2010 FAA Worldwide Airport Technology Conference Atlantic City, New Jersey April 20 – April 22.
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Transcript of 2010 FAA Worldwide Airport Technology Conference Atlantic City, New Jersey April 20 – April 22.
2010 FAA Worldwide Airport Technology Conference
Atlantic City, New JerseyApril 20 – April 22
2
Analysis and Design of Airfield Pavements Using Laboratory Tests
and Mechanistic – Empirical Methodology
Lorina Popescu, P.E., UCPRCRita Leahy, P.E., APACACarl Monismith, P.E., UCPRC
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
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
5
Establish Mix Design Criteria for Taxiways Using the Simple Shear
Test
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
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
8
Simple Shear Test (SST)
Evaluate the permanent deformation characteristics of FMFC cores;
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);
11
RSST test results on field extracted cores
1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
0 2 4 6 8 10 12
Air-Void Content
Re
petit
ions
to 5
% S
hear
Str
ain
High Stability Mixes
AR 8000 Mixes
95% reliability (5% probability of failure)
80%
10%
50%
12
Binder content selection
1.0E+03
1.0E+04
1.0E+05
1.0E+06
Asphalt content (percent)
Re
pe
titi
on
s t
o 5
pe
rcen
t s
he
ar
str
ain
(lo
g)
Design asphalt / binder content
N = 100,000 at 80 %
Each point is the average of 3 test results
13
Notes
Stiffness alone is not sufficient for mix design
Repeated loading used to arrive at design binder content
14
Estimate Permanent Deformation Using Laboratory
Tests and M-E Methodology
15
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;
16
NDIA project outlook
Environment - Desert
Avg temperature –> 40C (104F)May - Sep
Avg Annual Rainfall –70mm (2¾ in)Oct - Mar
17
NDIA Project outlook
Typical aircraft loading 51,250 to 56,000 lb/tire
Tire pressure 215 to 220 lb/in2
18
Rutting Susceptibility Laboratory Tests
Hamburg Wheel Tracking Device Captures the combined effects of rutting
and moisture damage; Mixture was both moisture and rut
resistant
19
Rutting Susceptibility Laboratory Tests
RSST-CH Asphalt content: optimum & optimum “+”
for sensitivity analysis 122F (50C) 5000 load cycles;
20
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.
21
Performance tests results
10
100
1000
10000
1.0E-06 1.0E-03 1.0E+00 1.0E+03 1.0E+06
Reduced Frequency, Hz (20C Reference Temp)
Dyn
amic
Mo
du
lus,
k/i
n2
Optimum Optimum Plus
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 1000 2000 3000 4000 5000
Load Cycle
Per
man
ent
Sh
ear
Str
ain
, %
Optimum Optimum Plus
22
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;
i = f(, e,N)
24
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;
25
Accumulation of Inelastic/Plastic Strain "Optimum" and "Optimum + 0.5% Mixes"
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0 300 600 900 1200 1500Number of days (5yrs x 244 days/yr)
Cum
ulat
ive
Inel
astic
/Pla
stic
Stra
in
Cumulative inelastic strain AC optimum Cumulative inelastic strain Opt + 0.5%
26
Notes
RSST-CH test helped identify the target binder content and the construction control limits (±0.25%)
27
Airfield Pavement Design Example Using Long-Life Highway Design
Concepts
28
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;
29
Pavement Structural Section Design for Wide-Bodied Aircraft
Use of ME procedure Multilayer elastic program Laboratory flexural fatigue and stiffness
data
30
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*TempFatigue Life PG 64-16:
E (ln nf) = -36.5184-0.6470*AV-6.5315*lnstn
31
Analysis – Pavement Structure
4 in PBA-6a*(PG64-40), 4.7% AC, 6% AV, E = f(Temp)
12 inches AB
(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)
SG
32
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 s
33
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
34
Yuma: Tensile Strain vs. Asphalt Layer Thickness
1
10
100
1000
10 15 20 25 30 35 40
Total AC Thickness (in)
Ten
sile
str
ain
(H
MA
bo
tto
m)
(mic
rost
rain
)
Yuma Aug-B777 Yuma Aug - B747 Yuma Aug - A380Yuma Jan - B777 Yuma Jan - B747 Yuma Jan - A380
35
Check Fatigue Resistance for 25in Asphalt Thickness
25in asphalt layer thickness: Aug: Avg t = 180 s, Nf=5*107
Jan: Avg t = 105 s, Nf=7*108
20 years: 5*106 operations 1.25*106 operations over 4 warmer
months 3.75*106 operations over 8 cooler months
36
Check Fatigue Resistance for 25in Asphalt Thickness
Apply linear summation of cycle ratio cumulative damage hypothesis – Miner criteria
Shell subgrade strain criteriav=2.8*10-2*N-0.25
37
Construction Considerations
38
Construction Considerations
NDIA project RSST-CH tests suggested tighter binder
content tolerances ±0.25% asphalt binder content
39
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.4 4.6 4.8 5 5.2 5.4
As-constructed average asphalt content (%)
Sim
ula
ted
ES
AL
s t
o 1
0%
ru
ttin
g (
15
mm
or
more
rut
de
pth
) exp
resse
d a
s f
ractio
n o
f ta
rge
t E
SA
Ls
0.114
0.19
0.266
As-constructed
standard deviation of
asphalt content (%)
Influence of As-Constructed Asphalt Content on Rutting Performance
40
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
41
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)
42
Concluding Notes
Potential savings: More effective use of materials Ability to estimate long term
performance
THANK YOU!