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Overlay Design Workshop for Flexible Pavements

Overlay Design Workshop for Flexible Pavements. James A. Crovetti Marquette University. WHRP Project Background. Project 0092-07-12: Implementation of Flexible Pavement Overlay Design Procedures

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Overlay Design Workshop for Flexible Pavements

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  1. Overlay Design Workshop for Flexible Pavements James A. Crovetti Marquette University

  2. WHRP Project Background • Project 0092-07-12: Implementation of Flexible Pavement Overlay Design Procedures • Project 0092-00-05: Development of Rational Overlay Design Procedures for Flexible Pavements (WHRP 05-12) • Project 0092-03-14: Development of Modulus-to-Temperature Relations for HMA Mixtures in Wisconsin (WHRP 05-11)

  3. Implementation of Flexible Pavement Overlay Design Procedures • Development of Overlay Design Software • Revisions to FDM • Knowledge Transfer • Follow-Up

  4. FDM 14-10-30 • Structural Number Approach – New • Design Traffic, Soil Support • Structural Deficiency Approach – Overlay • SNol = SNnew – SNeff • Design Reliability • Traffic, Materials

  5. Structural Deficiency Approach • New pavement designed using WisPAVE (SNnew) • Existing pavement analyzed to determine structural adequacy (SNeff) • FWD data • Component analysis • Overlay thickness developed to overcome SN shortage • hOL = (SNnew-SNeff)/0.44

  6. Traffic Analysis • Analyzed 2006 WIM data from 17 sites across the State • ESALs per truck computed based on AASHTO principles • Cumulative frequency of EALFs developed to select appropriate factors for variable levels of design reliability

  7. 85.6% Design Reliability EALF = 0.3 (WisDOT FDM 14-1-5)

  8. Traffic-Based Design Reliability

  9. 90% Design Reliability 67% Design Reliability EALF= 0.9 1.84

  10. Reliability-Based EALFs

  11. Recommended EALFs

  12. Overlay Design Software • Eri and/or SNeff variations determined based on FWD test results or component analysis • FWD provides SNeff and SSV without pavement coring • New pavement (SNnew) and overlay (SNOL) requirements determined based on current WisDOT procedures with varying levels of design reliability

  13. Component Analysis

  14. Component Analysis

  15. Component Analysis

  16. Overlay Design EquationsBased on FWD Data- No Milling Before Overlay - • Eri = 22.04 - 3.645 D36 + 0.158 D362 • AUPP = ½ (5D0 – 2D12 – 2D24 – D36) • E1/3T = 10(3.574 - 0.437 Log AUPP - 0.066 Log Eri) • SNeff = 0.0055 (E1/3T) - 0.0012 Eri + 0.144

  17. Subgrade EffectsEri = 22.04 - 3.645 D36 + 0.158 D362

  18. Seasonal Subgrade Stiffness Variations

  19. Subgrade Estimations

  20. Correction Factors for Subgrade Strength • FWD Testing during: • Critical Spring Period: 2.48 • Late Spring: 0.83 • Summer/Fall: 0.50

  21. Constructed Pavement Layer Variations F W D Strong Weak

  22. “Strong” Pavement AUPP

  23. “Weak” Pavement AUPP

  24. Pavement Strength, SNeff • Eri = 22.04 - 3.645 D36 + 0.158 D362 • AUPP = ½ (5D0 – 2D12 – 2D24 – D36) • E1/3T = 10(3.574 - 0.437 Log AUPP - 0.066 Log Eri) • SNeff = 0.0055 (E1/3T) - 0.0012 Eri + 0.144

  25. Modulus-to-Temperature Effects for HMA Log Mr = 6.83 + 0.018 P200 – 0.044 Vv – 0.00086 tp1.45 Pb.5

  26. Example Pavement 2” HMA E varies 3” HMA E=450ksi 12” CABC Stress Hardening 240” Subgrade Stress Softening Bedrock

  27. FWD Deflection Basins

  28. Temperature Corrected Deflections

  29. Overlay Design EquationsBased on FWD Data- With Milling Before Overlay - • AUPP2 = 8D0 – 6D8 – 2D12 • SNHMA = 20.058 (AUPP2)-0.590649 • a1 = SNHMA / THMA • SNpost-mill = SNeff – a1Tmill

  30. Overlay Design Example • 4-Lane State Trunk Highway • 20 year overlay design • CYADT=12,000; DYADT=17,000 • 7% Heavy Trucks • Existing pavement contains 10% alligator cracking and slight rutting • Thickness information from coring not available (8” HMA from plans) • FWD test data provided from September testing

  31. Let’s Explore • Importing FWD Data • Adjusting Traffic • Computing SN values and Overlay Thicknesses

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