Evaluation of Non-Linear and Tension Cutoff Material Modeling Features for Pavement Base Aggregate

Western Transportation InstituteMontana State University-Bozeman

Evaluation of Non-Linear Evaluation of Non-Linear and Tension Cutoff and Tension Cutoff Material Modeling Material Modeling

Features for Pavement Features for Pavement Base AggregateBase Aggregate

Jeffrey SharkeyJeffrey SharkeyUndergraduate Research AssistantUndergraduate Research Assistant

Dr. Steven PerkinsDr. Steven PerkinsAssistant ProfessorAssistant Professor


OutlineOutline

Background InformationBackground Information Project Design/MethodologyProject Design/Methodology Results and FindingsResults and Findings ConclusionsConclusions


BackgroundBackground

Pavement design analysisPavement design analysis– Historical methods using empirical methodsHistorical methods using empirical methods– Recent methods using Finite Element Recent methods using Finite Element

AnalysisAnalysis Finite Element AnalysisFinite Element Analysis

– Wide range of applicationsWide range of applications– NCHRPNCHRP11 Design Guide Design Guide

1 1 National Cooperative Highway Research ProgramNational Cooperative Highway Research Program





Goal: Simplify FE methodGoal: Simplify FE method– Increase throughput of a systemIncrease throughput of a system– Increased productivityIncreased productivity– More accessibleMore accessible


MethodologyMethodology

Two ways of simplifying FE models:Two ways of simplifying FE models:– Reducing mesh resolutionReducing mesh resolution– Removing model featuresRemoving model features

Time:

Accuracy:

Percentage (%)



Two featuresTwo features– Tension cutoff formulationTension cutoff formulation– Non-linear behaviorNon-linear behavior

Issues choosing modulusIssues choosing modulus

Six source modelsSix source models– High, medium, and low traffic loads for High, medium, and low traffic loads for

Firm and Weak pavement surface Firm and Weak pavement surface designs.designs.



Four sub-models:Four sub-models:A.A. Using both Using both

featuresfeatures

B.B. Removing Non-Removing Non-linear Behaviorlinear Behavior

C.C. Removing Tension-Removing Tension-cutoff Formulationcutoff Formulation

D.D. Removing both Removing both featuresfeatures

Non-Non-linear linear BehaviorBehavior

Linear Linear BehaviorBehavior

Tension-Tension-cutoffcutoff AA BBNo No Tension-Tension-cutoffcutoff CC DD


FindingsFindings

Examining completed modelsExamining completed models– Physical output variablesPhysical output variables– Pavement fatigue lifePavement fatigue life– Cycles to permanent deformationCycles to permanent deformation


Findings: UFindings: U22 and E and E2222

UU22 is deformation in vertical direction is deformation in vertical direction– Actual movementActual movement

EE2222 is strain in vertical direction is strain in vertical direction– Ratio of deformation to size of Ratio of deformation to size of

original un-deformed object.original un-deformed object.

EE22 22 = = ΔΔLL//LL00


High Firm EHigh Firm E2222

– LE: 19.3%LE: 19.3%– LETC: 19.3%LETC: 19.3%

High Firm UHigh Firm U22

– LE: 22.3%LE: 22.3%– LETC: 22.4%LETC: 22.4%


High Weak EHigh Weak E2222

– LE: 4.8%LE: 4.8%– LETC: 4.8%LETC: 4.8%

High Weak UHigh Weak U22

– LE: 17.7%LE: 17.7%– LETC: 17.7%LETC: 17.7%


Medium Firm EMedium Firm E2222

– LE: 18.7%LE: 18.7%– LETC: 19.0%LETC: 19.0%

Medium Firm UMedium Firm U22

– LE: 21.2%LE: 21.2%– LETC: 21.2%LETC: 21.2%


Medium Weak EMedium Weak E2222

– LE: 19.7%LE: 19.7%– LETC: 19.6%LETC: 19.6%

Medium Weak UMedium Weak U22

– LE: 30.1%LE: 30.1%– LETC: 30.0%LETC: 30.0%


Low Firm ELow Firm E2222

– LE: 17.0%LE: 17.0%– LETC: 16.9%LETC: 16.9%

Low Firm ULow Firm U22

– LE: 14.8%LE: 14.8%– LETC: 14.8%LETC: 14.8%


Low Weak ELow Weak E2222

– LE: 16.7%LE: 16.7%– LETC: 15.5%LETC: 15.5%

Low Weak ULow Weak U22

– LE: 33.1%LE: 33.1%– LETC: 41.0%LETC: 41.0%


Findings: UFindings: U22 and E and E2222

Physical output variablesPhysical output variables– Errors introduced into LE sub-models Errors introduced into LE sub-models

due to modulus calculation method.due to modulus calculation method.– Little difference noted when including or Little difference noted when including or

excluding tension cutoff formulation.excluding tension cutoff formulation. 0.28% (E0.28% (E2222), 1.68% (U), 1.68% (U22))

– Uniform results across source models.Uniform results across source models.


FindingsFindings

Pavement fatigue lifePavement fatigue life– High error compared to NLETC (24.2%)High error compared to NLETC (24.2%)– Average TC effectAverage TC effect

0.0% (high), 3.235% (med), 5.736% (low)0.0% (high), 3.235% (med), 5.736% (low)

Sub-model

High Firm

High Weak

Med Firm

Med Weak

Low Firm

Low Weak

LE 19.204 7.228 4.671 44.917 22.658 49.049

LETC 19.204 7.228 11.141 44.917 28.877 31.359


FindingsFindings

Cycles to permanent deformationCycles to permanent deformation– Again, high error compared to NLETC (22.0%)Again, high error compared to NLETC (22.0%)– Average TC effectAverage TC effect

0.0% (high), 0.616% (med), 5.034% (low)0.0% (high), 0.616% (med), 5.034% (low)

Sub-model

High Firm

High Weak

Med Firm

Med Weak

Low Firm

Low Weak

LE 12.332 7.208 4.146 49.838 14.783 16.480

LETC 12.332 7.208 5.378 49.838 11.339 29.991


ConclusionsConclusions

Non-linear behaviorNon-linear behavior– Can be removed Can be removed onlyonly when modulus is when modulus is

carefully chosen.carefully chosen. Tension cutoff formulationTension cutoff formulation

– Little difference notedLittle difference noted– More important for cycles calculations More important for cycles calculations

as traffic loads decrease.as traffic loads decrease. RecommendationsRecommendations


ConclusionsConclusions

Goal: Simplify FE methodGoal: Simplify FE method– Increase throughput of a systemIncrease throughput of a system– Increased productivityIncreased productivity– More accessibleMore accessible

Thank youThank you– Dr. Steven PerkinsDr. Steven Perkins– Western Transportation InstituteWestern Transportation Institute

Documents

Evaluation of Non-Linear and Tension Cutoff Material Modeling Features for Pavement Base Aggregate