m. emin kutay, phd, pe - michigan state universitykutay/training/session-1_v2.pdf• four classes of...

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING

M. Emin Kutay, PhD, PE

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Day 2 –Mechanistic-Empirical Pavement Design

1 • Commonpavementdesignapproaches

2 • PavementStructuralAnalysis

3 • PavementMEInputs

4 • PavementMEInputs(cont’d)andmodels

5 • Localcalibration

6 • Examples2

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Asphalt Pavement Design

Pavement structural design •  Determination of

•  Number of layers •  Thickness of the layers •  Type of materials to be used in each layer

Material design •  Asphalt mixture design

•  Determination of – Asphalt binder content – Aggregate gradation

•  Aggregate/soil mixture design •  Determination of

– Aggregate gradation –  Limit plasticity/swelling etc

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Pavement Design Procedures around the World Empirical: -  Based solely on engineering experience -  The result of the systematic collection of condition data over a period of time

and a statistical correlation of design variables with this performance information

Analytical: -  Employs a pavement response model to calculate stresses and/or strains,

induced by a wheel load . -  These calculated values are then compared with permissible values. -  The permissible values are obtained from a back-calculation of structures that

are known to perform well. Mechanistic/Empirical: -  Performance models à pavement deterioration -  Requires input data obtained from laboratory tests -  Predict the performance of pavements under specified traffic and climatic

conditions.

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Plans for Using MEPDG (As of 2014)

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING PavementMEDesignLicenseeMap-US

RI

DC

State

AZ

Puerto Rico

Pavement ME Design FY2018 (as of 9/1/17)

County/CityFHWA

not licensing - 10

Maricopa County

not yet renew ed in FY18 - 3

licensing - 41

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Pavement ME Design Licensee Map - Canada

Licensing

Not Yet Renewed

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Western Europe

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Green - temperate regions of north west Europe (cool summers and mild winters). Yellow- extreme climates of central and eastern Europe (hot summers and cold winters). Blue - colder countries of northern Europe. Red - hotter Mediterranean regions.

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Design Methods in EU

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING France (Analytical)

•  A linear, multi-layer elastic model (Burmister's model) is used to calculate •  Tensile stresses and strains at the bottom of the bound

layers •  Vertical compressive strains at the top of the unbound

layers •  Induced by an axle load of 130kN at 15oC.

•  Four classes of bearing capacity of the subgrade

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Germany (Empirical)

•  Pavements are initially assessed according to the requirement for frost resistance.

•  The natural ground and subgrade must meet minimum requirements in respect of load-bearing capacity and degree of compaction.

•  Layer thicknesses •  Different standard design types. •  The selection of design type is based upon economic

considerations •  Regional experience and environmental factors.

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Poland (Mechanistic)

•  A catalogue of typical flexible pavements •  Based on a mechanistic model and calculations of typical

structures. •  A multi-layer elastic model is used to calculate:

horizontal stress and strain at the bottom of the asphalt layer and vertical compressive stress and strain at the top of the subgrade.

•  Total thickness of asphalt pavements is designed to limit fatigue cracking of no more than 20% at the surface; a

•  Rutting no more than 12.5mm.

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Australia

•  The design method is an analytical approach employing the linear elastic program, CIRCLY.

•  Stress dependency of granular materials is considered

•  Granular layers are divided into sublayers with the stiffness modulus of a layer, up to a limiting value, depending on the layer beneath.

•  Generally direct measurement of material properties is preferred but the Shell nomogram can be used to estimate asphalt stiffness modulus.

•  The charts in the design guide have been established using the Shell asphalt fatigue criteria.

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Japan •  The Japanese method is an empirical method which is

based on results of the AASHO Road Trial that have been modified in the light of Japanese experience.

•  The method is based around traffic classification of the number of heavy vehicles per day.

•  For each class, a required coefficient of relative strength and a required thickness must be achieved dependent on subgrade CBR values and subject to economic considerations.

•  The structural number is determined from design curves associated with a pavement serviceability index of 2.5 and from this, the layer thicknesses are calculated using layer equivalencies. For cold regions, pavement thickness must exceed the frost penetration depth.

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING New Zealand •  New Zealand: The New Zealand method is based upon the

Shell method. •  Pavement thicknesses are determined from a cumulative

equivalent standard axle loading and a weighted mean annual air temperature of either 12° or 16°C.

•  Design curves calculated from criteria to control structural rutting of the subgrade and fatigue of the underside of the asphalt layer.

•  Terminal condition and distress are expressed as a serviceability index. Permissible values for this index arc dependent upon road classification.

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Shell Method

•  The Shell Pavement Design Manual is an analytical method that was first published in 1978

•  The subgrade strain criterion was determined from an analysis of the AASHO Road Trial. The permissible value of subgrade strain is associated with a present serviceability index of 2.5.

•  The fatigue criterion is based on laboratory test data multiplied by a shift factor to account for effects of climatic and loading conditions on the road.

•  Measured fatigue characteristics can be used but they are usually obtained from a nomogram. This also applies to asphalt stiffness modulus.

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING South Africa •  The country is divided into 3 climatic zones. For a specific

category of road the design life to strengthening is selected on economic grounds. For economically important roads it is 20 years.

•  The cumulative traffic in terms of 80 kN ESALs is estimated using the fourth power law.

•  The materials and the design CBR at the 10% level of significance are chosen.

•  The designer may use one of a number of design procedures; analytical, AASHTO.

•  CBR cover curves or catalogue design from the design manual. •  Whatever method is used, estimates of future maintenance

must be considered based on net present cost.

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Report – COST 333 - 2000

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Europe - Asphalt design thicknesses for ESAL = 100million

6”

12”

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Design Methods in EU

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AASHTO 1993 design

Asphalt Pavement Structural Design


Traffic Estimation

Soil Properties

Layer Properties

Components of a Pavement Design

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= + + +1 1 2 2 2 3 3 3 ...a D a D m aN D mS

Layer Properties: AASHTO1993designmethod

(Stiffness)

𝑎↓2 

𝑎↓3 

𝑎↓1  𝐷↓1 

𝐷↓2 

𝐷↓2 

𝐒𝐭𝐫𝐮𝐜𝐭𝐮𝐫𝐚𝐥 𝐍𝐮𝐦𝐛𝐞𝐫 (𝐒𝐍)→𝐂𝐚𝐩𝐚𝐜𝐢𝐭𝐲

Layer coefficient

Thickness Drainage coefficient


Layer Properties: AASHTO1993designmethod

𝑎↓2 

𝑎↓3 

𝑎↓1  𝐷↓1 

𝐷↓2 

𝐷↓2 


Functionoftraffic

𝑆𝑁>SNneeded

SNneeded

= + + +1 1 2 2 2 3 3 3 ...a D a D m aN D mS

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( )

⎡ ⎤Δ⎢ ⎥

−⎢ ⎥= + + − + + −⎢ ⎥+⎢ ⎥+⎣ ⎦

10

10 18 10 10

5.19

log4.2 1.5log (W ) 9.36 [log ( 1)] 0.20 2.32 log ( ) 8.071094

0.41

R o R

PSI

Z S SN M

SN

AASHTO 1993 design procedure

TrafficDeterioration Subgrade

stiffness

Structuralcapacity

Uncertainity

Structuralcapacity

givenSN SNgiven =structuralnumberprovided where ai= ith layer coefficient Di= ith layer thickness (inches) mi= ith layer drainage coefficient)

= a1D1 + a2D2m2 +a3D3m3 + .........

Stiffness/modulus

SN =structuralnumberneeded ≥givenSN SN

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Example AASHTO 1993 excel sheet

ESALs 38,000,000

Reliability, % 85 Zr -1.04

St. Dev. 0.45 Po 4.20 Pt 2.50

ΔPSI 1.70 CBR% 35.00

Subgrade Mr 24865 AC1 AC2 AC3 AC4 AC5 AC6 UNB1 UNB2 UNB3 UNB4 CBM1 CBM2

Layer Coefficient 0.44 0.44 0.40 0.14 Thickness (mm) 50 70 70 0 0 0 100

Thickness (in) 1.97 2.76 2.76 0.00 0.00 0.00 3.94 0.00 0.00 0.00 0.00 0.00Drainage Coefficient 1 1 1 1 1 1 1.20 1.20 1.00 1.00 1.00 1.00

ProvidedSNfromstructure(SNp)= 3.84

RequiredSNfromtraffic(SNreq)= 3.83 Chk.ESAL:37,979,484

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING TRAFFIC ASSESSMENT

(GF)(HGV%)(TF)(D%)(LN%)(365days/ yr)iESAL ADT=

ADTi = Average Daily Traffic (initial year) GF = Cumulative Growth Factor HGV% = Percentage of Heavy Goods Vehicles TF = Truck Factor (ESAL Factor) D% = Directional distribution LN% = Lane distribution

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING TRAFFIC ASSESSMENT

ESAL calculation Step 1: Measure/estimate initial Average Daily Traffic (ADTi) Step 2: Estimate growth rate (R) Step 3: Calculate Growth Factor (GF) Step 4: Calculate ESAL (GF)(HGV%)(TF)(D%)(LN%)(365days/ yr)iESAL ADT=

( )(1 ) f if iADT ADT R −= +

n(1 ) 1RGFR

+ −=

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Loads

Load characterization •  Tire loads •  Axle and tire configurations •  Load repetition •  Traffic distribution •  Vehicle speed

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Equivalent Single Axle Load (ESAL)

•  Converts wheel loads of various magnitudes and repetitions ("mixed traffic") to an equivalent number of "standard" or "equivalent" loads

•  Based on the amount of damage they do to the pavement •  Commonly used standard load is the 18,000 lb. equivalent

single axle load Load Equivalency Factor (LEF) or Truck Factor (TF) •  Generalized fourth power approximation

4Axle load relative damage factor18,000 lb.

TF LEF ⎛ ⎞= = =⎜ ⎟

⎝ ⎠

Loads

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Example of calculation of truck factor

Axle 1 = 17000 pounds = 17 kips Axle 2 = 22000 pounds = 22 kips

𝑇𝐹↓𝐴𝑥𝑙𝑒 1 = (17/18 )↑4 =0.8 𝐸𝐴𝐿𝐹↓𝐴𝑥𝑙𝑒 2 = (22/18 )↑4 =2.2

𝑇𝑟𝑢𝑐𝑘 𝐹𝑎𝑐𝑡𝑜𝑟= 𝐸𝐴𝐿𝐹↓𝐴𝑥𝑙𝑒 1 + 𝐸𝐴𝐿𝐹↓𝐴𝑥𝑙𝑒 2 =0.8+2.2=3.0

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Typical LEFs (or TFs)

Notice that cars are insignificant and thus usually ignored in pavement design.

1.351.85

5.11

0.100.00070

1

2

3

4

5

6

Car Delivery Truck Loaded 18-Wheeler Loaded 40' Bus Loaded 60'Articulated Bus

ESAL

s pe

r Veh

icle

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Resilient Modulus

Theresilientmodulusofaroadbedsoilisobtainedinthelabusingcyclicloadtriaxialtests.

Ho

Δz

r ro

σz=σ1

σr= σ3

Totalaxialstress=sustainedstress+cyclicstress+confiningpressure

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Normal Stresses, Strains and Poisson’s Ratio

IfadeformablecylinderofdiameterroandlengthHoisloadedverticallybyσ1andradiallybyσ3,thelengthwillshortenbyΔzandthediameterbyΔr=ro–r.Theverticalandradialstraincanthenbecalculatedasfollows:

Ho

Δz

r ro

σz

σr

█𝜀↓𝑣𝑒𝑟𝑡𝑖𝑐𝑎𝑙 = 𝛥𝑧/𝐻↓𝑜  ; 𝜀↓𝑟𝑎𝑑𝑖𝑎𝑙 = 𝛥𝑟/𝑟↓𝑜  @𝜇= 𝜀↓𝑟𝑎𝑑𝑖𝑎𝑙 /𝜀↓𝑣𝑒𝑟𝑡𝑖𝑐𝑎𝑙   

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RESILIENT MODULUS MR IS THE ELASTIC MODULUS BASED ON THE RECOVERED STRAIN UNDER CYCLIC LOAD TESTING.

r

dRM ε

σ=

Whereσd=DeviatoricStressεr=RecoveredStrain

For Granular and Fine Graded soils Triaxial Repeated Load Test is used to determine Mr under different combination of vertical as well as confining pressure

Subgrade Characterization – Resilient Modulus

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Subgrade Characterization – Resilient Modulus

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37

California Bearing Ratio (CBR) l  Defined as a comparison between the bearing capacity of

a material with respect to a well-graded crushed stone characterized by a reference CBR of 100%;

l  Measured by applying load to a small penetration piston (1,33 mm per minute) and recording the total load at penetrations ranging from 0.64 – 7.62 mm.

CBR(%) is computed as:

Where x is material load resistance (at 2.54 or 5.08 mm), and y is the standard pressure used for reference material

A common relationship between CBR and Mr (in lbs/in2):

⎟⎟⎠

⎞⎜⎜⎝

⎛=

yxCBR 100

CBRMr 1500=

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Subgrade Mr – CBR (California Bearing Ratio) relations

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= + + +1 1 2 2 2 3 3 3 ...a D a D m aN D mS

(Stiffness)

𝑎↓2 

𝑎↓3 

𝑎↓1  𝐷↓1 

𝐷↓2 

𝐷↓2 


Layer coefficient

Thickness Drainage coefficient

Layer Properties: AASHTO 1993 design method


1.20 1.00 0.80 0.60 0.40

1.30 - 1.20 1.15 - 1.00 1.00 - 0.80 0.80 - 0.60 0.75 - 0.40

1.35 - 1.20 1.25 - 1.15 1.15 - 1.05 1.05 - 0.80 0.95 - 0.75

1.40 - 1.35 1.35 - 1.25 1.25 - 1.15 1.15 - 1.05 1.05 - 0.95

Excellent Good Fair Poor

Very Poor

Greater than 25%

5 - 25% 1 - 5% Less than 1%

Quality of Drainage

Percent of time pavement structure is exposed to moisture levels approaching saturation

AASHTO Recommended Drainage Coefficient Values for Flexible Pavements

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Reliability

Reliabilityistheprobabilitythatthepavementsystemwillperformitsintendedfunctionoveritsdesignlifeandundertheconditionsencounteredduringoperation.

Bydefinition,reliabilityistheprobabilityofsuccessor100–theprobabilityoffailure.

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Probability of Failure

00.20.40.60.8

11.21.4

0 10 20 30 40 50 60

Stress (psi)

Freq

uenc

y

Stress Strength

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Reliability (R) and the Standard Normal Deviate (ZR) Reliability (ZR)

50 60 70 75 80 85 90 91 92

-0.000 -0.253 -0.524 -0.674 -0.841 -1.037 -1.282 -1.340 -1.405

Reliability (ZR) 93 94 95 96 97 98

99.9 99.9 99.99

-1.476 -1.555 -1.645 -1.751 -1.881 -2.054 -2.327 -3.090 -3.750

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Recommended Level of Reliability

FunctionalClassification

RecommendedlevelofReliability

Urban Rural

InterstateandotherfreewaysPrincipalarterialsCollectorsLocal

85to99.980to9980to9550to80

80to90.975to9575to9550to80

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Typical PSI vs. Time

Time

Serv

icea

bilit

y (P

SI)

p0

pt

p0-pt

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Serviceability Loss

Thetotallossofpavementserviceability(ΔPSI)isthesumofserviceabilitylossduetotraffic(ΔPSITraffic),swellingsoil(ΔPSISW),andfrostheave(ΔPSIFH).

IntheAASHTOdesignequation,ΔPSIistheportionofserviceabilitylossduetotrafficonly.

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MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Present Serviceability Index (PSI)

( ) PCSVPSI +−+−= 9.01log80.141.5

•  Values from 0 (worst) through 5 (best)

SV=meanoftheslopevarianceinthetwowheelpaths(measuredwiththeCHLOEprofilometerorBPRRoughometer)

C,P=measuresofcrackingandpatchinginthepavementsurface

C=totallinearfeetofClass3andClass4cracksper1000ft2ofpavementarea.AClass3crackisdefinedasopenedorspalled(atthesurface)toawidthof0.25in.ormoreoveradistanceequaltoatleastone-halfthecracklength.AClass4isdefinedasanycrackwhichhasbeensealed.

P=expressedintermsofft2per1000ft2ofpavementsurfacing.

MICHIGAN STATE UNIVERSITY!|!COLLEGE OF ENGINEERING Typical Problems in Pavement design Traffic •  No / limited traffic count •  Growth rate is arbitrarily selected •  Traffic estimation models are incorrectly used •  Truck damage effect is arbitrarily considered Soil Properties •  Limited (or NO) geotechnical investigation •  Incorrect interpretation Layer properties •  Important material properties are ignored •  Outdated/incorrect models used

Layer Properties

Traffic

Soil Properties

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o  AsphaltConcretestiffness/modulusØ  VehiclespeedØ  Temperature/ClimateØ  Loadlevel

o  Aggregate/Cement-boundBaseØ  Stiffness

•  MaterialComposition•  Loadlevel

Important issues ignored with empirical methods

Stiffne

ss

VehicleSpeed

Highspeed&Lowtemperature

Lowspeed&Hightemperature


End of Session

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m. emin kutay, phd, pe - michigan state universitykutay/training/session-1_v2.pdf• four classes of...

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