No deep structural distress
|
|
- Joseph McDaniel
- 5 years ago
- Views:
Transcription
1
2 What is a Perpetual Pavement? No deep structural distress
3
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
11
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
26
27 f Material Properties f Thickness
28 Performance Criteria
29 Traffic Volume Types of Axles
30 Functional Classification
31
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
38