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Pavement Design Tools & Pavement Design Tools & Their Relevance to Their Relevance to Canadian AirportsCanadian Airports
Susan Tighe, Ph.D, P.EngSusan Tighe, Ph.D, P.EngCanada Research Chair in Pavement Canada Research Chair in Pavement
& Infrastructure Management& Infrastructure ManagementAssociate ProfessorAssociate Professor
Civil EngineeringCivil EngineeringUniversity of WaterlooUniversity of Waterloo
2007 SWIFT Conference, CAPTG Workshop2007 SWIFT Conference, CAPTG WorkshopCalgary, ABCalgary, AB
September 16, 2007September 16, 2007
AcknowledgementsAcknowledgements
Leanne Whiteley, University of WaterlooLeanne Whiteley, University of Waterloo
Greater Toronto Airports AuthorityGreater Toronto Airports Authority
Natural Science & Engineering Research Natural Science & Engineering Research Council of CanadaCouncil of Canada
Presentation OutlinePresentation OutlineIntroductionIntroductionBackground: Airport Pavement DesignBackground: Airport Pavement DesignAirport Design ToolsAirport Design ToolsRelevance to Canadian AirportsRelevance to Canadian AirportsConclusionsConclusionsQuestionsQuestions
Introduction: DesignIntroduction: DesignPavement ThicknessPavement ThicknessFreezing Index (FI)Freezing Index (FI)Mean Annual Average Mean Annual Average Temperature (MAAT)Temperature (MAAT)Subgrade TypeSubgrade TypeDesign AircraftDesign AircraftWheel LoadWheel LoadMaximum Gross WeightMaximum Gross WeightMaximum TakeMaximum Take--Off WeightOff WeightTire Contact AreaTire Contact AreaConstruction ConstraintsConstruction Constraints
RESEARCHRESEARCH
WorkingWorking
ResearchResearch
Management LoopManagement Loop
LoopLoop
DATA BASEDATA BASE
Component Activities and DecisionsComponent Activities and Decisions
Planning andPlanning andProgrammingProgramming
DesignDesign ConstructionConstruction MaintenanceMaintenance InIn--ServiceServiceEvaluationEvaluation
IntroductionIntroduction
IntroductionIntroductionENVIRONMENTENVIRONMENT
LOADINGLOADING
CONSTRUCTIONCONSTRUCTION
STRUCTURESTRUCTURE
MAINTENANCEMAINTENANCE
Measure(s)Measure(s)ofof
ServiceabilityServiceabilityoror
DeteriorationDeterioration
LayerLayerThicknessesThicknessesLayer TypesLayer Types& Properties& Properties
VariationsVariationsin Thicknessin Thickness& Properties& Properties
SubgradeSubgrade TypeType& Properties& Properties
MoistureMoisture
RadiationRadiation
TemperatureTemperature(Min., Max,(Min., Max,
00 Days, etc.)Days, etc.)Freeze-thawFreeze-thaw
CyclesCycles
LoadsLoadsTire TypesTire Types& Pressures& Pressures
TreatmentsTreatmentsSpacing,Speed,Speed,RepetitionsRepetitions MethodsMethods
QualityQualityTimingTiming
TimingTiming
MethodsMethodsAs-Built QualityAs-Built Quality
VarianceVariance
AgeAge
Flexible Design MethodsFlexible Design Methods
Transport Canada (TC)Transport Canada (TC)Federal Aviation Administration Federal Aviation Administration (FAA) CBR Method(FAA) CBR MethodFAA Layered Elastic Design FAA Layered Elastic Design (LEDFAA)(LEDFAA)Asphalt Institute SWAsphalt Institute SW--11Australian Airport Pavement Australian Airport Pavement Structural Design System (APSDS) Structural Design System (APSDS)
BackgroundBackground
Transport Canada/Public Works airport Transport Canada/Public Works airport pavement design based onpavement design based on–– Frost protectionFrost protection
Freezing Index Freezing Index minimum depth of pavement structureminimum depth of pavement structure
–– Gear loadingGear loadingAircraft structural flexible design charts Aircraft structural flexible design charts pavement pavement equivalent granular thicknessequivalent granular thicknessAircraft structural rigid design charts Aircraft structural rigid design charts concrete slab concrete slab thicknessthickness
ASGASG--19, TC/PW19, TC/PW
INPUTSINPUTSFreezing IndexFreezing IndexSubgrade bearing Subgrade bearing strength/surface strength/surface bearing modulusbearing modulusAircraft (weight, tire Aircraft (weight, tire pressure, % on main pressure, % on main gear)gear)
OUTPUTSOUTPUTSFLEXIBLE: Pavement FLEXIBLE: Pavement equivalent granular equivalent granular thickness, tthickness, t
SWSW--1, Asphalt Institute 1, Asphalt Institute
INPUTSINPUTSMean annual air Mean annual air temperaturetemperatureAircraft typeAircraft typeMovements in design Movements in design periodperiodSubgrade strength Subgrade strength measuremeasure
OUTPUTSOUTPUTSRequired thickness of Required thickness of new HMA pavementnew HMA pavement
APSDS, MINCAD (Australia)APSDS, MINCAD (Australia)
INPUTSINPUTSTrafficTrafficWander statisticsWander statisticsLayered system Layered system (material, thickness (material, thickness and strength)and strength)
OUTPUTSOUTPUTSMaterial type (asphalt Material type (asphalt vs. subgrade)vs. subgrade)Maximum damage Maximum damage values (damage factor values (damage factor & critical strain) for & critical strain) for each aircrafteach aircraftMaximum of total Maximum of total damagedamage
LEDFAA , FAALEDFAA , FAA
INPUTSINPUTSPavement structure Pavement structure propertiesproperties–– Layer materialLayer material–– Layer thicknessLayer thickness–– Layer strengthLayer strength
Aircraft propertiesAircraft properties–– gross taxi weightgross taxi weight–– annual departuresannual departures–– % annual growth% annual growth
OUTPUTSOUTPUTSSurface, base, Surface, base, subbase, subgrade subbase, subgrade –– ThicknessThickness–– ModulusModulus–– Poisson’s RatioPoisson’s Ratio–– StrengthStrength
Aircraft CDF Aircraft CDF contribution, CDF Max contribution, CDF Max for Aircraftfor Aircraft
Equivalent Granular ThicknessEquivalent Granular Thickness
Granular Base Equivalency (GBE) is a measure Granular Base Equivalency (GBE) is a measure expressing the contribution of each pavement expressing the contribution of each pavement component of an equivalent thickness of granular component of an equivalent thickness of granular basebase
TAC, 1997
ComponentComponent Thickness (mm)Thickness (mm) GBEGBEAsphalt concreteAsphalt concrete 100100 100 x 2 = 200100 x 2 = 200Crushed baseCrushed base 250250 250 x 1 = 250250 x 1 = 250Granular baseGranular base 500500 500 x 1 = 500500 x 1 = 500Total thicknessTotal thickness 850850 EGT = 950EGT = 950
Design Method InputsDesign Method Inputs
Design MethodDesign Method ClimateClimate TrafficTrafficSubgradeSubgradeStrengthStrength
TCTC XX** XX1,21,2 XXFAAFAA XX** XX22 XXLEDFAALEDFAA XX XXSWSW--11 XX**** XX22 XXAPSDSAPSDS XX XX
* Freezing Index * Freezing Index ** ** Mean Average Air TemperatureMean Average Air Temperature11 No volume consideration No volume consideration 2 2 Design aircraft concept Design aircraft concept
AirportAirportDesign InputsDesign InputsToronto (YYZ)Toronto (YYZ) Waterloo (YKF)Waterloo (YKF)
FI (FI (ooCC--days)days) 598598 711711
MAAT (MAAT (ooC)C) 1010 7.27.2
TrafficTraffic AircraftAircraft A330A330--300, A340300, A340--300,300,A340A340--500/600, 500/600, B747B747--400, 400, B777B777--200ER,200ER,B777B777--200LR,200LR,B777B777--300ER, 300ER, LL--10111011--500500MDMD--1111
A320A320--200, BAe200, BAe--146146--100,100,Challenger, Dash 8, Challenger, Dash 8, Cessna 152, 172, 210,Cessna 152, 172, 210,650, 650, ConvairConvair 440,440,Falcon, DCFalcon, DC--4,4,GulfstreamGulfstream,,LearjetLearjet, Piper Seminole,, Piper Seminole,Saab 340Saab 340
SurfaceSurface 125 mm AC125 mm AC 100 mm AC100 mm AC
BaseBase 300 mm Granular A300 mm Granular A 300 mm Granular A300 mm Granular A
SubbaseSubbase 900 mm Granular B900 mm Granular B 340 mm Granular B340 mm Granular B
SubgradeSubgrade CBR=4.5, S=77.75CBR=4.5, S=77.75 CBR=4.5, S=77.75CBR=4.5, S=77.75
Material Material LayersLayers
ClimateClimate
Design InputsDesign Inputs
FlexibleFlexibleFlexible
-50%
-30%
-10%
10%
30%
50%TC
/PW
SW
-1
APS
DS
LEDF
AA
TC/P
W
SW
-1
APS
DS
LEDF
AA
YYZ YFK
Airport & Method
Equi
vale
nt G
ranu
lar
Thic
knes
s Re
lativ
e to
TC
/PW
Toronto (YYZ) Toronto (YYZ) -- FlexibleFlexible
YYZ - Flexible
-50%
-30%
-10%
10%
30%
50%
TC/PW SW-1 APSDS LEDFAA
Method
Equi
vale
nt G
ranu
lar
Thic
knes
s R
elat
ive
to
TC/P
W
CBR=3 CBR=4 CBR=4.5 CBR=5 CBR=6
Waterloo (YKF) Waterloo (YKF) -- FlexibleFlexible
YKF - Flexible
-50%
-30%
-10%
10%
30%
50%
TC/PW SW-1 APSDS LEDFAA
Method
Equi
vale
nt G
ranu
lar
Thic
knes
s Re
lativ
e to
TC
/PW
CBR=3 CBR=4 CBR=4.5 CBR=5 CBR=6
Sources of DataSources of Data20%
0%
13%
20%13%
34%AltanticQuebecOntarioPrairiePacificNorthern
60%13%
7%
7%
13%
National Airport SystemRegional/ LocalArcticRemoteUnclassified
Airport Region
Airport Type
Within Program Sensitivity AnalysisWithin Program Sensitivity Analysis
Subgrade StrengthSubgrade Strength–– California Bearing Strength California Bearing Strength
(CBR)(CBR)ClimateClimate–– Freezing Index (FI)Freezing Index (FI)–– Mean Annual Average Mean Annual Average
Temperature (MAAT)Temperature (MAAT)
TrafficTraffic–– Aircraft CharacteristicsAircraft Characteristics
Maximum Gross Maximum Gross Weight (MGW)Weight (MGW)Maximum TakeMaximum Take--Off Off Weight (MTOW)Weight (MTOW)Wheel LoadWheel LoadTire Contact AreaTire Contact Area
–– Aircraft Volume Aircraft Volume ((% annual growth)% annual growth)
Sample sensitivity analysis Sample sensitivity analysis EGT vs. MGW for TC flexibleEGT vs. MGW for TC flexible
Transport Canada Flexible
0250500750
1000125015001750
0 1000 2000 3000 4000
Design Aircraft Maximum Gross Weight (kN)
Equi
vale
nt
Gra
nula
r Th
ickn
ess
(mm
)
Very Low Low Medium High
(Very Low ) (Low ) (Medium) (High)
Asphalt Cement = 2 GBE Granular Base = 1 GBE Asphalt Cement = 2 GBE Granular Base = 1 GBE
GBE=Granular Base EquivalencyGBE=Granular Base Equivalency
Between Program Data AnalysisBetween Program Data Analysis
Variation significanceVariation significance
Airport specific thickness vs. design Airport specific thickness vs. design method analysismethod analysis
Airport specific design method relative Airport specific design method relative comparison comparison
Sample Sample –– Variation SignificanceVariation Significance
Flexible EGTFlexible EGTTC vs. TC vs.
Method VariabilityMethod VariabilitySignificanceSignificance
TCNFTCNF aa
FAAFAA rr
LEDFAALEDFAA aa
FEDFAAFEDFAA aa
SWSW--11 aa
APSDSAPSDS rr
aa denotes significant variability at a 95% confidence level denotes significant variability at a 95% confidence level rr denotes no significant variability at a 95% confidence leveldenotes no significant variability at a 95% confidence level
Sample Sample –– Airport vs. Design MethodAirport vs. Design Method
Very
Low
Low
Med
ium
Stro
ng
0
7.50
5001000
1500
2000
2500
Equivalent Granular
Thickness (mm)
CBR
% Annual Growth
LEDFAA Flexible - Toronto ON
Between Program Flexible ResultsBetween Program Flexible Results
SubgradeSubgrade strength & strength & annual growthannual growth
statistically significantstatistically significant
Change inChange in subgradesubgradestrength more significant strength more significant than an in traffic of up than an in traffic of up to 10%to 10%
TC with frost protection & TC with frost protection & FAA with stabilized base FAA with stabilized base
most conservative most conservative flexible pavement structureflexible pavement structure
LEDFAA & FAA with LEDFAA & FAA with stabilized base most stabilized base most closely relate to TC flexible closely relate to TC flexible design outputdesign output
ConclusionsConclusions
Layer thicknesses increase as CBR Layer thicknesses increase as CBR values decreasevalues decreaseSWSW--1 & APSDS are generally more 1 & APSDS are generally more conservative for large airports than conservative for large airports than TC/PWTC/PWSWSW--1 & APSDS are less conservative 1 & APSDS are less conservative for small airports than TC/PWfor small airports than TC/PW
ConclusionsConclusionsThe FAA flexible pavement thickness The FAA flexible pavement thickness increases dramatically once the increases dramatically once the subgradesubgrade is is reduced to a CBR of 6 (weak reduced to a CBR of 6 (weak subgradesubgradestrength)strength)
FAA flexible = f (design aircraft maximum FAA flexible = f (design aircraft maximum gross weight)gross weight)
LEDFAA, FEDFAA, SWLEDFAA, FEDFAA, SW--1, APSDS more 1, APSDS more sensitive to sensitive to subgradesubgrade (vs. traffic)(vs. traffic)
RecommendationsRecommendationsGeometric design analysisGeometric design analysis–– impact on pavement design and performanceimpact on pavement design and performance
Comparison new design methods (FAARFIELD)Comparison new design methods (FAARFIELD)
New stateNew state--ofof--the art designs do not necessarily account the art designs do not necessarily account for the climatic conditions experienced in Canadafor the climatic conditions experienced in Canada
Incorporate economic analysis into the design and Incorporate economic analysis into the design and planning stageplanning stage