dr. wa'el m. albawwab [email protected] ecgd4228 transportation engineering ii summer 2008...

Dr. Wa'el M. Albawwab albawwab@Dr. Wa'el M. Albawwab [email protected]

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ECGD4228ECGD4228Transportation Engineering IITransportation Engineering II

Summer 2008Summer 2008

Saturdays 15:30-18:30 PMSaturdays 15:30-18:30 PMK204K204


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Pavement Design MethodsPavement Design Methods

Design ParametersDesign Parameters

Flexible PavementFlexible Pavement

Rigid PavementRigid Pavement

Lecture 6Lecture 6


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A pavement consists of a number of layers of different A pavement consists of a number of layers of different materialsmaterials

Pavement Design Methods:Pavement Design Methods: AASHTO MethodAASHTO Method The Asphalt Institute Method for Flexible PavementsThe Asphalt Institute Method for Flexible Pavements Portland Cement Association (PCA) Method for Portland Cement Association (PCA) Method for

Concrete PavementsConcrete Pavements Texas DOT MethodTexas DOT Method Other methodsOther methods

Pavement Design MethodsPavement Design Methods


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AASHTO Road TestAASHTO Road Test

AASHTO: AASHTO: AAmerican merican AAssociation of ssociation of SState tate HHighway and ighway and TTransportation ransportation OOfficialsfficials

Objective: To relate axle load repetitions, pavement Objective: To relate axle load repetitions, pavement design configurations & distressesdesign configurations & distresses


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ASSHTO Design MethodASSHTO Design Method

Pavement PerformancePavement Performance Traffic Traffic Roadbed soils (subgrade materials)Roadbed soils (subgrade materials) Materials of constructionMaterials of construction EnvironmentEnvironment DrainageDrainage ReliabilityReliability Shoulder DesignShoulder Design Life-Cycle CostsLife-Cycle Costs


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AASHTO’s Formula Considers:AASHTO’s Formula Considers:(1) Pavement Performance(1) Pavement Performance

• Based on Pavement Serviceability conceptBased on Pavement Serviceability concept Serviceability was defined as the ability of a Serviceability was defined as the ability of a

pavement to serve its intended function under pavement to serve its intended function under existing conditionsexisting conditions

• During the test, road users rated pavements During the test, road users rated pavements PPavement avement SServiceability erviceability RRating (PSR)ating (PSR) Based on the pavement roughnessBased on the pavement roughness 0-1:0-1: VVeryery Poor; 1-2: Poor; 1-2: Poor; 2-3:Poor; 2-3: Fair; 3-4:Fair; 3-4: Good;Good; and and

4-5: V4-5: Veryery Good Good


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PSR’s used to develop design equations to predict Present Serviceability Index (PSI)

• Initial Serviceability Index = p0 (the servceability immediately after the construction of the pavement, recommended 4.2-4.5

• Terminal Serviceability = pt (2.5-major, 2.0-other), the minimum acceptable serviceability before resurfacing or reconstruction is needed.

• In the formula: Serviceability loss

(PSI) = p0 – pt

AASHTO’s Formula Considers:AASHTO’s Formula Considers:(1) Pavement Performance(1) Pavement Performance


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Pavement ConditionPavement Condition

Defined by users (drivers)Defined by users (drivers)Develop methods to relate physical attributes to driver Develop methods to relate physical attributes to driver

ratingsratingsResult is usually a numerical scaleResult is usually a numerical scale

From the AASHO Road Test(1956 – 1961)


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Typical PSI vs. TimeTypical PSI vs. Time

Time

Ser

vice

abil

ity

(PS

I)

p0

pt

p0 - pt

Terminal Serviceability Level


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The concept of ESAL – Equivalent Single-Axel LoadThe concept of ESAL – Equivalent Single-Axel Load

The traffic characteristics are determined in terms of the The traffic characteristics are determined in terms of the number of repetitions of an 18,000 single-axle load number of repetitions of an 18,000 single-axle load applied to the pavement on two sets of dual tires.applied to the pavement on two sets of dual tires.

Expressed in Equivalent 18-kip Single Axle Loads (WExpressed in Equivalent 18-kip Single Axle Loads (W1818))

Axle load equivalency factor was introduced to convert Axle load equivalency factor was introduced to convert different axle loads to Equivalent 18,000 lb (18-kip) different axle loads to Equivalent 18,000 lb (18-kip) Single Axle Loads.Single Axle Loads.

AASHTO’s Formula Considers:AASHTO’s Formula Considers:(2) Traffic(2) Traffic


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Vehicle TypesVehicle Types


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Vehicle Weight & Size LimitsVehicle Weight & Size Limits

Weight limits for whole vehicle, single axles & tandem Weight limits for whole vehicle, single axles & tandem axlesaxles

Size limits for length, width & heightSize limits for length, width & height


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By By LLoad oad EEquivalency quivalency FFactors (Factors (FEE), i.e., number of repetition of 18 kip single-axle ), i.e., number of repetition of 18 kip single-axle

load.load.

ESAL DeterminationESAL Determination

Axels (lb)Axels (lb) SingleSingle TandemTandem TridemTridem

1000010000 0.08770.0877 0.0070.007 0.0020.002

1800018000 1.01.0 0.0770.077 0.0170.017

4000040000 21.0821.08 2.082.08 0.4870.487


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Load QuantificationLoad Quantification

Load EquivalencyLoad Equivalency

–Generalized fourth power approximationGeneralized fourth power approximation


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For each axle category i; (single, tandem, For each axle category i; (single, tandem, tridem)tridem)

For all categories:For all categories:



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ffdd – design lane factor, which is the portion of total ESAL – design lane factor, which is the portion of total ESAL

acting on the design lane (any lane of two lane highway acting on the design lane (any lane of two lane highway and outside lane of multilane highway), from field data. and outside lane of multilane highway), from field data.

G – traffic growth factor for a specific design periodG – traffic growth factor for a specific design period

AADT – first year AADTAADT – first year AADT

N – number of axles (each axle will repeat one load when N – number of axles (each axle will repeat one load when vehicle is moving)vehicle is moving)

FFEE – Load equivalency factor – Load equivalency factor



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Resilient Modulus (Mr) of the soil is considered in design, Resilient Modulus (Mr) of the soil is considered in design, the value of Mr is normally known/given for designthe value of Mr is normally known/given for design

Another parameter needs to know but not directly used Another parameter needs to know but not directly used in the AASHTO’s formula is CBR – California Bearing in the AASHTO’s formula is CBR – California Bearing Ratio, which is a parameter indicative of soil’s strength. Ratio, which is a parameter indicative of soil’s strength. Relationship between Mr and CBR (or R value) is given Relationship between Mr and CBR (or R value) is given by:by:

Mr = 1500 CBR (for soils with CBR ≤ 10)Mr = 1500 CBR (for soils with CBR ≤ 10)

Mr = 1000 + 555 CBR ( for 10 < CBR ≤ 20)Mr = 1000 + 555 CBR ( for 10 < CBR ≤ 20)

AASHTO’s formula considers:AASHTO’s formula considers:(3) Subgrade materials(3) Subgrade materials


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SN – The Structural NumberSN – The Structural Number

AASHTO’s formula considers:AASHTO’s formula considers:(4) Materials of construction(4) Materials of construction


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SN – The Structural Number for the road profileSN – The Structural Number for the road profile DDii – depth of layer – depth of layer ii

mmii – drainage coefficient for layer – drainage coefficient for layer ii



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Subbase construction materials: layer coefficient aSubbase construction materials: layer coefficient a33 is used to is used to

represent the quality of the material AND convert the actual represent the quality of the material AND convert the actual thickness of the subbase to Structural Number (SN, is an thickness of the subbase to Structural Number (SN, is an engineering term indicative of the total pavement thickness).engineering term indicative of the total pavement thickness).

Base construction materials: a2, andBase construction materials: a2, and Surface Course Construction materials: a1.Surface Course Construction materials: a1.



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AASHTO’s formula considers:AASHTO’s formula considers:(5) Drainage (5) Drainage

Purpose: consider the effect of drainage on the Purpose: consider the effect of drainage on the performance of flexible pavementperformance of flexible pavement

Represented by: mRepresented by: mii, i =2,3 (represents the base and , i =2,3 (represents the base and

subbase layer.subbase layer.


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AASHTO’s formula considers:(6) Reliability

Reliability level: the reliability that the pavement Reliability level: the reliability that the pavement designed will survive for its design period. designed will survive for its design period.

E.g., a 50 percent reliability design level implies a 50% E.g., a 50 percent reliability design level implies a 50% chance for successful pavement performance.chance for successful pavement performance.

Presented by FPresented by FRR..


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AASHTO’s formula considers:(6) Reliability

ZZR R : Standard normal variation for a given reliability: Standard normal variation for a given reliability

SS0 0 : Estimated overall standard deviation: Estimated overall standard deviation


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Other IssuesOther Issues

DrainageDrainage JointsJoints Grooving (noise vs. hydroplaning)Grooving (noise vs. hydroplaning) Rumble stripsRumble strips ClimateClimate Level and type of usageLevel and type of usage Failure examples are primarily related to design or life-Failure examples are primarily related to design or life-

cycle, not constructioncycle, not construction


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Primary ReferencesPrimary References

Mannering, F.L.; Kilareski, W.P. and Washburn, S.S. Mannering, F.L.; Kilareski, W.P. and Washburn, S.S. (2005). (2005). Principles of Highway Engineering and Traffic Principles of Highway Engineering and Traffic

AnalysisAnalysis, Third Edition. Chapter 4, Third Edition. Chapter 4Muench, S.T.; Mahoney, J.P. and Pierce, L.M. (2003) Muench, S.T.; Mahoney, J.P. and Pierce, L.M. (2003)

The WSDOT Pavement Guide InteractiveThe WSDOT Pavement Guide Interactive. WSDOT, . WSDOT, Olympia, WAOlympia, WA..

http://guides.ce.washington.edu/uw/wsdothttp://guides.ce.washington.edu/uw/wsdotMuench, S.T. (2002) Muench, S.T. (2002) WAPA Asphalt Pavement GuideWAPA Asphalt Pavement Guide. .

WAPA, Seattle, WAWAPA, Seattle, WA..

http://http://www.asphaltwa.comwww.asphaltwa.com

dr. wa'el m. albawwab [email protected] ecgd4228 transportation engineering ii summer 2008...

Documents

pavement performance

pavement condition

pavement roughness

good slide

design equations

serviceability loss

singleaxle load

axle load repetitions