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2010 FAA Worldwide Airport Technology Conference

2010 FAA Worldwide Airport Technology Conference. Atlantic City, New Jersey April 20 – April 22. Analysis and Design of Airfield Pavements Using Laboratory Tests and Mechanistic – Empirical Methodology. Lorina Popescu, P.E., UCPRC Rita Leahy, P.E., APACA Carl Monismith, P.E., UCPRC. Outline.

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2010 FAA Worldwide Airport Technology Conference

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  1. 2010 FAA Worldwide Airport Technology Conference Atlantic City, New Jersey April 20 – April 22

  2. Analysis and Design of Airfield Pavements Using Laboratory Tests and Mechanistic – Empirical Methodology Lorina Popescu, P.E., UCPRC Rita Leahy, P.E., APACA Carl Monismith, P.E., UCPRC 2

  3. Outline • Introduction • Establish mix design criteria for taxiways using Simple Shear Test • Estimate permanent deformation using laboratory tests and M-E methodology • Airfield pavement design example using long-life performance concepts • Construction considerations & concluding notes 3

  4. Introduction • SHRP developed tests • Simple Shear Test (AASHTO T-320, ASTM D-7312) RSST-CH • Flexural Fatigue Test (AASHTO T-321, ASTM D-7460) • SHRP tests and new analysis methods adapted to evaluate HMA performance with large commercial aircraft loading 4

  5. Establish Mix Design Criteria for Taxiways Using the Simple Shear Test 5

  6. San Francisco International AirportProject outline • Distresses observed • shoving and rutting in AC turn areas of taxiway - slow moving and sharp turning • rutting distortions (dimpling) under static loading • Different trial mixes to mitigate rutting problem • Cores extracted from distressed areas 6

  7. San Francisco International AirportProject outline • AC mixes in full compliance with FAA mix design • Enhancements to FAA mix design to reduce observed rutting • High Stability mix • SHRP Simple Shear Test primary tool used to evaluate mix rutting performance 7

  8. Simple Shear Test (SST) • Evaluate the permanent deformation characteristics of FMFC cores; 8

  9. Simple Shear Test (SST) • Sample size: D=6 in, H=2 in; • Shear stress: 10 psi (69kPa) • Loading time 0.1 sec; 0.6 sec rest period; • Test temperature 122F (50C); 9

  10. RSST test results on field extracted cores 11

  11. Binder content selection 12

  12. Notes • Stiffness alone is not sufficient for mix design • Repeated loading used to arrive at design binder content 13

  13. Estimate Permanent Deformation Using Laboratory Tests and M-E Methodology 14

  14. Estimate rutting performance - NDIA project outlook • New Doha International Airport – due to open July 2011; • All HMA TW/RW • Built partially on reclaimed land; • Two parallel runways; • 40 gate terminal; 15

  15. NDIA project outlook Environment - Desert • Avg temperature – > 40C (104F) May - Sep • Avg Annual Rainfall – 70mm (2¾ in) Oct - Mar 16

  16. NDIA Project outlook • Typical aircraft loading • 51,250 to 56,000 lb/tire • Tire pressure • 215 to 220 lb/in2 17

  17. Rutting Susceptibility Laboratory Tests • Hamburg Wheel Tracking Device • Captures the combined effects of rutting and moisture damage; • Mixture was both moisture and rut resistant 18

  18. Rutting Susceptibility Laboratory Tests • RSST-CH • Asphalt content: optimum & optimum “+” for sensitivity analysis • 122F (50C) • 5000 load cycles; 19

  19. Rutting Susceptibility Laboratory Tests • Shear Frequency Sweep test data • Asphalt content:optimum & optimum “+” • 3 temperatures (4C, 20C and 46C); • 3 frequencies (0.1Hz, 1Hz and 10Hz); • Develop master curve to determine shear modulus with temperature and loading rate. 20

  20. Performance tests results 21

  21. Rutting Susceptibility Mechanistic Empirical Approach • Mechanistic approach to determine the accumulation of plastic strain; • Rutting in AC is assumed to be controlled by shear deformation; • Time hardening principle applied to calculate cumulative plastic strain due to shear deformation; • gi = f(t, ge,N) 22

  22. Rutting Susceptibility Mechanistic Empirical Approach • Analysis assumptions: • Aircraft operations uniformly distributed throughout the year; • Plastic strain accumulated during the warmest months; • Plastic strain accumulated 8 hrs/day; • 50% of aircraft operations at max. weight • No aircraft wander; 24

  23. 25

  24. Notes • RSST-CH test helped identify the target binder content and the construction control limits (±0.25%) 26

  25. Airfield Pavement Design Example Using Long-Life Highway Design Concepts 27

  26. Pavement Structural Section Design for Wide-Bodied Aircraft • Lab test data from I-710, LA County – Long Life Performance concept; • Carries traffic into and out of the Port of Long Beach; • ADT = 155,000 vehicles/day; • 13% trucks; 28

  27. Pavement Structural Section Design for Wide-Bodied Aircraft • Use of ME procedure • Multilayer elastic program • Laboratory flexural fatigue and stiffness data 29

  28. Estimate Elastic Modulus and Fatigue Life Elastic Modulus • PBA-6a*: E (ln stif) = 9.1116-0.1137*Temp • PG 64-16: E (ln stif) = 14.6459-0.1708*AV-0.8032*AC-0.0549*Temp Fatigue Life • PG 64-16: E (ln nf) = -36.5184-0.6470*AV-6.5315*lnstn 30

  29. Analysis – Pavement Structure 4 in PBA-6a*(PG64-40), 4.7% AC, 6% AV, E = f(Temp) (TBD) PG 64-16, 4.7% AC, 6% AV E=f(AV, AC, Temp) 3 in PG 64-16 RB, 5.2% AC, 3% AV E = f(AV, AC, Temp) 12 inches AB SG 31

  30. Data Analysis Factorial • Three wide-bodied aircraft types: • Boeing 747-400 • Airbus 380-800 • Boeing 777-800 • Design to strain levels at the bottom of the HMA layer: ~100, 200, 300 ms 32

  31. Data Analysis Factorial • Two climate zones: • Desert area – Yuma, AZ • Coastal region – San Francisco, CA • Temperature: • Aug (hotter month) • Jan (Yuma), Feb (SF) – colder month • Temperature at 1 in depth increments – EICM to determine layer stiffness for ME analysis 33

  32. Yuma: Tensile Strain vs. Asphalt Layer Thickness 34

  33. Check Fatigue Resistance for 25in Asphalt Thickness • 25in asphalt layer thickness: • Aug: Avg et =180 ms, Nf=5*107 • Jan: Avg et =105 ms, Nf=7*108 • 20 years: 5*106 operations • 1.25*106 operations over 4 warmer months • 3.75*106 operations over 8 cooler months 35

  34. Check Fatigue Resistance for 25in Asphalt Thickness • Apply linear summation of cycle ratio cumulative damage hypothesis – Miner criteria • Shell subgrade strain criteria ev=2.8*10-2*N-0.25 36

  35. Construction Considerations 37

  36. Construction Considerations • NDIA project • RSST-CH tests suggested tighter binder content tolerances • ±0.25% asphalt binder content 38

  37. Influence of As-Constructed Asphalt Content on Rutting Performance 39

  38. Construction Considerations • Long Life Performance project • AV 4% - 6% rut-resistant upper and intermediate HMA layer; • Desirable AV <=3% - rich bottom layer • Increased fatigue life – key for long life performance • Tack coat essential between lifts 40

  39. Concluding Notes • Shear Test was useful for: • HMA design • Establishing performance criteria under repeated trafficking on taxiways • Examine materials response at more than one binder content – more effective use of different quantities of binder (rich bottom concept) 41

  40. Concluding Notes • Potential savings: • More effective use of materials • Ability to estimate long term performance 42

  41. THANK YOU!

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