Easy-To-Use Perpetual Pavement Design Software

Transcription

1 Easy-To-Use Perpetual Pavement Design Software Rocky Mountain Asphalt Conference February 25, 2010 Dr. David Timm, P.E. Department of Civil Engineering Auburn University

2 What is a Perpetual Pavement? A pavement designed so there are no distresses deep in the pavement structure

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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 Designing Perpetual Pavements Newcomb, 2001

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

8 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

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

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11 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 Moisture Content = 10.8% Unit Weight = pcf Moisture Content = 18.0% Unit Weight = pcf Dense Graded HMA 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

12 Strain Measurements

13 Strain and Temperature 01-Nov Dec Mar Apr Jun Aug Oct Dec Feb Apr-08 Date Longitudinal Microstrain-Single Axle Mid-Depth Pavement Temperature,F N8-Temperature N9-Temperature N8-Strain N9-Strain

14 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

15 Strain History Section N8 11/1/ /1/ /31/2006 1/30/2007 3/1/2007 3/31/2007 4/30/2007 5/30/2007 6/29/2007 7/29/2007 8/28/2007 9/27/ /27/2007 Time Longitudinal Microstrain-Single Axles Temperature, F Temperature Strain

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

17 NCAT Test Track Results 100% Percentile 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Fatigue Cracking N N N N N N N N N N N N N N S S Microstrain

18 PerRoad 3.3 Sponsored by APA Developed at Auburn University / NCAT M-E Perpetual Pavement Design and Analysis Tool

19 Environmental Conditions Variability and Thresholds Layer Properties

20 f Material Properties f Thickness

21 Performance Criteria Location in Layer Pavement Response Threshold Transfer Function

22 Axle Weight Distribution Traffic Volume Types of Axles

23 Functional Classification Vehicle Frequency Number of Axles

24 Damage Accumulation Design Life Percent Below Threshold

25 PerRoadXPress For Low Volume Roads

26 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

27 Traffic Parameters Rural (Local) Collector vs. Urban Collector Volume 500, 1000 and 5000 AADT 0%, 1% and 3% Growth 1%, 5%, 10% and 20% Trucks Distribution Factors Assume 2-lane facility 100% Trucks in design lane 50% directional distribution Loadings Default Load Spectra in PerRoad Volume Range (over 30 years) 27,375 to 8,577,500 trucks

28 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

29 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

30 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

31 PerRoad XPress Traffic Soil Agg. Base HMA

32 AASHTO vs. PerRoad AASHTO-93 PerRoad HMA Thickness, in HMA (a 1 = 0.44) 6 Agg. Base (a 2 = 0.14) Subgrade (M r = 15,000 psi) Traffic, million ESALs

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