DETECTING INTERLAYER DELAMINATION IN ASPHALT AIRPORT PAVEMENTS USING STRAIN GAGE INSTRUMENTATION SYSTEMS

Transcription

1 DETECTING INTERLAYER DELAMINATION IN ASPHALT AIRPORT PAVEMENTS USING STRAIN GAGE INSTRUMENTATION SYSTEMS A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAIʻI AT MᾹNOA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN CIVIL AND ENVIRONMENTAL ENGINEERING DECEMBER 2014 By Karissa K. Cook Thesis Committee: Amarjit Singh, Chairperson Navneet Garg Lin Shen Keywords: Slippage Failure, Interface Debonding, Runway, Taxiway

2 ACKNOWLEDGEMENTS The author would like acknowledge and thank the Federal Aviation Administration National Airport Pavement Test Facility for the guidance and use of data files from the strain gage instrumentation system installed at Newark Liberty International Airport. Without their knowledge and support, this research would not have been possible. Support and coordination with the Port Authority of New York and New Jersey, Hawaiʻi Department of Transportation Airports Division, and the airport management at Kahului Airport were integral to the successful completion of this research. Finally, the author wishes to express sincere gratitude to the thesis committee members for their invaluable guidance and feedback. ii

3 ABSTRACT Slippage failures can be found in asphalt airport pavement areas where aircraft brake and turn, such as high-speed exits, as a result of high surface shear forces. At the intersection of Runway 4R-22L and High-Speed Taxiway N (HST-N) at Newark Liberty International Airport (EWR), interlayer delamination was determined to be the cause of slippage failure. In 2012, an asphalt strain gage system developed by the Federal Aviation Administration (FAA) National Airport Pavement Test Facility (NAPTF) was installed to detect the delamination. Delamination was successfully detected by the instrumentation installed at EWR Runway 4R-22L near the intersection of HST-N, by identifying large discrepancies in strain responses between gages installed in the upper and lower layers of pavement. Strain responses are shown to be affected by aircraft speed, temperature at the interface, and time, while statistical analysis confirms that the delamination measurements used are significant. iii

4 TABLE OF CONTENTS ACKNOWLEDGEMENTS... II ABSTRACT... III LIST OF TABLES... VI LIST OF FIGURES... VII LIST OF ABBREVIATIONS... X CHAPTER 1. INTRODUCTION OBJECTIVES METHODOLOGY SCOPE AND OUTLINE... 3 CHAPTER 2. BACKGROUND AND LITERATURE REVIEW BACKGROUND OF RUNWAY DISTRESS RESEARCH National Airport Pavement Test Facility Instrumentation Projects in the Field Asphalt Pavement Distress Types Literature Review of Pavement Interface Delamination and Slippage Failure HISTORY OF PAVEMENT DISTRESSES AT AIRPORTS OF INTEREST EWR Runway 4R-22L OGG CHAPTER 3. INSTRUMENTATION PROJECTS IN HAWAI`I ATTEMPTED INSTALLATION AT OGG IN Project Description and Goals Installation Components and Material Procurement Construction Scheduling Construction Regulations and Safety PLANNED INSTALLATION AT HNL IN CHAPTER 4. INSTALLED INSTRUMENTATION AT EWR INSTRUMENTATION LAYOUT DATA COLLECTION AND TRANSMISSION INFIELD PROGRAM Viewing Data Files from EWR Metadata ASPHALT STRAIN GAGE RESPONSES General Strain Gage Information Transverse Strain Gage Responses Longitudinal Strain Gage Responses iv

5 4.4.4 Effects of Aircraft Landing Configurations Other Strain Gage Behaviors Strain Gage Errors DATA COLLECTION METHODS Cataloguing Tests and Events of Interest Recording Event Data Peaks DETECTING DELAMINATION WITH ASPHALT STRAIN GAGES Evidence of Delamination in Strain Gage Responses DATA PLOTTING AND ANALYSIS Aircraft Speed Temperature at the Pavement Interface Responses with Respect to Time Magnitude and Center of Delamination with Respect to Time STATISTICAL ANALYSIS Frequency Distributions Kolmogorov-Smirnoff Test Analysis Difference between Means Correlation Analysis CHAPTER 5. SUMMARY AND CONCLUSIONS SUMMARY CONCLUSIONS APPENDICES APPENDIX A. TASK ANALYSIS FOR ATTEMPTED INSTRUMENTATION INSTALLATION AT OGG APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS APPENDIX C. STRAIN GAGE DATA TABLES AT ALL STRAIN GAGES APPENDIX D. DIFFERENCE BETWEEN MEANS T-TESTS AND Z-TESTS FOR INDIVIDUAL GAGE PAIRS REFERENCES v

6 LIST OF TABLES Table 1. Dynamic Strain Gage Specifications (Geocomp) Table 2. TC Readings for Changing Strain without a Loading Event Example Table 3. Tests of Interest Catalogue Table 4. List of All Significant Aircraft Event Loadings for Analysis Table 5. Catalogue of Strain Gage Delamination Evidence in ASG Pairs Table 6. KST Table of All Strain Events Table 7. Mean, Median, Mode, and Standard Deviation of Data Streams vi

7 LIST OF FIGURES Figure 1. National Airport Pavement Test Vehicle (NAPTV)... 5 Figure 2. Heavy Vehicle Simulator for Airports, Located at the NAPTF... 6 Figure 3. Map of Climactic Regions of Installed Instrumentation (Courtesy of FAA)... 7 Figure 4. Superposition of Forces in Airport Pavements in Braking and Turning Areas Figure 5. Cores from Slippage Areas of Runway 4R-22L (Bognacki et al. 2007) Figure 6. Visual Evidence of Slippage at Runway 4R-22L, August Figure 7. Alligator Cracking at OGG Figure 8. High Severity Longitudinal, Transverse, and Block Cracking at OGG Figure 9. Rutting at Runway 2-20 of OGG Figure 10. Surface Shoving at OGG Figure 11. Slippage Cracking in Keel Section of OGG Runway Figure 12. Data Collection and Transmission Architecture Figure 13. Side Profile of OGG Planned Installation Works Figure 14. Overhead View of Planned Installation at OGG Figure 15. DAQ Cabinet (Courtesy of FAA) Figure 16. Close-up of ASGs Embedded in Base Layer (milled HMA surface) at EWR Figure 17. Lighting Can Configuration Detail Figure 18. Wires Entering Pullbox through Conduit Openings (Courtesy of FAA) Figure 19. Proposed Location of Instrumentation and DAQ at HNL (Courtesy of FAA) Figure 20. Timeline of Instrumentation and Monitoring at EWR Figure 21. Location of the Intersection of Runway 4R-22L and HST-N at EWR Figure 22. Installation Location at EWR (Courtesy of FAA) Figure 23. Original Strain Gage Layout Design at EWR (Courtesy of FAA) Figure 24. Installed Strain Gage Layout at EWR Figure 25. Sensor Location at EWR Relative to Interface and Travel Direction Figure 26. Depths of TCs Installed at EWR Figure 27. Screenshot (1) from Camera Installed at EWR Figure 28. Screenshot (2) from Camera Installed at EWR Figure 29. Opening a File in InField Program Figure 30. Active Channels List Display in InField vii

8 Figure 31. Individual Sensor Plot in InField Figure 32. Highlighted Sensor Plot for Detailed Inspection in InField Figure 33. Close-up View of Sensor Loading Event in InField Figure 34. Side-by-side Individual Plot of a Sensor Pair in InField Figure 35. Overplot of Two Sensor Channels in InField Figure 36. Tabular Data Display in InField Figure 37. Selecting the Peak Strain Values in InField Figure 39. Guide to ASG Response Types Figure 40. Asphalt Stain Gage (Geocomp) Figure 41. Orientation and Layout of TSGs Figure 42. Response from TSG in Aircraft Wheel-path (Bonded) Figure 43. Response from TSG Outside of Aircraft Wheel path (Bonded) Figure 44. Compressive Strain Due to Rollover at TSG Pair 9 (Bonded) Figure 45. Individual Plots of Compressive Strain Due to Rollover at TSG 9 (Bonded) Figure 46. Orientation and Layout of TSGs Figure 47. Typical Strain Response Profile from LSG Pair (Bonded) Figure 48. Aircraft Landing Gear Configurations Figure 49. TSG Response for Dual Wheel Landing Gear Configuration Inside Wheel-path Figure 50. Boeing 737 Landing Gear Configuration Figure 51. TSG Response from Dual Tandem Configuration, Outside of Wheel-path Figure 52. Boeing 757 with Dual Tandem Landing Gear Figure 53. Changing Strain Response without a Loading Event Figure 54. Erratic Sensor Reading, TSG 7A Figure 55. Quiet Sensor Response, LSG 7A (Green) Figure 56. Final Layout of Working ASGs at EWR, Broken Gages Marked with X Figure 57. Data Collection for Dual Wheel Loads on TSGs (Side of TSG, Bonded) Figure 58. Data Collection for Dual Tandem Loads on TSGs (Side of TSG, Bonded) Figure 59. Data Collection Template for Dual Wheel Loads on LSGs (Bonded) Figure 60. Data Collection Template for Dual Tandem Loads on LSGs (Bonded) Figure 61. Neutral Axis Realignment as a Result of Interlayer Delamination Figure 62. Fully-Bonded Pavement Modelled as a Beam viii

9 Figure 63. Debonded Pavement Layers Modelled as a Beam Figure 64. No Delamination in LSG Pair Figure 65. Early Indications of Delamination in LSG Pair Figure 66. Delamination Evidence in LSG Pair Figure 67. Plot of Δ Strain vs. Aircraft Speed (Bonded) Figure 68. Plot of Δ Strain vs. Aircraft Speed (Delamination) Figure 69. Δ Strain vs. Temperature from TC-C at the Interface (Bonded) Figure 70. Δ Strain vs. Temperature from TC-C at the Interface (Delamination) Figure 71. Plot of Non-Delamination and Delamination Events vs. Time Figure 72. LSG Pair 6 Progression with Respect to Time Figure 73. Degree and Frequency of Delamination for All 2013 Events Figure 74. Degree and Frequency of Delamination for All 2014 Events Figure 75. Center of Delamination, Figure 76. Center of Delamination, Figure 77. Superposition of CODs on Runway 4R-22L at HST-N Figure 78. Magnitude of Total Delamination Scores Over Time Figure 79. Frequency Distributions of Δ Strain (Bonded, Delamination) Figure 80. Combined Frequency Distributions of Δ Strain Figure 81. Correlation of All TSG Pair Responses with No Delamination Evidence Figure 82. Correlation of All LSG Pair Responses with No Delamination Evidence Figure 83. Correlation of All TSG Pair Responses with Delamination Evidence Figure 84. Correlation of All LSG Pair Responses with Delamination Evidence ix

10 LIST OF ABBREVIATIONS AC Advisory Circular ASG Asphalt Strain Gage CEE Civil and Environmental Engineering COD Center of Delamination CSPP Construction Safety and Phasing Plan EWR Newark Liberty International Airport FAA Federal Aviation Administration FOD Foreign Object Debris HDOT-A Hawaiʻi Department of Transportation: Airports Division HMA Hot Mix Asphalt HNL Honolulu International Airport HST-N High-Speed Taxiway N HVS-A Heavy Vehicle Simulator for Airports KST Kolmogorov-Smirnoff Test LC Lighting Can LSG Longitudinal Strain Gage NAPTF National Airport Pavement Test Facility NAPTV National Airport Pavement Test Vehicle OGG Kahului Airport PANYNJ Port Authority of New York and New Jersey PCC Portland Cement Concrete TC Thermocouple TSG Transverse Strain Gage UH University of Hawai`i x

11 CHAPTER 1. INTRODUCTION The constant improvement of airport pavement design standards is of critical importance for maintaining high levels of safety and efficiency in air transportation. In an era of rapidly evolving aviation technology, pavement evaluation and testing methods must maintain pace with the latest innovations in aircraft design. The Federal Aviation Administration (FAA) constructed the National Airport Pavement Test Facility (NAPTF) in 1999 in an effort to address the concern of airport pavement being outmatches by the next generation of aircraft. The FAA NAPTF is the site of the most current research being conducted on asphalt and concrete runway pavements. The NAPTF is also responsible for studies conducted on in-situ runway loading responses, through the installation and monitoring of instrumentation systems at major American airports. While strain gage systems have been installed in many of the critical climactic regions of the United States, no research has been conducted on airport pavements in tropical climates. It is a goal of both the FAA and the Hawai`i Department of Transportation: Airports Division (HDOT-A) to install pavement response monitoring systems in runways in the state of Hawai`i, at both the Honolulu International Airport (HNL) on the island of Oahu, and the Kahului Airport (OGG) on the island of Maui. The instrumentation systems designed to be installed at HNL and OGG are designed primarily to measure slippage failure in hot mix asphalt (HMA) overlays as a result of pavement interface delamination. A similar instrumentation system is currently installed at Runway 4R- 22L approaching High-Speed Taxiway N (HST-N) of Newark Liberty International Airport (EWR), which serves as a key example for the design of the instrumentation layouts in the planned HNL and OGG instrumentation installations. The installation at EWR is the first of its design to be implemented for detecting in-situ pavement interface delamination. By verifying the success of the design, installation, and data analysis methods employed at EWR, a foundation for the planned instrumentation projects in the state of Hawai`i is formed. It is hoped that by 2016 HNL will be instrumented for study, and that OGG will follow suit during its next major reconstruction in the following years. In order for these installations to be successful, it is imperative that the lessons learned in the attempted installation of pavement monitoring instrumentation at OGG in 2014 be considered, and the already acquired installation items used. 1

12 1.1 Objectives The objectives of this investigation are: Detail the design process, construction planning, procurement efforts, and project insights from the attempted strain gage installation at OGG in Analyze data collected from the strain gage instrumentation system installed in Runway 4R-22L of EWR, approaching the intersection of HST-N. Verify the efficacy of the instrumentation installed at EWR by relating indications of delamination in the data patterns to recorded slippage indications on the surface of Runway 4R-22L. Incorporate the results of data analysis from EWR into the future design of runway instrumentation systems. Make recommendations regarding the installation of strain gage instrumentation systems at HNL in 2016, and OGG in Methodology For the analysis portion of this thesis, responses from the asphalt strain gages installed in EWR's Runway 4R-22L approaching HST-N are evaluated. Before any in-depth analysis is conducted on any of the data files, it is important that the validity of the strain gages be checked for broken, noisy, quiet, errant, or mislabeled sensors. Then, to determine whether or not the particular file contains readable data, an assortment of working sensor plots are opened and noticeable loading events are catalogued. During examination of the strain gage readings, indications of delamination manifest themselves as discrepant readings between the two halves of a sensor pair. The clearest indication of interlayer delamination is given by opposing readings in the base layer and overlay gages (tensile strain in one layer, with compressive strain in the other). In contrast, ASG readings are roughly the same between two pavement layers for homogenous interfaces. By closely examining visual representations of the data, verified by statistical analysis, delamination is detected and tracked. 2

13 1.3 Scope and Outline The scope of this thesis is limited to the discussion of ASG instrumentation projects in airport pavements. This includes the analysis of data collected from the existing installation at EWR, as well as the history and future of ASG installations in Hawai`i. Following the introductory Chapter 1, Chapter 2 contains the background of instrumentation installations installed by the FAA for the purpose of measuring pavement responses. Then the literature review of previously conducted studies on asphalt pavement slippage failure and interlayer delamination of asphalt airport pavements is discussed. The histories of distresses observed at Runway 4R-22L of EWR and Runway 2-20 of OGG are also presented in this chapter to provide background to local distress profiles for each runway pavement. Chapter 3 details the work conducted by the University of Hawai`i (UH) at Mānoa Department of Civil and Environmental Engineering (CEE) and HDOT-A, in an attempt to install a strain gage instrumentation system at OGG in This section is included to provide insight for the future installation of the data collection systems at HNL and OGG. The planned instrumentation installation in Runway 8L of HNL in 2016, and the concrete strain gage system installation at OGG during a major airport runway resurfacing scheduled for 2019, are also discussed in this chapter. Chapter 4 presents the data collected from the asphalt strain gage system installed in Runway 4R-22L near HST-N of EWR. The results of analysis performed to detect interlayer delamination in the asphalt concrete are presented. An explanation of the theories behind the instrumentation design, layout, and execution at EWR accompany the analysis. Statistical analysis methods are used to verify that the indications of delamination are significant. Chapter 5 summarizes the efforts required for installing instrumentation in airport pavements, and concludes the results of the data analysis at EWR. 3

14 CHAPTER 2. BACKGROUND AND LITERATURE REVIEW 2.1 Background of Runway Distress Research Since 1993, the Airport Technology Research and Development branch at the Federal Aviation Administration has made it a priority to validate the integrity of existing paved runways in preparation for future air-travel demands. Airplanes like the Boeing 777 and Airbus A380 called to attention the unbalanced efforts in air-travel research and development; aircraft are being designed faster than their runway pavements. Increased tire pressures, combined with the heavier loads of new aircraft, induce higher shear, tensile, and compressive stresses on runway pavements than they were previously designed for (Garg et al. 2014, Song and Garg 2010). If adequate resources are not allocated to close this developmental gap, unimproved pavement technologies could hinder the advancement of the Next Generation Air Transportation System (FAA 2012). Pavement designs are often based on highly-conservative assumptions, leading to overdesign and wasted resources. This is due in part to the FAA requirement that all airport pavements be designed for a minimum 20-year lifespan. At first, overdesign of such an integral safety concern does not seem like an issue, but when mapped out to approximately 9,000 airports in the United States, with nearly 6 billion square feet of paved runway surface, the cumulative cost implications become alarming (FAA 2012). To conserve resources and ensure that runway pavement design maintains pace with aircraft evolution, the FAA is constantly performing tests on airport pavements in its state-of-the-art testing facility, as well as installing and analyzing data collected from instrumentation systems in the field National Airport Pavement Test Facility In April 1999, the FAA opened the National Airport Pavement Test Facility (NAPTF) at the William J. Hughes Technical Center, as a joint research venture with the Boeing Company. With an initial construction cost of $21 million, the NAPTF is the largest indoor pavement testing facility in the world dedicated to modeling runway loadings. The NAPTF is home to a vehicular-load simulating machine (Figure 1) capable of reproducing aircraft loads of up to 1.3 million pounds in automated testing conditions, on both asphalt and concrete pavements. The 4

15 wheels of the loading rig can be repositioned to mimic any number of aircraft landing gear configurations, and are programmable to simulate normally-distributed aircraft wander patterns. Figure 1. National Airport Pavement Test Vehicle (NAPTV) Testing with the aircraft-load simulating machine has its limitations, however, and is not capable of measuring the effects of environmental factors and ambient temperatures on pavement structures. Thermal gradients in airport pavements have been shown to play a significant role in relation to loading responses, and with the new Heavy Vehicle Simulator for Airports (HVS-A) machine, shown in Figure 2, the NAPTF is beginning to collect data on the loading responses of heated pavements. 5

16 Figure 2. Heavy Vehicle Simulator for Airports, Located at the NAPTF The HVS-A includes pavement heating and monitoring equipment in addition to a loading vehicle. Tests conducted in August 2014 on pavements heated to upwards of 120 ºF. While providing exciting new data, even the HVS-A falls short of fully accounting for the variable environmental factors and loading conditions experienced by active airport pavements. For this reason the FAA actively pursues in-the-field installation projects in addition to NAPTF testing Instrumentation Projects in the Field The NAPTF is the parent and control center of the field-testing instrumentation systems currently in place at major airports nationwide. Data collected from real-world installations are used to verify existing analytical models of pavement analysis, and improve upon the design of instrumentation for future installations. Additionally, the data from select installations and the NAPTF populate an accessible database for study by researchers around the world. The FAA currently has instrumentation installed at the following airports: Denver International Airport (no longer collecting data), John F. Kennedy International Airport, LaGuardia Airport, Atlanta Hartsfield-Jackson International Airport, and EWR. The locations of 6

17 these installed instrumentation systems are intended to account for a wide array of climactic environments and operating conditions, including pavements subjected to freeze-thaw cycles or notable rainfall patterns. As demonstrated by Figure 3, the instrumented sites account for many of the environments seen in the contiguous United States, but do not include an installation in a Dry No Freeze environment. Couple this characteristic with the tropical year-round climate found in Hawai`i, and an ideal setting for pavement research is identified. It is for this reason that the FAA is working with the HDOT-A to install instrumentation systems at HNL and OGG in the near future. Figure 3. Map of Climactic Regions of Installed Instrumentation (Courtesy of FAA) Asphalt Pavement Distress Types While the key distress type investigated by this thesis is slippage failure as a result of pavement interface delamination, many distress types plague asphalt concrete pavements at airfields. Slippage failures are found in braking and turning areas of asphalt pavements, such as at the intersection of HST-N and Runway 4R-22L of EWR. According to the FAA (2004), 7

18 failure may be structural or functional in nature, categorized as sixteen distinct distress patterns that lead to failure. These distresses are defined as: alligator (fatigue) cracking, bleeding, block cracking, corrugation, depression, jet-blast erosion, joint reflection cracking (from underlying PCC slabs), longitudinal and transverse cracking, oil spillage, patching and utility cut patching, polished aggregate, raveling and weathering, rutting, shoving, slippage cracking, and swell distress. A brief definition of each type of asphalt concrete distress type identified by the FAA (2004) is given below, supplemented by definitions outlined by Mallick and El-Korchi (2009). 1. Alligator (Fatigue) Cracking is noticeable by the sprawling interconnected cracking at the surface of and asphalt overlay layer. This failure is due to repeated loading, and is initiated by high tensile strains produced at the bottom of the overlay. 2. Bleeding is defined as the propagation of asphalt binder at the top layer of the pavement due to excessive amounts of binder in the mix design. Bleeding can cause the surface of the pavement to become sticky. 3. Block Cracking describes large (over one square foot in size) rectangular shaped sections of asphalt created by cracking. This cracking can be caused by day-to-day temperature cycling, the hardening of the surface asphalt, or a change in volume of the base or the subgrade. This failure is not due to loading, but rather environmental factors. 4. Corrugation is a rippling effect in stop and start traffic areas where the surface mix or base has low stability. 5. Depressions are areas of pavement that have lower elevations than the surrounding asphalt. Depressions may be due to settling foundation soil or construction error. 6. Jet-blast Erosion describes darkened areas of pavement surface caused by burned asphalt binder. 7. Joint Reflection Cracking is a surface distress caused by the movement of the underlying PCC slabs due to moisture or temperature change conditions, combined with loading effects. 8. Longitudinal and Transverse Cracking may be caused by either the shrinkage/hardening of the asphalt surface layer or reflective cracking from cracks in layers below. Additionally, longitudinal cracking may also be the result of poorly constructed paving joints. 8

19 9. Oil Spillage degrades and softens the pavement surface. 10. Patching and Utility Cut Patching is an area of replaced pavement, and is considered a defect in the pavement surface even if performing perfectly. 11. Polished Aggregate develops as the asphalt binder wears away with repeated trafficking, leaving the coarse aggregate in the mix exposed. This leads to a loss of surface skid resistance. 12. Raveling and Weathering results in the erosion of fine aggregate, followed by coarse aggregate, as a result of binder loss in the surface layer. Foreign Object Debris (FOD) problems may arise if raveling and weathering is allowed to propagate. 13. Rutting is expressed as longitudinal depressive areas in the aircraft wheel-path, caused by repeated loading. A rut depth of 1 is considered functional failure. 14. Shoving is the first characterization of slippage failure, and manifests as a longitudinal displacement of the pavement surface. 15. Slippage Cracking is the one of the more advanced manifestations of slippage failure, and is defined as cracking that resembles crescent shapes in the direction of traffic. Slippage cracking is caused by either poor shear resistance in the surface mix, or delamination between the asphalt layers. 16. Swell Distress is recognizable by an area of pavement that bulges upwards, sometimes accompanied by cracking. This distress type is typically due to swelling in the soil layers, blowup in underlying PCC slabs, or frost action in the subgrade. Shoving and slippage cracking, as a result of interlayer delamination, are discussed in the next section to provide a basis for the theory behind the ASG instrumentation design used at EWR, and proposed for OGG (attempted 2014 installation) and HNL Literature Review of Pavement Interface Delamination and Slippage Failure According to the FAA Advisory Circular 150/5380-6B, slippage cracking is characterized by areas of pavement layers that slide and deform, causing crescent or half-moonshaped (cracks) with the two ends pointing away from the direction of traffic (2009b). Slippage failure is typically the result of delamination between layers of flexible pavement or the lack of shear strength within the surface asphalt concrete mix (FAA, 2004). Delamination is 9

20 characterized by the deterioration of the adhesion between two layers of asphalt pavement, causing the overlay to become debonded from the underlying base layer at the pavement interface. Shoving and slippage cracking are most often found in braking and turning zones, such as the intersection of HST-N and Runway 4R-22L of EWR. Airport pavement in runway areas leading into high-speed taxiways are subject to the vertical normal force from the weight of the aircraft, as well as the static frictional forces between the aircraft tires and the pavement surface, both in the directions of turning and braking. Frictional forces are calculated by multiplying the normal force with the coefficient of static friction for the materials. The magnitude of the normal force increases with aircraft load and tire pressure, inducing higher friction and surface shear forces (Song and Garg 2010). Three dimensional elasticity analysis conducted by Kimura (2013) suggests that the maximum shear stresses in the upper layers of the pavement structure, as caused by surface shear forces from turning and aircraft acceleration, may sometimes be even higher than the stresses induced by the weight of the aircraft. Barber (1962) recommends that a superposition of these forces is used in the design and analysis of pavement structures and their interfaces in braking and turning areas. Figure 4 provides a visual representation of these forces. Direction of Traffic Turning Shear Force Turning Shear Force Aircraft Weight Normal Force Braking Shear Force Aircraft Weight Normal Force Braking Shear Force Figure 4. Superposition of Forces in Airport Pavements in Braking and Turning Areas Before full slippage cracking occurs, surface shoving indicates that failure has begun in the pavement structure. It is critical that once shoving is recognized, plans are made for rehabilitation. Once slippage has initiated at the pavement interface, the effective stiffness of the pavement structure decreases, reducing the distribution of the surface and vertical loads on the 10

21 pavement subgrade (Shahin 1987). If shoving is allowed to progress to slippage cracking, FOD becomes a serious concern. This FOD consists of small asphalt pieces that can become dislodged from the cracking, and run the risk of being sucked into passing aircraft engines. When delamination between layers of asphalt airport pavement is detected, the root cause may stem from a number of factors. These factors include: improper construction practices, poor material selection, high loading intensity or frequency, and high-shear stresses in the pavement due to braking and the centrifugal forces induced by turning (Mooren et al. 2014). High ambient temperatures contribute to slippage failures by increasing the plastic deformation of HMA in loading conditions, and reducing the bonding strength between surface and base layers (Bognacki et al. 2007, Colop et. al 2009). Cohesion in the asphalt mix tends to decrease with temperature increase, indicating that cracking is most likely to occur in high ambient temperatures (Mooren et al. 2014). Preventing interlayer delamination is a serious concern in runway and taxiway resurfacing, but has proven a difficult issue to address. Constructing overlays with an adequate lift depth to dissipate shear forces is paramount for reducing interface shear forces, although strict guidelines regarding smoothness often cause contractors to pave in multiple thin layers (Bognacki et al. 2007, Hu and Walubita 2011). Construction factors like dusty or wet conditions at the time of repaving are also believed to weaken the interlayer bond (Garg 2013). As an attempt to increase bond strength at the time of construction, milling grooves into the surface of the existing pavement in a transverse direction helps to limit delamination by facilitating aggregate interlock between pavement layers (Mohammed et al. 2010). However, this method is impractical in implementation, due to the created inefficiencies in construction scheduling, and is very rarely used. Application of emulsified asphalt tack coat or binder between the existing surface and the HMA overlay is a commonly used technique for ensuring that the two layers perform as a homogenous pavement. Although a commonly practiced and accepted method, the use of tack coat materials lacks regulations for quality control. Defects in the tack coat layer are often due to variables in tack coat material selection and application, combined with low rates of quality assurance checks (Bae et al. 2010). Too liberal an application of tack coat may cause shear slippage at the interface, while a lack of tack coat may result in a concentration of tensile stresses at the bottom of the HMA overlay (Mohammed et al. 2003). It should also be noted that adequate 11

22 pavement and interface performance has been demonstrated in pavement structures installed without any tack coat whatsoever (Romanoschi 1999). Recent research illustrates that asphalt concrete slippage failures are rarely transparent in origin, although new discoveries about the progression of interlayer bond conditioning may point towards interesting preventative measures and solutions. Additionally, recent research shows that the normal forces induced by trafficking can actually increase the interlayer shear resistance and improve bonding conditions in specific instances. Examples include a study conducted by Mohammad et al. (2010), which determined that increased interface shear strength was achieved with increased asphalt density in field studies linking surface roughness to interface shear strength for roadway pavements (typically compacted at a lower density than airport pavements). Collop et al. (2009) concluded that internal shear strength increased by approximately 30% after one year of trafficking in both laboratory prepared samples and field cores. White (2014b) uses statistical analysis to show improvement in the interface shear strength and the HMA overlay layer s resilient modulus, after approximately two years of normal aircraft trafficking. The benefit in shear resistance at the interface may be due to interlayer bond solidification due to the compaction from repeated aircraft loadings, increased density of the surface layer, reorientation of aggregate particles (causing an increased total particle-to-particle contact area within the pavement structure), or any combination of the above (White, 2014b). It should be noted however, that these studies do not take into account surface shear forces, which could still damage the pavement even in ideal conditions. Asphalt slippage deformations, closely resembling the distress patterns found at the intersection of Runway 4R-22L and HST-N of EWR, are investigated in another recent report from Melbourne Airport. In 2011, shoving distress began to occur just six months after the completion of runway resurfacing, and it was concluded that the likely cause of the deformations was a lack of resistance to Cyclic Shear Creep in the asphalt mix (White, 2014a). While the appearance of the deformations found at Melbourne Airport match the distresses at EWR almost perfectly, in the Melbourne study the possibility of slippage failure due to interface delamination is ruled out due to the findings of prior investigations. 12

23 2.2 History of Pavement Distresses at Airports of Interest The two airports of interest covered by this thesis are OGG (with its current asphalt runway) and EWR. Both Runway 2-20 of OGG and Runway 4R-22L of EWR have reported signs of shoving and slippage cracking in critical areas of the asphalt surface over the years. The histories of the airports, as well as their respective recent distress findings, are discussed in this section EWR Runway 4R-22L EWR currently serves 33 million passengers each year. Runway 4R-22L acts as the primary landing strip for the airfield, handling approximately 190,000 aircraft operations every year. HST-N is one exit that aircraft have the option of taking near the 4R end of Runway 4R- 22L. In the summer months, aircraft typically land from north-to-south due to wind direction, therefore having the option of utilizing HST-N (Bognacki et al. 2007). With ambient temperatures occasionally reaching 100 ºF, and in-pavement temperatures often reaching 120 ºF, the risk of fatigue failure due to slippage is greatly increased. In the winter, wind conditions typically cause aircraft to land south-to-north on the runway. The stiffer pavement, due to colder climactic conditions in the winter, may be the reason why limited slippage distress is found in the taxiways at the 22L end of the runway (Bognacki et al. 2007). In 2005, slippage failure was documented at the keel (centerline) section of Runway 4R- 22L of EWR, just at the initiation of the turn onto HST-N. Investigative cores taken in 2005 showed no evidence of failure within the asphalt mix, while the interface shows signs of delamination, as shown in Figure 5. 13

24 Figure 5. Cores from Slippage Areas of Runway 4R-22L (Bognacki et al. 2007) At Runway 4R-22L of EWR, the history of slippage failure was linked directly to the type of stone used in 2004 s asphalt rehabilitation efforts. Between the two sources of stone used, Granitic-Gneiss and Traprock, only the areas of pavement where the top layer was comprised of Granitic-Gneiss developed symptoms of slippage failure (ibid). No subsequent laboratory testing revealed the reason for the disparity in slippage failure between the two materials. The current stone in the asphalt mix in use at EWR Runway 4R-22L is Traprock. Similar distress conditions have now been spotted in the same location of Runway 4R- 22L near the intersection with HST-N in August 2014, despite numerous preventative measures being taken during the last repaving during the summer of These measures included: milling without the use of water to prevent the formation of a slurry from forming on the milled surface, thorough cleaning of the milled surface, and increasing the application of tack coat from 0.05 to 0.10 gallons per square yard to 0.08 to 0.10 gallons per yard. All HMA surfacing pavements used at EWR also comply with the requirements outlined in FAA Item P-401. Figure 6 is a photograph, taken by agents of the Port Authority of New York and New Jersey, of Runway 4R-22L near the intersection with HST-N, in early August of

25 Figure 6. Visual Evidence of Slippage at Runway 4R-22L, August 2014 (Courtesy of PANYNJ) The pavement and instrumentation system at EWR was installed in summer 2012, and is the first in-situ ASG system installed by the FAA dedicated to detecting interlayer-bond failure by measuring the strain conditions at the pavement interface. The method of installing the ASGs served as the model for the planned installation at OGG in 2014, and is covered in the next chapter OGG Runway 2-20 of OGG is a 6,995-foot long x 150-foot wide asphalt concrete runway, and serves as the primary airstrip for takeoffs and landings at OGG. The runway consists of inches of layered asphalt concrete atop an 8-inch cinder base layer. Distresses in the surface of Runway 2-20 were outlined in a report by Leake and Singh (2013a). This report presents findings from detailed inspections in November 2005, and visual observations made thereafter during a 3-inch mill and overlay rehabilitation effort in Ten distress types were recorded at OGG, including: alligator cracking (Figure 7), bleeding, block cracking (Figure 8), depression, longitudinal and transverse cracking (Figure 8), patching, raveling/weathering, rutting (Figure 9), slippage/shoving, and swelling. Photographs for Figures 7-11 are taken from Leake and Singh (2013a). 15

26 Figure 7. Alligator Cracking at OGG Figure 8. High Severity Longitudinal, Transverse, and Block Cracking at OGG 16

27 Figure 9. Rutting at Runway 2-20 of OGG Keel sections (near the runway centerline) showed the most slippage failure distress. Figure 10 presents a picture of early-stage slippage failure reported along Runway 2-20 of OGG. Figure 11 illustrates the progression of surface shoving into slippage cracking. Figure 10. Surface Shoving at OGG 17

28 Figure 11. Slippage Cracking in Keel Section of OGG Runway 2-20 The largest concentration of distress, particularly in the form of slippage failure, was found near the runway intersection where braking and turning forces from aircraft are high. These conditions are similar to the distresses recorded at Runway 4R-22L near HST-N of EWR, and provided the inspiration for implementing a similar strain gage instrumentation project at Runway 2-20 of OGG. 18

29 CHAPTER 3. INSTRUMENTATION PROJECTS IN HAWAI`I OGG and HNL are the two main hubs of transportation connecting the state of Hawai`i to the rest of the world. The Hawai`i Department of Transportation: Airports Division (HDOT-A), in a contract with the University of Hawai`i (UH) Department of Civil and Environmental Engineering (CEE), is currently operating a 9-year project entitled Concrete Runway Pavement Monitoring for Kahului Airport. This project includes funds for the preliminary installation of ASGs at Kahului in an asphalt concrete repaving project, and for the primary installation of ASGs on the same runway during a full concrete repaving scheduled for Although the originally planned installation in the asphalt concrete runway at OGG was not completed in 2014 according to schedule, that preliminary installation of the project is now transferred to HNL Runway 8L. The planning, contracting, and construction procedures for installing ASG instrumentation systems at OGG and HNL borrow techniques from the ASG installation at EWR. The methods for installing instrumentation are detailed in this chapter. 3.1 Attempted Installation at OGG in 2014 The prospect of installing pavement monitoring instrumentation at the airports of Hawai`i is a unique opportunity for both the FAA and HDOT-A. The asphalt strain gauge instrumentation proposed for installation on Runway 2-20 of OGG in the summer of 2014 was to be the first project of its kind in the state of Hawai`i. The goals of installing asphalt strain gauges in the airports of Hawai`i is to provide information about the performance of asphalt in tropical environmental conditions, to facilitate the scheduling and optimization of maintenance activities at the airports, and to continue to form a comprehensive view of runway pavement performance nationwide. The installation of strain gage instrumentation will also provide future research opportunities for UH CEE, while benefitting the airports at which they are installed with realtime monitoring reports Project Description and Goals OGG was selected for instrumentation as it was already scheduled to undergo a full asphalt runway resurfacing in In 2018, OGG Runway 2-20 is planned to receive a full concrete runway replacement, which the FAA and HDOT-A hope to instrument with a concrete 19

30 strain gage system. It was originally intended that some of the same supporting infrastructure from the first installation at OGG be reused for the concrete runway instrumentation installation in the coming years, to minimize the overall cost and impact of installation. The instrumentation system as a whole is comprised of ASGs, thermocouples (TCs), connectors, wires, a Data Acquisition System (DAQ), power supply, and the supporting infrastructure that houses and protects these components. Thermocouples are responsible for reporting ambient and in-pavement temperatures at various depths. The DAQ is the computer that records and transmits the ASG and TC data. Figure 12 shows the data transmission architecture for the collection and dissemination of strain responses data files. The physical ASGs and DAQ operate as the foundational elements of the data system. If the program is not being accessed by the project manager however, the ASGs and the DAQ are not collecting or transmitting any data. Remote Access Login by Project Manager at FAA Data Files Transmitted and Downloaded Data Sent to Researchers for Analysis Aircraft Observed in Camera Data Collection Initated Loading Events Recorded by ASGs Data Collected at DAQ Figure 12. Data Collection and Transmission Architecture 20

31 The entire system is linear, from the sensors located on the runway, to the DAQ platform 500 feet away from the runway centerline. Figure 13 and Figure 14 give a comprehensive view of the supporting infrastructure required for the installation of the system. From left to right on the diagrams, the lighting cans (LCs) are installed next to the sensors on the runway, 4 below the runway surface. The LCs are the access point for the FAA technicians during installation, and serve to house the sensor wires and connectors so that they may be gathered together and pulled into the conduits. The LCs are also necessary due to the fact that the connectors cannot fit into the conduits themselves. The conduits connect to the bottom of the lighting cans, and protect the wires within the trench running from the lighting cans to the DAQ. The conduits are installed 20 below the surface on the runway in an excavated trench, and 18 below the surface off the runway per Advisory Circular guidelines (FAA 2009a). The trench is segmented by two large pullboxes, which must be installed for the pulling and temporary storage of the wires during construction. Due to the length of the trench, wires cannot be pulled continuously through the conduits from the runway to the DAQ platform. On the far right of the diagram is the DAQ platform. The DAQ platform is a 10 x 10 concrete slab on which the DAQ is located in its protective cabinet. The power supplying solar array and corresponding rechargeable battery unit, an obstruction light for visibility at night, and a lightning protection system are necessary components of the DAQ platform system. The entirety of the installation of the supporting infrastructure works are the responsibility of HDOT-A, airport management, and involved researchers. The FAA technicians from the NAPTF provide significant guidance and experience for the installation of the supporting works, although are only responsible for the actual installation of the gages during the night of the runway repaving, as well as the wiring of the DAQ in the subsequent days. Close coordination between all parties is essential for the accurate installation of the necessary infrastructure to ensure that the instrumentation installation is a success. 21

32 Figure 13. Side Profile of OGG Planned Installation Works Figure 13. Side Profile of OGG Planned Installation Works Figure 14. Overhead View of Planned Installation at OGG 22

33 Figure 14. Overhead View of Planned Installation at OGG 23

34 An actual picture of the DAQ cabinet and solar array is pictured in Figure 15, with a close-up view of the transverse gages in Figure 16. Figure 15. DAQ Cabinet (Courtesy of FAA) Figure 16. Close-up of ASGs Embedded in Base Layer (milled HMA surface) at EWR (Courtesy of FAA) 24

35 3.1.2 Installation Components and Material Procurement The procurement and planning efforts for the installation planned at OGG in 2014 were handled by the researchers in UH CEE. Unique challenges were encountered in the planning of the installation, which are included in this section for future reference in the upcoming projects at HNL and OGG. The lighting cans are used to house the ASG and TC connectors and wires. The lighting cans serve to feed the wires into conduits which are installed in a trench leading all the way to the DAQ platform. The lighting cans are also essential for bringing the wires from near the surface of the runway down to the requisite depth of 20 for buried on-runway utility lines. Most importantly, the lighting cans serve as the access point for the FAA technicians to access the connectors during the installation of the ASGs. To make the installation work as streamlined as possible, the lighting cans must be easily located and accessible. The lighting cans procured for use at OGG and HNL are 16 diameter, L-867 Class B light bases with blank covers. The LCs are installed upside down so that they may be accessed during the connection of the sensors to the wires. LCs are installed in the opposite direction when used for housing airport lights. Most LCs come with holes drilled into the side walls of the lighting cans, 2 from the base, through which the strain gage wires are pulled. It is necessary to also stipulate that a 2 hole be drilled on the side of the cans at near the other end of the can, perpendicular to the existing holes, for the purpose of connecting the conduits. Figure 17 shows an example of the LC hole locations. Removable Base Hole for ASG wires Hole for conduit Figure 17. Lighting Can Configuration Detail 25

36 During the installation of the lighting cans, an 18 diameter coring-rig is used to make holes in the asphalt on the runway. Next, the lighting cans are installed and connected to the conduits. The wires for the ASGs and TCs are then pulled through the lighting cans into the conduits, and coiled in the pullbox closest to the runway where they are temporarily stored (Figure 18). Figure 18. Wires Entering Pullbox through Conduit Openings (Courtesy of FAA) During backfilling, measures must be taken to avoid sealing the lighting-can hinges shut or letting concrete seep around the gaskets in the LC access holes. The cans need to be quickly accessible to the FAA technicians during the installation of the ASGs. All backfill of excavated areas on the runway is high early-strength concrete. Due to the fact that the lighting cans are in place before the milling machine removes the top 3 of asphalt for the repaving work, the lighting cans are installed at least 4 below the runway surface to ensure the cans are not damaged. A surveyor must also adequately mark the locations of the cans on the edge of the runway. This will make it possible to locate the LCs on the milled runway surface when it is dark or dusty, and the LCs are still covered by 1 of concrete backfill. 26

37 Like many aspects of the project, the trench design at OGG was not immune to significant change with project evolution. The minimum trench width sufficient for storing the conduits is 6. Unfortunately for the installation at OGG, the only trencher capable of digging the specified 6 wide trench was located on Oahu, and it was not transportable to Maui. The trench was redesigned for a 14 width to accommodate more standard excavating equipment that could be acquired on the island, but at a much higher cost of labor and backfilling materials. The 14 width provided enough space for a 12 backhoe bucket to excavate the trench without damaging the clean-cut edges of the trench on the runway. The on-runway trench must be refilled in high early-strength concrete, with a minimum 5000 psi strength achieved by the time that the runway opens for airplane traffic in the morning after construction. For a trench with a depth of 20, width of 14, and length of 85, as designed for the first OGG installation, the total quantity of concrete needed is approximately 7 cubic yards. Using Quikrete commercial DOT mix, this design requires the use of 278 bags of the mix, costing approximately $34 each when purchased in bulk from suppliers and shipped to Hawai`i. At a total cost of $9,452, using Quikrete is not cost effective for this type of project in Hawai`i. In the planning for OGG, a concrete supplier on Maui quoted the use of 5000 psi concrete with a sufficient curing time for under $2,000 including delivery and mixing. For HNL installation, local concrete suppliers will be pursued, with Quikrete likely serving as a fallback option. Although not an inherently critical portion of the overall installation, the design of the pullboxes requires careful consideration due to the high cost of fabrication, transportation, and installation. The pullbox design for the 2014 OGG installation underwent multiple rounds of revision. Originally, the pullboxes were designed to meet on-runway aircraft loading requirements. It was subsequently determined, however, that the specifications were well beyond the needs of a temporary access point so far to the side of the runway. In addition, the aircraftrated pullbox was exceedingly heavy to transport, and prohibitively expensive to construct. Accordingly, the pullbox rating was downgraded to roadway traffic standards, similar to what can be found on city streets, and the cost of constructing and transporting the pullboxes was halved. The depth of the pullbox is also a point of consideration, as a deeper pullbox facilitates easier wire pulling. But if the depth exceeds U.S. Department of Labor regulations for a confined space, additional ventilation and lighting precautions must be taken to ensure their safe use (US 27

38 Dept. of Labor 2007). There is also the option of casting the pullboxes in-situ to save costs in pre-casting and delivery. However, with casting in-situ, additional man-hours of work in the restricted runway area are required, and the cost and feasibility need to be compared to the relative savings in transport and installation. Installing video cameras in conjunction with strain gage systems has become a common practice for the FAA. The use of cameras can provide helpful context to raw sensor data, especially for remote monitoring and analysis. For example, at EWR the camera system is used to identify aircraft type, determine the direction for airplane landings, and gauge start and stop times for data acquisition. Cameras can also be useful in documenting surface deformations, FOD, and other externalities that can affect pavement performance. Automatic recording, pan, tilt, and zoom capabilities are attractive features for cameras accompanying ASG systems (Leake and Singh 2013b). Adequate housing for the camera system is also necessary due to the close proximity of both HNL and OGG to the Pacific Ocean, and the region s frequent exposure to high wind speeds and rain. To save power and to prevent the unnecessary recording of empty space, the camera is desired to automatically start and stop recording based on aircraft movement, and then automatically return to its original position to record the next aircraft. The data acquisition system and its accompanying power source are both supplied by the FAA in the case of the installations in Hawai`i. The DAQ itself is a small computer that can receive sensor data inputs, generate readable data files, and transmit them to a secure online database. The DAQ is housed in a supply cabinet and is powered by rechargeable batteries connected to a large solar array. Wires required for the transmission of signals from the ASGs and TCs to the DAQ are available for purchase in custom lengths or standard reels of 500 or Due to the long lead time for custom wires, 1000 lengths of wires were purchased for OGG installation in 2014, which must be cut to length before they can be installed. Another supply order setback from Kahului came by way of a minor item; the electronics potting compound used to seal the ends of the connector wires was deemed hazardous, and would not be shipped by air or sea by many manufacturers due to Department of Transportation restrictions. This is especially troubling for a project site in Hawai`i. The epoxy ultimately had to be custom mixed and shipped via UPS Red as a hazardous material, by a hard-sought supplier. 28

39 3.1.3 Construction Scheduling Unlike previously conducted installations, in which the entire runway is closed down for multiple days for all construction to be completed at once, the repaving at Kahului was to be undertaken during nights in which the airport could only be shut down for 5 hours. This translated to approximately 5 hours of actual working time for contractors to operate within, after accounting for the setup and breakdown of necessary safety lights and barricades. Construction scheduling for the installation at OGG in 2014 was one of the most critical phases in the planning of the installation. Due to the severe time constraints in the available working windows, tasks had to be planned down to the minute to be sure that all jobs were completed on time. The penalty of not finishing each night s work was the closure of the runway for the morning s flights, accompanied by severe fines associated with the subsequent rerouting of aircraft traffic to alternate landing locations. Delay is not an option when working on a runway. The first step to scheduling the work involved completing a detailed task analysis breakdown. The critical project functions are determined first, including the time required to complete each task, followed by the allocation of manpower and resources necessary to complete each job. The task analysis is an iterative project document that remained flexible enough to handle the ever-evolving nature of the demands of the project. The final task analysis includes the tasks, durations, equipment, operators (listed by name in the final schedule for use, replaced by initials for the purpose of this thesis), a visual bar chart, a manpower allocation diagram, and a histogram of the maximum workers required at any given time. These figures are provided in Appendix A. The primary solution to the imposed time constraint was to conduct the installation of the sensors in phases. The preliminary installation of supporting infrastructure was scheduled to be installed within a series of two weekends of two nights of work each, followed by a 2-hour window during the scheduled repaving in which FAA technicians from the NAPTF could come in and connect the gages. The construction would be completed with the installation of the DAQ in the days following. 29

40 The installation of the supporting infrastructure had four phases: 1. Phase 1 of the work is surveying and toning to be sure that no existing utilities are disturbed during construction. 2. Phase 2 (weekend 1 of work) consists of excavating and installing the second pullbox, and trenching 250 between the two pullboxes, installing the 2 conduits in which the wires will be housed, backfilling all excavated areas with packed earth, and installing the works at the DAQ platform including the obstruction light and lightning protection system. 3. Phase 3 (weekend 2 of work) includes the most critical tasks to be completed: coring for the lighting cans, cutting and breaking of the asphalt for trench excavation, placement of conduits and lighting cans, installation of pullbox, pulling of wire from lighting cans to pullbox 1, backfilling all exposed areas with high early strength concrete, and painting all new surface material black to match the rest of the runway. 4. Phase 4 describes the sensor installation by the FAA. On the scheduled runway repaving date, the main contractor mills off the existing surface to a 3 depth, the lighting cans are located and accessed, the sensors are installed by the FAA and connected to the wires in the lighting cans, and the runway portion is repaved. This phase includes the set-up of the DAQ system in the days following installation. The full bar charts for the construction scheduling and task analysis are included in Appendix A Construction Regulations and Safety Before the notice to proceed is issued to conduct any work on an airport runway, certain protocols must be followed to ensure that both the project and the agencies conducting the work are prepared to conform to all airport practices and standards. Completing the necessary items for construction approval is a time-intensive endeavor, and must be started months in advance of a proposed ASG installation. 30

41 The first requirement of new constructions on airport properties is the approval of the FAA 7460 form. This document details the size, purpose, construction time, permanence, and location of the proposed construction. For the installation of ASG systems, the 7460 pertains to the DAQ platform location and specifications. Due to the fact that this document needs to be reviewed by multiple departments of HDOT and FAA, the response time from submission to reception can be upwards of 6 weeks. It is essential that this document be checked thoroughly before it is sent to review, as an error may not be caught until late in review. Another time-sensitive process that is essential for airport construction projects is runway clearance training and badging for everyone involved in the project that needs to be present in the restricted area. At Kahului, badging includes classroom instruction and an exam, proof of identification with two government documents, fingerprinting, and a background check. This process is completed at the airport in which the project is to take place. Furthermore, if badged members of the construction team are going to be operating machinery on the runway at any point in the project, they must also be movement-area trained (FAA 2014). This training is an additional requirement after badging clearance is obtained, and is fulfilled by attending a movement-area-specific class and passing the associated test. Having at least one person radio-trained for each contracted company on the airport is another requirement that should be discussed early in the planning of projects. Radio training involves forty hours of class, taught in five calendar days at the airport. This training teaches the specific communication protocols to follow when in contact with the airport control tower. It is essential to have a radio trained technician on site at all times during project activity to maintain movement safety for both the project members and nearby aircraft. Although the installation of an instrumentation system is considered to be a relatively small project at an airfield, an approved Construction Safety and Phasing Plan (CSPP) is still required before any construction can take place. The approval of the CSPP involves an iterative back and forth process of feedback and adjustment, so contractors and project coordinators must plan on revising the document multiple times, with the help of airport management and HDOT- A, before approval is granted. The CSPP is a helpful and detailed document that outlines the procedures contractors will follow to ensure a safe work and runway environment at all times (Univ. of Hawai`i 2014). 31

42 Aside from the formal documented airport construction requirements, there are other considerations that project managers of sensor installation projects must be aware of. First, all aspects of the project must adhere to all released Advisory Circular documents published by the FAA for runway area constructions. Second, there must also be open channels of communication with project sponsors in the airport management, the FAA, and the HDOT-A. The airport management must always be kept in the loop with scheduling and project changes, as well as contacted for all training needs. The HDOT-A must be contacted to facilitate the scheduling of all airport runway closures and to check where existing utilities may be present on the airfield. 3.2 Planned Installation at HNL in 2016 Although external factors prevented the installation of the asphalt strain gages at OGG in 2014, the project was transferred to Runway 8L of HNL to be installed during repaving work scheduled for The strain gages are planned to be installed in the takeoff area of Runway 8L, in the asphalt section adjacent to the large concrete intersection, shown in Figure 19. This area is ideal for instrumentation due to the slow speed of aircraft (very little lift under the aircraft wings) in that section of the runway, and the extended loading time during the aircraft preparation for takeoff. Figure 19. Proposed Location of Instrumentation and DAQ at HNL (Courtesy of FAA) 32

43 CHAPTER 4. INSTALLED INSTRUMENTATION AT EWR After signs of slippage failure were detected at Runway 4R-22L near the intersection with HST-N of EWR in 2008, a rehabilitation effort was made to repair the damage before severe slippage cracking could occur. During the repaving, the NAPTF worked with the Port Authority of New York & New Jersey (PANYNJ) and airport management to install instruments at Runway 4R-22L approaching HST-N. The timeline of the project and its subsequent monitoring is given by Figure 20. The location of the instrumentation is indicated in Figure 21. Figure 20. Timeline of Instrumentation and Monitoring at EWR Figure 21. Location of the Intersection of Runway 4R-22L and HST-N at EWR (Courtesy of FAA) 33

44 Runway 4R-22L is an asphalt runway dedicated to handling aircraft landings. The portion of the runway leading into HST-N was experiencing slippage failure. The instrumentation is installed in the section of pavement indicated in Figure 22. Figure 22. Installation Location at EWR (Courtesy of FAA) The methods for installing the gages at EWR were the basis for the plans to install gages at OGG, and followed a similar process to construction scheduling described earlier. 4.1 Instrumentation Layout The design of the strain gage layout at EWR originally consisted of 32 total gages on the right-hand side of the taxiway lead line, and 16 gages on the left (looking in the direction of trafficking), as demonstrated by Figure 23. The gages are primarily positioned to capture the strains from the loadings of B /900 aircraft, the most common aircraft to land at EWR. The distance that the individual sensors are spaced apart is based on calculations performed at the NAPTF to ensure that no aircraft loading event would be inadequately recorded if the wheel path was between gages. 34

45 Figure 23. Original Strain Gage Layout Design at EWR (Courtesy of FAA) By the time of the actual installation at EWR, the design of the strain gages had been reduced by nearly half due to time constraints, much like at OGG. The final design is pictured in Figure 24, and features only the right-hand side of the original installation plan, completely eliminating the installation of ASGs on the left-hand side of the taxiway lead line. It should be noted that the labels for each ASG pair can be seen in the final layout design in Figure 24, and that the position of the overlay and base layer TSGs have been reversed from the original design in Figure

46 Figure 24. Installed Strain Gage Layout at EWR The labels of the gages at EWR are given by orientation, depth of installation, and number. Transverse gages are installed perpendicular to the direction of traffic, while longitudinal gages are parallel to the taxiway lead line. Sensors labelled with an A are installed in bottom of the HMA overlay, while sensors labelled B are installed in the top of the base layer. The TSGs are labelled 4-11, and the LSGs are labelled Figure 25 shows the relative locations of the gages with respect to the interface. Travel Direction HMA Overlay Longitudinal (B) Longitudinal (A) Transverse (A) Transverse (B) Preexisting Base Layer Figure 25. Sensor Location at EWR Relative to Interface and Travel Direction. 36

47 In addition to the ASGs, there are also four TCs installed at EWR for the purpose of recording in-pavement temperatures at various depths. The four TCs are located at depths of 0.5 (TC-A), 1.5 (TC-B), 3 (TC-C), and 5 (TC-D), as shown in Figure 26. The exact position of the TCs on the runway is not significant, as temperatures are assumed to be relatively consistent at nearby locations at the same depth. 0" 0.5" 1" 1.5" 2" 2.5" 3" 3.5" 4" 4.5" 5" 5.5" 6" TC A TC B TC C TC D Surface Overlay Interface Base Layer Figure 26. Depths of TCs Installed at EWR 4.2 Data Collection and Transmission The collection of all data in this particular type of instrumentation system is conducted remotely via the internet. Since automatic data collection can result in gigabytes of data that is too time consuming to analyze, data collection at EWR is done manually. While assisted by the installed camera monitoring system, the instrumentation at EWR is not set up to automatically detect and catalogue landing events on its own. Instead, aircraft landings can be monitored by camera to attempt to predict which aircraft may utilize HST-N, while the data recording is started and stopped at the discretion of the operator. Recordings are prioritized for especially high temperature periods of the year, when slippage failure due to delamination is theorized to occur most frequently. 37

48 4.3 InField Program The InField program is developed by HBM, for use with SoMat Data Acquisition Systems, and is a free downloadable program available at the company s website. InField is a capable plotting system that includes basic statistical analysis and filtering capabilities. For the purpose of this research, InField was used as the primary tool for displaying strain response data and cataloguing notable ASG readings. The version of InField used was version 2.5.1, released in May Viewing Data Files from EWR The native file format for data files in InField are type.sif and.sie, although the software is capable of reading and writing to more universally accessible file types like.asc and.txt for external scripting. While the number of data files analyzed for EWR was manageable by hand, for large sets of data spanning multiyear projects, it is highly suggested that an automated sorting method be programmed and employed. Data recording from the strain gages installed at EWR is controlled by the project manager at the FAA NAPTF, and is only accessible via a secure program which controls both the DAQ and camera system. Figures 27 and 28 show screenshots from the camera at EWR. Figure 27. Screenshot (1) from Camera Installed at EWR 38

49 Figure 28. Screenshot (2) from Camera Installed at EWR From the offices of the NAPTF, the camera at EWR can be angled towards the approach section of HST-N, and the recording of the strain gages can be toggled on and off as potential aircraft of interest enter the project area. Due to the geometry of the installation at EWR however, not all aircraft within the camera field pass over the sensors, because HST-N is not used by all aircraft landing on Runway 4R-22L. Additionally, even when the HST is taken, if aircraft are moving at high speeds, the strain gage readings will be miniscule due to the high amount of lift still present under the wings. Once the data files are recorded and relayed from the DAQ at EWR to the offices at the NAPTF, they are uploaded to the secure FTP site where the files can then be downloaded by researchers granted access. The files are named according to the airport code, date, and test number, and read similar to: EWR_ for a set of data obtained at EWR on February 11, 2013, in the second recorded test of the day. Opening a file in InField is straightforward, demonstrated by Figure

50 Figure 29. Opening a File in InField Program Once the data file is opened, the window will be populated with active data channels, one for each strain gage (Figure 30). Within each test there is the possibility of multiple runs being recorded. If this is the case, the list of active channels will be repeated, with the Run # column increasing for each new run. Figure 30. Active Channels List Display in InField 40

51 Double clicking on any particular channel will open up an individual plot of that sensor. Selecting a strain gage channel and clicking the button that resembles a red sinusoidal graph at the top of the window will also open an individual plot (Figure 31). Figure 31. Individual Sensor Plot in InField To view loading events in detail, plots are expanded by highlighting the portion of the plot to zoom in on, as seen in Figure 32, and then pressing the button labeled with a down-arrow. This will zoom to a close-up view of the selected plot area. Figure 33 is zoomed into the hundredths of a second on the x-axis, and is utilizing the Scale to Limits of Data function of InField to snap the y-axis to the best fit of the selected data. Figure 32. Highlighted Sensor Plot for Detailed Inspection in InField 41

52 Figure 33. Close-up View of Sensor Loading Event in InField From the close-up view, it is easy to find relevant data points for analysis, but the individual plot alone does not identify cases of possible delamination. Fortunately, InField is capable of plotting two individual sensor plots side by side (Figure 34), or up to 8 sensors at a time in an overplot (Figure 35). Figure 34. Side-by-side Individual Plot of a Sensor Pair in InField 42

53 Figure 35. Overplot of Two Sensor Channels in InField These two display options are most suited to illustrate comparisons in strain responses, as discrepancies between the readings of two gages in a pair are most easily recognized when displayed together. The overplot display is also useful for looking at many strain gage channels at once to determine if there are any consistently errant or quiet sensors. Another useful tool is to display the data sets in a tabular format for exporting to a Microsoft Excel spreadsheet. InField will take whichever portion of the plot is highlighted, and read out the exact strain responses in detail in a tabular format, as in Figure 36. Figure 36. Tabular Data Display in InField 43

54 To retrieve the peak data points, data can be selected by clicking on the points of interest in the plot (as shown by Figure 37) or by examining the numbers at timestamps of interest in the tabular format to find the maximum peak values (as above in Figure 36). Figure 37. Selecting the Peak Strain Values in InField By selecting the time at which a peak occurs, the value of each sensor at that timestamp is given as the y-coordinate at the top of the window. In this case, only the y-value of the selected base layer (blue) strain gage channel should be recorded, as indicated by the green highlighting in Figure 37. When selecting the data points of interest on the plot, it is essential to ensure that the correct data reading is identified, and that the y-coordinates for different sensor channels are not recorded incorrectly Metadata Each of the data files also contains information stored as metadata (i.e., data about the data). This metadata includes information regarding the start and stop time of the tests, which is important given that collection and analysis are performed at different times, in different locations, and by different people. Although some of the test files included notes from the time of data collection, it is helpful to use the information in the metadata to paint a clear picture of the conditions during each test. An example of the metadata display is given in Figure 38. It should be cautioned that unless otherwise programmed, the start and stop times of the data files may be displayed in Greenwich Standard Time (GST). 44

55 Figure 38. Metadata Display for Two Sensor Channels in InField Static Data Files The climatic information collected by installed thermocouples is referred to as static data. Every 30 minutes, the DAQ takes the readings of four embedded thermocouples at EWR, as well as the atmospheric temperature, and stores them in.dat type files. These files can be opened in an excel spreadsheet, and are useful when correlated to the strain gage readings of aircraft loading events. Using the metadata information regarding the start and stop time for each test, the average of the four embedded thermocouple readings for the nearest half hour timestamp is used in the data file analysis. The atmospheric temperature is also found in the static data files. To ensure that correct temperature readings were recorded at the DAQ, the temperature and weather conditions at EWR were cross-referenced with the Weather Underground website for comparison to the static data. The temperatures at the airport were correlated to the loading event times, and confirmed to be accurate to the nearest degree and hour. While the static data takes precedence over the online temperature readings at the airport, checking the temperatures also serves to check that the timestamps of the ASG tests are accurate as well. 4.4 Asphalt Strain Gage Responses Responses from ASGs vary with the orientation of the sensor (transverse or longitudinal), aircraft landing gear configuration, alignment of the wheel-paths, temperature, and interface condition. Identifying which scenario each aircraft loading event is a product of is the first step to understanding and analyzing the data. This is an especially critical step for the installation at 45

56 EWR, due to the lack of additional instrumentation which would give position, speed, weight, and type of each aircraft as it produced the loads. The maximum strain that can be recorded by the ASGs installed at EWR is ±1500 microstrains (for a total range of 3000 microstrains, as shown by Table 1). The strain in the pavement is affected by temperature, the normal force from the weight of the aircraft, the shear stresses from braking and turning, and mix properties of the pavement. As a viscoelastic material, asphalt concrete behaves differently under varying load durations. In testing at the NAPTF, it was determined that as the load duration period increases, the dynamic modulus of the pavement decreases, inducing higher strains in the asphalt concrete (Garg and Hayhoe 2001). In addition, when aircraft are traveling at high speeds, lift caused by the rapid movement of air under the wings of the aircraft reduces the strain response in the pavement layers. At Runway 4R-22L approaching HST-N of EWR, aircraft are traveling fast enough for the pavement response to be considered viscoelastic in nature. Figure 39 shows the different types of strain responses recorded at EWR for quick reference. The TSGs are shown in the first two rows, distinguishing between the types of responses recorded based on the lateral wheel position of the aircraft landing gear. The delamination evident case is shown in the right-hand column. The LSG responses are not sensitive to the lateral wheel position of the aircraft landing gear. The normal case is shown in the left column and the delamination evident case is shown in the right column. For landing gear configurations with more than once axle, the strain response behaviors remain unchanged, although will have as many visible strain peaks as landing gear axles. The subsections following will examine the differences between the strain response types in detail, and explain how each one is used to detect interlayer delamination. 46

57 Longitudinal Strain Gages Wheel Position Not Critical Wheel Next to TSG Transverse Strain Gages Wheel Over TSG Bonded Delamination Evident Overlay Base Layer Tension Compression *Not clear in delamination evident events whether wheel is directly over the gage pair or to the side. Overlay Base Layer Tension Compression Figure 39. Guide to ASG Response Types General Strain Gage Information The strain gages installed in Runway 4R-22L near HST-N of EWR and are used to measure horizontal elongation (tension) and shortening (compression) in asphalt layers. Hibbeler (2011) defines strain as normal strain, the elongation or contraction of a line segment per unit of length. The basic equation for strain is given as: ε = δ L ε = Strain (measured in microstrains) δ = Measured change in the length of the gage L = Starting length of the gage 47

58 The specific sensors installed at EWR are H-Bar Dynamic Asphalt Strain Gages (ASG/VASG) manufactured by Geocomp corporation. The gages are comprised of 4 active 350- ohm strain gages arranged in a full Wheatstone bridge circuit on a polyester bar, configured to detect longitudinal strains (Figure 40). The specifications for the gages are given in Table 1. The gages are specifically designed to withstand the high temperatures and vibratory compressive forces during asphalt installation, and are used to measure axial strains in flexible pavement in high frequency conditions (Garg 2010). This is in contrast to the thermocouples used to measure the temperature within the pavement, which produce low-frequency static data. Figure 40. Asphalt Stain Gage (Geocomp) Table 1. Dynamic Strain Gage Specifications (Geocomp) 48

59 4.4.2 Transverse Strain Gage Responses A Transverse Strain Gage (TSG) is oriented perpendicular to the direction of aircraft traffic, as shown in Figure 41. In the layout at EWR, the Overlay TSG experiences loading events prior to the Base Layer gage. Figure 41. Orientation and Layout of TSGs Transverse gages are very sensitive to the position of the passing aircraft wheels in relation to the gages. In a fully-bonded pavement interface, if a wheel passes directly over a TSG, the response is purely tensile. When a wheel is directly over a gage, the pavement bends under the vertical force of the wheel, resulting in tension in the TSG. Tension slowly relaxes back to zero after the wheel has passed, as shown in Figure 42, and the upper left corner of Figure 39 (Garg and Hayhoe 2001). Overlay Base Layer Tension Compression Figure 42. Response from TSG in Aircraft Wheel-path (Bonded) 49

60 In a fully-bonded pavement interface, any time the wheel passes to the side of the TSG the response will be purely compressive (shown in Figure 43, and central left column plot in Figure 39), because when a TSG directly under the wheel is in tension, the reactionary forces in the pavement cause the surrounding area TSGs to become compressed. Most TSG data comes from strain gages outside of the direct wheel-path. Overlay Base Layer <-- Tension Compression --> Tension Compression Figure 43. Response from TSG Outside of Aircraft Wheel path (Bonded) To see which gages the wheels of an aircraft passed over, an overlay plot of up to eight strain gages can be created, like the example shown in Figure 44. By the purely tensile readings in TSG 9 A and B (and by the reactionary compressive readings in the surrounding gages) it can be inferred that for this loading event the wheel of the aircraft passed directly over TSG pair 9. Overlay Base Layer Overlay Base Layer Overlay Base Layer Tension Compression Figure 44. Compressive Strain Due to Rollover at TSG Pair 9 (Bonded) 50

61 This same landing event (of Figure 44) can also be examined as a set of individual strain plots, as shown in Figure 45. It is still indicated that the rollover occurs at TSG pair 9 due to the purely tensile responses at that gage pair, and the purely compressive responses from the gage pairs directly to either side of TSG 9. Figure 45. Individual Plots of Compressive Strain Due to Rollover at TSG 9 (Bonded) Longitudinal Strain Gage Responses A Longitudinal Strain Gage is oriented parallel to the taxiway lead line, in line with the direction of aircraft traffic, as shown in Figure 46. The Base Layer LSGs at EWR are affected by aircraft prior to the Overlay gages. Figure 46. Orientation and Layout of TSGs 51

62 The response pattern is slight compression as the compressive wave in front of the first aircraft wheel approaches (rightmost box of Figure 44 above), sharp tension as the wheels pass the position of the LSG, followed by another slight (sometimes unnoticeable) compressive reading as the pavement recovers rapidly (Garg and Hayhoe, 2001). Responses from LSGs are not affected by the transverse position of passing aircraft wheels, and resemble Figure 47 (bottom right box of Figure 39) for a fully-bonded interface. Overlay Base Layer Tension Compression Figure 47. Typical Strain Response Profile from LSG Pair (Bonded) Effects of Aircraft Landing Configurations Different aircraft produce different loading patterns in the ASG responses. A large factor driving the difference in response is the configuration of the wheels in the aircraft landing gears. In general, there are two common categories of ASG response readings in relation to aircraft type, which can be classified by the number of peaks in the strain gage data plot. Most ASG plots will have only one peak, some will have two, and a limited number of data sets will include a strain response with three peaks. The three different loading types correspond to the three different landing gear configurations shown in Figure

63 Figure 48. Aircraft Landing Gear Configurations In the strain gage layout diagrams presented earlier in this chapter, the wheel plan of a Boeing /900 is superimposed to show the projected impact on the installed sensors. This wheel pattern corresponds to a dual wheel landing gear configuration, which is featured on the Airbus A320 as well. The dual wheel landing configuration, found on the B /900, produces one peak in the strain response plots, an example of which is given by Figure 49. A picture of a B737 dual wheel landing gear is shown in Figure 50. Overlay Base Layer Tension Compression Figure 49. TSG Response for Dual Wheel Landing Gear Configuration Inside Wheel-path (Bonded) 53

64 Figure 50. Boeing 737 Landing Gear Configuration 1 The B737 is the most trafficked aircraft model at EWR, and is therefore believed to be one of the key contributors responsible for the repeated distresses recorded at the intersection of Runway 4R-22L and HST-N. In contrast however, Mooren et al. (2014) indicate that the rigidity of multi-axle main gear configurations (dual tandem, i.e.) navigating tight turns impose the most excessive shear forces on asphalt pavements (in comparison to dual wheel configurations), due to the stiffness within the landing gear configurations of the multi-axle aircraft. Conclusions drawn from the Mooren et al. (2014) study apply primarily to tight radius pushback turns, as opposed to the gradual turns on a high-speed taxiway, and the high shear forces in the case of EWR are primarily due to high centrifugal forces. The dual tandem wheel arrangement is found on aircraft models like the Boeing 767 and Airbus A340. The consecutive wheel contact points in this landing gear configuration are responsible for creating a two-peak response in ASG event plots. In multi-axle aircraft passing over Transverse Strain Gages, the accumulation of tensile or compressive strains occurs if the following axle reaches the gage before the relaxation from the first axle has completed (Garg and Hayhoe 2001). This can be seen in Figure 51. It should be noted that the multi-axle aircraft may produce just one strain peak at gages beneath the nose gear of the aircraft, or away from the multi-axle gear in varied-gear configurations. A Boeing 767 and its dual tandem landing gear are shown in Figure

65 _A _B Incomplete Recovery Overlay Base Layer Strain Accumulation Tension Compression Figure 51. TSG Response from Dual Tandem Wheel Landing Gear Configuration, Outside of Wheel-path (Bonded) Figure 52. Boeing 767 with Dual Tandem Landing Gear 2 The final wheel arrangement strain response found at the Newark Airport is the triple dual layout. This wheel footprint is only found on the Boeing 777 and the Airbus A380. The triple dual configuration produces a three peaked strain gage response. There were no usable instances of responses containing three strain peaks in the data analyzed for this thesis Other Strain Gage Behaviors At the start of each of the recorded trials, the DAQ program is set to automatically reset every ASG data channel to zero to account for any accumulated strain in the ASGs. That means

66 that if the reading in an ASG is 100 microstrains at the moment the DAQ begins recording, the zero on the channel plot is actually a reading of 100 microstrains in the gage. While this is an incredibly useful feature, especially to account for inevitable noise and strain inherent to the pavement even at rest, this mechanism can produce skewed data trends based on how long the recording window is, and when the recording begins. One trend that tends to occur in longer recording periods is a sloped general data trend resembling Figure 53. This is likely a product of thermally induced strain produced in the pavement due to temperature change. Overlay Base Layer Overlay Base Layer Tension Compression Figure 53. Changing Strain Response without a Loading Event It should be recognized that the change in baseline readings are more pronounced in the A sensors, installed in the overlay HMA layer. The example shown in Figure 53 (above) is for Test 1 on July 16 th, 2013, recorded from 16:13 to 16:26 EST. Table 2 shows the TC readings for that time frame, and illustrates that the Temperature is highest in the overlay (1.8 ºF and 1.7 ºF), compared to the interface (0.4 ºF) and base layer (0.3 ºF), during the recording time for this particular test. Pavement Layer Overlay Interface Base Layer TC TC A TC B TC C TC D Depth 0.5 in 1.5 in 3 in 5 in Time Temperature (Fahrenheit) 16: : Temp Table 2. TC Readings for Changing Strain without a Loading Event Example 56

67 Thus, the overlay gages are more affected by the change in volume of the asphalt concrete due to the changing temperature in the pavement, and exhibit greater deviation in strain readings without the influence of a loading event. To prevent false zeroes from skewing the data, detected offsets from zero are accounted for by hand in the data collection for this thesis. The starting value of each strain gage, if not already zero, is determined and then subtracted from the recorded peak values, in order to re-zero the data channel and prevent abnormal readings Strain Gage Errors It is essential to check for broken and errant sensors throughout the course of the data collection to ensure that no misleading conclusions are drawn from faulty gage responses. Although most ASG failure is easy to recognize from the data plots, not all strain gage misreporting is obvious. The simplest gage failure to detect is an erratic sensor, as shown in Figure 54. Erratic responses are immediately recognizable in strain plots, and even need to be removed from the display so as not to interfere with the reading of the other channel plots. Overlay Base Layer Overlay Base Layer Tension Compression Figure 54. Erratic Sensor Reading, TSG 7A A difficult error to spot is a quiet sensor, like LSG 7A shown in Figure 55, as this type of sensor error can be misconstrued as delamination evidence if not examined carefully. A quiet sensor is characterized by consistently misreporting strain responses that are much lower than the surrounding gages. A large quantity of events must be examined before labelling a gage as faulty due to dampened readings. 57

68 Overlay Base Layer Overlay Base Layer Tension Compression Figure 55. Quiet Sensor Response, LSG 7A (Green) Sensors may also be missing from the data sets altogether, as in the case of TSG 4A. This may have been due to a dead connection in the sensor or DAQ, a mislabeled wiring, or the gage not being installed at all. In all, one sensor is missing (TSG 4A), one sensor is quiet (LSG 7A), and 2 sensors report errantly (TSG 7A, TSG 11A). The gages that do not work are shown with black X markings in Figure

69 Figure 56. Final Layout of Working ASGs at EWR, Broken Gages Marked with X 4.5 Data Collection Methods The data files used for analysis in this thesis were recorded between February 2013 and September Out of 34 total data files, only 17 of the files contained events with at least one response registering more than ±50 microstrains. To make use of these 17 tests, without the help of an automated program, it was imperative to outline a detailed method for reading, collecting, and sorting relevant data points Cataloguing Tests and Events of Interest The first step in data analysis is determining which tests are worth examining further. Creating a Test Characteristics Catalogue, as seen in Table 3, proved a worthwhile exercise initially for recording valuable tests, and then later on to catalogue evidence of delamination within each test. Green highlighting indicates that events within the test show aircraft loading. 59

70 Test Characteristics Catalogue Date-Test-Run Quality of Data Small events Good data Small events Good data No data No data No data No data Good data No data Good data Good data One small event No data No data No data No data Good data Good data Good data Good data Good data Good data Good data No data One small event One event No data Good data One small event One small event No data Good data Good data Table 3. Tests of Interest Catalogue Once the tests of interest have been determined, the next step is to select which specific loading events within each of the tests are of sufficient magnitude for further study. While there are many events in each of the tests, it is not beneficial to analyze every single aircraft loading 60

71 due to the fact that many of the responses are tiny blips on the plot. This is typically due to high aircraft speeds generating lift under the aircraft wings, minimizing the forces in the pavement. For this thesis, an event must contain at least one peak or trough registering at least ±50 microstrains to be considered usable. Additionally, it should be kept in mind that an aircraft loading event that produces significant strain in one pair of gages will not necessarily produce the same amount of stress in the gages that are farther away from the wheel point. Thus it is critical to examine all strain plots for all tests of interest, to see if there are any significant loading events. Once the loading events of sufficient magnitude are identified, the events of interest table is generated. Each of the events of interest are categorized by their date, test number, timestamp, time of day, ambient temperature, temperature in the thermocouples, aircraft landing gear configuration, and calculated aircraft speed. The time stamp is the location within each test where the event is located, and is useful for locating which strain is being examined within a given test. Aircraft landing gear configurations are inferred based on the types of strain gage response observed: one strain peak is classified as dual wheel landing configuration, and two strain peaks is labelled as dual tandem. The events of interest page is shown in Table 4. 61

72 No. Type of Landing Gear Date Test, Run Timestamp EVENTS OF INTEREST Time of Day Ambient Temp. TC A TC B TC C TC D Table 4. List of All Significant Aircraft Event Loadings for Analysis Avg Temp from TCs Aircraft Speed - - Units - Seconds Hours F F F F F F MPH 1 Dual Wheel 5/29/ : Dual Wheel 5/29/ : Dual Wheel 5/29/2013 2, : Dual Wheel 5/29/2013 2, : Dual Wheel 7/10/ : Dual Wheel 7/15/ : Dual Wheel 7/15/ : Dual Wheel 7/17/ : Dual Wheel 7/17/ : Dual Wheel 7/17/ : Dual Wheel 7/17/ : Dual Wheel 7/17/ : Dual Wheel 7/18/ : Dual Wheel 7/18/ : Dual Wheel 7/18/ : Dual Wheel 7/18/ : Dual Wheel 7/18/ : Dual Wheel 7/18/ : Dual Wheel 7/19/ : Dual Wheel 7/19/ : Dual Wheel 7/19/ : Dual Wheel 7/19/ : Dual Wheel 7/23/ : Dual Wheel 7/23/ : Dual Wheel 7/7/2014 2, : Dual Wheel 7/7/ : Dual Wheel 7/8/2014 1, : Dual Tandem 7/15/ : Dual Tandem 7/17/ : Dual Tandem 7/18/ : Dual Tandem 7/18/ : Dual Tandem 7/19/ : Dual Tandem 7/19/ : Dual Tandem 7/19/ : Dual Tandem 9/4/ : Dual Tandem 9/4/ : Recording Event Data Peaks Once the tests of interest have been paired down, the significant aircraft loadings within each test identified, and the broken sensors accounted for, data recording can begin. The four types of strain responses are TSG Dual Wheel, TSG Dual Tandem, LSG Dual Wheel, and LSG Dual Tandem. The TSG responses for the Boeing /900 s and similar aircraft with dual wheel landing gear patterns are the most straightforward to extract numerical data from. Singular data 62

73 peaks with a relatively slow recovery period define the loadings from dual wheel landing gear aircraft in TSGs (Figure 57). The points of interest are the respective peak strain responses and the differences between them, referred to as Δ Strain: Δ Strain = (Strain in Overlay) (Strain in Base Layer) Transverse Strain Gages for Dual Wheel Loading (Bonded) Δ Strain 1 Tension Compression Key Strain 1 Overlay Strain 1 Base Layer Overlay Base Layer Figure 57. Data Collection for Dual Wheel Loads on TSGs (Side of TSG, Bonded) The other loading responses seen in the TSG plots are created by dual tandem wheel configurations. Characterized by a two-peak response, the key data points include two strains for each gage, and therefore two Δ Strain values, as indicated in Figure 58. Whether the load is directly above the TSG, and the readings are compressive, or the load is to the side and the readings in compression (shown), the strain peaks recorded are always the most extreme points on the plot. Transverse Strain Gages for Dual Tandem Loading (Bonded) Δ Strain 1 Δ Strain 2 Tension Compression Key Strain 1 Overlay Strain 1 Base Layer Strain 2 Overlay Strain 2 Base Layer Overlay Base Layer Figure 58. Data Collection for Dual Tandem Loads on TSGs (Side of TSG, Bonded) 63

74 In the LSG data plots, there are more data points due to the compression-tension typical strain response pattern. For dual-wheel aircraft, the first compressive peak is labelled Compression 1, and the first tensile peak Strain 1. The difference between the individual strain responses is still given by Δ Strain, which is still the absolute difference between strain responses, as shown in Figure 59. The compression points are still recorded for reference. Longitudinal Strain Gages for Dual Wheel Loading (Bonded) Δ Strain 1 Tension Compression Key Compression 1 Overlay Compression 1 Base Layer Strain 1 Overlay Strain 1 Base Layer Overlay Base Layer Figure 59. Data Collection Template for Dual Wheel Loads on LSGs (Bonded) The most recording intensive ASG responses are the LSG plots for Dual Tandem wheel configurations. The compression and strain readings for each axle of the landing gear are recorded, and the two Δ Strain values are calculated according to Figure 60. Longitudinal Strain Gages for Dual Tandem Loading (Bonded) Δ Strain 1 Δ Strain 2 Tension Compression Key Compression 1 Overlay Compression 1 Base Layer Strain 1 Overlay Strain 1 Base Layer Compression 2 Overlay Compression 2 Base Layer Strain 2 Overlay Strain 2 Base Layer Overlay Base Layer Figure 60. Data Collection Template for Dual Tandem Loads on LSGs (Bonded) 4.6 Detecting Delamination with Asphalt Strain Gages Slippage failure is often discovered in areas of airport pavements regularly subjected to high shear forces. Delamination at the interface of asphalt layers is often to blame for the 64

75 slippage failure. An instrumented system designed to detect and measure interface debonding had not been implemented until EWR. The design for the instrumentation installed at EWR was created by the engineers at the NAPTF. The idea is based on the observation that for pavements with no slippage, the concentration of strain is located at the bottom of the original pavement layer, whereas in pavements that have begun to delaminate at the pavement interface, the maximum tensile strain concentration is located at the bottom of the overlay layer (Shahin 1987). This observation reflects the theory that once delamination occurs at the pavement interface, the two layers of asphalt pavement behave mechanically as separate entities. While the pavement is functioning properly and the interface is fully bonded, the asphalt layers behave as a homogenous material. The neutral axis is half way down the cross-section of the total pavement height, with a symmetrical distribution of strain throughout its entirety (Hibbeler 2011). Once delamination occurs however, the layers become independent of one another, each with their own strain distributions and neutral axes. As demonstrated by Figure 61, the realignment of the neutral axes creates a strain discrepancy at the interface, which under a shear stress results in a tensile strain in the bottom of the HMA overlay layer, and an opposing compressive strain in the top of the base layer. Figure 61. Neutral Axis Realignment as a Result of Interlayer Delamination 65

76 By placing asphalt strain gages in the bottom of the overlay and the top of the base layers of an airport pavement subjected to high shear forces, discrepancies between the readings of the ASG pairs can be identified. These instances of opposing readings are interpreted as delamination occurring at the interface. Furthermore, it was noted by Shahin (1987) that only a small amount of delamination is necessary to create strain responses in the pavement that are equal to the strain responses in a fully-debonded pavement. This indicates that as soon as the interface bond begins to weaken within the pavement layers, the strain gage pairs should be able to detect significant changes in the response pattern. Pavement layers can be modelled as beams for simplicity, and Figures 62 and 63 show the two cases. The respective neutral axes of the pavement layers are shown with dashed grey lines. In a fully-bonded pavement, both ASGs in a pair experience the same relative forces because they are located at approximately the same depth in a homogenous material experiencing forces at the surface (Figure 62). Figure 62. Fully-Bonded Pavement Modelled as a Beam In the case of delamination however, the loss of bonding at the interface causes a disruption in the shear force distribution, and the overlay ASG experiences tension, while the base layer gage experiences compression in the beam model. When the pavement layers in the delaminated pavement are modelled as a simply supported beam, or rather as two separate beams on top of one another, the ASG behavior is easily recognized as being the opposite between the sensors in a pair. Figure 63 demonstrates this model of the pavement, showing that the ASG installed in the bottom of the overlay is in tension, while the ASG in the top of the base layer gage is in compression. 66

77 Figure 63. Debonded Pavement Layers Modelled as a Beam It should be noted that tension in the overlay and compression in the base layer is not always the delamination evidence, due to wheel location and shear forces. Thus opposing signs of readings constitute evidence of delamination Evidence of Delamination in Strain Gage Responses Using the previously discussed theory, when the strain responses among pairs of ASGs are the approximately the same in value (whether in tension or compression), there is no evidence of delamination (Figure 64). Figure 64. No Delamination in LSG Pair 6 67

78 As delamination begins to occur, the difference in the strain gage responses within the ASG pair at that location begins to increase, as shown in Figure 65. These plots are classified as early indication cases, purely for reference. In the statistical analysis, early indications are still analyzed with the non-delamination cases. This ensures that the statistical analysis reflects that the instances labeled as clearly indicating delamination are significantly different than the more ambiguous responses. Figure 65. Early Indications of Delamination in LSG Pair 6 When strain responses vary drastically between two gages in a pair, it suggests that the gages are experiencing significantly different forces despite their close proximity to each other, providing evidence that delamination is occurring, and displaying the behavior demonstrated by Figure 61 (delaminated) and Figure 63. An example of visual indications of delamination in strain gages channel plots are shown below in Figure

79 Figure 66. Delamination Evidence in LSG Pair Data Plotting and Analysis After data collection is completed, the analysis begins with identifying strain peaks, as well as the differences in strain peaks (Δ Strain). These values are then compared to time of recording, temperature in the pavement, and calculated aircraft speed. Every pair of working strain gages was analyzed individually and the data tables can be found in Appendix B. A note about whether or not visual evidence of delamination is detected in the response plot is indicated for each data recording Aircraft Speed For data plotting and analysis, it is helpful to have an idea of approximately how fast an aircraft was traveling when it created the response in the strain gages. Given that the distance between gages in each gage pair are roughly 20 apart according to FAA records, the speed of the aircraft can be calculated from the lag between strain peaks between two gages in a pair. It should be stated that the speed of the aircraft is assumed to be the same if calculated at any gage pair, being that the gages are uniformly installed. Due to the principles of lift under aircraft 69

80 wings at higher velocities, it is expected that with increased speed comes deceased strain responses in the gage pairs. The basic equation for determining the speed of the aircraft is as follows: v = x t = (20 inches) time between gage readings v = velocity of the aircraft x = distance between gages t = time between strain peak responses By plotting the strain responses from the ASGs versus aircraft speed, it becomes apparent that the faster an airplane is traveling, the less of an impact on the pavement it has. Figure 67 illustrates a plot of Δ Strain versus aircraft speed for the non-delamination indicating events, and Figure 68 shows the comparison of speed and Δ Strain for the events that indicate delamination. A trend line is plotted in both Figures 67 and 68. Figure 67. Plot of Δ Strain vs. Aircraft Speed (Bonded) 70

81 Figure 68. Plot of Δ Strain vs. Aircraft Speed (Delamination) By plotting Δ Strain vs aircraft speed, it is possible to get a glimpse of what aircraft may cause the most evidence of delamination to be recorded in the ASG pairs. In both cases (bonded and delamination), it appears that the highest Δ Strain recordings were recorded at lower aircraft speeds, generally under 100 mph. This is consistent with the fact that strain is higher when the aircraft has no lift under its wings at lower speeds. It is believed that with more test data this trend would become even more apparent Temperature at the Pavement Interface Another useful comparison that can be made from the EWR data set is Δ Strain with respect to the temperature at the pavement interface, as reported by TC-C. Figures 69 and 70 illustrate the relationship between interface temperature and Δ Strain for the bonded pavement events and the delamination evident events respectively. 71

82 Figure 69. Δ Strain vs. Temperature from TC-C at the Interface (Bonded) Figure 70. Δ Strain vs. Temperature from TC-C at the Interface (Delamination) 72

83 In both the bonded and delaminated cases, as the interface temperature increases, Δ Strain increases. This data trend appears to be consistent with the hypothesis being explored by the installation at EWR, stating that delamination is most likely being caused during the hot summer months when in-pavement temperatures are very high. It is believed that with more data points this trend would be more substantial. Additionally, having data from the winter months at EWR (assuming that there are days in which HST-N is being utilized) would add a valuable perspective to this comparison, especially given that the lowest in-pavement temperature in the present recordings is over 80 ºF at the interface Responses with Respect to Time By plotting the Strain values with respect to time, spotting the emergence of delamination in each of the ASG pairs is, in theory, more readily apparent. Unfortunately, not much is easily discerned by plotting the Δ Strain values with respect to time for the data from EWR, as seen in Figure 71. A trend line is shown in both figures. The trend line reveals that Δ Strain increases with time for the shown delaminated segments, which can be expected due to the fact that once delamination has started, it only proceeds to get worse. Figure 71. Plot of Non-Delamination and Delamination Events vs. Time 73

84 Due to the somewhat intermittent schedule of recordings it is difficult to see when delamination begins overall, but by examining ASG pairs individually, a time-frame in which the delamination may have begun can be identified for a few of the gage pairs. The best example of this is LSG pair 6, which exhibits progressively more severe delamination evidence with respect to time, as shown in Figure 72. For the particular sensor pair (LSG 6), delamination appears to have started after July 2013, was fully delaminated by the first recordings in 2014, and regularly showed high Strain. The lowest Strain reading from 2014 is roughly equal to the highest Strain reading for LSG 6, and all delamination is confined to the most recent recording dates. This clearly suggests that while the pavement began as a homogenous structure at LSG 6 in 2013, by the following year the interlayer bond had deteriorated. While this is not the case for all ASG pairs installed at EWR, LSG pair 6 does show one possible progression of interlayer delamination over time (trend line shown on graph). Figure 72. LSG Pair 6 Progression with Respect to Time 74

85 In total, 7 of the 12 working ASG pairs exhibited evidence of delamination in at least one clear loading event in the data set. Table 5 illustrates the catalogued evidence of delamination in all ASG pairs with respect to the complete list of event tests. The first sign of delamination evidence for each ASG pair is in bold in the table. Table 5. Catalogue of Strain Gage Delamination Evidence in ASG Pairs After reviewing the data, it is evident that the strain gage instrumentation is successful in identifying areas of interface delamination, and determining the approximate time at which the interface failures begins to occur. For a more accurate depiction of the start of delamination in future installations, it is suggested that a highly frequent schedule of data recording be adhered to, and not limited to the summer months Magnitude and Center of Delamination with Respect to Time The ASGs that showed signs of delamination were generally located closer to the lead line of the taxiway, and no evidence of delamination was found at ASG pairs outside of 11 from the lead line. The most concentrated amount of delamination evidence was found in LSG pair 8, located 7 8 from the lead line, directly under the inner edge of the inside wheel of the superimposed B /900 landing gear configuration. Figure 73 and 74 show the 75

86 approximated degree and frequency of delamination in each of the ASGs for 2013 and 2014, respectively Key Transverse Base Layer Non-reporting 4B 5B 6B 7B 8B 9B 10B 11B Pair of non-reporting sensor 4A 5A 6A 7A 8A 9A 10A 11A Transverse Overlay No delamination indicated Longitudinal Overlay 6A 7A 8A 9A 10A 11A 12A 13A Heavy delamination 6B 7B 8B 9B 10B 11B 12B 13B Moderate delamnination Longitudinal Base Layer Minimal delamination Figure 73. Degree and Frequency of Delamination for All 2013 Events Green boxes describe only gage pairs that behave as a fully bonded interface, with no instances of delamination evidence. Minimal delamination is reserved for ASG pairs that exhibit evidence of delamination in less than 10% of the events. Moderate delamination describes gage pairs showing delamination in 20-40% of the cases. Heavy delamination is only used for gage pairs that behave like a delaminated pavement in over 40% of the recorded events Key Transverse Base Layer Non-reporting 4B 5B 6B 7B 8B 9B 10B 11B Pair of non-reporting sensor 4A 5A 6A 7A 8A 9A 10A 11A Transverse Overlay No delamination indicated Longitudinal Overlay 6A 7A 8A 9A 10A 11A 12A 13A Heavy delamination 6B 7B 8B 9B 10B 11B 12B 13B Moderate delamination Longitudinal Base Layer Minimal delamination Figure 74. Degree and Frequency of Delamination for All 2014 Events It should be noted that due to the limited data recorded, some of the sensor pairs do not have data recorded from It is assumed in these instances that the degree of interlayer delamination does not improve throughout the course of the year, and that the degree and frequency of delamination would be comparable to the previous year. 76

87 Comparing the above figures to one another, the increase in the frequency of reported delamination evidence is most evident in Longitudinal Strain Gage pair 6, which progressed from no indicated interface delamination in the 2013 recordings, to heavy delamination in Transverse Strain Gage 5 is the other sensor pair that shows an increase in the frequency of delamination occurrences, from no evidence in 2013 to one significant event showing delamination characteristics in 2014 (out of 5 total events in that year). Expanding upon the delamination maps generated above, it is possible to approximate the center of the delamination (COD) for each year. On a scale from 0-3, each of the gage pairs is given a ranking based on the previously-indicated degree and frequency of delamination evidence. For non-reporting pairs, the average of its neighboring gages is taken. If the gage has only one neighbor, the value of the neighboring gage is used. Next, the assigned weights are multiplied by their approximate position from the midline of the gage layout, shown between the two rows of gages in the following two figures, and then the average of those values is taken. The COD for 2013 is shown in Figure 75, and the COD for 2014 is given by Figure 76. Center of Delamination, 2013 Transverse Gages Avg. Non-reporting sensors No delamination indicated Heavy delamination Moderate delamination Longitudinal Gages 1 Minimal delamination Center of Delamination: -0.7 Total Extrapolated Score: 12 Total Real Score: 9 Center of Delamination, 2014 Figure 75. Center of Delamination, 2013 Figure 76. Center of Delamination, Scale Scale Transverse Gages Avg. Non-reporting sensors No delamination indicated Heavy delamination Moderate delamination Longitudinal Gages 1 Minimal delamination Center of Delamination: -2.2 Total Extrapolated Score: 19 Total Real Score: 13

88 The centers of delamination, the total sums of the delamination scores, and the sums of the real scores (only including the numbers assigned to reporting sensors) are tabulated for each year. For 2013, with a COD score of -0.6 from center, the center of delamination for 2013 is estimated at approximately 106 from the taxiway lead line, just to the outside of TSG 7 and LSG 9. The COD for 2013 is shown with an orange dashed line in Figure 75 and Figure 77. With a result of -2, the COD for 2014 is shown with a blue dashed line in Figure 76 and Figure 77, and corresponds to approximately 92 from the taxiway lead line. Figure 77 demonstrates that over time the instrumented pavement section closest to the taxiway lead line is experiencing the most total and new failure in Studies have shown that aircraft traffic follows a laterally distributed normal curve, with the most traffic down the centerline of the runway (as intended), which is likely a large part of the reason for the strain increases near the centerline (AC 150/5320-6E). The movement of the COD is entirely caused by the emergence of delamination indications in TSG pair 5 and LSG pair 6. The focal point of the delamination distribution is located to the inside of where the innermost wheel of a B /900 is estimated to make contact with the runway surface. For a right-hand curve, in which this area represents the outside edge of the wheels in relation to the turn, it makes sense that there is significant shear force at this location due. The locations of these results are consistent with the fact that the B /900 is the most trafficked aircraft at EWR. In addition to the shifting of the COD, this weighting system yields information concerning the magnitude of the overall evidence of delamination. By plotting the magnitude of delamination with respect to time, it is possible to see the acceleration of interlayer delamination. In Figure 78, the Real Score for the magnitude of delamination (only including grades from reporting sensors) is plotted in blue, and the Extrapolated Score (including the estimated values for missing gage pairs) is plotted in maroon. It is clear to see that between the summers of 2013 and 2014, delamination at the interface is reportedly increasing in magnitude and frequency. 78

89 Figure 77. Superposition of CODs on Runway 4R-22L at HST-N Figure 78. Magnitude of Total Delamination Scores Over Time 79

90 4.8 Statistical Analysis To determine whether the differences (Δ Strain) in ASG responses in recognized delamination events are significantly different than the responses lacking delamination evidence, statistical analysis methods are necessary. The frequency distributions are examined for both the delaminated and bonded events, and the data sets are compared using the Kolmogorov-Smirnoff Test. Then, correlation comparisons are used to identify the relationship between the recorded strain responses within each gage pair to see if the overlay gages are responding in the same manner as the base layer gages for the bonded cases, while responding differently in the delamination cases Frequency Distributions Frequency distributions of the Δ Strain values for the bonded and delaminated events are shown in Figure 79, and highlight how different the Δ Strain values are between the data streams. Figure 79. Frequency Distributions of Δ Strain (Bonded, Delamination) The Δ Strain values for the non-delamination (bonded) events are localized near 0, and are consistently very small, as expected due to the similar behavior between the ASGs in each gage pair. The Δ Strain values for the delamination evident events can be very loosely approximated to a normal distribution, and show a considerably larger range. By plotting the two frequency distributions on the same graph, the relationship between the Δ Strain distributions is 80

91 clearly dissimilar, as given by Figure 80. Appendix C contains the data sets from which these charts and tables are generated. Figure 80. Combined Frequency Distributions of Δ Strain Kolmogorov-Smirnoff Test Analysis The total distribution of strain gage responses for all sensor pairs are analyzed as a whole, using the Kolmogorov-Smirnoff Test (KST) to compare the Δ Strain values between delamination and non-delamination evident responses. The KST makes no assumptions about the distribution of the data, as it is a non-parametric and distribution free test, and can be used for non-normal data (Kolmogorov-Smirnov Test 2014). Using the cumulative frequencies established in the previous section, the KST is set up in Table 6. 81

92 The KST is then calculated as follows: Table 6. KST Table of All Strain Events λ α = λ = n = n 1 n 2 n 1 +n 2 = = D* = max F1*x - F2*x = λ stat = n D* = = λ α < λ stat 82

93 Thus the KST confirms that the Δ Strain values for the delamination evident events and the Δ Strain values for the bonded events are statistically different with a degree of confidence of over 99.9%. This indicates that the responses from ASGs in bonded pavement areas are different from the responses from ASGs in delamination evident areas. This is important because it confirms that the responses in the two cases are statistically and significantly different. Appendix C contains the original data sets from which these calculations were conducted Difference between Means For each strain gage pair exhibiting signs of delamination, individual statistical analysis tests are conducted to determine if the mean value of all of the delamination Δ Strain values are significantly different than the mean of the non-delamination Δ Strain and values. First, by just observing the mean, median and mode of each data stream, it is clear that the Δ Strain values are highly dissimilar for the bonded and delamination indicating events. Table 7 shows the means, medians, modes, and standard deviations of each data stream respectively. BONDED DELAMINATED Mean Median Mode Standard Deviation Table 7. Mean, Median, Mode, and Standard Deviation of Data Streams For even greater verification at the individual ASG pair level, either the Student s t-test for sample sizes fewer than 30, or the modified z-test for larger data sets is chosen to explore the statistical difference between means. All tests are grouped irrespective of aircraft landing gear type, and all Δ Strain values are considered. Once t or z has been calculated using the formulas below, the confidence (that the data sets are significantly different) is determined from standard normal and t-test distribution charts. While the individual Δ Strain distributions for each strain gage pair are not all normally distributed, the Student s t-test and z-tests are robust to deviations from normality if the sample size is not very small, (Skovlund and Fenstad 2001) and are used here only to establish an 83

94 additional layer of statistical credibility for the small data sets generated by each individual ASG pair. The formulas for the t-test and modified z-test are as follows: z = (x 1 x 2) ( σ 1 2 n 1 ) + ( σ 2 2 n 2 ) x = average of responses σ = standard deviation of responses n = number of responses Formula for z-test. t = (x 1 x 2) ( s 1 2 n 1 ) + ( s 2 2 n 2 ) x = average of responses s = standard deviation of responses n = number of responses Formula for Student s t-test. The results of this analysis further indicate that the use of Δ Strain values is a statistically significant way to detect and determine differences in responses between delamination evident pavement areas and bonded pavement areas, with confidence levels over 99% at every gage pair for the t and z tests. Appendix D contains each table for the difference between means t-tests and z-tests at individual ASG pairs Correlation Analysis Finally, correlation is used to examine the relationship between the raw strain responses in the HMA overlay ASGs with the strain responses from their respective pairs in the base layer. In a pavement with a fully bonded interface, a positive one-to-one correlation is expected and 84

95 observed (meaning low Δ Strain), as the strain responses in both layers should report highly similar strain responses. Figure 81 and Figure 82 show the correlation for fully-bonded pavement interfaces for TSGs and LSGs respectively. The correlation for the TSG normal case is 0.92, and the correlation for the LSG normal case is 0.93, which are both significantly correlated at a confidence of 99.5% (Freund and Williams 1972). Figure 81. Correlation of All TSG Pair Responses with No Delamination Evidence Figure 82. Correlation of All LSG Pair Responses with No Delamination Evidence 85

96 For areas in which delamination has begun to occur, the strain response correlations are not positively correlated, meaning that the responses in the overlay do not match the responses in the base layer, and therefore some discontinuity has started to emerge (high Δ Strain). Figures 83 and 84 demonstrate the correlations determined for TSGs and LSGs respectively. The correlations of the strain gage responses that indicate delamination have correlations of for the TSGs and 0.12 for the LSGs, which are both statistically insignificant (Freund and Williams 1972). Both plots clearly indicate that a deviation from the ideal strain gage responses is being measured. Figure 83. Correlation of All TSG Pair Responses with Delamination Evidence 86

97 Figure 84. Correlation of All LSG Pair Responses with Delamination Evidence 87

98 CHAPTER 5. SUMMARY AND CONCLUSIONS 5.1 Summary Airport pavement instrumentation provides invaluable research data for the behavior of asphalt and concrete pavement in the field. Although asphalt instrumentation systems are relatively straightforward projects to install, they become complicated by restricted construction windows and strict FAA guidelines. Additional difficulties were encountered in the attempted installation at OGG in 2014 due to location-specific variables and unforeseen circumstances. By learning from OGG, future installations at HNL and OGG are more likely to succeed. Asphalt concrete pavements are prone to many distress types, one of which being slippage failure as a result of interlayer delamination. Prior research suggests that delamination is more likely to occur in hot ambient and in-pavement temperature conditions, and at areas of high shear stresses. Runway 4R-22L of EWR experienced slippage failures near the intersection of HST-N, and was instrumented in The area of instrumented pavement is frequently subjected to high shear forces due to braking and turning, as well as very high pavement temperatures in the summer months. The instrumentation design installed in Runway 4R-22L leading into HST-N of EWR proved to be a sufficient means of detecting interfacial delamination in airport asphalt pavements. The Δ Strain for delamination cases and non-delamination cases were found to be significantly distinct. Correlation was also used to show the difference between delamination cases and non-delamination cases, by illustrating that strain responses between gages that are not delaminated are almost identical, and have a strong positive correlation. For ASG pairs reporting delamination, however, there is no correlation between the responses within the gage pairs, meaning that a discrepancy exists between the behaviors of the pavement layers. By calculating the magnitude of delamination, it was clear that overall evidence of delamination occurrences increased over time, consistent with expectations. By calculating the approximate center of delamination, the most rapidly deteriorating pavement interface locations are located closer to the taxiway lead-line, almost directly under the projected wheel path of the B737, the most-trafficked aircraft at EWR. 88

99 5.2 Conclusions The instrumentation installed in Runway 4R-22L near the intersection of HST-N of EWR successfully identified areas of interfacial delamination. The key indicator of delamination is referred to as Δ Strain in the analysis conducted within this thesis. The values for Δ Strain were markedly higher for strain gage pairs in delamination-evident areas, in comparison to areas where the pavement integrity remained high. Between 2013 and 2014 the Center of Delamination was shown to shift closer to the taxiway lead-line as more instances of new delamination evidence in 2014 were found in the innermost (lower numbered) gage pairs. The presence of delamination and slippage failure detected in the data are also confirmed by photographs taken in August 2014 showing surface shoving in the instrumented area. The delamination indicator, Δ Strain, was found to be statistically significant when comparing delamination-evident data to non-delamination-evident data, by the Kolmogorov- Smirnoff Test for all data, further supported by the difference-between-means test on an individual ASG pair level. Correlation analysis was used to illustrate that the strain gage data collected from ASG loading events not displaying evidence of delamination were highly positively correlated (0.92, 0.93), and had low Δ Strain, while the events indicating delamination had correlations closer to zero and -1 (0.12, -0.63), with higher Δ Strain values. This indicates that for ASG pairs not exhibiting signs of delamination, the responses in the overlay gages closely match the responses in the base-layer gages, indicating a bonded interface. This is not the case for delaminated pavements, which is reflected in the poor correlations in strain responses within ASG pairs. For the future strain gage installations at HNL and OGG, it is recommended that a similar strain gage instrumentation layout design be used as at EWR. It advised that the agencies responsible for conducting any future instrumentation projects in the state of Hawai`i remain cognizant of the challenges faced during the first attempted installation at OGG in Unique challenges face the implementation of a strain gage instrumentation system in Hawai`i, although monitoring pavement strains at OGG and HNL would benefit all involved agencies, and should be pursued vigorously. 89

100 APPENDICES APPENDIX A. TASK ANALYSIS FOR ATTEMPTED INSTRUMENTATION INSTALLATION AT OGG APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS APPENDIX C. STRAIN GAGE DATA TABLES AT ALL STRAIN GAGES APPENDIX D. DIFFERENCE BETWEEN MEANS T-TESTS AND Z-TESTS FOR INDIVIDUAL GAGE PAIRS

101 APPENDIX A. TASK ANALYSIS FOR ATTEMPTED INSTRUMENTATION INSTALLATION AT OGG 2014 Appendix A provides the task analysis for the proposed construction at OGG in Tasks are broken down into 4 phases: Surveying & Toning, Off-Runway Works, On-Runway Works, and FAA Responsibilities. All construction works are broken down further into more specific tasks, which are marked in 15-minute blocks of work. In phases 2 and 3, each task is assigned to the specific operator responsible for accomplishing the task, indicated by initials. The equipment required to complete each task is detailed in its own column. In phase 4, the FAA technicians responsible for installing the strain gages have completed all tasks with the assistance of hired contractors. This schedule is dictated by the FAA. 91

102 APPENDIX A. TASK ANALYSIS FOR ATTEMPTED INSTRUMENTATION INSTALLATION AT OGG 2014 PHASE 2 - NIGHT 1: OFF-RUNWAY FIRST WEEKEND - OFF-RUNWAY FIRST NIGHT Tasks Excavate pullbox 1 45 Backhoe LT Excavate pullbox 2 45 Excavator GK Place 12" base gravel, level and compact PB1 Place 12" base gravel, level and compact PB2 Place pullbox2 30 Excavator GK Excavate DAQ platfrom & lighting post footing Dur. (min) Form and prep DAQ plaform 30 Pour DAQ platform and pullboxes 90 Clean up 45 Remoe Equipment 60 Equipment 45 Backhoe, compactors LT 30 Backhoe,post digger LT SCHEDULE Operator Personnel 45 Excavator,compactors GK Place Pullbox 1 30 Backhoe LT Time (hours) FT FT FT HT CT CT CT LT LM LM LM FT PU PU PU MT MT MT MT SM HT HT HT CT SM SM SM SL SS SS SS SS LM LM LM GK PU PU PU MT MT MT HT HT HT SM SM SM SS SS SS FT FT CT CT LM LM PU PU MT MT HT HT SM SM SS SS FT FT CT CT LM LM PU PU MT MT HT HT SM SM SS SS FT FT CT CT LM LM PU PU MT MT HT HT SM SM SS SS FT FT FT FT FT FT CT CT CT CT CT CT LM LM LM LM LM LM PU PU PU PU PU PU MT MT MT MT HT HT HT HT SM SM SM SM SS SS SS SS SM SM FT SS SS CT SL SL LM PU MT MT FT FT HT HT CT CT LM LM PU PU MT MT HT HT SM SS Initial FT FT FT LM CT CT CT PU 92

103 APPENDIX A. TASK ANALYSIS FOR ATTEMPTED INSTRUMENTATION INSTALLATION AT OGG 2014 PHASE 2 - NIGHT 2: OFF-RUNWAY FIRST WEEKEND - OFF-RUNWAY SECOND NIGHT Tasks Dur. (min) Excavate trench for 2" Conduits 150 Excavator, Backhoe LT, GK Remove Pullbox Formworks 45 Place 2" conduits on trench 45 Backfill conduit trench 90 Backhoe, bobcat LT, GK Clean up 45 Remove Equipment 60 Equipment SCHEDULE Operator Personnel Time (hours) SS SS SS SS SS SS SS SS SS SS HT LM LM LM LM LM LM LM LM LM LM LT MT MT MT MT MT MT MT MT MT MT FT FT FT FT FT FT FT FT FT FT FT MT SM SM SM SM SM SM SM SM SM SM SM CT CT CT CT CT CT CT CT CT CT CT PU SL SL SL GK PU PU PU HT HT HT SS SS SS LM LM LM MT MT MT FT FT FT SM SM SM CT CT CT PU GK PU PU PU PU PU PU HT HT HT HT HT HT LM SS SS SS MT MT MT LM LM LM FT FT FT LT SM SM SM SM CT CT CT CT SS GK Initial SL SL SL SL SL SL SL SL PU PU PU PU PU PU PU SS HT HT HT HT HT HT HT LM 93

104 APPENDIX A. TASK ANALYSIS FOR ATTEMPTED INSTRUMENTATION INSTALLATION AT OGG 2014 PHASE 3 - NIGHT 1: ON-RUNWAY SECOND WEEKEND - ON-RUNWAY FIRST NIGHT Tasks Penhall coring 120 Coring Rig Penhall rep. HT Penhall Company Penhall saw cutting 120 Concrete saw 18" deep Penhall rep. LT Unload, connect 2" conduits, lay in trench; lighting cans Dur. (min) Breaking AC Pull wire from lighting cans to Pullbox 1 60 Clean-up work area 30 Remove all equipment and tools 14 Equipment Excavator, Backhoe, Hoeram Vacuum, wire pulling tool Backfill on-runway trench w/concrete 60 Vibrator, trowels Laborers Water truck, power wash SCHEDULE Operator Personnel LT, GK Paint runway 30 Paint brushes, rollers Laborers SL Laborers Time (hours) SS SS SS SS SS SS SS SS SS SS FT LM LM LM LM LM LM LM LM LM LM MT MT MT MT MT MT MT MT MT SM CT CT CT CT CT CT CT CT CT FT FT FT FT FT FT SL SM SM SM SM SM SM SS FT FT FT FT FT FT LM SM SM SM SM SM SM PU HT HT PU PU PU PU GK PU PU MT MT MT MT CT CT CT CT SL SL SL SL FT FT SM SM PU PU MT MT MT MT CT CT CT CT SL SL SL SL FT FT FT FT SM SM SM SM PU PU PU PU GK GK GK GK LT LT LT LT HT HT HT HT SL SL SL SL SS SS LM LM FT FT SM SM CT CT LT LT PU PU GK GK HT HT SL SL Initial 94

105 APPENDIX A. TASK ANALYSIS FOR ATTEMPTED INSTRUMENTATION INSTALLATION AT OGG 2014 PHASE 3 - NIGHT 2: OFF-RUNWAY - ELECTRICAL SECOND WEEKEND - OFF-RUNWAY SECOND NIGHT Tasks Install electrical wiring for obstruction light and lightning conductor Dur. (min) 150 Remove all equipment and tools 30 Equipment SCHEDULE Operator Personnel Pull wire from pullbox 1 to DAQ platform 120 SL Clean-up work area 30 SL Time (hours) MT MT MT MT MT MT MT MT HT CT CT CT CT LT SL SL SL SL SL SL SL SL FT FT FT FT FT MT SM SM SM SM SM SM SM SM SM PU PU PU PU PU PU PU PU CT GK GK GK GK GK GK GK GK SL LT LT LT LT LT LT LT LT SS HT HT HT HT LM SL SL SL SL SL SL SL SL PU HT HT HT HT HT HT HT HT HT GK CT CT CT CT CT CT CT CT CT FT FT FT FT FT FT FT FT FT MT MT SL SL SM SM PU PU GK GK LT LT SL SL MT MT SL SL SM SM PU PU GK GK LT LT SL SL Initial 95

106 APPENDIX A. TASK ANALYSIS FOR ATTEMPTED INSTRUMENTATION INSTALLATION AT OGG 2014 PHASE 4 - FAA Installation Kahului Airport Sensor Installation - Operations of Sensor Installation on Runway 2-20 Dur (hrs.) Locate lighting can & chip off concrete 1 HR Remove can lid & chip concrete away near ports/openings for cables 1/2 HR Lay out sensor configuration on Runway 1 HR Cross cut with walk-behind saw (Dwg. 2) 1 HR Side cuts with hand saw (Dwg. 2) 1 HR Saw cuts to light can 1/2 HR Shop vac, dusting, cleaning 5 HR Asphalt binder/tack coat 1 HR Install milled surface sensors & binder over 1 HR Place lid on light can 1/2 HR Collect all cables/wires into Handhole 1 1/2 HR Pack up & Get out 1/2 HR Responsibility Special Instructions FAA use demolition hammer FAA to run wires from sensors to light cans Notes: 1. Sensors will be installed when the milling takes place at the section. Wires from sensors to be connected to lighting can on same night. 2. Lighting can location marking should be made Wires with connectors installed before FAA arriva 4. The schedule activities and durations are subject to change and improvements. 5. This schedule is only a guide. 96

107 No. Date Test No. Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain in Bottom of Overlay (Rebound 1) Strain in Top of Base Layer (Rebound 1) Strain Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Appendix B contains all data sheets for each strain gage pair. Every strain gage pair that contains two working gages has its own table of recorded values (all ASGs not shown are either broken or missing). These are the original tables in which strain responses were recorded, Strain calculated, and the presence of delamination evidence determined. Longitudinal Strain Gage Landing Events ASG: 6 L Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D D-C 1 5/29/ : no event 2 5/29/ : no event 3 5/29/2013 2, : no event 4 5/29/2013 2, : no event 5 7/10/ : no 6 7/15/ : no event 7 7/15/ : no 8 7/17/ : no event 9 7/17/ : no event 10 7/17/ : no event 11 7/17/ : early ind. 12 7/17/ : no event 13 7/18/ : no 14 7/18/ : no 15 7/18/ : no 16 7/18/ : no 17 7/18/ : no 18 7/18/ : no event 19 7/19/ : no event 20 7/19/ : early ind. 21 7/19/ : no event 22 7/19/ : no event 23 7/23/ : no 24 7/23/ : no event 25 7/7/2014 2, : delam. 26 7/7/ : delam. 27 7/8/2014 1, : delam. 97

108 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression in Bottom of Overlay Compression in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Compression 2 in Bottom of Overlay Compression 2 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 2 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 6 L Dual Tandem Loadings Units Units No. Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D E F G H D-C H-G 28 7/15/ : no 29 7/17/ : no event 30 7/18/ : no 31 7/18/ : no event 32 7/19/ : no event 33 7/19/ : no event 34 7/19/ : no 35 9/4/ : delam. 36 9/4/ : delam. 98

109 No. Date Test No. Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 1 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG 8 L Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D D-C 1 5/29/ : early ind. 2 5/29/ : early ind. 3 5/29/2013 2, : early ind. 4 5/29/2013 2, : early ind. 5 7/10/ : no event 6 7/15/ : no event 7 7/15/ : early ind. 8 7/17/ : no event 9 7/17/ : early ind. 10 7/17/ : early ind. 11 7/17/ : early ind. 12 7/17/ : delam. 13 7/18/ : delam. 14 7/18/ : delam. 15 7/18/ : delam. 16 7/18/ : delam. 17 7/18/ : delam. 18 7/18/ : delam. 19 7/19/ : no event 20 7/19/ : delam. 21 7/19/ : delam. 22 7/19/ : delam. 23 7/23/ : early ind. 24 7/23/ : early ind. 25 7/7/2014 2, : no event 26 7/7/ : no event 27 7/8/2014 1, : delam. 99

110 Longitudinal Strain Gage Landing Events ASG 8 L Dual Tandem Loadings No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 2 in Top of Base Layer Compression 2 in Bottom of Overlay Compression 2 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 4 Delamination Evidence Units Units No. Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D E F G H D-C H-G 28 7/15/ : no event 29 7/17/ : no 30 7/18/ : erly. Ind. 31 7/18/ : erly. Ind. 32 7/19/ : no event 33 7/19/ : delam. 34 7/19/ : delam. 35 9/4/ : delam. 36 9/4/ : delam. APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS 100

111 No. Date Test No. Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 1 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 9 L Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D D-C 1 5/29/ : no 2 5/29/ : no event 3 5/29/2013 2, : no 4 5/29/2013 2, : no 5 7/10/ : no event 6 7/15/ : no event 7 7/15/ : no event 8 7/17/ : no 9 7/17/ : no event 10 7/17/ : no 11 7/17/ : no 12 7/17/ : no 13 7/18/ : no 14 7/18/ : no event 15 7/18/ : no 16 7/18/ : early ind. 17 7/18/ : no 18 7/18/ : delam. 19 7/19/ : no 20 7/19/ : delam. 21 7/19/ : early ind. 22 7/19/ : no event 23 7/23/ : no event 24 7/23/ : no event 25 7/7/2014 2, : no event 26 7/7/ : no event 27 7/8/2014 1, : early ind. 101

112 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Compression 2 in Bottom of Overlay Compression 2 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 2 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 9 L Dual Tandem Loadings Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Fahrenhe it Units Units No. Seconds Hours MPH F F F F Labels A B C D E F G H D-C H-G 28 7/15/ : no 29 7/17/ : no event 30 7/18/ : no 31 7/18/ : no 32 7/19/ : no event 33 7/19/ : no 34 7/19/ : no 35 9/4/ : no 36 9/4/ : no event 102

113 No. Date Test No. Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 1 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 10 L Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D D-C 1 5/29/ : no 2 5/29/ : no 3 5/29/2013 2, : no 4 5/29/2013 2, : no event 5 7/10/ : no event 6 7/15/ : delam. 7 7/15/ : delam. 8 7/17/ : no event 9 7/17/ : no 10 7/17/ : no 11 7/17/ : no 12 7/17/ : delam. 13 7/18/ : no 14 7/18/ : no 15 7/18/ : no 16 7/18/ : no event 17 7/18/ : delam. 18 7/18/ : delam. 19 7/19/ : early ind. 20 7/19/ : no 21 7/19/ : no 22 7/19/ : no 23 7/23/ : early ind. 24 7/23/ : no event 25 7/7/2014 2, : no event 26 7/7/ : no event 27 7/8/2014 1, : no event 103

114 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Compression 2 in Bottom of Overlay Compression 2 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 2 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 10 L Dual Tandem Loadings Units Units No. Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D E F G H D-C H-G 28 7/15/ : early ind. 29 7/17/ : /18/ : early ind. 31 7/18/ : no 32 7/19/ : no 33 7/19/ : no 34 7/19/ : no event 35 9/4/ : no 36 9/4/ : no event 104

115 No. Date Test No. Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 1 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 11 L Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D D-C 1 5/29/ : no 2 5/29/ : no 3 5/29/2013 2, : no 4 5/29/2013 2, : no 5 7/10/ : no event 6 7/15/ : no 7 7/15/ : no 8 7/17/ : no event 9 7/17/ : no event 10 7/17/ : no 11 7/17/ : no 12 7/17/ : no 13 7/18/ : no 14 7/18/ : no event 15 7/18/ : no 16 7/18/ : no 17 7/18/ : no event 18 7/18/ : no 19 7/19/ : no 20 7/19/ : no event 21 7/19/ : no event 22 7/19/ : no 23 7/23/ : no event 24 7/23/ : no 25 7/7/2014 2, : no event 26 7/7/ : no event 27 7/8/2014 1, : no event 105

116 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Compression 2 in Bottom of Overlay Compression 2 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 2 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 11 L Dual Tandem Loadings Units Units No. Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D E F G H D-C H-G 28 7/15/ : no event 29 7/17/ : /18/ : no 31 7/18/ : no 32 7/19/ : no 33 7/19/ : no 34 7/19/ : no event 35 9/4/ : no 36 9/4/ : no event 106

117 No. Date Test No. Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 1 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 12 L Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D D-C 1 5/29/ : no 2 5/29/ : no 3 5/29/2013 2, : no event 4 5/29/2013 2, : no 5 7/10/ : no event 6 7/15/ : no 7 7/15/ : no 8 7/17/ : no event 9 7/17/ : no event 10 7/17/ : no event 11 7/17/ : no event 12 7/17/ : no 13 7/18/ : no 14 7/18/ : no event 15 7/18/ : no event 16 7/18/ : no event 17 7/18/ : no event 18 7/18/ : no 19 7/19/ : no 20 7/19/ : no event 21 7/19/ : no event 22 7/19/ : no 23 7/23/ : no event 24 7/23/ : no event 25 7/7/2014 2, : no event 26 7/7/ : no event 27 7/8/2014 1, : no event 107

118 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Compression 2 in Bottom of Overlay Compression 2 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 2 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 12 L Dual Tandem Loadings Units Units No. Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D E F G H D-C H-G 28 7/15/ : no event 29 7/17/ : no 30 7/18/ : no 31 7/18/ : no 32 7/19/ : no 33 7/19/ : no 34 7/19/ : no event 35 9/4/ : no 36 9/4/ : no event 108

119 No. Date Test No. Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 1 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 13 L Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D D-C 1 5/29/ : no event 2 5/29/ : no 3 5/29/2013 2, : no event 4 5/29/2013 2, : no event 5 7/10/ : no event 6 7/15/ : no event 7 7/15/ : no 8 7/17/ : no event 9 7/17/ : no event 10 7/17/ : no event 11 7/17/ : no event 12 7/17/ : no event 13 7/18/ : no event 14 7/18/ : no 15 7/18/ : no event 16 7/18/ : no event 17 7/18/ : no event 18 7/18/ : no event 19 7/19/ : no event 20 7/19/ : no event 21 7/19/ : no event 22 7/19/ : no 23 7/23/ : no event 24 7/23/ : no event 25 7/7/2014 2, : no event 26 7/7/ : no event 27 7/8/2014 1, : no event 109

120 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Compression 1 in Bottom of Overlay Compression 1 in Top of Base Layer Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Compression 2 in Bottom of Overlay Compression 2 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 2 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Longitudinal Strain Gage Landing Events ASG: 13 L Dual Tandem Loadings Units Units No. Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains Labels A B C D E F G H D-C H-G 28 7/15/ : no event 29 7/17/ : no 30 7/18/ : no 31 7/18/ : no 32 7/19/ : no 33 7/19/ : no 34 7/19/ : no event 35 9/4/ : no event 36 9/4/ : no event 110

121 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 1 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Transverse Strain Gage Landing Events ASG: 5 T Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains A B A-B 1 5/29/ : no 2 5/29/ : no event 3 5/29/2013 2, : no 4 5/29/2013 2, : no 5 7/10/ : no event 6 7/15/ : no event 7 7/15/ : no event 8 7/17/ : no 9 7/17/ : no 10 7/17/ : no 11 7/17/ : no 12 7/17/ : no 13 7/18/ : no 14 7/18/ : no 15 7/18/ : no 16 7/18/ : no 17 7/18/ : no 18 7/18/ : no 19 7/19/ : no 20 7/19/ : no 21 7/19/ : no 22 7/19/ : no event 23 7/23/ : no 24 7/23/ : no 25 7/7/2014 2, : delam. 26 7/7/ : no 27 7/8/2014 1, : no 111

122 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 2 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Transverse Strain Gage Landing Events ASG: 5 T Dual Tandem Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains A B C D A-B C-D 28 7/15/ : no 29 7/17/ : no event 30 7/18/ : no 31 7/18/ : no 32 7/19/ : no 33 7/19/ : no 34 7/19/ : no event 35 9/4/ : no 36 9/4/ : no 112

123 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 1 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Transverse Strain Gage Landing Events ASG: 6 T Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains A B A-B 1 5/29/ : no 2 5/29/2013 2, : no 3 5/29/ : no event 4 5/29/2013 2, : no 5 7/10/ : no event 6 7/15/ : no event 7 7/15/ : no 8 7/17/ : no 9 7/17/ : no 10 7/17/ : no 11 7/17/ : no 12 7/17/ : delam. 13 7/18/ : no 14 7/18/ : no 15 7/18/ : no 16 7/18/ : early ind. 17 7/18/ : no 18 7/18/ : early ind. 19 7/19/ : no 20 7/19/ : no 21 7/19/ : no 22 7/19/ : delam. 23 7/23/ : no 24 7/23/ : no 25 7/7/2014 2, : no 26 7/7/ : no event 27 7/8/2014 1, : early ind. 113

124 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 2 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Transverse Strain Gage Landing Events ASG: 6 T Dual Tandem Loadings Units Units Seconds Hours MPH F F F F F microstrain microstrain microstrain microstrain microstrain microstrain A B C D A-B C-D 28 7/15/ : no 29 7/17/ : no 30 7/18/ : no 31 7/18/ : no 32 7/19/ : delam. 33 7/19/ : no 34 7/19/ : no 35 9/4/ : no 36 9/4/ : no 114

125 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 1 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Transverse Strain Gage Landing Events ASG: 8 T Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains A B A-B 1 5/29/ : no 2 5/29/ : no event 3 5/29/2013 2, : no 4 5/29/2013 2, : no 5 7/10/ : no event 6 7/15/ : no 7 7/15/ : delam. 8 7/17/ : early ind. 9 7/17/ : no event 10 7/17/ : no 11 7/17/ : no 12 7/17/ : delam. 13 7/18/ : early ind. 14 7/18/ : no 15 7/18/ : no 16 7/18/ : no 17 7/18/ : delam. 18 7/18/ : delam. 19 7/19/ : no 20 7/19/ : no 21 7/19/ : no 22 7/19/ : no 23 7/23/ : no 24 7/23/ : yes 25 7/7/2014 2, : no event 26 7/7/ : no event 27 7/8/2014 1, : no 115

126 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 2 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Transverse Strain Gage Landing Events ASG: 8 T Dual Tandem Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains A B C D A-B C-D 28 7/15/ : no 29 7/17/ : no 30 7/18/ : no 31 7/18/ : no 32 7/19/ : no 33 7/19/ : early ind. 34 7/19/ : no 35 9/4/ : delam. 36 9/4/ : no event 116

127 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 1 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Transverse Strain Gage Landing Events ASG: 10 T Dual Wheel Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains A B A-B 1 5/29/ : no event 2 5/29/ : no 3 5/29/2013 2, : no event 4 5/29/2013 2, : no event 5 7/10/ : no event 6 7/15/ : no 7 7/15/ : no 8 7/17/ : no event 9 7/17/ : no event 10 7/17/ : no 11 7/17/ : no 12 7/17/ : no 13 7/18/ : no event 14 7/18/ : no event 15 7/18/ : no event 16 7/18/ : no event 17 7/18/ : no event 18 7/18/ : no 19 7/19/ : no 20 7/19/ : no event 21 7/19/ : no event 22 7/19/ : no 23 7/23/ : no event 24 7/23/ : no event 25 7/7/2014 2, : no event 26 7/7/ : no event 27 7/8/2014 1, : no event 117

128 No. Date Test Timestamp Time of Day Speed TC A TC B TC C TC D Ambient Temperature Strain 1 in Bottom of Overlay Strain 1 in Top of Base Layer Strain 2 in Bottom of Overlay Strain 2 in Top of Base Layer Strain 1 Strain 2 Delamination Evidence APPENDIX B. INDIVIDUAL STRAIN GAGE RESPONSE REPORTS Transverse Strain Gage Landing Events ASG: 10 T Dual Tandem Loadings Units Units Seconds Hours MPH F F F F F Microstrains Microstrains Microstrains Microstrains Microstrains Microstrains A B C D A-B C-D 28 7/15/ : no event 29 7/17/ : no 30 7/18/ : no 31 7/18/ : no 32 7/19/ : no 33 7/19/ : no 34 7/19/ : no event 35 9/4/ : no event 36 9/4/ : no event 118

129 APPENDIX C. STRAIN GAGE DATA TABLES AT ALL STRAIN GAGES Appendix C contains the charts from which the KST calculations for all gage pairs were conducted. The first chart is for all events that do not appear to be evident of delamination, labelled as Bonded Pavement, and the second chart is for the Delaminated Pavement. 119

130 APPENDIX C. STRAIN GAGE DATA TABLES AT ALL STRAIN GAGES 120

131 APPENDIX D. DIFFERENCE BETWEEN MEANS T-TESTS AND Z-TESTS FOR INDIVIDUAL GAGE PAIRS For the charts in Appendix D, only full gage pairs that have events which are characterized as indicative of delamination are included. Thus if one of the gages in a gage pair is malfunctioning, or there is no evidence of delamination at that ASG pair during this trial, no statistical analysis of this type is performed at that gage. The gages included are: L6, L8, L9, L10, T5, T6, and T8. LSG Pair 6 T-test for the Difference between Means 121

132 APPENDIX D. DIFFERENCE BETWEEN MEANS T-TESTS AND Z-TESTS FOR INDIVIDUAL GAGE PAIRS LSG Pair 8 T-test for the Difference between Means 122

133 APPENDIX D. DIFFERENCE BETWEEN MEANS T-TESTS AND Z-TESTS FOR INDIVIDUAL GAGE PAIRS LSG Pair 9 T-test for the Difference between Means 123

134 APPENDIX D. DIFFERENCE BETWEEN MEANS T-TESTS AND Z-TESTS FOR INDIVIDUAL GAGE PAIRS LSG Pair 10 T-test for the Difference between Means 124

135 APPENDIX D. DIFFERENCE BETWEEN MEANS T-TESTS AND Z-TESTS FOR INDIVIDUAL GAGE PAIRS TSG Pair 5 Z-test for the Difference between Means 125

136 APPENDIX D. DIFFERENCE BETWEEN MEANS T-TESTS AND Z-TESTS FOR INDIVIDUAL GAGE PAIRS TSG Pair 6 Z-test for the Difference between Means 126

137 APPENDIX D. DIFFERENCE BETWEEN MEANS T-TESTS AND Z-TESTS FOR INDIVIDUAL GAGE PAIRS TSG Pair 8 Z-test for the Difference between Means 127