, traffic graphs, layer moduli, joint load transfer for JPCP, and other factors to assess their reasonableness. For flexible pavements, the output includes the AC Dynamic Modulus (E*) and resilient modulus (Mr) for unbound layers for each month over the design period. For rigid pavements, the slab elastic modulus and flexural strength, the joint load transfer efficiency (LTE), the base course elastic modulus, and subgrade k-value are also provided for each month throughout the design period.
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If the trial design has either input errors, material output anomalies, or has exceeded the performance criteria at the given level of reliability, revise the inputs/trial design and rerun the program. Iterate until the performance criteria have been met or use the optimization tool to determine the minimum layer thickness for the design features selected. When the target reliability level has been achieved, the trial design is a feasible design strategy. Note that PennDOT minimum design thickness is occasionally exceeded. When this occurs, inputs should be rechecked, but the minimum thickness specified by agency should be utilized. Step 6: Revise the trial design, as needed. If any of the criteria has not been met (e.g., target reliability not achieved), determine how this deficiency can be remedied by altering the materials used, the layering of materials, layer thickness, or other design features and rerun the software until all criteria have been met at the target reliability level. While layer thickness is important, many other design factors also affect distress and IRI or smoothness. The designer needs to examine the performance prediction and determine which design feature to modify to improve performance (e.g., layer thickness, material properties, layering combinations, geometric features, dowel diameter, and other inputs).
This User Input Guide identifies the design features commonly used in Pennsylvania that should be considered to improve specific performance indicators. Tables 2.4 through 2.6 provide some general guidelines for revising a design for which the calculated reliability of a specific distress is less than the target value. In addition, the MEPDG Manual of Practice (AASHTO, 2015) provides guidance on revising the trial design when the performance criteria have not been met.
This “trial and error” process allows the pavement designer to essentially “build the pavement in his/her computer” prior to building it in the field to see if it will perform. If there is a problem with the design and materials for the given subgrade, climate, and traffic, it can be corrected and an early field failure avoided.
2.4 INPUT CATEGORIES
The inputs are grouped into five categories: (1) General Project Information (including the performance criteria), (2) Traffic, (3) Climate, (4) Design Features, and (5) Structure (including material properties). Each one of these is discussed separately in latter chapters. The PennDOT Pavement ME database contains predefined project elements for traffic, climate, and materials inputs. This User Input Guide discusses the various categories of default inputs available in PennDOT’s Pavement ME database or input library. NOTE 1
Some of the features listed in Tables 2.4 through 2.6 include layer properties that should not be changed when doing traditional designs. There are cases, however, when those features can be revised in achieving an acceptable design—as an example, design-build type projects where materials may be directly measured.
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Table 2.4—Example Design Features to Revise for Flexible Pavement and AC Overlay Designs Not Meeting the Design Criteria or Target Reliability
Distress & IRI Design Feature Revisions to Minimize or Eliminate Distress
Alligator Cracking (Bottom Initiated)
• Increase thickness of AC layers. • For thicker AC layers (> 5 inches), increase dynamic modulus by using stiffer
or harder asphalt. • For thinner AC layers (<3 inches), reduce dynamic modulus by using softer
asphalt. • Use a polymer modified asphalt in the lower AC layer. • Increase density, reduce air void of AC base layer. • Use an unbound granular aggregate base with a higher resilient modulus.
Thermal Transverse Cracking
• Use softer asphalt in the wearing surface or asphalt with a colder lower temperature grade.
• Reduce the creep compliance of the AC surface mixture. • Increase the indirect tensile strength of the AC surface mixture. • Increase the thickness of the AC layers. • Increase the asphalt content of the surface mixture.
Rutting in HMA
• Increase the dynamic modulus of the AC layers by using harder or stiffer asphalt.
• Use a polymer modified asphalt in the layers near the surface. • Reduce the asphalt content in the AC layers. • Increase the amount of crushed aggregate. • Increase the amount of manufactured fines in the AC mixtures.
Rutting in Unbound Layers and Subgrade
• Increase the resilient modulus of the aggregate base; increase the density of the aggregate base.
• Stabilize the upper foundation layer for weak or collapsible soils. • Use a thicker layer of a granular aggregate base layer. • Place a layer of select embankment material with adequate compaction. • Increase the AC thickness.
IRI HMA
• Reduce the predicted distresses that deteriorate smoothness. • Require more stringent smoothness criteria and greater incentives (building the
pavement smoother at the beginning). • Improve the foundation; use thicker layers of non-frost susceptible materials • Stabilize any expansive soils • Place subsurface drainage system to remove groundwater.
Reflection Cracking
• Use an engineered interlayer to mitigate reflective cracks. • Increase AC overlay thickness. • Increase the modulus of the AC overlay. • Properly repair existing pavement alligator cracking to reduce the percent input
(this is very effective, especially medium and high severity). • Improve transverse joint load transfer efficiency (LTE) through retro-fit dowel
bars of existing JPCP.
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Table 2.5—Example Design Features to Revise for JPCP and Overlay Designs Not Meeting the Design Criteria or Target Reliability
Distress & IRI Modifications to Minimize or Eliminate
Joint Faulting
• Use dowels and increase their diameter as needed. • Do not increase slab thickness to achieve faulting criteria. • Increase erosion resistance of base (specific recommendations for each type of
base). • Minimize permanent curl/warp through curing procedures that eliminate built-in
temperature gradient (e.g., construct pavement at night, or pave in late afternoon to avoid high solar radiation prior to concrete set).
• PCC tied shoulder. • Widened slab (by 1 foot maximum to 13 feet). • Reduce transverse joint spacing. • Use PCC with lower coefficient of thermal expansion. • Build JPCP to set at lower temperature (cool PCC, place at cooler temperatures).
Slab Transverse Fatigue Cracking
• Increase slab thickness. • Use PCC with lower coefficient of thermal expansion. • Increase PCC strength (but not more than 10 percent). • Reduce transverse joint spacing. • Minimize permanent curl/warp through curing procedures that eliminate built-in
temperature gradient (e.g., construct pavement at night, or pave in later afternoon to avoid high solar radiation).
• PCC tied shoulder (separate placement or monolithic placement is better). • Widened slab (by 1 foot maximum to 13 feet).
Joint Crack Width (to reduce joint faulting)
• Decrease transverse joint spacing. • Reduce PCC coefficient of thermal expansion. • Build JPCP to set at lower temperature (cool PCC, place at cooler temperatures). • Reduce drying shrinkage of PCC (increase aggregate size, decrease water-cement
ratio, decrease cement content). • Use stabilized base (e.g., asphalt or cement stabilized) that provides greater
slab/base friction.
Joint LTE (to reduce joint faulting)
• Use mechanical load transfer devices (dowels). • Increase diameter of dowels (very significant). • Reduce joint crack width (see joint crack width recommendations). • Increase the size of the larger aggregate particles.
IRI JPCP
• Reduce the predicted joint faulting and cracking distresses that will reduce roughness.
• Require more stringent smoothness criteria and greater incentives (e.g., reduce the initial as-constructed IRI, which is very effective).
• Improve the foundation; use thicker layers of non-frost susceptible granular materials and use appropriate percent fines as input.
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Table 2.6—Example Design Features to Revise for CRCP and Overlay Designs Not Meeting the Design Criteria or Target Reliability
Distress & IRI Modifications to Minimize or Eliminate
Transverse Crack width
• Build CRCP to set at lower temperature (cool PCC, place during cooler temperatures).
• Reduce drying shrinkage of PCC (increase aggregate size, decrease water-cement ratio, decrease cement content).
• Increase percent longitudinal reinforcement. • Reduce depth of reinforcement (minimum cover over steel: 3.5 in). • Reduce PCC coefficient of thermal expansion (change larger aggregate).
Transverse Crack LTE • Reduce crack width (see crack width recommendations).
Punchouts
• Increase slab thickness. • Increase percent longitudinal reinforcement. • Reduce crack width over analysis period (see crack width
recommendations). • Increase PCC strength (maximum of 10 percent). • Increase erosion resistance of base (specific recommendations for each type
of base). • Minimize permanent curl/warp through curing procedures that reduce built-
in temperature gradient. • PCC tied shoulder or widened slab (by 1 foot to 13 feet maximum).
IRI CRCP
• Reduce the predicted distresses that cause smoothness. • Require more stringent smoothness criteria and greater incentives (e.g.,
reduce the initial IRI at construction, which is very effective). • Improve the foundation; use thicker layers of non-frost susceptible granular
materials and use appropriate percent fines as input.
2.4 HIERARCHICAL APPROACH FOR DETERMINING INPUTS
The hierarchical input approach provides the designer with a great deal of flexibility to obtain the inputs for a project based on the importance of the parameter and/or project and available resources. The hierarchical approach to input selection1 is employed with regard to traffic level, materials, and condition of existing pavement. Three levels for most of the inputs are available to the designer. Table 2.7 defines each input level. One of three levels can be used to estimate the values for each input. However, the highest level of input available was used in calibrating the Pavement ME transfer functions, both at the global and regional levels. For a given design project, inputs are almost always obtained using a mix of levels, such as dynamic modulus of AC mixtures from Level 1, traffic load spectra from Level 3, and subgrade resilient modulus from Level 2. It is important to realize that no matter what input design levels are used, the computational algorithm for damage and distress is exactly the same. The same models or transfer functions are used to predict distress and smoothness no matter what input levels are used. However, it is obvious that more
1 The hierarchical approach for determining the inputs needed by the MEPDG is a feature not found in existing versions of the AASHTO Guide (AASHTO 1986, 1993) and other ME-based methods. Currently, input level has no effect other than accuracy of the input parameter (which is important for critical inputs), except for low-temperature thermal cracking of AC wearing surfaces. For thermal cracking, the standard error of the transfer function is dependent on the input level (see Chapter 9 of this User Input Guide or Section 5 of the MEPDG Manual of Practice [AASHTO, 2015]).
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accurate and reasonable trial design inputs result in much more reliable pavement designs. Thus, Level 1 and Level 2 inputs, as available, should be utilized for improved accuracy in the designs.
Table 2.7—Hierarchical Input Levels Input Level Definition of the Level
1
Input parameter based on site-specific data and testing. Level 1 represents the case when the user has the greatest knowledge about the input parameter for the specific project. This input level has the highest level of testing (data collection costs) for determining the input value. Gathering Level 1 inputs requires more time and resources than inputs at other levels and is typically used for designing heavily trafficked pavements, for projects having unusual site features and/or considering the use of new materials, and for whenever there are dire safety or economic consequences for early failure.
2
Regression equations are often used to determine the input value, such as California bearing ratio (CBR) correlation with resilient modulus of soils. The data collection and testing for this input level is simpler and less costly. Level 2 Inputs for Pavement ME are estimated, using correlations of simpler tests with the more complicated inputs. Input level 2 is recommended for use for routine pavement designs and standard materials, and in cases when resources/testing equipment are not available to conduct tests to determine Level 1 inputs.
3
Level 3 inputs are user-selected values or typical averages for a region. The Level 3 inputs are generally based on global or regional default values. This input level requires the minimum amount of testing, and as such, results in the least knowledge about the input parameter for the specific project. Input level 3 is recommended for less critical inputs, as in lower volume roadways, where there are minimal safety or economic consequences of early failure and when there are inadequate resources to obtain input data at other levels.
The designer should consider gathering inputs that are appropriate and practical for the importance of the projects under design. For example, more accurate design inputs must be used for larger or more significant projects.
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CHAPTER 3—GENERAL PROJECT INFORMATION This chapter provides guidance on determining the input values for the General Project Information parameters for designing new and rehabilitated pavements in Pennsylvania. Example screen shots are included at the end of this chapter.
3.1 DESIGN AND PAVEMENT TYPE STRATEGIES
3.1.1 New/Reconstructed Flexible Pavements and AC Overlays
New and reconstructed AC surfaced pavements, as well as AC overlays, included in the Pavement ME software are listed below in two groups: those from LTPP sites and those from non-LTPP pavement management sections. If pavement design strategies that were not included in the local calibration process are used, the global calibration factors have to be used.2
• Flexible Pavements Included in Verification-Local Calibration Process. PennDOT calibration coefficients of the transfer functions are provided for all of the following flexible pavement types (see Chapter 9): 1. Conventional flexible pavements: Thin AC layers (total AC thickness less than 7 inches)
and thick aggregate base layers (crushed gravel and soil-aggregate mixtures), greater than 10 inches in thickness with and without stabilized subgrades.
2. Deep strength and full-depth flexible pavements: Full-depth and deep-strength were combined into one type of flexible pavement for the PennDOT calibration study. Full-depth is defined as AC layers placed directly on the prepared embankment or on a stabilized subgrade. Deep-strength is defined as a thick AC (a wearing surface, a binder layer, and a base layer exceeding 7 inches in thickness) placed over a granular aggregate base (GAB) material with or without a stabilized subgrade.
3. AC Overlays of all conventional, deep-strength, and full-depth flexible pavements, and JPCP.
• Flexible Pavements Not Included in Verification-Local Calibration Process. Calibration coefficients of the transfer functions and layer inputs were established and recommended from other agency studies for the following pavement types (see Chapter 9): 1. AC Overlays of CRCP, as well as AC overlays of fractured JPCP and CRCP. 2. Flexible Pavements with asphalt-treated permeable base (ATPB) layers. 3. Semi-rigid Pavements with CTB or lean concrete as base course. 4. Inverted pavements which include an AC surface over an unbound aggregate layer over a
CTB or soil cement layer.
2 Ten baseline files (five for new pavement designs and five for rehabilitation designs) will be included in the PennDOT database library, which can be used as a starting point in setting up the trial design structure. These baseline files contain the appropriate PennDOT calibration coefficients for each transfer function, even for the design strategies used on an infrequent basis in Pennsylvania. The 10 baseline files are listed and defined in Chapter 9 of this User Input Guide.
NOTE 2 The final research report for this project provides more detailed
discussion on the types of pavement included in the local calibration and
verification process.
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3.1.2 New/Reconstructed Rigid Pavements and PCC Overlays
New and reconstructed PCC surfaced pavements, as well as PCC overlays, that were included or excluded from the local calibration refinement process are listed below.3
• Rigid Pavements Included in Verification-Local Calibration Process. PennDOT calibration coefficients of the transfer functions are provided for all of the following rigid pavement types (see Chapter 9): 1. Jointed Plain Concrete Pavements: JPCP include transverse joints spaced to accommodate
temperature gradient and drying shrinkage stresses to minimize cracking. The joints include dowels to complement the aggregate interlock in providing load transfer. PennDOT JPCP sections used in the calibration had a thickness range of 8 to 12 inches and were placed on HMA, cement stabilized, and granular aggregate bases. Joint spacing ranged from 15 to 30 feet.
• Rigid Pavements Not Included in Verification-Local Calibration Process. Calibration
coefficients of the transfer functions and layer inputs were established and recommended from other agency studies (see Chapter 9): 1. Continuously Reinforced Concrete Pavements: PCC slabs cast without transverse joints
and containing longitudinal steel typically in the range of 0.65 – 0.8 percent of the cross-sectional area. The PCC surface develops closely spaced transverse cracks and the design should ensure that the cracks remain tight and provide good load transfer during the service life of the pavement. No CRCP sections were included in the verification-calibration process for PennDOT. Global calibration factors should provide reasonable predictions for CRCP critical distresses for limited usage.
2. PCC Overlays of all types of rigid and flexible pavements, including bonded PCC overlay
of rigid pavements, unbonded PCC overlay of rigid pavements, and PCC overlay of flexible pavements. The same Pennsylvania local calibration factors obtained for new JPCP can be used for these designs.
3 Footnote 2 also applies to rigid pavements.
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3.1.3 Pavement Preservation and Preventive Maintenance
Pavement preservation treatments applied to the surface of AC layers early in their life can have an impact on the structural performance and regional calibration factors (Von Quintus and Moulthrop, 2007a and 2007b). Most of the roadway segments included within the local calibration process for PennDOT included the use of pavement preservation and/or preventive maintenance strategies, with the exception of the LTPP Specific Pavement Studies (SPS) projects. Thus, the local calibration values presented in Chapter 9 include the effect or impact from pavement preservation and preventive maintenance activities commonly used by PennDOT. Pavement preservation treatments applied to the surface of JPCP layers can also have an impact on the joint faulting, fatigue cracking, and IRI performance. These pavements with pavement preservation treatments (such as diamond grinding) were not included in the “new” pavement grouping for calibration. They can be designed under “restoration” as explained Chapter 8.
3.2 PROJECT FILE/NAME
The designer should use a simple but descriptive name for the analysis that can be easily identified in the project files created by the Pavement ME software. The designer should enter appropriate information to identify the project for pavement design purposes and future reference. The amount of detail is up to the designer.4 The information for this category of inputs has no impact on the analyses or distress predictions.
3.3 DESIGN LIFE
The design life of a newly reconstructed pavement is defined as the time from opening to traffic post-initial construction (or rehabilitation) until the pavement has structurally deteriorated to the point when significant rehabilitation/reconstruction is needed (exceeding one of the threshold values or design criteria). The design life for all new pavement and rehabilitation designs is provided in Table 3.1.
4 The name of the baseline files included in the PennDOT database library can be used as an example (see Chapter 9).
NOTE 3 If PennDOT’s preservation/maintenance policies
change over time, the local calibration factors should be checked to validate whether there is a further reduction
in structural-related distresses (bias between the predicted and observed values).
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Table 3.1—Design Life for Flexible and Rigid Pavement and Rehabilitation Pavement Type Design Life (years) Long-Life Design Life (years)
Flexible 20 40 Rigid (JPCP, CRCP) 30 40 AC Overlays 15 NA PCC Overlays 30 40 Restoration JPCP 15 NA The software can handle design lives from one year (e.g., detour) to over 50 years. In fact, the software program has the ability to analyze 100-year designs. The design life for “long-life” pavements is defined as 35 to 50 years.
3.4 BASE AND PAVEMENT CONSTRUCTION & TRAFFIC OPENING DATES
3.4.1 New Construction
Construction completion and traffic opening dates are site construction features. These dates are keyed to the monthly traffic loadings and monthly climatic inputs that affect all layer moduli, including the subgrade modulus. The time reference is keyed to the first day of the month. In the case of rigid pavements, the construction month also determines the PCC set (or zero-stress) temperature, strength, and elastic modulus. The set temperature provides the temperature baseline for the calculation of joint openings during the design life. The strength and elastic modulus vary monthly over the entire design life and are used in fatigue cracking and joint faulting predictions. Different construction months can affect pavement performance as result of the prevailing climatic conditions for that month. For designs on larger projects, these dates are difficult to accurately define. The designer should select the most likely month for construction and opening the roadway to traffic. These dates are more important for rigid pavements than for flexible pavements, and more importantly, distresses are less sensitive to these dates than to other inputs, except for designing temporary pavement structures for detours. Table 3.2 provides the recommended months when the roadway is periodically opened to traffic, as different segments of the project are completed or if the dates are unknown because construction scheduling and phasing have yet to be defined. Month in Pavement ME is defined as the first day of that month. For large projects that extend into different paving seasons, each paving season can be evaluated separately.
Table 3.2—Construction and Traffic Opening Dates (General Suggestions) Design Pavement
Type Base Construction
Month Pavement Construction
Month Traffic Opening
Month New
Construction Flexible May June July Rigid N/A June August
Rehabilitation AC Overlay N/A June June PCC Overlay N/A June August
N/A – Not applicable
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3.4.2 Rehabilitation
The construction completion date of the existing pavement is required for all rehabilitation designs. This date should represent the approximate time when pavement construction was completed. The predicted distresses and performance indicators are less sensitive to this date than to the construction and opening to traffic date for the overlay. Table 3.1 lists the recommended overlay and traffic opening months for rehabilitation projects when they are unknown. Another issue related to rehabilitation design is when an overlay is being designed for an existing pavement with one or more overlays, because only one overlay can be simulated in the program. The following provides some guidance on determining the date of original construction.
1. If the existing overlay is thin or most of it is being milled as part of the rehabilitation strategy, the year the original pavement was opened to traffic should be entered.
2. If a thick structural overlay exists (relative to the existing original pavement surface) and most of that overlay is left in place, the year the structural overlay was opened to traffic should be entered for the original pavement construction.
3. If unsure of what date to use, the user should enter the date the original pavement was built or constructed, or just assume that the pavement is 30 years old.
3.5 SCREEN SHOTS FOR GENERAL INFORMATION
The following are screen shot examples that show the General Information for the rehabilitation of flexible (AC over AC) and rigid pavements (AC over JPCP). The drop-down arrows are used to access or select different design and pavement types and other information for a specific project.
AC over AC AC over JPCP
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CHAPTER 4—PERFORMANCE CRITERIA Performance criteria are used to ensure a new pavement or rehabilitation design strategy performs satisfactorily over its design life. Performance of a pavement is measured in terms of the key distresses and smoothness, as measured by the IRI (refer to Table 2.1 in Chapter 2 of this User Input Guide). The designer selects performance criteria or threshold limits that relate directly to the need for rehabilitation. Example screen shots showing the performance criteria are included at the end of this chapter.
4.1 INITIAL INTERNATIONAL ROUGHNESS INDEX (IRI)
The initial IRI is the average IRI value measured after construction and is entered into the input screen for the performance criteria. This initial value should be determined from construction records of previously placed AC or PCC surfaces under comparable conditions. The IRI reported by PennDOT is based on a half car simulation of the longitudinal profile data, while the IRI reported by LTPP and used in the development of the global IRI regression equation was based on a quarter car simulation. The values resulting from a quarter car simulation will be consistently higher in comparison to a half car simulation. As such, the PennDOT initial IRI values cannot be entered directly in the Pavement ME and an adjustment may be needed. Some of the values in Table 4.1 were measured in Pennsylvania and others measured in other states for different pavement types.
Table 4.1—Initial IRI Values Type of
Pavement Type of Wearing Surface Initial IRI Rating, in./mi.
Flexible & AC Overlays
Open-Graded Friction Course/PEM 53 SMA and SR Mixtures 59
Dense-Graded AC – State Routes 64 Dense-Graded AC – Urban Routes 84
Rigid JPCP 64 CRCP 50
Restore JPCP(Diamond Grinding) 75
4.2 DISTRESS CRITERIA OR THRESHOLD VALUES
Performance criteria (or Analysis Parameters on the software window) are used to ensure that a pavement design will perform satisfactorily over its design life. Critical limits are selected and used by the designer to judge the adequacy of a design. These limits represent pavement conditions that trigger some type of major rehabilitation or reconstruction activity. These criteria are similar in concept to the current AASHTO Design Guide (AASHTO, 1993) with the use of only the terminal serviceability index levels. These design criteria should not represent levels of distress or surface conditions that trigger only some type of maintenance or non-structural repair. Distress-specific design criteria are a policy decision of PennDOT and determined from past experience and information included in PennDOT’s pavement management databases: Pavement Condition Evaluation System (PACES) for flexible pavements and Concrete Pavement Condition Evaluation
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System (CPACES) for rigid pavements. The consequence of a project exceeding a performance criterion is the requirement of an earlier-than-programmed major rehabilitation. The distress or performance indicator values recommended for design at the design reliability are listed in Tables 4.2 to 4.7 by type of pavement, which are defined and measured in accordance with the Distress Identification Manual (FHWA, 2003). The following paragraphs provide more discussion on the Pavement ME design criteria relative to the PennDOT values and policy decisions.
Table 4.2—Flexible Pavement Design Criteria or Threshold Values
Roadway Type (number of lanes are in both directions)
Performance Indicator (Maximum Value at End of “Design Life” at Design Reliability)A
Total Permanent Deformation (Rut
Depth)B, in.
Thermal Cracking, ft./mi.
Bottom-Up Fatigue Cracking,
% lane area
Non-Interstate 2-Lane State Route 0.40 1,500 15 4-Lane Roadway 0.40 1,500 10
Interstate Rural and Urban 0.35 1,000 10 Note A: AC longitudinal fatigue cracking (top-down) is not considered in AC pavement design in Pennsylvania. Note B: Two permanent deformation values need to be entered; see section 4.2.3.
Table 4.3—AC Overlay of Existing Flexible Pavement Design Criteria or Threshold Values
Roadway Type (number of lanes are in both directions)
Performance Indicator (Maximum Value at End of “Design Life” at Design Reliability)A
Total Permanent
Deformation (Rut Depth)B,
in.
Thermal Cracking,
ft./mi.C
AC Total Transverse
Cracking (Thermal + Reflective), ft./mi.
Bottom-Up Fatigue
CrackingC, %
AC Total Fatigue Cracking (Bottom-Up + Reflective),
% lane area
Non-Interstate
2-Lane State Route 0.40 1,500 1,500 15 15 4-Lane Roadway 0.40 1,500 1,500 10 10
Interstate Rural and Urban 0.35 1,000 1,000 10 10 Note A: AC longitudinal fatigue cracking (top-down) is not considered in AC pavement design in Pennsylvania. Note B: Two permanent deformation values need to be entered; see section 4.2.3. Note C: This value is considered only at 50 percent reliability.
Table 4.4— JPCP Design Criteria or Threshold Values
Roadway Type (number of lanes are in both directions)
Performance Indicator (Maximum Value at End of “Design Life” at Design Reliability)
Mean Faulting, in. Slabs Transversely Cracked, %
Non-Interstate 2-Lane, State Route 0.15 15.0 4-Lane Roadway 0.15 10.0
Interstate Rural and Urban 0.12 10.0
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Table 4.5— CRCP Design Criteria or Threshold Values Roadway Type (number of lanes are in
both directions)
Performance Indicator (Maximum Value at End of “Design Life” at Design Reliability)
Number of Punchouts per Mile
Non-Interstate 2-Lane, State Route 10 4-Lane Roadway 10
Interstate Rural and Urban 5
Table 4.6—Semi-Rigid Pavement Design Criteria or Threshold Values
Roadway Type (number of lanes are in both directions)
Performance Indicator (Maximum Value at End of “Design Life” at Design Reliability)A
Total Permanent
Deformation (Rut Depth)B,
in.
Thermal Cracking,
ft./mi.C
AC Total Transverse
Cracking (Thermal + Reflective), ft./mi.
Bottom-Up Fatigue
CrackingC, %
AC Total Fatigue Cracking (Bottom-Up + Reflective),
% lane area
Non-Interstate
2-Lane State Route 0.40 1,500 1,500 15 15 4-Lane Roadway 0.40 1,500 1,500 10 10
Interstate Rural and Urban 0.35 1,000 1,000 10 10 Note A: AC longitudinal fatigue cracking (top-down) is not considered in AC pavement design in Pennsylvania. Note B: Two permanent deformation values need to be entered; see section 4.2.3. Note C: This value is considered only at 50 percent reliability. Note D: Use 10% for chemically stabilized layer – fatigue fracture (% lane area). This value is considered only at 50 percent reliability.
Table 4.7—Composite Pavement Design Criteria or Threshold Values
Roadway Type (number of lanes are in both directions)
Performance Indicator (Maximum Value at End of “Design Life” at Design Reliability)A
Total Permanent
Deformation (Rut Depth)B,
in.
Thermal Cracking,
ft./mi.C
AC Total Transverse Cracking
(Thermal + Reflective),
ft./mi.
Bottom-Up Fatigue Cracking,
%
JPCP Slabs Transversely CrackedD, %
CRCP Number of Punchouts per MileE
Non-Interstate
2-Lane State Route 0.40 1,500 1,500 15 15 10 4-Lane Roadway 0.40 1,500 1,500 10 10 10
Interstate Rural and Urban 0.35 1,000 1,000 10 10 5 Note A: AC longitudinal fatigue cracking (top-down) is not considered in AC pavement design in Pennsylvania. Note B: Two permanent deformation values need to be entered; see section 4.2.3. Note C: This value is considered only at 50 percent reliability. Note D: This performance criteria is considered only for AC overlay of existing JPCP. Note E: This performance criteria is considered only for AC overlay of existing CRCP.
4.2.1 Terminal IRI Criterion
The terminal IRI for which the pavement is considered too rough and requires some type of rehabilitation is a required input. The terminal IRI is defined as the lowest acceptable value, which when exceeded, triggers a need for resurfacing or reconstruction of the particular highway class. Typically, the terminal IRI value that is selected is similar to that used in pavement management to establish when a roadway requires rehabilitation.
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The IRI is predicted over time from the initial IRI and other predicted distresses and a site factor, which is explained in Section 5 of the MEPDG Manual of Practice (AASHTO, 2008). Table 4.8 lists the terminal IRI ratings considered to be too rough. Table 4.8—Terminal IRI and Corresponding PennDOT Half-Car Roughness Index (HRI) Ratings
or Values
Roadway Type (number of lanes are
in both directions)
Pavement Type Flexible Pavements
& AC Overlays Semi-Rigid JPCP CRCP
IRI
Rating; in/mi
IRI
Rating; in/mi
IRI
Rating; in/mi
IRI
Rating; in/mi
Non-Interstate
Route
2-Lane, State 200 200 200 175
4-Lane Roadway 175 175 175 175
Interstate Route
Rural & Urban 175 175 175 175
4.2.2 Fatigue (Load-Related) Cracking Criterion—Flexible Pavements
Two types of load-related cracking that occur in flexible pavements are included in the Pavement ME software: alligator or bottom-up fatigue cracking in terms of percent of total lane area and longitudinal or top-down fatigue cracking in terms of feet per mile (refer to Table 2.1). In the Pavement ME design methodology, bottom-up fatigue (alligator) cracking is assumed to initiate at the bottom of all AC layers, while top-down (longitudinal) fatigue cracking is assumed to initiate at the surface of the AC wearing surface (top-down cracking). Alligator or bottom-up fatigue cracking should be used as the design criteria. The surface initiated-longitudinal cracking is not recommended for use as a design criterion at this time due to prediction model deficiencies. The designer should review the predicted longitudinal cracking values but not make any design changes based on the predicted length of longitudinal cracks. Bottom-up fatigue cracking is the input design criteria for new construction design problems, while AC total cracking (bottom-up plus reflective cracks) is the input design criteria for a rehabilitation design (AC overlays) problem. Reflective cracking calculated by the Pavement ME design software is the percentage of cracks in the existing wearing surface that reflect through the AC overlay. Total cracking is the combined area of new bottom-up fatigue cracks in the AC overlay plus any cracks in the existing AC wearing surface that have reflected through the AC overlay.
4.2.3 Permanent Deformation (Rut Depth) Criterion—Flexible Pavements
The Pavement ME Design software requires the entry of two rut depth (permanent deformation) design criteria for flexible pavements: AC rutting only and total rutting. The design criteria should be the same for both the AC rutting and total rutting.
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4.3 DESIGN RELIABILITY
The design reliability included in the Pavement ME design methodology is similar, in concept only, to that in the AASHTO Design Guide (AASHTO 1993)—the probability that the pavement will not exceed any of the performance criterion limits over the design period. For example, a design reliability of 90 percent represents the probability (9 out of 10 projects) that the mean rutting for the project will not exceed the total rut depth criterion over the design life. Pavement projects exceeding performance criteria usually result in earlier-than-programmed maintenance and rehabilitation activities rather than a dire structural collapse consequence such as in bridge design, for which the design reliability is much higher. The design reliability should be selected in balance with the performance criteria. For example, the selection of a high design reliability level (e.g., 99 percent) and a very low performance criterion (3 percent alligator cracking) might make it almost impossible (i.e., very costly) to obtain an adequate design. The selection of a very high level of design reliability (e.g., greater than 97 percent) is not recommended at the present time, because this may significantly increase construction costs with limited benefits to performance. Design reliability must be selected for each performance indicator and different values can be entered for different distresses. Table 4.9 lists the reliability levels recommended for use for different types of roadways for all types of distresses or performance indicators. These levels of reliability increase for heavier traffic facilities due to the more serious consequences of exceeding the design criteria. One consequence is increased cost of rehabilitation and maintenance; another is increased lane closures to perform rehabilitation or maintenance; and with higher traffic levels, there will be more traffic delays due to lane closures. The design reliability for thermal cracks is 50 percent, which is hard-coded in the software.
Table 4.9—Reliability Level Recommended for Use with Pavement ME Design Type of Roadway Recommended Reliability Level, %
Interstate & Primary Arterials 95 Minor Arterials & Major Collectors 90 Low Volume (less than 500 trucks per day in both directions) & Local Roadways 75
4.3 SCREEN SHOTS FOR THE PERFORMANCE CRITERIA
This section of Chapter 4 includes screen shot examples that show the Performance Criteria inputs discussed within this chapter for the rehabilitation of flexible and rigid pavements. The same distresses are used for new flexible and rigid pavement designs, with the exception of reflection cracking. The specific pavement distresses are dependent on the pavement type selected for a specific project. The following are screen shots for the major pavement types (AC, JPCP).
NOTE 4 Reliability is the probability that the design criterion for a specific
distress will not be exceeded within the design life.
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Performance Criteria: New Flexible Pavement Designs
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Performance Criteria: AC over AC
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Performance Criteria: JPCP
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Performance Criteria: AC over JPCP
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CHAPTER 5—TRAFFIC INPUTS This chapter summarizes the truck traffic inputs used for evaluating the adequacy of a design strategy. Example screen shots showing the traffic inputs are included at the end of this chapter. PennDOT’s Bureau of Planning and Research (BPR) can generate most of the traffic inputs for a specific project. For roadway segments where project-specific traffic data are unavailable, the default values are recommended to be used for design. Wherever possible, these traffic default values were developed based on analysis of traffic data from PennDOT’s weigh-in-motion (WIM) and continuous automated vehicle classification (CAVC) traffic monitoring sites. However, for several truck traffic input parameters, supporting data were not available within PennDOT’s truck traffic database. For these parameters, the global default values are recommended for use in design. They are defined and discussed within the NCHRP Project 1-37A reports (ARA, 2004a). Specific values and recommendations for the default inputs are provided in this chapter. These values were used in the regional validation/calibration refinement performed for Pennsylvania. They are required for predicting distresses in both flexible and rigid pavements. The traffic default values are included in the PennDOT Pavement ME Design data library. These traffic input libraries were established to save time in entering the traffic data.
5.1 AVERAGE ANNUAL DAILY TRUCK TRAFFIC (TRAFFIC VOLUME INPUTS)
The following traffic input parameters relate to traffic volume and are considered site-specific and should be obtained from the PennDOT BPR. If this information is unavailable, the following subsections provide the recommended default values (input level 3) to be used.
• Two-way average annual daily truck traffic (AADTT): A project-specific AADTT at the beginning of the design period is required for every design. AADTT is a weighted average between weekday and weekend truck traffic. The designer should enter two-way, not one-way, AADTT values.
• Number of Lanes: The number of lanes in the
design direction.
• Percent trucks in the design direction or directional distribution factor (DDF): The percentage of trucks in the design direction or DDF is defined by the vehicle class 4 through 13 for the roadway. If sufficient truck volume data is unavailable, a DDF value of 50 percent should be used.
• Percent trucks in the design lane or lane distribution factor (LDF): The percentage of trucks
in the design lane is defined by the vehicle class 4 through 13 for the roadway. If sufficient truck volume data is unavailable, the values listed in Table 5.1 should be used.
NOTE 5 BPR typically provides one-way
traffic volumes, so those values need to be multiplied by 2 as an input to
the Pavement ME software.
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Table 5.1—Lane Distribution Factor Recommended for Use with Pavement ME Number of Lanes (Two-Directions) Lane Distribution Factor, %
2 100 4 90 6 80
>6 60 • Operational speed: This input parameter is taken as the posted speed limit or the average truck
speed of the heavier or larger trucks through the project segment. Lower speeds result in higher incremental damage values calculated by the Pavement ME design methodology.
5.2 TRAFFIC CAPACITY
This input factor (traffic capacity cap) does not have any impact on the predictions of the performance indicators until it reaches the capacity of the roadway. This input is used to determine if the expected growth in truck traffic over time will exceed the truck capacity of the “design lane.” Typically, truck capacity will not be exceeded. However, higher volumes with higher growth rates over longer design periods can often lead to unrealistic projected truck volumes for the heaviest trafficked “design lane.” This input is essentially a check on the assumed LDF. The Pavement ME software can simply be run with Traffic Capacity Enforced to determine if there exists a capacity problem. If so, the program will automatically reduce the number of trucks in the “design lane” over the design period to a maximum number used in the pavement design. This reduction can range from a few percent to over 50 percent.
5.3 AXLE CONFIGURATION
• Average axle width: The average distance between the outside edge of the tires of an axle – 8.5 feet, the Pavement ME default value.
• Dual tire spacing: The average distance between the center of the two tires – 12 inches, the
Pavement ME default value.
• Tire pressure (hot inflation pressure): The average hot tire pressure – 120 psi, assumed for both single and dual tires.
• Tandem axle spacing: The average distance between the two axles of a tandem axle – 51.6 inches, the Pavement ME default value.
• Tridem axle spacing: The average distance between the three axles of a tridem axle – 49.2 inches, the Pavement ME default value.
• Quad axle spacing: The average distance between the four axles of a quad axle – 49.2 inches, the Pavement ME default value.
Table 5.2 summarizes the axle configuration for Pennsylvania.
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Table 5.2—Axle Configuration for Pennsylvania (see Figure 5.1b) Truck Features Mean Values
Average axle width 8.5 ft (outside to outside of truck tires) Dual tire spacing 12 in Dual tire pressure 120 psi Tandem axle spacing 51.6 in Tridem axle spacing 49.2 in Quad axle spacing 49.2 in
5.4 LATERAL WANDER
• Mean Wheel Location: The average distance from the outer edge of the wheel to the pavement edge marking (lane paint stripe) – 18 inches, the Pavement ME default value. This input is only required for a rigid pavement design analysis.
• Truck traffic wander standard deviation: The lateral distribution of trucks traveling down the
roadway – 10 inches, the Pavement ME default value. Truck lateral wander is illustrated in Figure 5.1a.
• Design Lane Width: The width of the lane between the pavement lane designation markings as defined in Figure 5.1d. This is not necessarily the slab width. This input is a design feature and not a traffic input. It is included with the other traffic inputs because it has a significant impact on the stresses in the PCC slab based on the location of the wheel load relative to the edge of the slab. The value is selected by the pavement designer for the specific project. This input is only required for a rigid pavement design analysis. For example, a typical design lane width is 12 feet (from edge marker to edge marker). The actual slab could be slightly wider such as 13 or 14 feet for structural design benefits.
5.5 WHEEL BASE
The wheel base is defined in Figure 5.1c. The average axle spacing and percentage of trucks within each spacing are only required for a rigid pavement design analysis. The following are the Pavement ME default values recommended for use in Pennsylvania as shown in Table 5.3:
• Average axle spacing o 12 ft. for short axle spacing. o 15 ft. for medium axle spacing. o 18 ft. for long axle spacing.
• Average percentage of trucks within each axle spacing
o 17 percent for short axle spacing. o 22 percent for medium axle spacing. o 61 percent for long axle spacing.
Table 1—Wheelbase for Pennsylvania (see Figure 5.1c)
Wheelbase Short Medium Long Average axle spacing 12 ft 15 ft 18 ft Percentage of trucks 17% 22% 61%
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Figure 5.1—Schematic Illustration of Mean Wheel Location
5.6 VEHICLE CLASS DISTRIBUTION AND GROWTH
Distribution Factors: Normalized vehicle (truck) class volume distribution. Determine the percentage of each vehicle or truck class within mixed traffic (vehicle class 4 through 13, as defined by FHWA). These percentages represent the normalized distribution of truck volumes by vehicle class and are provided by BPR. Vehicle class types are defined according to FHWA and AASHTO definitions, as shown in Figure 16. Level 1 vehicle class distribution (VCD) is the actual measured site data over 24 hours and must be used for highways with heavy seasonal recreational and agricultural traffic (contact BPR).
a
b
c
d
a. Wheel location b. Axle configuration c. Wheelbase d. Lane width
Outside Lane
Shoulder
Direction of traffic
Wheelbase
LANE WIDTH
SLAB WIDTH
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Figure 5.2—Illustration of FHWA/AASHTO vehicle class type description
Vehicle class volume data is readily available for 40 CAVC sites. The normalized vehicle class distribution can be obtained from BPR for some pavement designs. If vehicle class volume data is unavailable, or if it is for a new roadway (new alignment), the default normalized vehicle class volume distribution factors developed based on PennDOT data can be used.
Pavement ME Input Level 2 VCDs were estimated from vehicle classification data obtained from the FHWA LTPP program sites located in Pennsylvania and from PennDOT CAVC sites. They represent Pennsylvania average values defined by highway functional class (FC) and Traffic Pattern Group (TPG) established for Pennsylvania roads (ref. PA 2013 Traffic Data report PUB 601 (9-14)). Table 5.4 presents a description of TPGs. Traffic data analysis indicated that VCDs observed on Pennsylvania roads could be grouped into several clusters. A description of the four VCD clusters is presented in Table 5.5. Figure 5.3 presents a graph showing VCD values. These default values are recommended for pavement design when site-specific VCD is not available. Selection of the appropriate VCD for a given site must be based on project location and highway functional class or TPG, as a minimum.
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Table 5.4—Traffic Pattern Group (TPG) in Pennsylvania Traffic Pattern
Group Description
TPG 1 Urban – Interstate
TPG 2 Rural – Interstate
TPG 3 Urban – Other Principal Arterials
TPG 4 Rural – Other Principal Arterials
TPG 5 Urban – Minor Arterials, Collectors, Local Roads
TPG 6 North Rural – Minor Arterials
TPG 7 Central Rural – Minor Arterials
TPG 8 North Rural – Collectors and Local Roads
TPG 9 Central Rural – Collectors and Local Roads
TPG 10 Special Recreational
Table 5.5—Recommended Vehicle Class Distribution Inputs for Level 2 Design for Pennsylvania Roadways
Vehicle Class
Urban Principal Arterial – Interstate
(PA TPG 1)
Rural Principal Arterial – Interstate
(PA TPG 2)
Other Principal Arterial
(PA TPG 3 & 4)
Minor Arterials, Collectors, and Recreational (PA TPG 5 to
10) 4 2.79 0.9 2.03 3.5
5 13.52 9.64 29.41 47.51
6 5.68 3.53 8.46 12.92
7 2.05 1.59 3.92 3.48
8 7.29 3.63 7.03 10.39
9 62.64 74.42 46.91 21.07
10 0.91 0.58 0.71 0.67
11 3.36 4.25 1.01 0.31
12 1.37 1.31 0.24 0.04
13 0.39 0.15 0.28 0.11
Total 100 100 100 100
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Figure 5.3—Default Vehicle Class Distributions for Pennsylvania by FC and TPG
Values presented in Table 5.5 are in a close agreement with several Pavement ME VCD defaults for the following Pavement ME Truck Traffic Classifications (TTCs). The TTC groups common to PA roadways are presented in Table 5.6.
Table 5.6—Truck Traffic Classification Groups Common to Pennsylvania Roadways for Level 3 Design
Road Functional Class and TPG TTC for Pavement ME VCD Default
Urban Principal Arterial – Interstate (PA TPG 1) TTC 2 Rural Principal Arterial – Interstate (PA TPG 2) TTC 1
Other Principal Arterial (PA TPG 3 & 4) TTC 6 Minor Arterials, Collectors, and Recreational (PA TPG 5 to 10) TTC 12
To speed up the input process for AASHTO Pavement Design software, the global VCD default values for theses TTCs can be selected as the alternative input values. Growth rate of truck traffic. Estimate the increase in truck traffic over time. The growth of truck traffic is difficult to accurately estimate because there are many site and social-economic factors that cannot be predicted 20-plus years into the future. In most cases, the growth rate for each vehicle class will be provided by the BPR for a particular roadway segment. The type and magnitude of the growth rate can be entered in the Pavement ME software for each truck class. The user has three options in choosing a traffic growth function, as listed below.
• No Growth: Truck volume for a specific truck class remains the same throughout the design life. • Linear Growth: Truck volume increases by a constant percentage of the base year traffic for the
specific truck class. • Compound Growth: Truck volume increases by a constant percentage of the preceding year
traffic for the specific truck class.
0
10
20
30
40
50
60
70
80
4 5 6 7 8 9 10 11 12 13
Perc
enta
ge, %
Vehicle Class
Urban Interstates(TPG-1)
Rural Interstates(TPG-2)
Other PrincipalArterials (TPG-3 to 4)
Minor Arterials,Collectors andRecreational (TPG-5to 10)
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Negative Growth is not an option in the Pavement ME software. If truck traffic is expected to decrease within the design life, use the average truck volume throughout the design life for that truck class and assume no growth.
5.7 MONTHLY ADJUSTMENT
The monthly adjustment factors (MAF) represent the relative amount of trucks traveling on the roadway segment during any month within a typical year. The available truck volume by class data was not sufficient to identify specific MAF for specific types of roads. MAF are highly site-specific and vary from location to location. Therefore, where possible, site-specific values should be used. The site-specific MAF can be provided by the BPR. In addition, results from PA 2013 Traffic Data report PUB 601 (9-14) state that truck seasonal variation charts, which are based on truck traffic studies, indicate that truck traffic varies little for both the Interstate and non-Interstate systems. Day of the week by month adjustment factors from that report were used to establish one set of default MAF, shown in Table 5.7. The values in Tables 5.7 should be used when sufficient truck volume data are unavailable. Table 5.7—Recommended Monthly Adjustment Factor Inputs for Level 2 Design for Pennsylvania
Roadways
Month Truck Classification
4 5 6 7 8 9 10 11 12 13 January 0.83 0.83 0.83 0.83 0.83 0.83 0.83 0.83 0.83 0.83
February 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0.84 0.84 March 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 0.90 April 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 May 1.04 1.04 1.04 1.04 1.04 1.04 1.04 1.04 1.04 1.04 June 1.09 1.09 1.09 1.09 1.09 1.09 1.09 1.09 1.09 1.09 July 1.11 1.11 1.11 1.11 1.11 1.11 1.11 1.11 1.11 1.11
August 1.12 1.12 1.12 1.12 1.12 1.12 1.12 1.12 1.12 1.12 September 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10 1.10
October 1.07 1.07 1.07 1.07 1.07 1.07 1.07 1.07 1.07 1.07 November 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 December 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92 0.92
5.8 HOURLY ADJUSTMENT
Hourly distribution factors (HDF) are only required for rigid pavement analyses; they are not used for predicting distresses of flexible pavements and AC overlays of flexible pavements.
NOTE 6 The default MAF can be imported into the Pavement ME from the truck traffic data
library established for PennDOT. The values in Table 5.7 are provided in this User Input Guide for checking the values imported into
the software.
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The HDF factors that are recommended for pavement design are based on information provided by the PennDOT BPR Transportation Planning Division (2013 Pennsylvania Traffic Data Report, PUB 601 (9-14)). These factors are based on 2,000 AVC counts, collected and verified over the last five years. Based on these data, two HDF defaults could be defined for two groups of roads: Interstates and non-Interstates. Figure 5.4 and Table 5.8 lists the Pennsylvania HDF defaults for each road type.
Figure 5.4—Default Vehicle Class Distributions for Pennsylvania by FC and TPG
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Table 5.8—Recommended Hourly Distribution Factor Inputs for Level 2 Design for Pennsylvania Roadways
Hour Interstates Non-Interstates 1 2.5 0.91 2 2.28 0.83 3 2.26 0.9 4 2.44 1.15 5 2.77 1.69 6 3.37 2.97 7 4.2 5.13 8 4.66 6.68 9 4.9 6.96 10 5.14 6.68 11 5.31 6.69 12 5.39 6.75 13 5.37 6.7 14 5.43 6.78 15 5.56 7.11 16 5.58 7.17 17 5.38 6.27 18 5.05 5.08 19 4.63 3.79 20 4.2 2.89 21 3.84 2.34 22 3.59 1.88 23 3.28 1.47 24 2.87 1.18
5.9 AXLES PER TRUCK CLASS
The average number of axles per truck class was determined from an analysis of PennDOT and LTPP WIM data for Pennsylvania sites. The default number of axles per truck class is listed in Table 5.9. These values are also included in the traffic library as part of the PennDOT database. Table 5.9 is provided for checking the values imported into the Pavement ME software for a specific project.
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Table 5.9—Recommended Number of Axles per Truck Class Inputs for Level 2 Design for Pennsylvania Roadways
Truck Class Number of Axles per Truck Class
Single Axles Tandem Axles Tridem Axles Quad Axles 4 1.61 0.39 0 0 5 2.03 0.06 0 0 6 1.03 0.98 0 0 7 1.05 0.02 0.97 0 8 2.24 0.79 0 0 9 1.28 1.84 0 0 10 1.13 1.02 0.92 0 11 4.94 0 0 0 12 3.37 1.28 0 0 13 1.39 0.77 0.81 0.27
5.10 AXLE LOAD DISTRIBUTION FACTORS
Four normalized axle load spectra (NALS) defaults are recommended for use in the design. The default NALS were determined based on available data from PennDOT WIM sites and the LTPP database. These defaults represent various loading conditions observed on roads maintained by PennDOT. The Pennsylvania NALS defaults were developed using methodology described in the LTPP report FHWA-HRT-13-089 Long-Term Pavement Performance Pavement Loading User Guide (LTPP PLUG) with a focus on identifying differences in loading distribution of class 9 trucks. Class 9 trucks were found to be the most dominant among heavy truck classes in Pennsylvania and, thus, responsible for a higher percentage of total pavement damage. If a different truck type becomes more dominant in the future, these defaults should be revised. It is recommended that the BPR should review and update these defaults every five years based on the recent data from the permanent WIM sites. Figures 5.5 and 5.6 include a graphical comparison of the four default NALS. As shown, the default NCHRP 1-37A NALS includes an appreciable percentage of overloaded trucks.
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Figure 5.5—Comparison of the Four NALS Defaults for Vehicle Class 9 Tandem Axles – Entire
Range of Axle Loads
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Figure 5.6—Comparison of the Four NALS Defaults for Vehicle Class 9 Tandem Axles – Axle
Loads between 24,000 and 54,000 lbs (heavy loads and overloads) In addition, the Pennsylvania Statewide default NALS was compared with recently released LTPP Global NALS (representing the average loading condition from the LTPP research-quality WIM sites). These NALS were found to be similar, especially for class 9 trucks, and resulted in similar pavement design outcomes. One difference with the LTPP default was much heavier class 7 vehicles in the Pennsylvania Statewide default NALS. Because the percentage of the class 7 vehicles is typically very small, when tested, this difference did not result in differences in pavement design outcomes. Table 5.10 lists the files with the NALS or distribution factors included in the PennDOT database library. This table provides a description of the default NALS and recommendations for selecting the default NALS for design. The files containing defaults save time in entering the axle load distribution data and provide input for the sites that do not have site-specific WIM data. In selecting a default NALS, it is recommended that the expected traffic loading pattern be understood along the project site or roadway segment. To get an understanding of the loading pattern, an analysis of the truck traffic characteristics should include the following:
• The percentage of through trucks versus local delivery trucks. • The dominant commodities being carried by the trucks. • The normalized truck volume distribution. • The loading condition for dominant heavy trucks (typically class 9 trucks).
Pavement distress predictions that are most affected by the NALS selection include JPCP slab cracking and AC fatigue cracking. Slab cracking is highly sensitive to overloaded axles (i.e., loads weighing over
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the legal weight limit) and AC fatigue cracking is highly sensitive to both heavy legal loads and overloads. Table 5.11 presents a comparison of NALS factors for vehicle class 9 tandem axles among four NALS defaults.
NALS factors received from the database library can be directly imported into Pavement ME. In addition, the BPR can provide site-specific NALS using PrepME software for the roads where permanent WIM sites are installed on Pennsylvania’s roadways.
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Table 5.10—Normalized Axle Load Distribution Files included in the PennDOT Database Library Axle Loading Default Name
Description of Normalized Axle Load Distribution
Recommendations for Use Road Functional Classes Served
Pavement ME Default Global default axle load distributions developed under NCHRP 1-37A; not specific to PennDOT roadways and includes higher percentages of overloaded trucks.
Use for design where a high percentage of overloaded trucks is expected.
Any, when a high percentage of overloaded trucks is expected.
PennDOT_Statewide (Typical)
Statewide default based on data from multiple PennDOT WIM sites. This default represents average loading conditions observed on PA roads, most frequently observed on PA primary roads: with more than a third but less than a half of the class 9 trucks being heavily loaded.
Use for designs where no information about the nature of traffic loading is available, except for low truck volume roads. Also, use for designs of roads used by both the freight and the local delivery trucks.
Any, except for low truck volume roads, when no inferences to expected traffic loading characteristics can be made. Primary arterials with lower than average volume and percentage of class 9 trucks for each respective road functional class (Rural Interstate, Urban Interstate, Rural Other Principal Arterial).
PennDOT_Light Default based on PennDOT WIM data for sites with lower volume and percentage of class 9 trucks. About one third of the class 9 trucks are heavily loaded.
Use for designs of roads that primarily serve local deliveries and are located away from major warehouses or other facilities that dispatch or receive heavily loaded class 9 trucks.
Minor arterials, collectors, and other principal arterials with low volume of freight trucks (FHWA classes 8-13). Low truck volume roads and roads located primarily in urban or suburban areas, away from major industrial or agricultural facilities.
PennDOT_Heavy Default based on PennDOT WIM data for sites mostly observed on rural primary arterial routes. More than a half of the trucks are heavily loaded.
Use for designs of roads primarily used by long-haul freight trucks and roads serving major warehouses or other facilities that dispatch or receive heavily loaded class 9 trucks, such as major industrial or agricultural facilities.
Rural primary arterials with higher than average volume and percentage of class 9 trucks for each respective road functional class (Rural Interstate, Rural Other Principal Arterial), i.e. freight routes. Also, secondary roads serving major warehouses or other facilities that dispatch or receive heavily loaded class 9 trucks.
Table 5.11—Normalized Axle Load Distribution Factors for Vehicle Class 9 Tandem Axles (values in percentages)
Axle Loading Classification
Tandem Axle Weight for Class 9 Trucks, lbs. 30,000-31,999 32,000-33,999 34,000-35,999 36,000-37,999 38,000-39,999 40,000-41,999 42,000-43,999
PA_Light 7.63 5.84 3.11 1.28 0.49 0.20 0.09 PA_Heavy 10.75 10.85 6.54 2.84 1.11 0.43 0.18 PA_Statewide (Typical) 9.51 8.64 4.93 2.03 0.77 0.30 0.14 NCHRP 1-37A Global 6.28 5.67 4.46 3.16 2.13 1.41 0.91
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5.11 SCREEN SHOTS FOR THE TRAFFIC INPUTS
This section of Chapter 5 includes screen shot examples for the different traffic inputs discussed within this chapter. The drop-down arrows are used to access or select specific information for the project. Overall Screen Shot for Traffic
Vehicle Class Distribution and Growth
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Monthly Adjustments
Number of Axles Per Vehicle (Truck) Class
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AADTT, Traffic Capacity, Axle Configuration, Lateral Wander, and Wheelbase Note: Average axle width, mean wheel location, design lane width, and all wheelbase inputs are only used for the rigid pavement analyses. These input parameters are not used in the flexible pavement analyses. Normalized Axle Load Distribution
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Hourly Adjustment Note: Hourly adjustments are only used in the rigid pavement analyses and are not used in the flexible pavement analyses.
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CHAPTER 6—CLIMATE INPUTS Detailed climatic data are required to use the Pavement ME software for predicting pavement distress and roughness over time. These data include hourly temperature, precipitation, wind speed, relative humidity, and cloud cover. Example screen shots showing the climate inputs are included at the end of this chapter. Climate hourly data are used to predict the temperature distribution in each of the PCC slab and AC pavement, base, and subgrade layers, as well as provide moisture distribution in all of the unbound aggregate and subgrade. Additionally, there are climate inputs to the JPCP joint opening/closing and faulting models as well as the site factors for the IRI regression equations for all pavement types. All of these hourly climate data are available from weather stations, generally located at airfields around the United States.
6.1 PROJECT LOCATION INFORMATION
The average latitude, longitude, elevation for the project mid-point location should be determined and entered in the software. The Pavement ME software will identify the weather stations that are closest to the project location so the designer can select a specific weather station, or two or more stations that are applicable to the project location, for creating a virtual weather station.
6.2 DEPTH TO WATER TABLE
The depth to the water table is a parameter that the designer has to input on the climate screen. The depth to the water table or “free” water is the average distance between the pavement surface and the depth at which free water is encountered. This depth should be an average representative of cuts and fills along the project location. The depth to a water table is best measured from the borings taken along the project location. The depth to the water table has an effect on the moisture content of the unbound layers above the water table. The following provides some guidance in determining the depth to the water table or free water.
1. The depth of borings usually does not exceed 10 feet for pavement design purposes, while the depth to the water table exceeds 10 feet in many locations. In addition, the borings are usually not monitored or left open over a sufficient amount of time to measure the depth to water over time. If seasonal or perched water table depths are known to exist along the project site, these seasonal values should be entered into the software.
2. The depth to the water table should be determined based on the designer’s local experience and/or
from a geotechnical engineer knowledgeable of the local conditions along the specific project. For example, the water depth from historical borings for bridges and other similar structures can be used to estimate the depth.
3. Pennsylvania water table data for various locations and counties can be found at the U.S.
Geological Survey web site: http://pa.water.usgs.gov/.
NOTE 7 The latitude, longitude, and elevation for a project can be found on various websites such as elevationmap.net, LatLong.net and Google Earth for a given address.
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4. If borings are unavailable and no information can be obtained from other sources adjacent to the
project, Table 6.1 can be used as a guide in selecting the annual values to be used.
Table 6.1—Annual Depth to Water Table Recommended for Use Location Annual Depth to Water Table, ft.
Northern Counties 10 Southern Counties 15 Mountainous Areas or Higher Elevation Counties 20
6.3 CLIMATE STATIONS
The Pavement ME software has a number of national weather stations embedded in the software for ease of use. Table 6.2 lists the Pennsylvania weather stations that are currently available in the Pavement ME software national database. There are also weather stations in adjacent States close to the state line that can be used. Figure 6.1 shows all of these weather stations in a map format. The Pavement ME design procedure recommends two or more of these climate stations be selected as close to the project as possible to provide hourly temperature, precipitation, wind speed, relative humidity, and cloud cover information. This allows the user to create a virtual climate station at the project location and minimizes the errors associated with missing information in the database.
NOTE 8 In selecting a climate station, pay attention to the elevation of the
station. A climate station should be selected with a similar elevation to
the project, if possible.
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Figure 6.1—Pennsylvania and Neighboring States Default Weather Stations in Pavement ME
Software
Table 6.2— Pennsylvania Climate Stations Available in Pavement ME
Station Longitude Latitude Elevation Date from which Weather Data is
Available
Date to which Weather Data is
Available ALLENTOWN 40.651 -75.449 385 07/01/1996 02/28/2006 ALTOONA 40.3 -78.317 1468 07/01/1999 02/28/2006 BRADFORD 41.803 -78.64 2109 01/01/1997 02/28/2006 CLEARFIELD 41.047 -78.412 1511 02/01/2000 02/28/2006 DOYLESTOWN 40.33 -75.123 380 08/01/1999 02/28/2006 DU BOIS 41.178 -78.899 1808 07/01/2000 02/28/2006 ERIE 42.08 -80.183 728 07/01/1996 02/28/2006
HARRISBURG 40.217 -76.851 336 10/01/2000 02/28/2006 40.194 -76.763 300 12/01/2000 02/28/2006
JOHNSTOWN 40.301 -78.834 2277 09/01/2000 02/28/2006 LANCASTER 40.12 -76.294 400 03/01/1999 02/28/2006 MEADVILLE 41.626 -80.215 1407 07/01/1997 02/28/2006 MOUNT POCONO 41.139 -75.379 1892 10/01/1999 02/28/2006 PHILADELPHIA 40.082 -75.011 101 07/01/1996 02/28/2006
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Table 6.2— Pennsylvania Climate Stations Available in Pavement ME
Station Longitude Latitude Elevation Date from which Weather Data is
Available
Date to which Weather Data is
Available PHILADELPHIA 39.868 -75.231 107 07/01/1996 02/28/2006
PITTSBURGH 40.355 -79.922 1240 02/01/1999 02/28/2006 40.501 -80.231 1118 07/01/1996 02/28/2006
POTTSTOWN 40.238 -75.557 291 03/01/1999 02/28/2006 READING 40.373 -75.959 333 02/01/1999 02/28/2006 SELINSGROVE 40.821 -76.864 450 09/01/1997 02/28/2006 WILKES-BARRE/SCRANTON 41.339 -75.727 953 07/01/1996 02/28/2006 WILLIAMSPORT 41.243 -76.922 525 07/01/1996 02/28/2006 YORK 39.918 -76.874 472 09/01/1997 02/28/2006
6.4 CREATION OF SIMULATED CLIMATE STATION
After selecting the appropriate climate stations in the vicinity of the project and providing the depth to the water table, the user can select one station or simulate a virtual weather station that is most representative of the project location. The simulated or virtual climate station is saved by the software so that it can be used for all future trial designs or sensitivity studies relevant to a specific location. The virtual weather station can be selected for future use through the import option and by choosing the simulated climate station file created for the specific project.
6.5 SCREEN SHOTS FOR THE CLIMATE INPUTS
The following are screen shot examples that show the climate inputs discussed within this chapter. The drop-down arrows are used to access or select specific information and other input values for the project.
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Overall Screen Shot for Climate
Depth to Water Table
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Climate Station
As stated previously, a single weather station can be selected or a virtual weather station created for a specific project location. The above screen shot is for a creating a virtual weather station for the specific project location coordinates.
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CHAPTER 7—DESIGN FEATURES AND LAYER PROPERTY INPUTS Different features and properties are required by the Pavement ME software for different pavement types or materials. This chapter discusses the features and properties required for specific pavement types. Example screen shots showing the design features and layer property inputs are included at the end of each section within this chapter.
7.1 AC (HMA) LAYER PROPERTIES: NEW AND EXISTING LAYERS
7.1.1 Multi-Layer Rutting Calibration Parameters
The most recent version of the Pavement ME software (version 2.2) permits the user to input layer specific plastic deformation parameters of the rut depth transfer function. The local calibration will determine whether the same plastic deformation calibration factors can be used for all asphalt layers or whether layer-specific calibration factors are available.
7.1.2 AC Surface Shortwave Absorptivity
Use the default value of 0.85 for the AC surface shortwave absorptivity for all new pavement and rehabilitation designs. This value should not be changed without revising the local calibration parameters.
7.1.3 Endurance Limit
The Pavement ME software permits the user to input an endurance limit value for AC layers or mixtures. The endurance limit represents the tensile strain at which no fatigue cracking damage accumulates within that layer. The global calibration of the fatigue cracking transfer function completed under NCHRP project 1-40D did not include the endurance limit as a mixture property or design feature. Similarly, the PennDOT local calibration of the bottom-up fatigue cracking transfer function will not include the endurance limit as a mixture property or design feature. Thus, it is recommended that the endurance limit not be used in design.
7.1.4 Layer Interface Friction
All global and regional calibration studies have been completed assuming full friction between each layer, because there is no standardized test for measuring this value. An interface friction value of 1.0 represents full friction in the Pavement ME design methodology. Thus, a value of 1.0 should be used for design purposes. An interface friction value of 0 represents no friction between two adjacent layers (e.g., not including a tack coat between an existing AC surface and AC overlay). Zero friction should only be used for forensic investigations to answer “what if” questions. Interface friction values less than 1.0 will significantly increase AC rutting and fatigue cracking. All pavement designs should be completed with full interlayer friction.
NOTE 9 The pavement layered
structure should be set up prior to entering any of the
layer features and properties.
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7.1.5 Rehabilitation: Condition of Existing Flexible Pavement
The condition of the existing flexible pavement surface is estimated from the distress measurements (condition surveys [input levels 2 or 3]) or determined from back-calculated elastic modulus (input level 1). Rehabilitation input level 1 should be used when deflection basin data are available from falling weight deflectometer (FWD) testing. For input levels 2 or 3, the distresses on the existing pavement can be obtained from current condition surveys. The following summarizes the use of different input levels for rehabilitation designs for both AC and PCC overlays of an existing flexible pavement. Rehabilitation Input Level 1 Deflection basins measured on the project provide valuable information and are believed to result in more reliable rehabilitation designs. Measured deflection basins are used to estimate the in-place “damaged” elastic modulus values for each structural layer and subgrade of the existing pavement. Thus, FWD testing should be carried out in cracked (that will not be repaired) and non-cracked areas. Back-calculation of the elastic layer modulus values are determined or calculated external to the Pavement ME software. There are several effective back-calculation programs including Modulus 6, EverCalc, Elmod, ModComp etc. The average back-calculated values for a specific design section should be entered for each pavement layer and subgrade soil. Often there are outliers that should be deleted from the analysis. These elastic modulus values for each pavement layer and subgrade are discussed in the next chapter of the User Input Guide. The average total amount of thermal or transverse cracking in terms of feet per mile should be entered for the project. In addition, the severity rating of transverse cracking should be selected from three options: low, medium, and high. This is a critical input that affects the rate at which reflection cracks come through the AC overlay. The severity level depends on actual severity of existing cracks. The designer can also use the distress data and information included in PennDOT’s pavement management database. The other input required for rehabilitation input level 1 is the average rut depth within each pavement layer and subgrade. Since this is difficult to measure, Table 7.1 lists the percentages to be used in distributing the total rut depth measured at the surface to each pavement layer and subgrade.
Table 7.1—Ratios to Distribute Total Rut Depth to Individual Layers Flexible Pavement Layer Ratio of Total Rut Depth Distributed
to Each Layer1 AC 0.75 Granular Aggregate Base 0.10 Subgrade 0.15
1A total rut depth of 0.5 in. would have 0.75*0.5 = 0.375 in. rut depth in the AC layer, 0.05 in. in the granular aggregate base, and 0.075 in. in subgrade.
These percentages were determined through the global calibration process under NCHRP projects 1-37A and 1-40D, and based on a limited number of studies at the global and local levels (Colorado, Montana, etc.). The values will be verified based on the local calibration study for PennDOT using the LTPP and non-LTPP roadway segments by determining the values that result in the lowest standard error of the rut depth transfer function.
NOTE 10 This section covers determining the condition and moduli of an existing flexible pavement for both AC and PCC overlays.
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Rehabilitation Input Level 2 If deflection testing and data are unavailable to estimate the in-place condition of the AC layers, the use of input level 2 is reasonable without significantly increasing the cost of the pavement evaluation. For input level 2, three inputs are required to determine the condition of the existing pavement layers. These inputs are listed and defined below.
1. The average total amount of fatigue or alligator cracking within the wheel path area in terms of percent of total lane area should be entered for the project. In addition, the severity rating of alligator cracking should be selected from three options: low, medium, and high. The designer can also use the distress data and information included in PennDOT’s pavement management database.
2. The average total amount of thermal or transverse cracking and severity, which is the same as for rehabilitation input level 1, as defined above.
3. The average rut depth within each pavement layer and subgrade, which is the same as for rehabilitation input level 1, as defined above.
Rehabilitation Input Level 3 Five subjective pavement ratings (structural and environmental) are used to describe the condition of the pavement surface. They are defined in the MEPDG Manual of Practice (AASHTO, 2015) and considered appropriate for PennDOT. Table 7.2 relates the subjective structural condition survey ratings included in the Pavement ME software to the percent of fatigue or alligator cracking (all levels) of total lane area. Table 7.3 relates the subjective environmental condition survey ratings included in the Pavement ME software to feet per mile thermal or transverse cracking (all levels). Select appropriate condition rating in the software.
Table 7.2—Pavement ME Level 3 Condition Ratings Related to Existing Alligator Cracking in Percent Lane Area
Structural Rating Existing Alligator Cracking in Percent Lane Area (All levels of severity)
Excellent < 5 Good 5-15 Fair 15-35 Poor 35-50
Very Poor >50
Table 7.3— Pavement ME Level 3 Condition Ratings Related to Existing Transverse Cracking in Feet per Mile
Environmental Rating Existing Transverse Cracking in Feet per Mile (All levels of severity)
Excellent < 50 Good 50-150 Fair 150-400 Poor 400-800
Very Poor >800
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The other input required for input level 3 is the average total rut depth measured at the surface of the AC layer. The Pavement ME Design software distributes that total rut depth measured at the surface to the different layers using the layer percentages determined under the NCHRP Project 1-37A.
7.1.6 Milled Thickness of Existing AC Layers
Milling a portion of the existing AC is a common rehabilitation activity prior to placing the AC overlay. The planned milled thickness is entered in the AC Layer Properties screen under Rehabilitation. The input is the thickness of existing AC actually specified to be milled off. The milled-thickness is used for damage computations based on the dynamic modulus and is not subtracted from the existing AC layer thickness. Therefore, if the actual thickness of an AC layer is 5 inches, and 2 inches are to be milled, enter 2 inches as milled thickness and 3 inches as existing AC layer thickness. Additional discussion is provided under Section 8.1 on entering the thickness of the existing AC layers when one or more overlays have already been placed on the original flexible pavement and/or when more than three AC layers are placed.
7.1.7 Screen Shots for the AC Layer Properties: New and Existing Layers
The following are screen shot examples that show the AC Layer Property inputs discussed within this section of Chapter 7. The drop-down arrows are used to access or select specific information and other input values for the project.
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Overall Screen Shot for the AC Layer Properties
AC Layer Properties Screen
Rehabilitation Screen Note: this drop down screen is only applicable for rehabilitation or overlay projects of flexible pavements.
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7.2 JPCP: NEW AND EXISTING LAYERS
7.2.1 PCC Surface Shortwave Absorptivity
Use the default value of 0.85 for the PCC surface shortwave absorptivity for all new pavement and rehabilitation designs.
7.2.2 Joint Spacing
Pavement ME Design allows two options for the joint spacing of JPCP: a constant or random joint spacing ranging from 10 to 20 feet. PennDOT currently requires the use of a constant perpendicular joint spacing of 15 feet for JPCP. This spacing provides a good balance between minimization of transverse cracking and joint costs. For local agencies designing slabs thinner than 8 inches, it is recommended to use a shorter joint spacing of 12 feet. The Pavement ME Design does not yet consider the short slab designs such as 6 feet by 6 feet. This design capability is currently being implemented and may be available in August 2016.
7.2.3 Sealant Type
Pavement ME Design allows two options for the type of sealant used in the transverse joints: preformed and other sealants. The other sealants listed in the Pavement ME Design software include liquid (hot and cold poured) sealants, silicone, and/or no sealant. Pennsylvania currently seals the joint with silicone, so the ‘other sealant’ option should be used.
7.2.4 Dowels
PennDOT typically uses dowels in all transverse joints of JPCP, because properly sized dowels control joint faulting. The trial diameter and spacing of the dowels are inputs to Pavement ME Design. PennDOT typically uses 1.5 inch dowels for pavements 10 inches or thicker (see Publication 408 for details) and 1.25 inch dowels for pavements less than 10 inches. The program outputs predicted joint faulting that must meet the faulting criteria at the designated reliability level. Table 7.4 provides recommended guidelines to select the initial dowel diameter.
Table 7.4—Recommended Dowel Diameter
Slab Thickness, in. Dowel Diameter, inches Recommended Value Minimum Maximum
8 to less than 10 1.25 1.25 1.25 Equal to or greater than 10 1.50 1.25 1.625
7.2.5 Widened Slab
Pennsylvania currently does not allow widened slab designs. Widened slabs are used to reduce the edge stresses from wheel loads. The user enters the width of the widened slab for the specific project. A maximum width of 13 feet should be used. This provides for a 1-foot widening of the slab beyond the paint stripe, which remains located at 12 feet. Wider slabs increase the possibility of longitudinal cracking.
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7.2.6 Tied Shoulders
Tied concrete shoulders are used to reduce the edge stresses from the wheel loads. The tied shoulder should always be tied to the JPCP to provide long-term edge support. A longitudinal joint load transfer efficiency of 40 percent should be used.
7.2.7 Erodibility Index of Base Course
The erodibility index for JPCP is defined by the type of base material for the specific project and is classified in five categories, which are listed in Table 7.5. More erosion-resistant base material results in lower predicted joint faulting and improved joint load transfer.
7.2.8 PCC-Base Contact or Interface Friction for JPCP
JPCP design should be based on full friction between the slab and base course, and nothing should be done in construction to break the bond between layers. Some base types, however, are prone to de-bond after a few years, and this increases stress in the slab, leading to cracking. The following lengths of time for full contract friction between the PCC slab and base course are recommended (means and range obtained from the national or global calibration). This is one of the reasons PennDOT uses either AC (or asphalt stabilized base) or granular base layer under the PCC slabs.
• Asphalt Stabilized Base: Use full design analysis period (e.g., 240 months for a 20-year design life).
• Cement Stabilized Base: Use up to 120 months as there is a good chance of de-bonding after this time.
• Lean Concrete Base: Use zero (0) months if base is finished smooth and cured with wax-based curing compound. Otherwise, if surface is textured with regular curing compound, follow cement stabilized base recommendations.
• Unbound Granular Aggregate Base: Use full design analysis period.
Table 7.5—Erodibility Category Index Recommended for Different Base Materials Erodibility Category Recommendation Based on Type of Base Material
1 Extremely Erosion Resistant Asphalt-stabilized layer or AC and permeable asphalt or permeable cementitious treated base.
2 Very Erosion Resistant Cement-treated or lean concrete base layer.
3 Erosion Resistant Dense-graded crushed stone base materials with less than 8 percent fines.
4 Fairly Erodible Dense-graded or granular aggregate base materials with more than 8 percent fines.
5 Very Erodible Silts and other non-cohesive fine-grained soils and cohesive soils.
7.2.9 Pavement Curl/Warp Effective Temperature Difference
Use the default value for the PCC pavement curl/warp effective temperature difference for all new pavement and rehabilitation designs; a value of -10°F.
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7.2.10 Foundation Support for Rehabilitation of Rigid Pavements
The foundation support resilient modulus at optimum moisture content and maximum dry unit weight conditions can be estimated based on soil class or California Bearing Ratio (CBR) and entered for rehabilitation design similar to the design of new rigid pavements. Recommendations for estimating the subgrade resilient modulus is provided in Section 8.62 and Table 8.10. For rehabilitation design, it is far more accurate to measure the subgrade dynamic K-value along the project, and enter it directly into the Pavement ME Design software for the month tested. The subgrade dynamic K-value can be measured through FWD testing. This process is by far the most accurate approach that gives subgrade support along the project.
• The project dynamic K-value is determined by back-calculation from deflections from FWD deflection testing.
• Note that the “dynamic” K-value is approximately twice the “static” K-value, which is the input used in the AAHSTO 1993 design procedure. Thus, a static K-value of, for example, 100 psi/in used in the old AASHTO procedure for the subgrade would represent a dynamic K-value of 200 psi/in.
• Procedures to calculate the project subgrade dynamic K-value are found in Section 8.6.2.
7.2.11 Condition of Existing PCC Surface for JPCP Rehabilitation Design
These inputs describe the amount of cracking and slab repairs of the existing PCC slabs and any repairs previously made to the JPCP and the transverse joint load transfer efficiency. Two inputs are required for the existing PCC layer when designing an AC overlay of an existing JPCP or for restoration (e.g., diamond grinding, slab replacement, etc.):
1. Percentage of slabs that are transversely cracked or have been replaced before rehabilitation. This input could range from 0 to over 20 percent.
2. Percentage of slabs that will be replaced as part of the rehabilitation project. This could range from 0 up to the percent cracked before rehabilitation. (Note: The Pavement ME software input text for this input is an error. This input is defined as the percentage of cracked slabs or replaced slabs replaced during rehabilitation).
The following examples explain the inputs and results achieved:
o If 0 percent slabs cracked prior to rehab and 0 percent slabs are replaced as a part of rehabilitation, then the future prediction will start at 0 percent slabs cracked.
o If 10 percent slabs are cracked prior to rehab and 0 percent slabs are replaced as a part of rehabilitation, then the future prediction will start at 10 percent.
o If 10 percent slabs are cracked prior to rehab and 3 percent slabs are replaced as a part of rehabilitation, then the future prediction will start at 7 percent slabs cracked. The future prediction will, however, be greater than if there were 0 slabs cracked prior to rehab due to past damage (as indicated by cracked slabs). The inputs for this example are thus 10 percent (before) and 3 percent (during) restoration.
These two inputs are important because they define the in place fatigue damage of the JPCP which is used to predict future damage and cracking of the PCC slabs. The transverse joint load transfer efficiency (LTE) input is used in the AC overlay reflection cracking prediction. The joint LTE can range from less than 25 percent (very poor) to above 80 percent (very
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good). The LTE can be measured at a representative number of joints using the FWD in the outer wheel path of the slab in cooler weather when the air temperature is 80°F or less. If FWD testing is not possible, then the following guidelines are provided:
• Doweled joint: 80 percent • Non-doweled joint with stabilized base course: 55 percent • Non-doweled joint with granular base course: 30 percent
7.2.12 Screen Shots for the JPCP Layer Properties: New and Existing Layers
The following are screen shot examples that show the JPCP Design Property and other inputs discussed within this section of Chapter 7. The drop-down arrows are used to access or select specific information and other input values for the project. Overall Screen Shot for the JPCP Design Properties, Foundation Support, and JPCP Rehabilitation
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JPCP Design Properties Screen
Sealant Type Screen Shot
Erodibility Index Screen Shot
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Foundation Support
JPCP Rehabilitation
*Note: Second input should read: “Slabs repaired/replaced during restoration (%).” If there are 10 percent cracked slabs prior to restoration, and 3 percent of them are replaced during restoration, there will be 7 percent remaining and the future prediction will start at 7 percent.
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7.3 CRCP: NEW AND EXISTING LAYERS
7.3.1 Inputs
Some CRCP was constructed in Pennsylvania many years ago, but insufficient sections for calibration exist. CRCP was not locally calibrated in Pennsylvania. However, if such a design is desired, the global calibration coefficients provided in the software can be reasonably used. The inputs for the CRCP layer are the same as for JPCP listed above, except as summarized below.
• Shoulder type: The type of shoulder is determined by the user. Four shoulder types are available for consideration: (1) tied PCC, placed separately; (2) tied PCC, placed monolithically, (3) asphalt, and (4) gravel or turf material. A roller-compacted concrete can be assumed as an asphalt shoulder since it is not tied into the PCC slab.
• Percent longitudinal steel included in the PCC slab is a project-specific design input and varies
between 0.65 and 0.80 percent area of the slab. This is a critical input to the design.
• Bar diameter of the longitudinal steel reinforcement is a project-specific design input (0.625 to 0.75 inches).
• Depth of the longitudinal steel reinforcement is a project- specific design input. The longitudinal steel is usually placed at mid-depth or higher in the PCC slab. Placement just above mid-depth is recommended (with a minimum 3.5 inches of concrete cover), however, this will result in tighter cracks and improved performance.
• Base/Slab friction coefficient or the coefficient of friction at the interface of the CRCP and layer supporting the CRCP. There is no test method for measuring the coefficient of friction between two pavement layers. Table 7.6 summarizes the default values recommended for design that are included in the latest global calibration (Vanderbossche, 2014).
Table 7.6—Base/Slab Friction Coefficient Recommended for Different Layers below CRCP
Base Type Friction Coefficient
Asphalt treated base 8.3 Cement treated base 9.6
Lime treated base 11.5 Granular aggregate base 3.5
7.4 INVERTED PAVEMENTS: NEW CONSTRUCTION
The Pavement ME Design can be used to design inverted or “sandwich” type structures. This section of the User Input Guide provides some discussion on using the Pavement ME Design software for designing these pavements. It should be understood, however, that inverted pavements were not included in the global calibration process completed under NCHRP Projects 1-37A and 1-40D or under the PennDOT local calibration study (refer to Table 2.1).
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The structure for an inverted pavement is entered just like a new flexible pavement design problem. The only difference is that the untreated granular base layer is defined as a “sandwich layer” between the lower cementitious stabilized layer and the upper AC layers. All layer properties are entered the same as a new flexible pavement structure. Section 8.5 provides the recommended resilient modulus values for the untreated granular base layer when used within an inverted pavement.
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CHAPTER 8—LAYER/MATERIAL PROPERTY INPUTS The inputs to define the structure are straightforward and include the material type and thickness of each layer included in the design strategy. Figure 8.1 shows the pavement layer structure typically required by PennDOT, and Table 8.1 lists the minimum and maximum layer thickness, if applicable, to be used. The source for Table 8.1 is the 2011 guidelines for Superpave and other mix type selection guidelines and the Geotechnical QA/QC Manual.5
8.1 PAVEMENT LAYERS FOR FLEXIBLE PAVEMENT DESIGN
The following provides a recommendation for creating the pavement structure used in a new or rehabilitated flexible pavement analysis (see Figure 8.1).
• AC and Asphalt Stabilized Base Layers: For both new construction and rehabilitation designs, thin AC layers (less than 1.0 inch in thickness) should be combined with an adjacent structural layer. As an example, open graded or porous friction courses, 4.75 mm mixture, and other thin layers should be combined with the lower or adjacent dense-graded AC Superpave mixture or layer.
o For new construction or reconstruction
problems, limit the number of AC layers to three. The lower layer controls bottom-up or alligator cracking, while the upper layers have more control on the predictions of rut depth and longitudinal top-down cracking.
When combining thin surface layers with a lower dense-graded AC layer for new construction, the layer thickness ratios in Table 8.2 should be used in determining the equivalent thickness of the lower dense graded AC layer in accordance with equation 1 to be entered in the Pavement ME Design software.
(1) Where: Dequivalent - Thickness of the equivalent dense-graded mix. DDense-Graded - Use thickness of the lower dense-graded mix, see Table 8.1. R - Equivalent thickness ratio of the thin layer to the dense-graded layer;
provided in Table 8.2. DThin-Layer - Thickness of the thin layer which is identified in Tables 8.1 and 8.2.
5 The number of layers used in an analysis has an effect on the Pavement ME run time—using more layers, increases the run time.
NOTE 11 For flexible pavements and AC overlays, the designer should
iterate on the lower AC layer in determining the required total
thickness (see Table 8.1).
[ ]( )LayerThinGradedDenseequivalent DRDD −− +=
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Figure 8.1—New Pavement Structures Typically Required by PennDOT
JPCP or CRCP (Table 8.1)
Rigid Pavement
Granular Aggregate Base or Stabilized Base (Table 8.1)
Subgrade
Semi-Rigid Pavement
Cement Stabilized Base or Soil Cement
Subgrade
AC Base Layer (Table 8.1)
AC Binder Layer (Table 8.1)
AC Surface (Table 8.1)
Flexible
Granular Aggregate Base (Table 8.1)
Subgrade
AC Base Layer (Table 8.1)
AC Binder Layer (Table 8.1)
AC Surface (Table 8.1)
Inverted Pavement (A-
Cement Stabilized Base
Subgrade
AC Base Layer (Table 8.1)
AC Binder Layer (Table 8.1)
AC Surface (Table 8.1)
Granular Aggregate Base (GAB)
Interlayer
NOTE: Interlayer is typically used for interstates and high truck volume roadways.
NOTE: Inverted pavements have typically not been used in Pennsylvania.
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Table 8.1—Minimum and Maximum Layer Thicknesses
Layer/Material Designation Layer ThicknessA, in. Min. Max.
JPCP
PCC
Interstate and other freeways 9 20 Arterials 9 20 Collectors 8 20 Local roads 7 20
Treated Permeable Base Course (TPBC)
All routes 4B 4 Interstate and other freeways, alternate option 3 4
Class 2A Subbase All routes 4 6 Interstate and other freeways, alternate option 6 6
Flexible Pavement
AC
9.5 mm, Superpave, Fine Grade Wearing Course 1 <1.5
9.5 mm, Superpave, Wearing Course 1.5 2 12.5 mm, Superpave, Wearing Course 2 3 19 mm, Superpave, Binder Course 2.5 4.5 25 mm, Superpave, Binder Course 3 5.5
25 mm, Superpave, Base Course 3 As required by design
37.5 mm, Superpave, Base Course C 4.5 As required by design
Base Course
Granular Aggregate Base (GAB) Course 6 16 Asphalt Treated Base (ATB) Course 5 12 Asphalt Treated Permeable Base (ATPB) Course 3 15
Cement Base Course 5 12 PCC Base Course 5 12
Subbase 6 As required by design
Note A: Once the required thickness is determined, round up or down to the nearest half inch (e.g., 10.244 inches becomes 10.0 inches and 10.525 inches becomes 10.5 inches). Note B: TPBC may be eliminated on low-volume/local roads, but the depth of 2A will be 6 inches. Note C: Use only when material quantity requirement is greater than 5,000 tons. For Superpave Maximum Construction Lift Thicknesses reference Publication 408, Specifications, Section 309.3(h)1.b.
Table 8.2—AC Layer Thickness Ratios (R) to be Used in Combining Thin Layers with Lower Dense-Graded AC Layers
Thin Layers Ratio to a Dense-Graded Layer Open-Graded or Porous Friction Course 0.75 PEM 0.75 4.75 mm Mix 1.0 The above ratios were determined based on the equivalent stiffness method.
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o For rehabilitation, the existing AC and overlay layers are restricted to three layers. When two layers are entered to represent the existing AC, only one overlay layer can be used. Conversely, if two overlay layers are entered, only one layer can be used to represent the existing AC layers. Results from deflection basin testing and the back-calculation of elastic layer modulus values should be used to determine whether the existing AC layers are confined to one or two layers.
• Base Layers: PennDOT typically uses dense-graded asphalt stabilized base, asphalt treated
permeable base (ATPB), and granular aggregate base. Asphalt stabilized base layers were noted above, while the others are discussed in the bullets below.
o Asphalt Treated Dense-Graded Base (ATB) Layers: ATB layers are similar to dense graded AC base course. The inputs for the ATB layer are the same as for the AC layers.
o Asphalt Treated Permeable Base (ATPB) Layers: APTB mixtures have high air voids (generally greater than 20 percent for a well-draining mixture). High air voids will significantly reduce the fatigue strength, and thus, increase the predicted fatigue cracking that is inconsistent with the measured or observed values. Thus, the ATPB layer is simulated as a high quality crushed stone layer for which the resilient modulus remains constant during the design period; an annual representative resilient modulus value that does not change with the season. An elastic modulus of the ATPB layer recommended for use is 80,000 psi.
o Unbound Granular Aggregate Base Layers: Limit the compacted aggregate base layers to two for both new and rehabilitation design; most of the designs will include only one aggregate base layer that is placed in two lifts. If more than two layers are being considered within the design strategy, combine similar materials, especially any layer that is relatively thin (less than 6 inches). For rehabilitation design, the number of unbound GAB layers of the existing pavement structure should coincide with the pavement structure used to back-calculate elastic layer modulus values from deflection basin data.
Stabilized Subgrade: Stabilization is used only to improve an embankment or subgrade for construction purposes. Common soil stabilization in Pennsylvania includes: (1) lime, (2) lime-fly ash, and (3) soil cement with 5 to 10 percent of cement. PennDOT measures the compressive strength of these stabilized materials, with typical compressive strengths from mix design between 200 to 250 psi. PennDOT also considers and allows the use of FWD testing to back-calculate the modulus of these materials.
• No more than one layer of a stabilized subgrade should be used in the analysis. It is permissible to include a stabilized aggregate base layer and stabilized subgrade within the same pavement structure. Stabilized subgrades simulated in the Pavement ME, however, are treated separately and should be simulated as such in accordance with the following guidance.
NOTE 12 For rehabilitation, it is
recommended that the existing AC layers be combined as one layer, unless there is a specific
reason why two layers should be simulated.
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o If the stabilized subgrade is used as a construction platform with only minimum additive for improving the strength, the layer should be combined with the subgrade layer and not treated as a separate layer, because the improved strength may not last long.
o Conversely, a stabilized subgrade for improving the structural strength of the pavement is entered as a separate layer with a constant elastic or resilient modulus value for that layer. The inputs for these stabilized soils are included in Section 8.7 of the User Input Guide.
• Embankment/Foundation Layers or Subgrade: The subgrade should be limited to two layers:
a compacted embankment layer and a natural or undisturbed soil layer. The exception to this recommendation is when a water table is located near the surface (less than 10 feet) and the type of soil changes significantly between the water table and lower pavement layer because the properties of the soils can have a significant effect on the amount of water being moved through the subgrade—lowering the resilient modulus of the upper soil strata.
• Bedrock: For some projects, bedrock or a very stiff layer may be encountered. The maximum thickness of the subgrade above a rigid layer, however, is 100 inches. For depths greater than 10 feet, the bedrock has little impact on the predicted distresses. When bedrock is encountered within 10 feet of the surface, the designer can enter it as a separate layer.
The material properties needed for each layer are discussed in separate sections of this chapter.
8.2 PAVEMENT LAYERS FOR RIGID PAVEMENT DESIGN
Inputs in this category primarily define the structural layers of the PCC pavement including the material types and thicknesses (see Figure 8.1). Similar to the process defined in Section 8.1 for flexible pavements, each layer of the trial section is inserted by selecting the material type, the actual material classification, and the thickness. The guidance for setting up the pavement structure used in a rigid pavement analysis is provided below.
• JPCP or CRCP Layers: For new construction, the rigid pavement is limited to one PCC layer and two PCC layers for rehabilitation designs of rigid pavements (PCC overlay and existing PCC layer).
• Base Layers: ATPB and cement treated permeable base (CTPB) materials are used as base
layers.
o AC or Asphalt Stabilized Base Layers: For new construction or reconstruction problems, AC or stabilized base layers are placed below the PCC slabs and are limited to one layer. The inputs for the asphalt stabilized base layer are the same as for the flexible pavements.
o Asphalt Treated Permeable Base (ATPB) Layers: These mixtures have high air voids
(generally greater than 20 percent for a well-draining mixture). Pavement ME Design does not predict the fatigue cracking or damage of this layer below PCC slabs. Thus, the high air voids will have no impact on the damage of this layer, and it can be treated as an asphalt layer (with high air voids) rather than assumed to be a high-quality crushed stone layer, as discussed under Section 8.1 for flexible pavements. It is recommended that the ATPB layer be treated as an asphalt layer with 20 percent air voids with full friction to
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the slab when placed beneath PCC slabs, because this will provide a more accurate level of the modulus of the layer to support the slab and high friction with the slab.
o Unbound Granular Base Layers: Limit the compacted unbound granular base layers to
one for both new and rehabilitation design of rigid pavements. If more than one layer is used within the design strategy, combine similar materials, especially any layer that is relatively thin (less than 6 inches). The number of aggregate base layers of the existing pavement structure for rehabilitation design should coincide with the pavement structure used to back-calculate elastic layer modulus values from deflection basin data.
• Stabilized Subgrade: No more than one layer of a stabilized subgrade should be considered in
the analysis. It is permissible to consider or simulate a stabilized subgrade layer. Common soil stabilization in Pennsylvania includes: (1) lime, (2) lime-fly ash, and (3) soil cement with 5 to 10 percent of cement. PennDOT does measure the compressive strength of these stabilized materials, with typical compressive strengths from mix design between 200 to 250 psi.
• Embankment/Foundation Layers or Subgrade: The subgrade should be limited to no more than two layers; a compacted embankment layer and a natural or undisturbed soil layer. The exception to this recommendation is when a water table is located near the surface (less than 10 feet) and the type of soil changes significantly between the water table and lower pavement layer, because the properties of the soils can have a significant effect on the amount of water being moved through the subgrade—lowering the resilient modulus of the upper soil strata.
The material properties needed for each layer are discussed in separate sections of this chapter.
8.3 ASPHALT CONCRETE (AC)
The layer or material properties for the AC or AC layers are grouped into three categories: volumetric, mechanical, and thermal properties. Example screen shots showing the AC material property inputs are included at the end of this section.
8.3.1 Mixture Volumetric Properties
The volumetric properties include air voids, effective asphalt binder content by volume, aggregate gradation, mix unit weight, and asphalt grade. Gradation is included under the mechanical properties because it is only used to calculate the dynamic modulus of the mix for input levels 2 and 3. The volumetric properties should represent the mixture after compaction at the completion of construction. Obviously, the project-specific values will be unavailable to the designer because the project has yet to be built. These parameters should be available from previous construction records and can be analyzed to determine typical values for inputs. The following summarizes the recommended input parameters for AC mixtures. Air voids, effective asphalt content by volume, and unit weight: Use the average values from historical construction records for a particular type of AC mixture. Table 8.3 includes the volumetric properties based on the target values for common AC mixtures used in Pennsylvania.
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Table 8.3—Volumetric Properties for Pennsylvania’s Dense-Graded Mixtures
Volumetric Property Superpave Mixtures
Surface Mixtures Binder Base 9.5 mm 12.5 mm 19 mm 25 mm 25 mm 37.5 mm
Average Air Voids, % Effective Asphalt Content by Volume, %
Density, pcf The following volumetric equations can be used to estimate the input parameters. Air Voids, Va:
100*1
−=
mm
mba G
GV (2)
Void In Mineral Aggregate, VMA:
( )
−=
se
smb
GPG
VMA 100 (3)
Effective Asphalt Content by Volume, Vbe: abe VVMAV −= (4) Where: Va = Air voids. VMA = Voids in mineral aggregate. Vbe = Effective asphalt content by volume. Gmb = Bulk specific gravity of the AC mixture. Gmm = Maximum theoretical specific gravity of the AC mixture. Gse = Effective specific gravity of the combined aggregate blend. Ps = Percentage of aggregate in mix by weight, % (Ps=100-Pb).
Poisson’s Ratio: Use the temperature-calculated values from the regression equation included in Pavement ME Design.
8.3.2 Mechanical Properties
Dynamic modulus: Table 8.4 is a matrix of the AC dense-graded mixtures that are included in the PennDOT materials library in relation to the typical binder grades used in Pennsylvania. For those mixtures and binder grades not included in the PennDOT materials library, input level 3 values need to be entered into the Pavement ME software.
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Table 8.4—Binder Grades Typically Used in Pennsylvania’s Dense-Graded Mixtures
Mix Size Designation Asphalt Binder Designation PG58-28 PG64-22 PG64-28 PG76-22
9.5 mm √ 12.5 mm √ √ √ 19 mm √ √ √ 25 mm √ √ √
37.5 mm √ √ Note: A check mark in the above columns indicates the mixture is included in the PennDOT materials library.
• New AC Mixtures: If an AC mixture is included in a design strategy that is not included within the materials library, it is recommended that level 3 inputs be used to estimate the dynamic modulus values. Level 1 dynamic modulus inputs from the materials library can be entered directly into the software. The dynamic modulus values were measured in accordance with AASHTO TP 62, Standard Method of Test for Determining Dynamic Modulus of Hot Mix Asphalt (HMA), for a combination of five test temperatures and four test frequencies, as required for Pavement ME level 1. The results are presented in Table 8.5. Aggregate gradation is needed when input levels 2 or 3 are used for dynamic modulus. The Pavement ME software internally computes dynamic modulus values from aggregate gradation. Use either the values that are near the mid-range of the project specifications or the average values from previous construction records for the particular type of mix. Table 8.6 includes the gradation or percent passing for the common mixtures used in Pennsylvania.
• Existing AC Mixtures: For rehabilitation design of flexible pavements, the dynamic modulus of
the existing AC layers is needed. For rehabilitation input levels 2 and 3, the dynamic modulus inputs are the same as for new AC mixtures discussed above. For rehabilitation input level 1, the dynamic modulus values represent the back-calculated elastic modulus values. Deflection basins should be measured over a range of temperatures, even if the deflection testing is completed within the same day so that the back-calculated elastic layer modulus values can be determined for at least two temperatures: one representing the morning hours and one representing the late afternoon hours. If there is no significant difference between the back-calculated elastic modulus values, one average value can be used.
Two other inputs are needed: (1) the frequency of deflection testing—a default value of 20 Hz is recommended and (2) the temperature representative of the average back-calculated elastic modulus value—the mid-depth temperature of the layer used in the back-calculation process measured during deflection testing.
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Table 8.5—Dynamic Modulus Values of Typical PennDOT Dense-Graded Mixtures Mix ID Temperature (°F) Testing Frequency
0.5 Hz 1 Hz 10 Hz 25 Hz
Mix 1
14 40 70
100 130
Mix 2
14 40 70
100 130
Mix 3
14 40 70
100 130
Mix 4
14 40 70
100 130
Mix 5
14 40 70
100 130
Mix 6
14 40 70
100 130
Mix 7
14 40 70
100 130
Mix 8
14 40 70
100 130
Mix 9
14 40 70
100 130
Mix 10
14 40 70
100
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130
Table 8.6—Gradation for Pennsylvania’s Dense-Graded Mixtures
Sieve Size Superpave Mixtures
Surface Mixtures Binder Base 9.5 mm 12.5 mm 19 mm 25 mm 25 mm 37.5 mm
1.5 in (37.5 mm) 1 in. (25.0 mm) 0.75 in. (19 mm) 0.5 in. (12.5 mm) 3/8 in. (9.5 mm) No. 4 (4.75 mm) No. 8 (2.36 mm) No. 200 (75 μm)
Select HMA Estar predictive model: Two options are provided for estimating dynamic modulus using input levels 2 and 3: (1) NCHRP 1-37A (viscosity-based model), and (2) NCHRP 1-40D (dynamic shear rheometer [DSR] based model). Either one can be used, but the DSR model was derived from the viscosity-based model. It is recommended that the viscosity-based model be used. Reference temperature: Use 70°F. All of the PennDOT calibration factors are tied to this default value. Asphalt binder: Pavement ME level 1 inputs require the use of laboratory-measured rheology properties of asphalt binders (viscosity, η, or complex shear modulus, G*, and phase angle, δ, at different temperatures) in conjunction with the laboratory-measured dynamic modulus (E*) of asphalt concrete mixtures. Binder characterization tests were not performed to measure the rheology properties of the binders used in Superpave mixtures listed in Table 8.5. To allow the use of laboratory-measured E* values in the Pavement ME software, G* and δ values were backcast using the estimated E* shift factors and G*– η conversion relationships in the Pavement ME. Table 8.7 presents the assumed G* and δ values at different temperatures for each Superpave mixture listed in Table 8.5. The values presented in Table 8.7 are approximate; however, these binder G* estimates are compatible with mixture E* values. Pavement ME level 3 asphalt binder requires only binder grade. If an AC mixture is included in a design strategy that is not included within the materials library, it is recommended that input level 3 is selected.
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Table 8.7—Complex Shear Modulus (G*) and phase angle (δ) Values of Typical PennDOT Dense-Graded Mixtures
Mix ID Temperature (°F)
Binder G* (Pa)
Phase Angle (degree)
Mix 1
Mix 2
Mix 3
Mix 4
Mix 5
Mix 6
Mix 7
Mix 8
Mix 9
Mix 10
Creep compliance and indirect tensile strength: Creep compliance and the indirect tensile strength are needed for the low temperature transverse cracking transfer function. For input level 3, default values from the regression equations included in Pavement ME, which are based on volumetric properties, gradation, and either the asphalt binder grade or the test results from the DSR, are used for estimating creep compliance and the indirect tensile strength inputs. If an AC mixture is included in a design strategy that is not included within the materials library, it is recommended that level 3 inputs be used to estimate the creep compliance and indirect tensile strength values. Input levels 1 or 2 are required user inputs. Level 1 creep compliance and indirect tensile strength inputs from the materials library can be entered directly into the software. Laboratory testing for creep compliance was done using AASHTO TP 322, Standard Method of Test for Determining the Creep Compliance and Strength of Hot-Mix Asphalt (HMA) Using the Indirect Tensile Test Device. The test results are presented in Table 8.8. The indirect tensile strength testing was done according to AASHTO TP 322. The reference test temperature was 14 °F. The test results are presented in Table 8.9.
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Table 8.8—Creep Compliance Values of Typical PennDOT Dense-Graded Mixtures
Mix ID Loading Time (s)
Testing Frequency 0.5 Hz 1 Hz 10 Hz 25 Hz
Mix 1
1 2 5
10 20 50
100
Mix 2
1 2 5
10 20 50
100
Mix 3
1 2 5
10 20 50
100
Mix 4
1 2 5
10 20 50
100
Mix 5
1 2 5
10 20 50
100
Mix 6
1 2 5
10 20 50
100
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Table 8.9—Indirect Tensile Strength Values of Typical PennDOT Dense-Graded Mixtures Mix ID Indirect Tensile Strength at 14˚F Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6
8.3.3 Thermal Properties
Thermal conductivity of asphalt: Use default value set in program of 0.67 BTU/ft*h*°F. All of the PennDOT calibration factors are tied to this default value. Heat capacity of asphalt: Use default value set in program of 0.23 BTU/lb*°F. All of the PennDOT calibration factors are tied to this default value. Coefficient of thermal contraction of the mix: Use default values set in the Pavement ME Design software for different mixtures and aggregates. The software will calculate this value. All of the PennDOT calibration factors are tied to the global default values calculated by the software.
8.3.4 Screen Shots for the AC Properties: New and Existing Layers
The following are screen shot examples that show the AC material property inputs discussed within this section of Chapter 8. The drop-down arrows are used to access or select specific information and other input values for the project.
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Overall Screen Shot for the Asphalt Concrete Material Properties
Asphalt Concrete
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Dynamic Modulus of New AC Layer Asphalt Binder of Superpave Performance Grade
Dynamic Modulus of Existing Asphalt Concrete Layer
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8.4 PORTLAND CEMENT CONCRETE (PCC) – NEW MIXES
The layer or material properties for the PCC layers are grouped into four categories: general, thermal, mix, and strength properties. Example screen shots showing the PCC material property inputs are included at the end of this section.
8.4.1 General Properties
Unit Weight of PCC: Use the average value from historical construction records for a particular type of PCC mixture. The unit weight, however, is not readily available for many of the PCC mixes. In those cases, use a default value of 150 pcf. Poisson’s Ratio: Use the default value of 0.20. This input does not affect design significantly.
8.4.2 Thermal Properties
PCC Coefficient of Thermal Expansion (CTE): CTE is a very critical design input that will affect the pavement design and performance. PennDOT operates the lab testing equipment for CTE for level 1 input, and this is always recommended due to the high design sensitivity of this input. Default level 2 CTE values are determined based on PCC coarse aggregate geological class. Designers must determine the source of PCC coarse aggregate and, thus, the predominant geological class. With this information, select the most appropriate CTE value from the recommendations presented in Table 8.10. If the source of coarse aggregate is unknown, assume 4.7. Note that for each of these aggregate sources, the CTE ranges from 0.5 plus and minus, which is a wide range. Thus level 1 testing is strongly recommended for project design. Additionally, certain aggregate sources result in very high CTE values and, if not measured and used in design, can lead to premature cracking from high slab curling.
Table 8.10—Recommended CTE Values for PCC Mixtures in Pennsylvania that Contain Type I Portland Cement and Natural Sand (Based on PennDOT and LTPP data) Coarse Aggregate Type CTE (10-6/°F) Defaults
Granite 4.8 US Dolomite 4.7 PA Limestone 4.4 PA
Basalt 4.4 US Quartzite 5.2 US
Chert 6.1 US Sandstone 5.8 US
Thermal Conductivity of PCC: Use default value set in program of 1.25 BTU/ft*hr*°F. All of the PennDOT calibration factors are tied to this default value. Heat Capacity of PCC: Use default value set in program of 0.28 BTU/lb*°F. All of the PennDOT calibration factors are tied to this default value.
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8.4.3 Mix Physical Properties: New and Intact Existing PCC Slabs
The Pavement ME Design software requires a lot of inputs for the PCC mix physical properties, which are listed below. The default values for these mix properties recommended for use represent the average value from the mixes included in the PennDOT calibration. Cement Type: Most of the PennDOT PCC mixtures are produced with Type I Portland cement. Type I should be used, unless Type II or III is specified for a specific design. Type I Portland cement was used for all of the PCC mixtures included in the calibration. Cement Content: The cement content (plus fly ash content) should be available from historical construction records for the different PCC mixtures used in Pennsylvania. A local default value of 588 lb./yd.3 total cementitious material should be used if information is unavailable to the user. Water/Cement Ratio: The water-cement ratio is available from historical construction records for the different PCC mixtures. A local default value of 0.42 should be used if information is unavailable to the user. Coarse Aggregate Type: The common type of coarse aggregates used in the PCC mixes are listed in Table 8.10. Zero-Stress Temperature (New and Existing Intact PCC): Zero stress temperature (Tz) occurs after placement concrete has cured and hardened sufficiently that the temperature begins to drop, resulting in tensile stress. It can be input directly or calculated by the software from monthly ambient temperature and cement content using the equation 5. It is recommended that the user allow the software to calculate this input parameter. Tz = (CC*0.59328*H*0.5*1000*1.8/(1.1*2400) + MMT) (5) Where: Tz = Zero stress temperature (allowable range: 60 to 120 degrees Fahrenheit). CC = Cementitious content, lb/yd3. H = -0.0787+0.007*MMT-0.00003*MMT2. MMT = Mean monthly temperature for month of construction, degrees Fahrenheit. Ultimate Shrinkage: The ultimate shrinkage can be entered manually or calculated by the software. It is recommended the ultimate shrinkage be calculated by the software, because this value was unavailable for the PCC mixes used in Pennsylvania. All of the PennDOT calibration factors were determined based on the software calculating the ultimate shrinkage. Reversible Shrinkage: Use default value set in program of 50 percent. All of the PennDOT calibration factors are tied to this default value. Time to Develop 50 percent of Ultimate Shrinkage: Use default value set in program of 35 days. All of the PennDOT calibration factors are tied to this default value. Curing Method: Two options are available within the software: wet curing or curing compound. Curing compound is typically used for PennDOT PCC construction. Thus, it is recommended that curing compound be selected unless the designer knows that wet curing will be used for some reason.
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8.4.4 Strength Properties
Two mix strength properties are required for using the Pavement ME Design software: flexural or compressive strength and elastic modulus. Input levels 1 and 2 require time-dependent flexural and compressive strengths, respectively. Time-dependent flexural or compressive strengths are unavailable from PennDOT historical construction records. Thus, input level 3 is recommended for use: 28-day strength and elastic modulus. 28-Day Compressive or Flexural Strength: Note that the mean strength must be used in design, not the minimum construction specification. The mean value from the University of Pittsburg tests for five projects for the 28-day compressive strength 6,078 psi (excluding one test of 8000 psi). It is recommended this mean value be used in routine design. The mean flexural strength calculated from this compressive strength value is 702 psi using the ACI equation: Flexural Strength (3rd Point Load) = 9 * (Compressive Strength) 0.5 Table 8.11 includes 28-day compressive strength for the common PCC mixtures used in Pennsylvania
Table 8.11—28-Day Compressive Strength Values of Typical PennDOT PCC Mixtures Mix ID 28-Day Compressive Strength, psi Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6
28-Day Elastic Modulus: The mean elastic modulus can be entered manually or calculated by the program based on the 28-day flexural or compressive strength value. Elastic moduli were obtained from the same University of Pittsburg 2011 study that provides a mean of 4,100,000 psi at 28-days. It is recommended that the value be calculated by the software, which employs the widely used ACI equation.
Elastic Modulus = 57000 * (Compressive Strength) 0.5 Table 8.12 includes 28-day elastic modulus for the common PCC mixtures used in Pennsylvania.
Table 8.12—28-Day Elastic Modulus Values of Typical PennDOT PCC Mixtures Mix ID 28-Day Elastic Modulus, psi Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6
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8.4.5 Screen Shots for the PCC Properties: New Layers
The following are screen shot examples that show the PCC material property inputs discussed within this section of Chapter 8. The drop-down arrows are used to access or select specific information and other input values for the project. Overall Screen Shot for the PCC Material Properties
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PCC Material Properties
PCC Strength and Modulus
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Cement Type
Aggregate Type
Curing Method
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8.5 PORTLAND CEMENT CONCRETE (PCC) – EXISTING FOR REHABILITATION DESIGNS
8.5.1 AC or PCC Overlay of Existing Intact PCC Slabs
Existing intact PCC properties are required for AC overlay, restoration, and for unbonded PCC overlay. Example screen shots showing the PCC material property inputs are included at the end of this section. The PCC properties are the same as for new PCC mixes with the following exceptions. The modulus of elasticity of the existing PCC slab is determined through an assessment of the amount of slab cracking (include all types: longitudinal, transverse, corner, diagonal). An effective (or damaged) modulus of elasticity value is estimated as follows:
• If the percent of cracked slabs is less than 10 percent, the effective modulus of elasticity is the same as that of the intact slab. There is no modulus reduction. See note below if the PCC slab elastic modulus is back-calculated from FWD deflections for reduction factor.
• If the percent of cracked slabs is 10 percent or greater, the effective modulus is selected from Table 8.13.
Table 8.13—Recommended Effective Modulus Values for Existing Intact PCC Slabs
Qualitative Description of Pavement Condition Typical Modulus Ranges, psi Default Modulus, psi
Good/Adequate (10 to 20 percent cracked slabs) 2 to 4 x 106 3.0 x 106
Marginal (20 to 50 percent cracked slabs) 1 to 2 x 106 1.6 x 106
Poor/inadequate (>50 percent cracked slabs) 0.2 to 1 x 106 0.65 x 106
Note that for FWD back-calculation of PCC slab elastic modulus for uncracked slabs, the resulting modulus value is essentially a dynamic value that must be reduced by multiplying by 0.8 to obtain a static uncracked value to input into the Pavement ME.
Pavement ME is now able to calculate the amount of AC overlay reflection cracking over time that emanates from transverse joints and transverse cracks.
• AC total transverse cracking: thermal plus reflective (feet/mile). • The thermal cracking is from low temperature stresses (not joint or crack). • The reflective cracking is from transverse joints plus transverse cracking. • Thus a JPCP with 15-foot joint spacing has a total of 4,224-feet of transverse joint length. If the
input joint LTE is low, reflection cracking will occur through all of the transverse joints very rapidly. If aggressive maintenance is accomplished, these cracks may survive for several years before deteriorating into potholes and roughness.
The program requires the input of transverse joint LTE that exists at the joints. LTE can be measured using an FWD when the air temperature is less than 800F. The level depends heavily on the presence of dowel bars at the joint. If FWD testing cannot be accomplished, the following can be used as default LTE values.
• No dowel bars, granular base: 30 percent LTE. • No dowel bars, stabilized base: 55 percent LTE.
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• Dowel bars exist: 80 percent LTE.
8.5.2 Fractured PCC Slabs
Existing fractured PCC slab properties are required for AC or PCC overlays over fractured PCC pavements. The two common methods of fracturing JPCP slabs include: (1) crack and seat and (2) rubblization. Of the two, the most effective to minimize reflection cracking is rubblization, where the PCC slabs are broken into aggregate-sized pieces (less than 6 inches in diameter) that behave similarly to a high-quality crushed aggregate layer. The Pavement ME can be used directly to design a PCC overlay of rubbilized concrete pavement similar to a new rigid pavement design. The Pavement ME can be used to directly design an AC overlay of rubblized concrete similar to a new flexible pavement design. The recommended elastic modulus of the rubblized PCC is given in Table 8.14. Crack and seat involves cracking the JPCP slab into larger pieces (e.g., 3- to 6-foot pieces) where the key design approach is to provide adequate AC thickness to reduce deflections in the cracked JPCP. This is done to prevent the slab pieces from becoming loose and rocking over time, which leads to reflection cracking. The Pavement ME can now be used to directly design a crack and seat project. A reflection-cracking model has been added to the software in version 2.2 that requires the additional inputs in Table 8.14.
Table 8.14—Recommended Inputs for Crack and Seat Fractured Slab and Rubblized PCC Slabs Fractured PCC Type Default Parameter
Rubblized (into crushed granular like material) 50,000 psi Elastic Modulus
Crack and seat 1,500,000 psi Elastic Modulus of sound uncracked PCC
Crack and seat crack LTE%* 50 percent* *Load Transfer Efficiency that will exist long term. (this needs calibration) Pavement ME is now able to calculate the amount of reflection cracking over time that emanates from crack and seat and AC overlay projects. The primary output prediction is as follows:
• AC total transverse cracking: thermal plus reflective (feet/mile) over time. • The thermal cracking is from low temperature stresses (not joints or cracks). • The reflective cracking is from fractured slab pieces. • The crack LTE is a critical input that affects when reflection cracks will develop. They will be at
the boundaries of the fractured pieces of PCC, not from transverse joints. • AC overlay thickness is also very critical as thinner overlays experience much higher reflection
cracking and experience much higher deflections which lead to rocking of the concrete pieces. Pennsylvania has constructed many miles of jointed reinforced concrete pavement (JRCP) that includes reinforcing steel. The Pavement ME cannot be used directly to design this type of pavement unless the existing slab is “broken” and seated, meaning the reinforcement is fractured across all fractured cracks
NOTE 13 PennDOT does not routinely consider fracturing PCC slabs as part of their
rehabilitation strategies. Guidance and the recommended input values for
fractured PCC slabs are provided for future considerations.
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(spaced between 3- and 6-foot, similar to JPCP). Since this is very difficult to achieve for JRCP, complete rubblization is generally recommended to eliminate reflection cracking.
8.5.3 Restoration of JPCP
The restoration of a JPCP may include any of the following treatments, depending on the condition of the existing pavement.
• Diamond grinding for joint faulting and other unevenness that may exist is always required. Restoration cannot be run without grinding.
• Slab replacement and partial slab replacement for slab cracking or joint deterioration. • Spall repair for joint spalling and deterioration. • Tied PCC shoulder to increase structural capacity of the outer lane. • Dowel bar retrofit for undoweled faulted JPCP.
Most of these projects are not “designed” using any structural procedure, but are based on applying a repair treatment to an existing JPCP that has various distresses and roughness. Pavement ME provides the ability to check the structural capacity of the restored pavement to handle future traffic loads. Pavement ME also provides the ability to predict the future service life of the restored pavement after various treatments. For example, if after slab replacement and diamond grinding a restored JPCP develops significant fatigue transverse cracking within 10 years, then this may not be a good candidate for restoration. Or, if a JPCP develops significant faulting within a few years, then retrofit dowels may be required. The design of a restored JPCP requires the same inputs as a new JPCP design with the following exceptions.
• The percent slabs cracked prior to restoration and percent cracked slabs replaced during restoration as described in Section 7.2.11 are required inputs. This affects the future amount of fatigue transverse cracking predicted initially and into the future.
• The modulus of elasticity of the PCC slab at the time of restoration must be determined. This can be done through coring and running a compressive strength that can be used to estimate the modulus of elasticity. The modulus can also be estimated through FWD testing and back-calculation to obtain a “dynamic” E value. This is then multiplied by a factor of 0.8 to adjust to a static E value. Note: the modulus of elasticity of an old, intact PCC slab should always be greater than 4 million psi. This should be the minimum input value.
• If future transverse fatigue crack prediction is significant, a tied PCC shoulder can be included to reduce future cracking.
• If the JPCP has no dowels, then this must be entered into the Pavement ME. If future faulting is severe, then retrofit dowels of proper size can be entered into the program and the future faulting observed.
• The expected initial IRI must be input after diamond grinding. This value may be higher than traditionally achieved on new construction due to subgrade movement over the years.
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8.5.4 PCC Overlay of Existing Flexible AC Pavement
This section addressed the overlay design of a JPCP overlay over an existing flexible pavement (JPCP over existing AC). The key aspects of this design are as follows:
• The material inputs and design inputs are similar to that of new JPCP design. The Pavement ME
has some limitations including longitudinal joint spacing of 12-foot minimum (6-foot by 6-foot slabs cannot be designed currently), transverse joint spacing of 10 to 20 feet, and slab thickness of a minimum of 6 inches.
• The condition and damaged modulus of the existing AC layers is critical and must be assessed using either Levels 1, 2, or 3 as described in Section 7.2.11.
• The friction between the new JPCP overlay and the existing AC layer is critical to the success of the overlay.
o Milling of the existing surface is recommended to level up the existing surface so that the PCC slab can be placed with uniform thickness to provide a smooth surfacing.
o Milling of the existing surface is recommended to achieve a strong bond and friction between the existing AC layer and the PCC overlay. This bond/friction is essential for joint formation and for good structural performance of a composite slab/AC layers. Enter the “PCC-Base Contact Friction, Months Before Friction Loss” as the full design life of the JPCP overlay.
• The subgrade is modeled using a resilient modulus. The resilient modulus can be best estimated from back-calculation (level 1), but also from estimation from subgrade soil testing (level 2) or soil classification (level 3) as described in Section 8.6.2.
8.5.3 Screen Shots for the Fractured PCC Properties
The following are screen shot examples that show the PCC material property inputs for the fractured slabs, as discussed within this section of Chapter 8. The drop-down arrows are used to access or select specific information and other input values for the project.
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Overall Screen Shot for the JPCP Fractured Slabs
Fractured JPCP Layer Properties
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8.6 UNBOUND AGGREGATE BASE MATERIALS AND SOILS
The material properties needed for the unbound aggregate base or subbase layer and embankment or subgrade soils are the same in the Pavement ME as for flexible and rigid pavement designs. Example screen shots showing the unbound aggregate base and subgrade soil or embankment material property inputs are included at the end of this section. The PennDOT database or library of materials includes one file for each of the different unbound base materials typically used in construction and one file for each of the major PennDOT soil classifications found in Pennsylvania. The following subsections simply describe the properties included in these files.
8.6.1 General Physical and Volumetric Properties
The following unbound layer and embankment soil properties are site-specific and easily determined from laboratory tests.
• Gradation of the material. • Atterberg limits tests. • Maximum dry density or the in-place density at the time of construction. • Optimum water content or the in-place water content at the time of construction.
A subsurface investigation or soil survey should be planned to determine the above inputs for the project. If a soil survey and/or pavement investigation is not completed prior to design, the geotechnical engineer can provide values for these inputs based on historical information. The geotechnical engineer should be consulted to determine representative values for each design segment along the project.
• For the soils that are not disturbed during construction, the in-place moisture content and dry density should be entered.
• For the crushed gravel and other aggregate base materials used in Pennsylvania or the embankment soils that are compacted, the mid-range of the specifications or construction data from previous projects can be used to determine the input values. The expected moisture content and dry density after compaction should be entered.
8.6.2 Resilient Modulus
• Level 1 Lab Testing. Lab resilient modulus testing at optimum moisture and density is the required level 1 input. Pennsylvania has conducted repeated load resilient modulus tests on typical aggregate base materials and on the more common subgrade soils encountered in Pennsylvania.
NOTE 14 The resilient modulus values listed in Tables 8.15 and 8.16 for the unbound
material/soil layers should be used with the water contents and dry densities also
included in these tables.
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Table 8.15—Resilient Modulus Level 3 Values for Granular Aggregate Base Materials in Pennsylvania
Type of Material or Soil Optimum Water Content, %
Maximum Dry Density, pcf
Typical Mean Resilient
Modulus, psi Group Source Type
Note: Optimum water content must be entered into the Pavement ME under “Optimum gravimetric water content” input. Similar entry for maximum dry density.
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Table 8.16—Resilient Modulus Values Derived for Selected Subgrade Soils in Pennsylvania Type of Material or Soil Optimum
Water Content, %
Maximum Dry Density, pcf
Typical Mean Resilient
Modulus, psi Location or
County GA Soil Class AASHTO Class
Note A: The optimum water content and maximum dry density listed in this table were determined using the Modified Proctor compaction effort. Note B: Optimum water content must be entered into the Pavement ME under “Optimum gravimetric water content” input. Similar entry for maximum dry density.
• Level 2 FWD testing, back-calculation, and adjustment for Flexible Pavement. FWD testing can be conducted along the rehabilitation project and the resulting elastic modulus at each point determined through back-calculation. The mean resilient modulus for each layer is then computed by deleting any major outliers, following which the mean layer values are adjusted to lab conditions at optimum moisture and density for each unbound base and subgrade layer. Table 8.17 lists the adjustment ratios that should be applied to the unbound layers for use in design. More importantly, the in-place water content and dry density need to be entered in the Pavement ME Design software when the in-place resilient modulus values are used.
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Table 8.17—Summary of the Adjustment Factors Recommended for Use in Pennsylvania to Convert Back-Calculated Layer Modulus Values to Laboratory Equivalent Modulus Values
Layer & Material Type Layer Description
Adjustment Factor, (MR/E) FHWA
Pamphlet Pennsylvania
Sites
Aggregate Base Layers
Granular base under a PCC surface 1.32 --- Granular base under a CAM layer, semi-rigid pavement --- 0.75
Granular base above a stabilized material (a Sandwich Section) 1.43 ---
Granular base under an AC surface or base 0.62 0.60
Subgrade Soil/Foundation
Soil under a CAM layer, no granular base --- 1.00 Soil under a semi-rigid pavement with a granular base/subbase --- 0.50
Soil under a stabilized subgrade 0.75 --- Soil under a full-depth AC pavement 0.52 --- Soil under flexible pavement with a granular base/subbase 0.35 0.50
Cement Aggregate Base Layer Cement stabilized or treated aggregate layers --- 1.50
AC Mixtures AC surface and base layers, 41 °F 1.00 0.9 AC surface and base layers, 77 °F 0.36 0.6 AC surface and base layers, 104 °F 0.25 0.5
• Level 2 FWD testing and back-calculation for existing Rigid Pavement. For rehabilitation of
concrete pavements, the dynamic k-value of the subgrade and the month tested are input to the software. The dynamic k-value from FWD back-calculation represents the stiffness of the unbound compressible soils (to at least 10 or more feet deep into the subgrade) beneath the JPCP slab. The dynamic k-value is approximately twice as high as the conventional static k-value obtained from slow plate loading (which is the input used in the 1993 AASHTO report). A spreadsheet will be provided that calculates the back-calculated dynamic k-value at points along the subgrade from given FWD deflection data.
• Conduct FWD deflection testing along the JPCP or composite (AC/PCC) project in the
center of the slab at regular intervals (200 to 500 feet apart at mid-point between nearby transverse joints). The k-value can be calculated for any “heavy” FWD load level but it is recommended to use a load at or greater than 9,000 lbs. to ensure a modulus that matches typical heavy wheel loadings.
• Back-calculate the dynamic subgrade dynamic k-value from FWD deflections at the slab surface using the following equation. The k-value can be calculated for any sensor location (e.g., 0, 12, 36 in.), however, the center of plate sensor is recommended as performed in the spreadsheet.
K (subgrade) = P * (F/Dr) / l2
Where:
P = FWD load, lbs [example 9,000 lbs]
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Dr = Deflection at r distance from center of load plate, in [Use r = 0 in] Example Dr = 0.00426 in, at center of plate where the k-value is calculated] F= 0.1245*(EXP(-0.14707*EXP(-0.07565*l)))
l = Radius of relative stiffness, in = {Ln [(72-Area) / 242.385] / -0.442)2.205
Area = 6+[12* D12 +12* D24 +12* D36+12* D48 +12* D60 + 6* D72 ] / D0
Example for one point along project (D0=0.00426, D12 = 0.00328, D24 = 0.00252, D36 = 0.00180, D48 = 0.00127, D60 = 0.00078, D72 = 0.00065-in)
Area = 6+[12* 3.28 +12* 2.52 +12* 1.8+12*1.27+12* 0.78+ 6* 0.65 ] / 4.26
Area = 34.1 in
l = {Ln [(72 – 34.1) / 242.385] / -0.442}2.205 = 35.7 in
F = 0.1245*(EXP(-0.14707*EXP(-0.07565*35.7))) = 0.1215
P = 9,000 lbs
Dynamic k-value = 9,000 * (0.1215/0.00426) / 35.72 = 459 psi / in
(deflection at center of the load plate was used to calculate k-value) The dynamic k-value is a dynamic (moving load) modulus measured in the field, averaged over the subgrade depth and width with in situ moisture and density. Very soft soils have dynamic k-values of 200 psi/in. or less, while very stiff soils have k-values greater than 400 psi/in.
Prepare plot of point by point k-values along the project and evaluate the results.
o First, determine if there are sections with significantly higher or lower k-values that could be divided into separate design sections. Note that this may result in a change in design thickness along the project that may not be desirable from a practical standpoint.
o Second, there often exists large point-to-point variation along a project, and it may be appropriate to remove some unusual points (particularly, very high values may be indicative of large rock areas) so as not to distort the mean value used in design.
The mean dynamic k-value can be input directly into the Pavement ME software along with the month of FWD testing. This k-value then provides the needed subgrade support modulus for design purposes. It is not required to input a subgrade resilient modulus (Mr).
• Level 2 Dynamic Cone Penetrometer (DCP) or CBR testing. Resilient modulus can be
estimated from the Dynamic Cone Penetrometer (DCP) test in the field and CBR lab test, which is input level 2. For new alignments or new designs, as well as rehabilitation designs, Tables 8.15 and 8.16 provide the suggested level 3 mean resilient modulus and the range of those values for the different unbound materials that were used in the calibration refinement for Pennsylvania and
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derived from the repeated load resilient modulus tests for the granular aggregate base and subgrade soils, respectively. The optimum water content is generally provided for the different unbound materials and soils encountered along a project. Figure 8.2 can be used to estimate the resilient modulus from the optimum water content for most Pennsylvania soils and granular aggregate base materials.
PennDOT generally does not use the DCP for pavement evaluations and in estimating the resilient modulus of the unbound materials and soils. However, the DCP was used in the field investigation of all non-LTPP roadway segments included in the local calibration process. Equation 6 was used to calculate the resilient modulus from the penetration rate measured with the DCP. It is suggested that the DCP be considered for future use for rehabilitation design for the unbound pavement layers and subgrade, especially when FWD deflection basin data are unavailable.
( )
( )DCPR CDPI
M64.0
12.1
2926.17
= (6)
Where: MR = Resilient modulus of unbound material, MPa. DPI = Penetration rate or index, mm/blow. CDCP = Adjustment factor for converting the elastic modulus to a laboratory resilient
modulus value.
The subgrade resilient modulus can be estimated (level 2) from the DCP tests using equation 6, but those values need to be adjusted to laboratory conditions. Table 8.16 provides the adjustment factors recommended for use in estimating resilient modulus from the DCP penetration rate. (It should be noted and understood that the Pavement ME Design does not adjust the resilient modulus values calculated from the DCP, and the values in Table 8.18 have not been field-verified for PennDOT).
Table 8.18—Resilient Modulus Values Derived for Subgrade Soil from DCP Tests for Use in
Pennsylvania Material/Soil Type Condition Adjustment Factor, CDCP
Fine-Grained; Low Plasticity Soil
Clay-Silt Above Optimum Water Content 1.90
Soil-Sand Mix At or Below Optimum Water Content 1.05
Soil-Aggregate Mix with Large Aggregate
At or Below Optimum Water Content 0.60
Coarse-Grained Material
Soil-Aggregate Mix At or Below Optimum Water Content 0.60
Crushed Aggregate At or Below Optimum Water Content 1.04
The subgrade resilient modulus can also be estimated approximately from the CBR test, which can be entered into the software (level 2). Note that this equation is in the Pavement ME software.
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Mr = 2225*CBR0.64 Where: Mr = Resilient Modulus, psi (at CBR test specimen moisture
content) CBR = Soaked CBR value, % (AASHTO T193) (Valid for 2 to 12
% water) (Note: Water content on CBR specimen must be entered into the Pavement ME under “Optimum gravimetric water content” input.
• Limiting Ratio of Unbound Material Resilient Modulus of Layers. The resilient modulus of
aggregate or granular base/subbase is dependent on the resilient modulus of the supporting layers. As a rule of thumb, the resilient modulus entered into Pavement ME for a granular base layer should be less than three times the resilient modulus of the supporting layer to avoid decompaction of that layer. This layer modulus ratio is dependent on the type of base and thickness of the base layer. Figure 8.3 can be used to adjust the resilient modulus of the unbound aggregate base layer to ensure that it is in agreement with the above rule of thumb. Note that as the base comprises a single layer, only a single adjustment based on base layer thickness and subgrade resilient modulus is required.
Thus, if a subgrade modulus was determined to be 10,000 psi, the overlying unbound base course modulus should not be greater than about 30,000 psi.
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Figure 8.2—Limiting Layer Modulus Criterion of Unbound Aggregate Base Layers
Note: For 12 inch GAB layers, simply use the 10 inch line in this graph.
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8.6.3 Poisson’s Ratio
Poisson’s ratio is another input parameter needed for the unbound materials and soils. Table 8.19 lists the values that were used during the regional calibration refinement effort and are recommended for use in future design runs.
Table 8.19—Poisson’s Ratio Suggested for Use for Unbound Layers Type of Soil Poisson’s
Ratio PennDOT Soil Designation Description
IIB4 High plasticity fine-grained soils (clays and silts). 0.45 IIB2 to IIB3 Low plasticity fine-grained soils (clays and silts). 0.40
IIB1 or Better Non-plastic or low plasticity fine-grained soil or coarse-grained soil with more than 35 percent fines or material passing the #200 sieve. 0.35
I or Base Soil-aggregate base materials which are predominately coarse-grained. 0.35 Unbound
Aggregate Base Crushed gravel or crushed stone base materials used as a base or subbase layer. 0.30
8.6.4 Hydraulic Properties
The other input parameters for the unbound layers are more difficult to measure and were not readily available for use in the regional calibration refinement effort. For these inputs, the default values recommended in the Pavement ME were used to predict the distresses. Therefore, the Pavement ME default values also are recommended for use in Pennsylvania for the following properties.
• Soil saturated hydraulic conductivity. • Soil-water characteristics curves.
8.6.5 Screen Shots for the Unbound Base and Subgrade Layer Properties
The following are screen shot examples that show the unbound base and subgrade layer property inputs, as discussed within this section of Chapter 8. The material and layer properties are the same between the aggregate base and subgrade or embankment layers. The drop-down arrows are used to access or select specific information and other input values for the project.
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Overall Screen Shot for the Unbound Layers
Resilient Modulus Drop Down Arrow Sieve; Gradation and Other Engineering
Properties Drop Down Arrow
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8.7 CEMENT AGGREGATE BASE MIXTURES
The compressive strength (modulus of rupture), elastic modulus, and density are required inputs to the Pavement ME for any cementitious or pozzolonic stabilized material. The agency-specific calibration factors are determined based on the quality of the CAM material. The LTPP database for test sections with cementitious layers did not contain material properties for these test sections. The layer and material properties inputs for the cement aggregate base mixtures are the same as for the stabilized subgrade layers under Section 8.8. Chemically stabilized materials are no longer used as a base material in Pennsylvania, they are only used for subgrade improvement.
8.8 STABILIZED SUBGRADE FOR STRUCTURAL LAYERS
Stabilized subgrade soils are assumed to be the same as for the unbound materials and soils, with the exception that the resilient modulus is recommended to be constant throughout the design period—a representative annual resilient modulus value for this layer. Thus, the other material properties needed for stabilized subgrade soils are the same as for unbound aggregate base or subbase layer and embankment or subgrade soils. Table 8.20 lists the recommended resilient modulus and Poisson’s ratio values to be used for the stabilized subgrade layer. When the AC mixture is placed directly over the stabilized subgrade soil for a full-depth flexible pavement, it is considered a semi-rigid pavement. As noted in previous chapters, semi-rigid pavements were not calibrated during the original global calibration studies, as well as for the PennDOT local calibration study. Example screen shots showing the stabilized layer material property inputs are included at the end of this section.
Table 8.20—Resilient Modulus and Poisson’s Ratio Values Suggested for Use for Stabilized Subgrade Layers
Type of Stabilized Subgrade Recommended Representative Annual Resilient Modulus, psi
Recommended Poisson’s Ratio
Soil Cement and Cement Stabilized Soils 100,000 0.2
Lime-Fly Ash Stabilized Soils 50,000 0.30
Lime Stabilized Soils Three times the resilient modulus of the
underlying subgrade soil at optimum water content and maximum dry unit weight.
0.35
8.8.1 Screen Shots for the Stabilized Base Layer Properties
The following are screen shot examples that show the stabilized base or subgrade layer property inputs, as discussed within this section of Chapter 8. The material and layer properties are the same between the cement stabilized base layers and the cement or lime stabilized subgrade soil. The drop-down arrows are used to access or select specific information and other input values for the project.
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Overall Screen Shot for the Stabilized Base Layers
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8.9 BEDROCK
Table 8.21 provides guidance on determining the inputs for a bedrock layer when it exists within the project limits. For locations where the depth to bedrock exceeds 100 inches (or has more than 100 inches of soil above it), assume the subgrade is infinite and does not enter the bedrock layer. An example screen shot showing the bedrock material property inputs are included at the end of this section.
Table 8.21—Layer Properties for Bedrock Bedrock Parameters Recommended Input Value
Depth to Bedrock Estimate based on the soil borings or topography.
Elastic Modulus Severely Weathered Bedrock 50,000 psi Highly Fractured Bedrock 500,0000 psi Massive and Continuous Bedrock 1,000,000 psi
Poisson’s Ratio Severely Weathered Bedrock 0.30 Highly Fractured Bedrock 0.20 Massive and Continuous Bedrock 0.15
Unit Weight 140 pcf
8.9.1 Screen Shots for the Bedrock Properties
The following are screen shot examples that show the bedrock layer property inputs, as discussed within this section of Chapter 8. The drop-down arrows are used to access or select specific information and other input values for the project. Overall Screen Shot for Bedrock
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Bedrock Layer Properties
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CHAPTER 9—PENNSYLVANIA CALIBRATION FACTORS Both LTPP and non-LTPP test sections were used to estimate the precision and bias of the Pavement ME transfer functions for predicting the performance indicators (distress and roughness) of PennDOT’s pavements. The resulting distress prediction models, or transfer functions, can be used to optimize new pavement and rehabilitation design strategies and in forecasting maintenance, repair, rehabilitation, and reconstruction costs.
9.1 BASELINE FILES FOR THE CALIBRATION FACTORS
After local calibration, some of the PennDOT calibration factors for both flexible and rigid (JPCP) pavements might be different than the global calibration factors. Ten baseline files will be created that include the PennDOT calibration factors, so the designer does not have to manually enter these values for every design problem. The following is a listing of the baseline files.
1. New Pavement Reconstruction Design Strategy a. New flexible pavement: conventional, deep-strength or full-depth design strategy. The
baseline file was set up as a conventional and deep-strength pavement without subgrade stabilization. If a full-depth pavement is considered, the granular aggregate base layer would need to be removed or deleted; and if a stabilized subgrade is needed, that layer would need to be added. The calibration factors for all transfer functions for these design strategies are the same. This baseline file is also applicable to the fractured PCC slab with an AC overlay strategy.
b. Inverted (sandwich) pavement design strategy. c. New rigid pavement: JPCP design strategy.
2. Rehabilitation Design Strategy a. Rehabilitation of flexible pavement: AC overlay design strategy. b. Rehabilitation of flexible pavement: JPCP design strategy. c. Rehabilitated rigid pavement or JPCP: AC overlay strategy. This baseline file is also
applicable to the fractured PCC slab with an AC overlay strategy. d. Rehabilitated rigid pavement or JPCP: Unbonded JPCP overlay strategy. e. Restoration of JPCP: Diamond grinding, slab replacement, and retrofit dowels (if
needed) strategy. The designer will need to open the appropriate Pavement ME Design file listed above, do a “save as” in accordance with the PennDOT Pavement ME Design Software Manual, and then make the appropriate revisions or changes to the baseline problem using project-specific features and layer properties.
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9.2 TRANSFER FUNCTION CALIBRATION COEFFICIENTS
The remainder of this chapter lists the PennDOT calibration factors for each transfer function for both flexible and rigid pavements. Tables 9.1 to 9.4 list the appropriate flexible pavement calibration factors from the PennDOT local calibration study, which are included in the above baseline files in the PennDOT library, and Tables 9.5 and 9.12 list the appropriate rigid pavement (JPCP) calibration factors. The calibration coefficients for the IRI regression equation for both the flexible and rigid pavements are not included within this chapter because the local calibration factors are the same as for the global calibration factors — they remained unchanged. Example screen shots showing the calibration factor inputs are included at the end of this section.
Table 9.1—AC Rutting: PennDOT Calibration Factors Transfer Function
Coefficient Global Value PennDOT Value
K1 -3.35412 TBD K2 1.5606 TBD K3 0.4791 TBD
Standard Deviation 0.24 * Pow(RUT,0.8026) + 0.001 TBD
Table 9.2—Unbound Layer Rutting: PennDOT Calibration Factors Transfer Function
Coefficient Global Value PennDOT Value
Coarse-Grained, Bs1 1.0 TBD Standard Deviation 0.1477 * Pow(BASERUT,0.6711) + 0.001 TBD Fine-Grained, Bs1 1.0 TBD Standard Deviation 0.1235 * Pow(SUBRUT,0.5012) + 0.001 TBD
NOTE 15 The values highlighted in Tables 9.1 to 9.6 represent the PennDOT calibration factors that differ from
the global calibration factors.
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Table 9.3—AC Bottom-Up Alligator Cracking: PennDOT Calibration Factors Transfer Function
Coefficient Global Value PennDOT Value (Typical AC
Mixtures)
K1 0.007566 TBD K2 3.9492 TBD K3 1.281 TBD C1 1.0 TBD C2 1.0 TBD C3 6000 TBD
Standard Deviation
1.13 + 13/(1+exp(7.57-15.5*LOG10(BOTTOM+0.0001))) TBD
Table 9.4—AC Thermal Transverse Cracking: PennDOT Calibration Factors Transfer Function
Coefficient Global Value PennDOT Value (Typical AC
Mixtures)
Bt1 1.5 TBD Bt3 1.5 TBD
Table 9.5—AC Reflective Fatigue Cracking: PennDOT Calibration Factors (AC over AC only) Transfer Function
Coefficient Global Value PennDOT Value (Typical AC
Mixtures)
K1 0.012 TBD K2 0.005 TBD K3 1 TBD C1 0.38 TBD C2 1.66 TBD C3 2.72 TBD C4 105.4 TBD C5 -7.02 TBD
Standard Deviation
1.1097 * Pow(FATIGUE,0.6804) + 1.23 TBD
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Table 9.6—AC Reflective Transverse Cracking: PennDOT Calibration Factors (AC over AC only) Transfer Function
Coefficient Global Value PennDOT Value (Typical AC
Mixtures)
K1 0.012 TBD K2 0.005 TBD K3 1 TBD C1 3.22 TBD C2 25.7 TBD C3 0.1 TBD C4 133.4 TBD C5 -72.4 TBD
Standard Deviation
70.98 * Pow(TRANSVERSE,0.2994) + 30.12 TBD
Table 9.7—AC IRI: PennDOT Calibration Factors Transfer Function
Coefficient Global Value PennDOT Value
C1 40 TBD C2 0.4 TBD C3 0.008 TBD C4 0.015 TBD
Table 9.8—JPCP Mid-Slab Cracking: PennDOT Calibration Factors (Use for all JPCP Applications: Overlays and Restoration)
Transfer Function
Coefficient Global Value PennDOT Value
C1 2.0 2.0 C2 1.22 1.22 C4 0.52 TBD C5 -2.17 TBD
Standard Deviation 3.5522*Pow(CRACK,0.3415)+0.75 TBD
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Table 9.9—JPCP Faulting: PennDOT Calibration Factors (Use for all JPCP Applications: Overlays and Restoration)
Transfer Function
Coefficient Global Value PennDOT Value
C1 0.595 TBD C2 1.636 TBD C3 0.00217 TBD C4 0.00444 TBD C5 250 TBD C6 0.47 TBD C7 7.3 TBD C8 400 TBD
Standard Deviation 0.07162*Pow(FAULT,0.368)+0.00806 TBD
Table 9.10—JPCP IRI: PennDOT Calibration Factors (Use for all JPCP Applications: Overlays and Restoration)
Transfer Function
Coefficient Global Value PennDOT Value
J1 0.8203 TBD J2 0.4417 TBD J3 1.4929 TBD J4 25.24 TBD
Table 9.11—CRCP Punchout: PennDOT Calibration Factors (All CRCP Applications) Transfer Function
Coefficient Global Value PennDOT Value
C1 2 2 C2 1.22 1.22 C3 107.73 107.73 C4 2.475 2.475 C5 -0.785 -0.785
Standard Deviation 2.208*Pow(PO,0.5316) 2.208*Pow(PO,0.5316)
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Table 9.12—CRCP IRI: PennDOT Calibration Factors (All CRCP Applications) Transfer Function
Coefficient Global Value PennDOT Value
C1 3.15 3.15 C2 28.35 28.35
9.4 SCREEN SHOTS FOR THE CALIBRATION COEFFICIENTS
The following are screen shot examples that show the calibration coefficient inputs, as presented within this section of Chapter 9.
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Overall Screen Shot for Calibration Coefficients – Flexible Pavements
Overall Screen Shot for Calibration Coefficients –Flexible Pavements Rehabilitation
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Overall Screen Shot for Calibration Coefficients – Rigid Pavements
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Flexible Pavement Calibration Coefficients
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Flexible Pavement Rehabilitation Calibration Coefficients
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Rigid Pavement Calibration Coefficients
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CHAPTER 10—INPUT WORKSHEET This chapter of the Input User Guide provides a series of worksheets or checklists for the designer to use, at least in the beginning, for setting up a design problem and selecting the inputs. One worksheet each is provided for flexible pavements and rigid pavements. Each worksheet includes the recommended default values for those input parameters that should remain unchanged and references the sections and/or appropriate tables in this User Input Guide.
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Checklist of Inputs for New and Rehabilitated FLEXIBLE Pavement Designs
Input Parameter PennDOT Input Value Comment
General Information
Design Type New Pavement or Overlay
Section 3.1.1
Pavement Type Flexible Pavement or AC over AC
Design Life, years (20)* Section 3.3 Base/Subgrade Construction Date Section 3.4; Table 3.1 Pavement Construction Date Traffic Opening Date
Performance Criteria
Initial IRI, in./mi. Section 4.1, Table 4.1 Terminal IRI, in./mi. Section 4.2.1, Table 4.6 Top-Down Fatigue Cracking, ft./mi. (5,000)** Not considered in design. Bottom-Up Fatigue Cracking, % Section 4.2, Tables 4.2
and 4.5 Thermal (Transverse) Cracks, ft./mi. Permanent Deformation (Total & HMA/AC Rut Depth), inches
AC Total Cracking (Overlays), % Section 4.2, Table 4.2 Reliability Level, percent Section 4.3, Table 4.7
Traffic, Site Features
Two-Way Average Annual Daily Truck Traffic Section 5.1
Number of Lanes in Design Direction Percent Trucks in Design Direction (DDF) (50)*
Percent of Trucks in Design Lane (LDF) Section 5.1; Table 5.1 Operational Speed Section 5.1 Traffic Capacity Cap (Not Enforced)* Section 5.2
General Traffic, Axle Configuration
Avg. Axle Width (8.5)* Section 5.3; use global default values Dual Tire Spacing (12)*
Tire Pressure (120)* Tandem Axle Spacing (51.6)* Tridem Axle Spacing (49.2)* Quad Axle Spacing (49.2)*
Traffic; Lateral Wander
Mean Wheel Location (18)** Section 5.4; not used.
Traffic Wander, Standard Deviation (10)* Section 5.4; use global default values
Design Lane Width (12)** Section 5.4; not used. *Default values should be used. **Excessively high value used so that top-down cracking does not control design when the optimization tool is being used.
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Traffic, Wheelbase
Average Axle Spacing (short/medium/long) 12/15/18* Section 5.5; not used Percent trucks within each axle spacing
(short/medium/long) 17/22/61*
Traffic; Volume
Normalized Vehicle Class Distribution (TTC Group) Section 5.6, Table 5.2
Growth Rate & Function Section 5.6
Monthly Adjustment Factors (PennDOT Defaults)*
Section 5.7: Tables 5.3 or 5.4
Number of Axles per Truck Type (PennDOT Defaults)*
Section 5.9, Table 5.6
Hourly Distribution Factors (Defaults) Section 5.8; not used.
Traffic; Axle Loads
Single Axles
Section 5.10; Table 5.7 Tandem Axles Tridem Axles Quad Axles
Climate Location:
Longitude Section 6.1
Latitude Elevation, ft.
Depth to Water Table, ft. Section 6.2; Table 6.1 Climate Station Section 6.3, Table 6.2
AC (HMA) Layer Properties: New and Existing Layers
Multi-Layer Rutting Parameters False Section 7.1.1; not used
Shortwave Absorptivity (0.85)* Section 7.1.2; use global default value
Endurance Limit Applied False Section 7.1.3; not used
Layer Interface (Interface Friction) (1)* Section 7.1.4; use global default value for all layers
Rehabilitation (Condition of existing flexible pavement)
Milled Thickness Section 7.1.6 Fatigue Cracking; input level 2 Section 7.1.5, Figure 7.1
Pavement Rating; input level 3 Section 7.1.5, Table 7.2
Rut Depth in existing layers; input levels 1 & 2
(Layer Percentages)*
Section 7.1.5, use global default values; Table 7.1
Total Rut Depth, input level 3 Section 7.1.5, use global
default values
Bedrock
Elastic Modulus, psi Section 8.9, Table 8.15, use default values; used only when subgrade thickness is less than 100 inches.
Poisson’s Ratio
Unit Weight, pcf (140)*
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Subgrade (embankment and natural soil layers)
Thickness, inches (if applicable) Section 8.6 Poisson’s Ratio Section 8.6.3, Table 8.13 Resilient Modulus Section 8.6.2, Table 8.10 Coefficient of Lateral Pressure (0.50)* Not used.
Is Layer Compacted? Always check this box for the upper subgrade layer, if used.
Specific Gravity (2.7)* Section 8.6.1 Saturated Hydraulic Conductivity (5.051e-02) Section 8.6.4 Soil-Water Characteristic Curve Calculated Water Content Section 8.6.1, Table 8.10 &
Figure 8.2 Dry Unit Weight Gradation Section 8.6.1 Plasticity Index Liquid Limit
Stabilized Subgrade Layer; Soil Cement and Lime Stabilized Soil
Thickness, inches Section 8.8 Poisson’s Ratio Section 8.8, Table 8.14 Coefficient of Lateral Earth Pressure (0.50)* Section 8.7, not used
Resilient Modulus Section 8.8, Use annual representative modulus value; Table 8.14
AASHTO Soil Classification (A-1-b)* Section 8.8 Specific Gravity (2.7)* Section 8.8, use default
values for an A-1-b soil Saturated Hydraulic Conductivity (1.803e-03)* Soil-Water Characteristic Curve Calculated Water Content; Optimum (9.3)* Dry Unit Weight; Modified Proctor (124.0)* Gradation Plasticity Index (1)* Liquid Limit (6)*
Unbound Granular Aggregate Base (GAB) Layer
Thickness, inches Section 8.6 Poisson’s Ratio Section 8.6.3, Table 8.13 Coefficient of Lateral Earth Pressure (0.50)** Not used. Classification (Crushed Stone)* Section 8.6.2, Table 8.9;
software calculates monthly resilient modulus Resilient Modulus
Is Layer Compacted? Yes Always check this box when the layer is compacted.
Specific Gravity (2.7)* Section 8.6.1; Use global default values for a Crushed Stone
Saturated Hydraulic Conductivity (5.054e-02)* Soil-Water Characteristic Curve Calculated Water Content; Optimum (7.4)* Section 8.6.1, Table 8.9 Dry Unit Weight; Modified Proctor (127.2)* Gradation Section 8.6.1; Use global
default values for a Crushed Stone
Plasticity Index (1)* Liquid Limit (6)*
Asphalt Stabilized or Treated Base
The inputs for an asphalt stabilized or treated base layer are the same as for an AC/AC layer
See AC/AC layer inputs.
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Cement Stabilized or Treated Base Layer
Thickness, inches Section 8.1 & 8.7 Unit Weight, pcf (150)* Section 8.1 Poisson’s Ratio (0.20)* Minimum Elastic Modulus, psi Modulus of Rupture, psi Section 8.1 Elastic/Resilient Modulus, psi Thermal Conductivity (1.25)* Section 8.1 Heat Capacity (0.28)*
AC/AC (Existing) Layer(s)
Same inputs as for new AC/AC layers, except for modulus or condition of existing layer.
Section 8.1 and 8.3
Number of existing HMA/AC layers No more than 2 layers.
Thickness after milling Upper Lower
Existing AC – Back-calculated Modulus Section 8.3 (input level 1)
New AC/AC Layers – Base Layer; if present
Thickness, inches Section 8.1, Table 8.1 Unit Weight, pcf Section 8.3.1, Table 8.3 Effective Asphalt Content by Volume, % Section 8.3.1, Table 8.3 Air Voids, % Section 8.3.1, Table 8.3
Poisson’s Ratio True (Calculated)* Section 8.3.1, use global default values
Dynamic Modulus Section 8.3.2 Gradation Section 8.3.2, Table 8.5
Estar Predictive Model; G*-based model False (Calculated)* Section 8.3.2, use global default equation
Reference Temp., °F (70)* Section 8.3.2, use global default value
Asphalt Binder Grade Section 8.3.2, Table 8.4
Tensile Strength, psi (Calculated)* Section 8.3.2, use global default value
Creep Compliance (Calculated)* Section 8.3.2, use global default value
Thermal Conductivity (0.67)* Section 8.3.3, use global default value Heat Capacity (0.23)*
Thermal Contraction (Calculated)*
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New AC/AC Layers – Binder Layer; if present
Thickness, inches Section 8.1, Table 8.1 Unit Weight, pcf Section 8.3.1, Table 8.3 Effective Asphalt Content by Volume, % Section 8.3.1, Table 8.3 Air Voids, % Section 8.3.1, Table 8.3
Poisson’s Ratio True (Calculated)* Section 8.3.1, use global default values
Dynamic Modulus Section 8.3.2 Gradation Section 8.3.2, Table 8.5
Estar Predictive Model; G*-based model False (Calculated)* Section 8.3.2, use global default equation
Reference Temp., °F (70)* Section 8.3.2, use global default value
Asphalt Binder Grade Section 8.3.2, Table 8.4
Tensile Strength, psi (Calculated)* Section 8.3.2, use global default value
Creep Compliance (Calculated)* Section 8.3.2, use global default value
Thermal Conductivity (0.67)* Section 8.3.3, use global default value Heat Capacity (0.23)*
Thermal Contraction (Calculated)*
New AC/AC Layers – Wearing Surface or Surface Layer
Thickness, inches Section 8.1, Table 8.1 Unit Weight, pcf Section 8.3.1, Table 8.3 Effective Asphalt Content by Volume, % Section 8.3.1, Table 8.3 Air Voids, % Section 8.3.1, Table 8.3
Poisson’s Ratio True (Calculated)* Section 8.3, use global default values
Dynamic Modulus Section 8.3.2 Gradation Section 8.3.2, Table 8.5
Estar Predictive Model; G*-based model False (Calculated)* Section 8.3.2, use global default equation
Reference Temp., °F (70)* Section 8.3.2, use global default value
Asphalt Binder Grade Section 8.3.2, Table 8.4
Tensile Strength, psi (Calculated)* Section 8.3.2, use global default value
Creep Compliance (Calculated)* Section 8.3.2, use global default value
Thermal Conductivity (0.67)* Section 8.3.3, use global default value Heat Capacity (0.23)*
Thermal Contraction (Calculated)*
Pennsylvania Calibration Factors
Bottom-Up Fatigue Cracking Section 9; Table 9.3 Permanent Deformation (AC Rut Depth) Section 9; Table 9.1 Permanent Deformation (Rut Depth); Coarse-Grained Soil Section 9; Table 9.2
Permanent Deformation (Rut Depth); Fine-Grained Soil
AC IRI Regression Equation Section 9 Reflection Cracking Section 9
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Checklist of Inputs for New and Rehabilitated RIGID Pavement Designs: JPCP
Input Parameter PennDOT Input Value Comment
General Information
Design Type New Pavement, Overlay, or Restoration
Section 3.1.2
Pavement Type AC over JPCP; JPCP over JPCP or CRCP
(bonded & unbonded) Design Life, years (20)* Section 3.3 Base/Subgrade Construction Date Section 3.4; Table 3.1 Pavement Construction Date Traffic Opening Date
Performance Criteria
Initial IRI, in./mi. Section 4.1, Table 4.1 Terminal IRI, in./mi. Section 4.2, Table 4.6 JPCP Transverse (Mid-Slab) Cracking, % Section 4.2, Tables 4.3 JPCP Joint Faulting, inches Reliability Level, percent Section 4.3, Table 4.7
Traffic, Site Features
Two-Way Average Annual Daily Truck Traffic Section 5.1
Number of Lanes in Design Direction Percent Trucks in Design Direction (DDF) (50)* Percent of Trucks in Design Lane (LDF) Section 5.1, Table 5.1 Operational Speed Section 5.1 Traffic Capacity Cap (Not Enforced)* Section 5.1; not used
General Traffic, Axle Configuration
Avg. Axle Width (8.5)* Section 5.3; use global default values Dual Tire Spacing (12)*
Dual Tire Pressure (120)* Tandem Axle Spacing (51.6)* Tridem Axle Spacing (49.2)* Quad Axle Spacing (49.2)*
Traffic; Lateral Wander
Mean Wheel Location (18)** Section 5.4
Wander, Standard Deviation (10)* Section 5.4; use global default values
Design Lane Width (12)** Section 5.4
Traffic, Wheelbase
Average Axle Spacing (short/medium/long) (12/15/18)*
Section 5.5 Percent Trucks within each axle spacing (short/medium/long) (17/22/61)*
*Default values should be used.
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Traffic; Volume
Normalized Vehicle Class Distribution (TTC Group) Section 5.6, Table 5.2
Growth Rate & Function Section 5.6
Monthly Adjustment Factors (Use PennDOT Defaults)* Section 5.7; Tables 5.3 or 5.4
Hourly Distribution Factors (Use PennDOT Defaults)* Section 5.8, Table 5.6 Number of Axles per Truck Type (Use PennDOT Defaults)* Section 5.9, Table 5.5
Traffic; Axle Loads
Single Axles
Section 5.10; Table 5.7 Tandem Axles Tridem Axles Quad Axles
Climate Location:
Longitude Section 6.1
Latitude Elevation, ft.
Depth to Water Table, ft. Section 6.2; Table 6.1 Climate Station Section 6.3, Table 6.2
JPCP Design Properties
Shortwave Absorptivity (0.85)* Section 7.2.1; use global default value
PCC Joint Spacing, ft. Section 7.2.2 Sealant Type Section 7.2.3 Dowelled Joints Section 7.2.4 Widened Slabs Section 7.2.5 Tied Shoulders Section 7.2.6 Erodibility Index Section 7.2.7, Table 7.3 PCC Base Contact Friction Section 7.2.8 Permanent Curl/Warp Effective Temperature Difference (-10F)* Section 7.2.9
Foundation Support
Modulus of Subgrade Reaction or Resilient Modulus (Calculated)* Section 7.2.10
JPCP (Existing) Rehabilitation
Same inputs as for new JPCP except for modulus or condition of existing layer.
See PCC Layer
Slabs cracked or replaced before restoration Section 7.2.11
Slabs repaired or replaced after restoration Section 7.2.11
Bedrock
Resilient Modulus, psi Section 8.9, Table 8.15, use default values; used only when subgrade thickness is less than 100 inches.
Poisson’s Ratio
Unit Weight, pcf (140)*
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Subgrade (embankment and natural soil layers)
Thickness, inches (if applicable) Section 8.6 Poisson’s Ratio Section 8.6.3, Table 8.13 Resilient Modulus Section 8.6.2, Table 8.10 Coefficient of Lateral Pressure (0.50)* Not used.
Is Layer Compacted? Check this fox for a compacted layer, if used.
Specific Gravity (2.7)* Section 8.6.1 Saturated Hydraulic Conductivity (5.051e-02) Section 8.6.4 Soil-Water Characteristic Curve Calculated Water Content Section 8.6.1, Table 8.10
and Figure 8.2 Dry Unit Weight Gradation Section 8.6.1 Plasticity Index Liquid Limit
Stabilized Subgrade Layer; Soil Cement and Lime Stabilized Soil
Thickness, inches Section 8.8 Poisson’s Ratio Section 8.8, Table 8.14 Coefficient of Lateral Earth Pressure (0.50)* Section 8.7, not used
Resilient Modulus Section 8.8, Use annual representative modulus value; Table 8.14
AASHTO Soil Classification (A-1-b)* Section 8.8 Specific Gravity (2.7)* Section 8.8, use default
values for an A-1-b soil Saturated Hydraulic Conductivity (1.803e-03)* Soil-Water Characteristic Curve Calculated Water Content; Optimum (9.3)* Dry Unit Weight; Modified Proctor (124.0)* Gradation Plasticity Index (1)* Liquid Limit (6)*
Unbound Granular Aggregate Base (GAB) Layer
Thickness, inches Section 8.6 Poisson’s Ratio Section 8.6.3, Table 8.13 Coefficient of Lateral Earth Pressure (0.50)** Not used. Classification (Crushed Stone)* Section 8.6.2, Table 8.9;
software calculates monthly resilient modulus Resilient Modulus
Is Layer Compacted? (Yes)* Always check this box for a compacted layer.
Specific Gravity (2.7)* Section 8.6.1; Use global default values for a Crushed Stone
Saturated Hydraulic Conductivity (5.054e-02)* Soil-Water Characteristic Curve Calculated Water Content; Optimum (7.4)* Section 8.6.1, Table 8.9 Dry Unit Weight; Modified Proctor (127.2)* Gradation Section 8.6.1; Use global
default values for a Crushed Stone
Plasticity Index (1)* Liquid Limit (6)*
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Cement Stabilized or Treated Base Layer
Thickness, inches Section 8.1 & 8.7 Unit Weight, pcf (150)* Section 8.1 Poisson’s Ratio (0.20)* Minimum Elastic Modulus, psi Modulus of Rupture, psi Section 8.1 & 8.6 Elastic/Resilient Modulus, psi Thermal Conductivity (1.25)* Section 8.1 Heat Capacity (0.28)*
AC/AC Layer or Interlayer
Thickness, inches Section 8.1, Table 8.1 Unit Weight, pcf Section 8.3.1, Table 8.3 Effective Asphalt Content by Volume, % Section 8.3.1, Table 8.3 Air Voids, % Section 8.3.1, Table 8.3
Poisson’s Ratio True (Calculated)* Section 8.3.1, use global default values
Dynamic Modulus Section 8.3.2 Gradation Section 8.3.2, Table 8.5
Estar Predictive Model; G*-based model False (Calculated)* Section 8.3.2, use global default equation
Reference Temp., °F (70)* Section 8.3.2, use global default value
Asphalt Binder Grade Section 8.3.2, Table 8.4
Tensile Strength, psi (Calculated)* Section 8.3.2, use global default value
Creep Compliance (Calculated)* Section 8.3.2, use global default value
Thermal Conductivity (0.67)* Section 8.3.3, use global default value Heat Capacity (0.23)*
Thermal Contraction (Calculated)*
PCC Layer
Thickness, inches Section 8.2, Table 8.1 Unit Weight, pcf (150)* Section 8.4.1 Poisson’s Ratio (0.2)* Section 8.4.1 Coefficient of Thermal Expansion Section 8.4.2, Table 8.6 Thermal Conductivity (0.67)* Section 8.4.2 Heat Capacity (0.23)* Cement Type (Type I)* Section 8.4.3 Cementitious Material Content (660)* Water to Cement Ratio (0.45)* Aggregate Type Section 8.4.3, Table 8.6 PCC Zero-Stress Temperature (Calculated)* Section 8.4.3, Use global
default value Ultimate Shrinkage (Calculated)* Reversible Shrinkage (50)* Time to develop 50% ultimate shrinkage, days
(35)*
Curing Method Section 8.4.3
PCC Strength, psi Flexural (705)* Section 8.4.4 Compressive (6097)*
Elastic Modulus, ksi (4,500)* Pennsylvania Calibration
Mid-Slab Cracking, % Section 9; Table 9.5 Joint Faulting, inches Section 9; Table 9.6
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Factors IRI, in./mi. Section 9; Table 9.7
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Checklist of Inputs for New and Rehabilitated RIGID Pavement Designs: CRCP
Input Parameter PennDOT Input Value Comment
General Information
Design Type New Pavement, Overlay, or Restoration
Section 3.1.2
Pavement Type AC over CRCP; CRCP
over JPCP or CRCP (bonded & unbonded)
Design Life, years (20)* Section 3.3 Base/Subgrade Construction Date Section 3.4; Table 3.1 Pavement Construction Date Traffic Opening Date
Performance Criteria
Initial IRI, in./mi. Section 4.1, Table 4.1 Terminal IRI, in./mi. Section 4.2, Table 4.6 CRCP Punchouts per mile Section 4.2, Table 4.4 Reliability Level, percent Section 4.3, Table 4.7
Traffic, Site Features
Two-Way Average Annual Daily Truck Traffic Section 5.1
Number of Lanes in Design Direction Percent Trucks in Design Direction (DDF) (50)*
Percent of Trucks in Design Lane (LDF) Section 5.1, Table 5.1 Operational Speed Section 5.1 Traffic Capacity Cap (Not Enforced)* Section 5.1; not used
General Traffic, Axle Configuration
Avg. Axle Width (8.5)* Section 5.3; use global default values Dual Tire Spacing (12)*
Dual Tire Pressure (120)* Tandem Axle Spacing (51.6)* Tridem Axle Spacing (49.2)* Quad Axle Spacing (49.2)*
Traffic; Lateral Wander
Mean Wheel Location (18)** Section 5.4
Wander, Standard Deviation (10)* Section 5.4; use global default values
Design Lane Width (12)** Section 5.4
Traffic, Wheelbase
Average Axle Spacing (short/medium/long) (12/15/18)*
Section 5.5 Percent Trucks within each axle spacing (short/medium/long) (17/22/61)*
*Default values should be used.
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Traffic; Volume
Normalized Vehicle Class Distribution (TTC Group) Section 5.6, Table 5.2
Growth Rate & Function Section 5.6
Monthly Adjustment Factors (Use PennDOT Defaults)* Section 5.7; Tables 5.3 or 5.4
Hourly Distribution Factors (Use PennDOT Defaults)* Section 5.8, Table 5.6 Number of Axles per Truck Type (Use PennDOT Defaults)* Section 5.9, Table 5.5
Traffic; Axle Loads
Single Axles
Section 5.10; Table 5.7 Tandem Axles Tridem Axles Quad Axles
Climate Location:
Longitude Section 6.1
Latitude Elevation, ft.
Depth to Water Table, ft. Section 6.2; Table 6.1 Climate Station Section 6.3, Table 6.2
Foundation Support
Modulus of Subgrade Reaction or Resilient Modulus (Calculated)* Section 7.2.10
CRCP Design Properties
Shortwave Absorptivity (0.85)* Section 7.2.1; use global default value
Shoulder Type Section 7.3 Permanent Curl/Warp Effective Temperature Difference (-10F)* Section 7.2.9
Steel, percent reinforcement Section 7.3 Bar Diameter, in. Steel Depth, in. Base/Slab Friction Coefficient Section 7.3, Table 7.4
Generate Crack Spacing (True)* Software calculates crack spacing.
CPCP (Existing) Rehabilitation
Same inputs as for new CRCP except for modulus or condition of existing layer.
See PCC Layer for CRCP
Number of Punchouts per mile Section 7.3
Bedrock
Resilient Modulus, psi Section 8.9, Table 8.15, use default values; used only when subgrade thickness is less than 100 inches.
Poisson’s Ratio
Unit Weight, pcf (140)*
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Subgrade (embankment and natural soil layers)
Thickness, inches (if applicable) Section 8.6 Poisson’s Ratio Section 8.6.3, Table 8.13 Resilient Modulus Section 8.6.2, Table 8.10 Coefficient of Lateral Pressure (0.50)* Not used.
Is Layer Compacted? Check this fox for a compacted layer, if used.
Specific Gravity (2.7)* Section 8.6.1 Saturated Hydraulic Conductivity (5.051e-02) Section 8.6.4 Soil-Water Characteristic Curve Calculated Water Content Section 8.6.1, Table 8.10
and Figure 8.2 Dry Unit Weight Gradation Section 8.6.1 Plasticity Index Liquid Limit
Stabilized Subgrade Layer; Soil Cement and Lime Stabilized Soil
Thickness, inches Section 8.8 Poisson’s Ratio Section 8.8, Table 8.14 Coefficient of Lateral Earth Pressure (0.50)* Section 8.7, not used
Resilient Modulus Section 8.8, Use annual representative modulus value; Table 8.14
AASHTO Soil Classification (A-1-b)* Section 8.8 Specific Gravity (2.7)* Section 8.8, use default
values for an A-1-b soil Saturated Hydraulic Conductivity (1.803e-03)* Soil-Water Characteristic Curve Calculated Water Content; Optimum (9.3)* Dry Unit Weight; Modified Proctor (124.0)* Gradation Plasticity Index (1)* Liquid Limit (6)*
Unbound Granular Aggregate Base (GAB) Layer
Thickness, inches Section 8.6 Poisson’s Ratio Section 8.6.3, Table 8.13 Coefficient of Lateral Earth Pressure (0.50)** Not used. Classification (Crushed Stone)* Section 8.6.2, Table 8.9;
software calculates monthly resilient modulus Resilient Modulus
Is Layer Compacted? (Yes)* Always check this box for a compacted layer.
Specific Gravity (2.7)* Section 8.6.1; Use global default values for a Crushed Stone
Saturated Hydraulic Conductivity (5.054e-02)* Soil-Water Characteristic Curve Calculated Water Content; Optimum (7.4)* Section 8.6.1, Table 8.9 Dry Unit Weight; Modified Proctor (127.2)* Gradation Section 8.6.1; Use global
default values for a Crushed Stone
Plasticity Index (1)* Liquid Limit (6)*
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Cement Stabilized or Treated Base Layer
Thickness, inches Section 8.1 & 8.7 Unit Weight, pcf (150)* Section 8.1 Poisson’s Ratio (0.20)* Minimum Elastic Modulus, psi Modulus of Rupture, psi Section 8.1 & 8.6 Elastic/Resilient Modulus, psi Thermal Conductivity (1.25)* Section 8.1 Heat Capacity (0.28)*
AC/AC Layer or Interlayer
Thickness, inches Section 8.1, Table 8.1 Unit Weight, pcf Section 8.3.1, Table 8.3 Effective Asphalt Content by Volume, % Section 8.3.1, Table 8.3 Air Voids, % Section 8.3.1, Table 8.3
Poisson’s Ratio True (Calculated)* Section 8.3.1, use global default values
Dynamic Modulus Section 8.3.2 Gradation Section 8.3.2, Table 8.5
Estar Predictive Model; G*-based model False (Calculated)* Section 8.3.2, use global default equation
Reference Temp., °F (70)* Section 8.3.2, use global default value
Asphalt Binder Grade Section 8.3.2, Table 8.4
Tensile Strength, psi (Calculated)* Section 8.3.2, use global default value
Creep Compliance (Calculated)* Section 8.3.2, use global default value
Thermal Conductivity (0.67)* Section 8.3.3, use global default value Heat Capacity (0.23)*
Thermal Contraction (Calculated)*
PCC Layer
Thickness, inches Section 8.2, Table 8.1 Unit Weight, pcf (150)* Section 8.4.1 Poisson’s Ratio (0.2)* Section 8.4.1 Coefficient of Thermal Expansion Section 8.4.2, Table 8.6 Thermal Conductivity (0.67)* Section 8.4.2 Heat Capacity (0.23)* Cement Type (Type I)* Section 8.4.3 Cementitious Material Content (660)* Water to Cement Ratio (0.45)* Aggregate Type Section 8.4.3, Table 8.6 PCC Zero-Stress Temperature (Calculated)* Section 8.4.3, Use global
default value Ultimate Shrinkage (Calculated)* Reversible Shrinkage (50)* Time to develop 50% ultimate shrinkage, days
(35)*
Curing Method Section 8.4.3
PCC Strength, psi Flexural (705)* Section 8.4.4 Compressive (6097)*
Elastic Modulus, ksi (4,500)*
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Pennsylvania CRCP Calibration Factors
Number of Punchouts per mile Section 9; Table 9.7
IRI, in./mi. Section 9; Use global calibration factors.
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REFERENCES American Association of State Highway and Transportation Officials, AASHTO Guide for Design of
Pavement Structures, Washington, DC, 1986. American Association of State Highway and Transportation Officials, AASHTO Guide for Design of
Pavement Structures, Washington, DC, 1993. American Association of State Highway and Transportation Officials, Mechanistic-Empirical Pavement
Design Guide—A Manual of Practice, Publication Code: MEPDG-1, ISBN: 978-1-56051-423-7, AASHTO, Washington, DC, 2008.
American Association of State Highway and Transportation Officials, Mechanistic-Empirical Pavement
Design Guide—A Manual of Practice, Second Edition, Publication Code: MEPDG-2, ISBN: 978-1-56051-597-5, AASHTO, Washington, DC, July, 2015.
Applied Research Associates, Inc, Guide for Mechanistic-Empirical Design of New and Rehabilitated
Pavement Structures: Part 1-Introduction and Part 2-Design Inputs, Final Report, NCHRP Project 1-37A, National Cooperative Highway Research Program, Transportation Research Board, National Research Council, Washington, DC, 2004a.
Applied Research Associates, Guide for Mechanistic-Empirical Design of New and Rehabilitated
Pavement Structures: Part 3-Design Analysis and Part 4-Low Volume Roads, Final Report, NCHRP Project 1-37A, National Cooperative Highway Research Program, Transportation Research Board, National Research Council, Washington, DC, 2004b.
Applied Research Associates, Inc, Guide for Mechanistic-Empirical Design of New and Rehabilitated
Pavement Structures: Appendices A to C, Final Report, NCHRP Project 1-37A, National Cooperative Highway Research Program, Transportation Research Board, National Research Council, Washington, DC, 2004c.
Applied Research Associates, Inc, Guide for Mechanistic-Empirical Design of New and Rehabilitated
Pavement Structures: Appendix D – User’s Guide, Final Report, NCHRP Project 1-37A, National Cooperative Highway Research Program, Transportation Research Board, National Research Council, Washington, DC, 2004d.
Buchanan, Shane, Traffic Load Spectra Development for the 2002 Design Guide, Report Number
FHWA/MS-DOT-RD-04-165, Mississippi Department of Transportation, Research Division, Jackson, Mississippi, July 2004.
Federal Highway Administration, Distress Identification Manual for Long Term Pavement Performance
Program (Fourth Revised Edition), Publication No. FHWA-RD-03-031, Federal Highway Administration, Washington, DC, 2003.
PennDOT Pavement ME Design Preliminary User Input Guide Report # FHWA/PA-DOT-RD-XXX-XXXX
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National Cooperative Highway Research Program, Changes to the Mechanistic-Empirical Pavement Design Guide Software Through Version 0.900, NCHRP Research Results Digest 308, NCHRP Project 1-40D, Transportation Research Board, National Research Council, Washington, DC, 2006.
Pavement Policy Manual, Publication 242, Pennsylvania Department of Transportation, May 2015
Edition. Pennsylvania Traffic Data, Publication 601, Pennsylvania Department of Transportation, 2013 Edition. Von Quintus, H.L. and J.S. Moulthrop, Performance Prediction Models: Volume I Executive Research
Summary, Publication Number FHWA/MT-07-008/8158-1, Montana Department of Transportation, Research Programs, Helena, MT, 2007a.
Von Quintus, H.L. and J.S. Moulthrop, Performance Prediction Models: Volume II Reference Manual,
Publication Number FHWA/MT-07-008/8158-2, Montana Department of Transportation, Research Programs, Helena, MT, 2007b.