LTPP Data Analysis
IMPROVING USE OF FWD AND
LONGITUDINAL PROFILE MEASUREMENTS
Linda M. Pierce
Timin Punnackal
Sarah Lopez
Nick Weitzel
Alberto Rocher
Nichols Consulting Engineers, Chtd
Reno, NV
Joshua Li
Xue (Helen) Yang
Oklahoma State University
Stillwater, OK
Steve M. Karamihas
University of Michigan
Ann Arbor, Ml
Conduct of Research Report for NCHRP Project 20-50(22)A
Submitted August 2024
NCHRP Web-Only Document 416
LTPP Data Analysis
IMPROVING USE OF FWD AND LONGITUDINAL PROFILE MEASUREMENTS
© 2024 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trademarks of the National Academy of Sciences. All rights reserved.
Digital Object Identifier: http://doi.org/10.17226/28570
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COOPERATIVE RESEARCH PROGRAMS
CRP STAFF FOR NCHRP WEB-ONLY DOCUMENT 416
Monique R. Evans, Director, Cooperative Research Programs
Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program
Amir Hanna, Senior Program Officer
Oulimata Khoule, Senior Program Assistant
Natalie Barnes, Director of Publications
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Jennifer Correro, Assistant Editor
NCHRP PROJECT 20-50(22)A PANEL
Field of Special Projects
Sejal B. Barot, Maryland Department of Transportation, Hanover, MD (Chair)
Fan Gu, Changsha University of Science and Technology, Changsha
Xiaoyang Jia, Tennessee Department of Transportation, Nashville, TN
Seungwook Lim, California Department of Transportation, Sacramento, CA
Tommy E. Nantung, Indiana Department of Transportation, West Lafayette, IN
Larry A. Scofield, American Concrete Pavement Association, Mesa, AZ
Larry J. Wiser, FHWA Liaison
AUTHOR ACKNOWLEDGMENTS
The research reported herein was performed under NCHRP Project 20-50(22)A by Nichols Consulting Engineer, Chtd (NCE), the University of Michigan, and the University of Oklahoma. NCE was the contractor for this study, with the University of Michigan and the University of Oklahoma as subconsultants.
Dr. Linda M. Pierce, P.E., Principal Engineer at NCE, was the Principal Investigator. The other authors of this report are Mr. Timin Punnackal, Ms. Sarah Lopez, Mr. Nick Weitzel, and Mr. Alberto Rocher, of NCE, Dr. Joshua Li and Xue (Helen) Yang of the Oklahoma State University, and Dr. Steve M. Karamihas of the University of Michigan.
TABLE OF CONTENTS
CHAPTER 2 Climatic Effects on Pavement Properties and Performance
Temperature Adjustment of FWD Measurements
CHAPTER 3 LTPP Seasonal Monitoring Program
CHAPTER 4 Evaluation of Climatic Conditions
AASHTO 1993 Guide Seasonal Adjustment Model
Enhanced Integrated Climatic Model
Comparison of AASHTO 1993, EICM, and LTPP
CHAPTER 5 FWD Deflection Analysis and Adjustment
Comparisons of Daily Measurements
Temperature and Moisture Adjustments
Case Example: Arizona SMP 04-0113
CHAPTER 6 Longitudinal Profile Analysis and Adjustment
CHAPTER 7 Guidelines for Assessing and Adjusting FWD Measurements
CHAPTER 8 Guidelines for Assessing JPCP Curl and Warp from Longitudinal Profile
APPENDIX A Agency Survey and Responses
APPENDIX B SMP Section Summaries
APPENDIX C LTPP SMP Data Tables
APPENDIX D LTPP SMP Climate Data
APPENDIX E Season Definition by SMP Section
APPENDIX F Subgrade Seasonal Adjustment Factor (AASHTO 1993)
APPENDIX H Seasonal Adjustment Factors (PMED)
APPENDIX I EICM and LTPP Layer Modulus
APPENDIX J IRI Seasonal Adjustment Factors – Asphalt Pavements
Guidelines for Determining Impacts of Curl and Warp on Jointed Plain Concrete Pavements
LIST OF TABLES
Table 1. Summary EICM Inputs (NCHRP 2004)
Table 2. Summary EICM Outputs (NCHRP 2004)
Table 3. ME Model Coefficients for Coarse- and Fine-Grained Materials
Table 4. Subgrade Moduli for Asphalt Institute Method
Table 5. Monthly Granular Base k1 Values
Table 6. Air Temperature and Precipitation Summary Statistics
Table 7. Subsurface Temperature Summary Statistics
Table 8. Subsurface Moisture Content Summary Statistics
Table 9. Frost Penetration Summary Statistics
Table 10. Depth to Water Table Summary Statistics
Table 11. Deflection Sensor Offset
Table 12. MnDOT Season Definitions
Table 13. Climatic Data Sources
Table 14. Season Criteria – DF Climatic Zone
Table 15. Season Criteria – WF Climatic Zone
Table 16. Season Criteria – DNF Climatic Zone
Table 17. Season Criteria – WNF Climatic Zone
Table 18. ANOVA Results – p-values
Table 19. Summary of Deflection Basins by Climatic Zone
Table 20. Example of Subgrade Resilient Modulus (Minnesota)
Table 21. PMED Input Parameters
Table 22. PMED intermediate Files
Table 23. PMED and LTPP Average Moduli and Standard Deviations – Asphalt Layer
Table 24. PMED and LTPP Average Moduli and Standard Deviations – Base Layer
Table 25. PMED, LTPP, and AASHTO 1993 Average Moduli and Standard Deviations – Subgrade
Table 26. ANOVA Layer Modulus Results AASHTO 1993 vs LTPP
Table 27. ANOVA Results PMED vs LTPP Layer Moduli
Table 28. Pearson’s Correlation Coefficients per Climatic Zone
Table 29. Number of FWD Tests and Outliers per Climatic Zone
Table 30. TDR Moisture Content Statistical Summary
Table 31. Air and Pavement Layer Temperature Statistical Summary
Table 32. Rainfall Seven Days before FWD Testing Statistical Summary
Table 33. Water Table Depth Statistical Summary
Table 34. Asphalt Layer and Total Pavement Thickness Statistical Summary
Table 35. PSC Statistical Summary
Table 36. FWD Measured Deflections and Deflection Basin Parameters Statistical Summary
Table 37. Hierarchical Significance Levels
Table 38. Variable Selection for Temperature Adjustment of Deflections
Table 39. ß1 Coefficients for Temperature Adjustment of Deflections
Table 40. Variable Selection for Moisture Adjustment of Deflections
Table 41. ß1 Coefficients for Moisture Adjustment of Deflections
LIST OF FIGURES
Figure 1. Example of temperature impact on asphalt layer modulus
Figure 2. Example of distress due to concrete volume change
Figure 3. Example of asphalt pavement damage due to moisture
Figure 4. Example change in measured deflection with increasing temperature (Section 01-0101)
Figure 5. Ice lens development
Figure 7. Schematic of the EICM process
Figure 8. Incorporation of EICM into PMED
Figure 9. Asphalt Institute temperature adjustment factor
Figure 10. Center deflection temperature adjustment factors
Figure 11. Temperature correction factors
Figure 12. Example calculation of effective modulus for asphalt pavements
Figure 13. Example diurnal curvature analysis where slabs are mostly curled up
Figure 14. Agencies responding to questionnaires
Figure 15. LTPP SMP sections by climatic region
Figure 16. Average years of available SMP data
Figure 17. LTPP SMP typical instrumentation layout
Figure 18. Subsurface temperature measurements (Section 06-3042)
Figure 19. Example FWD testing scheme for SPS-1
Figure 20. Average monthly air temperature and FI (all climatic zones)
Figure 21. Average precipitation vs month (all climatic zones)
Figure 23. Average monthly air temperature and percent air temperature difference (DF sections)
Figure 24. Average layer modulus vs drop height (all FWD tests)
Figure 25. Example of decreasing deflections (Section 27-1028)
Figure 26. Subgrade seasonal adjustment factor per climatic zone
Figure 27. Tukey Test for Minnesota asphalt sections – subgrade
Figure 28. Asphalt layer seasonal adjustment factors
Figure 29. Seasonal adjustment factors for aggregate base and subgrade
Figure 30. PMED predicted vs LTPP backcalculated aggregate base moduli
Figure 31. PMED predicted vs LTPP backcalculated subgrade moduli
Figure 32. Asphalt layer modulus frequency distribution by climatic zone
Figure 33. Asphalt layer backcalculated modulus (Section 27-6251)
Figure 34. Outlier determination (Section 27-6251, FWD pass 672)
Figure 35. Box plot of coefficient of variation by sensor
Figure 36. Change in asphalt layer modulus and maximum deflection as a function of temperature
Figure 37. Instrumentation installation (Zollinger et al. 2008)
Figure 38. Number of FWD measurements needing diurnal temperature adjustment
Figure 39. Section 04-0113 pavement structure (https://infopave.fhwa.dot.gov)
Figure 40. Section 04-0113 pavement condition
Figure 41. Regression of D1 and mid-depth temperature (Station 155)
Figure 42. Example of IRI changes over time (Section 01-0101)
Figure 43. IRI difference factors for all SMP asphalt sections by climatic zone
Figure 44. Progression of left and right wheel path IRI deterioration over time (Section 18-3002)
Figure 45. Example of Section 18-3002 pavement deterioration
Figure 46. Section 39-0204 pavement structure
Figure 47. High-pass filter, normalized profile for joint detection
Figure 48. Isolated raw slab profile (Section 39-0204, October 20, 1999)
Figure 49. Detrended and fitted slab profile (Section 39-0204, October 20, 1999)
Figure 50. PSG values for individual slabs, right wheel path (Section 39-0204, October 20, 1999)
Figure 51. Segment-wide PSG versus age, Section 39-0204
Figure 52. IRI versus age (Section 39-0204)
Figure 53. IRI versus PSG (Section 39-0204)
Figure 54. Background IRI versus age (Section 39-0204)
Figure 55. Example regression analysis
Figure 56. High-pass filter, normalized profile for joint detection
Figure 57. Detrended and fitted slab profile (Section 39-0204, October 20, 1999)
