AASHTOPavementThicknessDesignGuideSHTO路面厚度设计指南

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1、AASHTOPavementThicknessDesignGuideWhendesigningpavementthicknessforflexibleandrigidpavements,thefollowingconsiderationsshouldbeused.1.Performancecriteria(serviceabilityindexes).Conditionofpavementsareratedwithapresentserviceabilityindex(PSI)rangingfrom5(perfectcondition)to0(impossiblet

2、otravel).a.Initialserviceabilityindex(Po)–PoisconsideredtobethatPSIimmediatelyafterthepavementisopen.AASHTOvaluesare4.5forrigidpavementand4.2forflexiblepavement.b.Terminalserviceabilityindex(Pt)–PtisconsideredtobethatPSIthatrepresentsthelowestacceptablelevelbeforeresurfacingorreconstru

3、ctionbecomesnecessary.•Pt=2.00forSecondaryRoads,LocalResidentialStreets.•Pt=2.25forMinorCollectors,IndustrialandCommercialStreets.•Pt=2.50forMajorCollectorsandallArterials.c.Serviceabilityloss(dPSI)–dPSIisthedifferencebetweenPoandPt(Po‐Pt).ThedPSIisthebasisforthepavementdesign.2.Design

4、variablesa.Analysisperiod(n)–nistheperiodoftimeforwhichtheanalysisistobeconducted.Normally50yearsforconcreteand30yearsforasphalt.b.DesignTraffic(ESALs)–ESALsistheestimateofnumberofEquivalent18kipSingleAxleLoads(ESALs)duringtheanalysisperiodisrequired.Thisvaluecanbeestimatedbasedon:•The

5、AverageAnnualDailyTraffic(AADT)inthebaseyear•Theaveragepercentageoftrucksexpectedtousetheroad•Theaverageannualtrafficgrowthrate,and•TheanalysisperiodToestimatethedesignESALs,thefollowingproceduremaybeused.1.)ObtainanestimateofthedesignAADTforthebeginning,orbaseyearoftheanalysisperiod.2

6、.)ObtainanestimateoftheaveragepercentageoftheAADTthatwillbetrucks.3.)CalculatetheESALsforthebaseyear.4.)Calculatethegrowthfactorbasedontheannualtrafficgrowthrate(r ‐ %)andtheanalysisperiod(n).GrowthFactor=(((1+r)^n)–1)/r5.)MultiplythebaseyearESALsbytheGrowthFactortoobtainthetotalESALsf

7、ortheanalysisperiod.1c.Reliability(R ‐ %)/NormalDeviation(ZR)–Ristheprobabilitythatthedesignwillsuccedforthelifeofthepavement.Thefollowingreliabilityandnormaldeviation(ZR)valuesarerecommended.•LocalStreets:R=80%,ZR= ‐0.841•CollectorStreets:R=88%,ZR= ‐1.270•ArterialStreets:R=95%,ZR= ‐