FAA Worldwide Airport Technology Conference by sanmelody

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									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



                         2
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
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
 Establish Mix Design Criteria for
Taxiways Using the Simple Shear
               Test




                 5
San Francisco International Airport
         Project 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
San Francisco International Airport
         Project 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
Simple Shear Test (SST)


                   Evaluate the
                    permanent
                    deformation
                    characteristics of
                    FMFC cores;




              8
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
RSST test results on field extracted
cores
                                  10,000,000
                                                                                  High Stability Mixes
                                   1,000,000
                                                                                  AR 8000 Mixes
Repetitions to 5 % Shear Strain




                                    100,000


                                                                                                         95% reliability
                                     10,000
                                                                                                         (5% probability
                                                                                                         of failure)
                                       1,000
                                                                                                         80%

                                                                                                         50%
                                        100

                                                                                                         10%
                                         10


                                          1
                                               0   2   4          6           8                 10             12
                                                           Air-Void Content


                                                           11
                    Binder content selection
                                              1.0E+06
Repetitions to 5 percent shear strain (log)




                                              1.0E+05                     N = 100,000
                                                                          at 80 %


                                                                                        Each point is
                                                                                        the average
                                                                                        of 3 test
                                              1.0E+04
                                                                                        results



                                                                   Design asphalt /
                                                                   binder content
                                              1.0E+03
                                                        Asphalt content (percent)




                                                           12
 Notes

 Stiffness alone is not sufficient for mix
  design

 Repeated loading used to arrive at
  design binder content




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



              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
NDIA project outlook


Environment - Desert

 Avg temperature –
    > 40C (104F)
    May - Sep

 Avg Annual Rainfall –
    70mm (2¾ in)
    Oct - Mar

                          16
 NDIA Project outlook


 Typical aircraft loading
   51,250 to 56,000 lb/tire

 Tire pressure
   215 to 220 lb/in2




                        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
        Rutting Susceptibility
          Laboratory Tests



 RSST-CH
  Asphalt content: optimum & optimum “+”
   for sensitivity analysis
  122F (50C)
  5000 load cycles;



                    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
                         Performance tests results
                                           Optimum    Optimum Plus                                                               Optimum   Optimum Plus
                        10000                                                                                   3.0
2




                                                                                    Permanent Shear Strain, %
                                                                                                                2.5
Dynamic Modulus, k/in




                         1000                                                                                   2.0

                                                                                                                1.5

                          100
                                                                                                                1.0

                                                                                                                0.5
                           10
                           1.0E-06     1.0E-03     1.0E+00    1.0E+03     1.0E+06                               0.0
                                                                                                                      0   1000      2000     3000     4000   5000
                                 Reduced Frequency, Hz (20C Reference Temp)                                                          Load Cycle




                                                                              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
     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
                                                    Accumulation of Inelastic/Plastic Strain
                                                   "Optimum" and "Optimum + 0.5% Mixes"
                           0.35
Inelastic/Plastic Strain




                           0.30

                           0.25
      Cumulative




                           0.20

                           0.15

                           0.10

                           0.05

                           0.00

                                  0         300             600                  900          1200           1500
                                                        Number of days (5yrs x 244 days/yr)

                                                                 25
                           Cumulative inelastic strain AC optimum            Cumulative inelastic strain Opt + 0.5%
Notes

 RSST-CH test helped identify the
  target binder content and the
  construction control limits (±0.25%)




                   26
Airfield Pavement Design Example
 Using Long-Life Highway Design
             Concepts



               27
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
Pavement Structural Section
Design for Wide-Bodied Aircraft

 Use of ME procedure
   Multilayer elastic program
   Laboratory flexural fatigue and stiffness
    data




                      29
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
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
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
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
Yuma: Tensile Strain vs. Asphalt
       Layer Thickness
                                             1000
 Tensile strain (HMA bottom) (microstrain)




                                             100




                                              10




                                               1
                                                    10   15             20               25            30          35    40
                                                                             Total AC Thickness (in)

                                                              Yuma Aug-B777       Yuma Aug - B747      Yuma Aug - A380
                                                              Yuma Jan - B777     Yuma Jan - B747      Yuma Jan - A380

                                                                                    34
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
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
Construction Considerations




             37
Construction Considerations

 NDIA project
   RSST-CH tests suggested tighter binder
    content tolerances
     ±0.25% asphalt binder content




                     38
Influence of As-Constructed
Asphalt Content on Rutting
Performance
                                                    4.00                                                                As-
                                                                                                                    constructed
 Simulated ESALs to 10% rutting (15mm or more
 rut depth) expressed as fraction of target ESALs




                                                                                                                     standard
                                                    3.50                                                            deviation of
                                                                                                                      asphalt
                                                                                                                    content (%)
                                                    3.00
                                                                                                                       0.114
                                                    2.50                                                               0.19
                                                                                                                       0.266
                                                    2.00


                                                    1.50


                                                    1.00


                                                    0.50


                                                    0.00
                                                           4.4   4.6         4.8           5            5.2   5.4

                                                                 As-constructed average asphalt content (%)


                                                                                     39
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
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
Concluding Notes

 Potential savings:
   More effective use of materials
   Ability to estimate long term
    performance




                     42
THANK YOU!

								
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