No deep structural distress

Transcription

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2 What is a Perpetual Pavement? No deep structural distress

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4 Limit Cracking to top-down

5 Goal of Perpetual Pavement Design Design so there are no deep structural distresses Bottom up fatigue cracking Structural rutting All distresses can be quickly remedied from surface Result in a structure with Perpetual or Long Life

6 Do Perpetual Pavements Exist? Perpetual Pavements are NOT a new concept Full-depth Mill and inlay Deep strength Perpetual Pavement Award 35+ years No structural failures 13+ year rehab interval

7 Designing Perpetual Pavements Newcomb, 2001

8 M-E Perpetual Pavement Design P Log e A Threshold Strain e t D 1 E 1 D 2 E 2 Log N e v No Damage Accumulation D 3 E 3

9 Strain, (10E-06) Normal Range for Fatigue Testing Endurance Limit E+08 Number of Loads to Failure Normal Fatigue Testing Results Versus Endurance Limit Testing

10 What is the Endurance Limit for HMA? 1972 Monismith estimates about 70 me 2001 I-710 designed at 70 me me used by APA 2007 NCHRP 9-38 Lab Study 100 me for unmod binders 250 me for mod binders More severe than field 2007 MEPDG uses 100 to 250 me 2008 Field measurements show higher strains

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12 N8 and N9 0.0 Lift 1 N8 Section SMA N9 2.3 PG Lift 1 Depth From Pavement Surface, in Lift 2 Lift 3 Lift PG Dense Graded HMA 250 mm 350 mm Moisture Content = 10.8% Unit Weight = pcf Moisture Content = 18.0% Unit Weight = pcf Dense Graded HMA PG Rich Bottom Layer PG Aggregate Base (Track Fill) Subgrade (A-7-6 Soil) Moisture Content = 12.9% Unit Weight = pcf Moisture Content = 17.2% Unit Weight = pcf Lift 2 Lift 3 Lift 4 Lift 5

13 Strain Measurements

14 Strain and Temperature Longitudinal Microstrain-Single Axle N8-Temperature N9-Temperature N8-Strain 0 01-Nov Dec Mar Apr Jun Aug Oct Dec Feb Apr Mid-Depth Pavement Temperature,F N9-Strain 0 Date

15 Strain vs. Temperature 1200 Longitudinal Microstrain-Single Axle Section Axle Type C 1 C 2 R 2 Single N8 Tandem Steer Single N9 Tandem Steer N8 Strain = e 0.033*Temp R 2 = N9 Strain = e *Temp R 2 = Mid-Depth Pavement Temperature, F

16 Strain Distributions 100% 90% 80% 70% N9 N8 Percentile 60% 50% 40% 30% 20% 10% 0% Longitudinal Strain

17 End Result

18 NCAT Test Track Results Percentile 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% No Fatigue Fatigue N N N N N N N N N N N N N N S S Microstrain

19 2003 Test Sections Fatigue Cracking Occurred Fatigue Ratio Fatigue Cracking Absent Max Ratio = N N N N N N N Section

20 2006 Test Sections Fatigue Cracking Occurred Fatigue Ratio Fatigue Cracking Absent Max. Ratio = N N N N N N N S Section

21 Probabilistic Design Monte Carlo Simulation f Axle Weight f Monte Carlo Random Sampling Mechanistic Model f Material Properties f % Below Threshold % Above Threshold Thickness Pavement Response

22 % Below Threshold Design should have high % below threshold f % Below Threshold How much damage does this area correspond to? Pavement Response

23 Damage Computation For responses exceeding threshold, compute N using transfer function User defined Calculate damage accumulation rate Damage / Maxles f % Below Threshold Damage Million Axles Pavement Response

24 Estimated Long Life Convert damage rate into an estimated time Use traffic volume and growth Calculate when damage = 0.1

25 PerRoad 3.5 Sponsored by APA Developed at Auburn University / NCAT M-E Perpetual Pavement Design and Analysis Tool

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27 f Material Properties f Thickness

28 Performance Criteria

29 Traffic Volume Types of Axles

30 Functional Classification

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32 PerRoadXPress For Low Volume Roads

33 Methodology - Overview Develop a set of boundary conditions Execute PerRoad analysis to determine required thickness for each design Develop design regression equations Guiding Principles Limit number of required inputs Make design procedure simple/efficient

34 Structural Cross Section Layer Stiffness Poisson s Ratio HMA 400,000 to 1,000,000 psi 0.35 Variable Aggregate Base 20,000 psi in. 10,000 psi to 30,000 psi Subgrade Soil 0.45 Infinite

35 Number of Simulations # Simulations = X X X X X X 2 Highway Classifications 3 Traffic Volumes 3 Growth Rates 4 Percent Trucks 3 Soil Stiffnesses 3 HMA Stiffnesses 3 Base Thicknesses 1,944 Pavement Designs

36 Design Equation HMA = C 0 + C 1 *AADT + C 2 *%Trucks + C 3 *%Growth + C 4 *Soil Stiffness + C 5 *Base Thickness + C 6 *HMA Stiffness

37 PerRoad XPress Traffic Soil Agg. Base HMA

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