Pavement Design Session 09-12

2. Pavement DesignSession 09-12 Matakuliah : S0753 – Teknik Jalan Raya Tahun : 2009

3. Contents Pavement Classification Load & Stress Distribution Load Analysis Pavement design for Rigid Pavement Pavement Design for Flexible Pavement Overlay Pavement Construction

4. Pavement Classification Classification : • Flexible Pavement • Rigid Pavement • Composite

5. Flexible Pavement Those which are surfaced with bituminous / asphalt materials. These types of pavements are called "flexible" since the total pavement structurebendsor deflects due to traffic loads. A flexible pavement structure is generally composed of several layers of materials which can accommodate this "flexing".

6. Flexible Pavement

7. Types of Flexible Pavement Dense-graded Open-graded Gap-graded CEE 320Steve Muench

8. Rigid Pavement Rigid pavements. Those which are surfaced with portland cement concrete (PCC). These types of pavements are called "rigid" because they are substantially stiffer than flexible pavements due to PCC's high stiffness.

9. Rigid Pavement

10. Types of Rigid Pavement • Jointed Plain Concrete Pavement (JPCP) CEE 320Steve Muench

11. Types of Rigid Pavement • Continuously Reinforced Concrete Pavement (CRCP) CEE 320Steve Muench Photo from the Concrete Reinforcing Steel Institute

12. Rigid Pavement JOINT

13. Composite • Composite. Those which are surfaced with portland cement concrete (PCC) and bituminous / asphalt materials as overlay construction

14. Flexible Pavement Load & Stress Distribution

15. P ( Load ) Surface Base Subbase Subgrade Load & Stress Distribution Flexible Pavement

16. Rigid Pavement Load & Stress Distribution

17. P ( Load ) Surface Subbase or base Subgrade Load & Stress Distribution Rigid Pavement

18. Pavement Design • Several typical methods • Design catalog • Empirical • 1993 AASHTO method • Mechanistic-empirical • New AASHTO method (as yet unreleased)

19. Design Catalog Example design catalog from the Washington Asphalt Pavement Association (WAPA) for residential streets

20. Empirical • 1993 AASHTO Flexible Equation • 1993 AASHTO Rigid Equation

21. Terms – Flexible • W18 (loading) • Predicted number of ESALs over the pavement’s life. • SN (structural number) • Abstract number expressing structural strength • SN = a1D1 + a2D2m2 + a3D3m3 + … • ΔPSI (change in present serviceability index) • Change in serviceability index over the useful pavement life • Typically from 1.5 to 3.0 • MR (subgrade resilient modulus) • Typically from 3,000 to 30,000 psi (10,000 psi is pretty good)

22. Terms – Rigid • D (slab depth) • Abstract number expressing structural strength • SN = a1D1 + a2D2m2 + a3D3m3 + … • S’c (PCC modulus of rupture) • A measure of PCC flexural strength • Usually between 600 and 850 psi • Cd (drainage coefficient) • Relative loss of strength due to drainage characteristics and the total time it is exposed to near-saturated conditions • Usually taken as 1.0

23. Terms – Rigid • J (load transfer coefficient) • Accounts for load transfer efficiency • Lower J-factors = better load transfer • Between 3.8 (undoweled JPCP) and 2.3 (CRCP with tied shoulders) • Ec (PCC elastic modulus) • 4,000,000 psi is a good estimate • k (modulus of subgrade reaction) • Estimates the support of the PCC slab by the underlying layers • Usually between 50 and 1000 psi/inch

24. Pavement design for Rigid Pavement The following input variables are needed for the AASHTO rigid pavement design procedure: ¨ 28-day Concrete Modulus of Rupture, psi¨ 28-day Concrete Elastic Modulus, psi¨ Effective Modulus of Subbase/Subgrade Reaction, pci¨ Serviceability Indices ¨ Load Transfer Coefficient ¨ Drainage Coefficient ¨ Overall Standard Deviation ¨ Reliability, %¨ Design Traffic, 18-kip Equivalanet Single Axle Load (SEAL).

25. Pavement design for Rigid Pavement 28-day Concrete Modulus of Rupture, Mr The Mr of concrete is a measure of the flexural strength of the concrete as determined by breaking concrete beam test specimens. A Mr of 620 psi at 28 days should be used with the current statewide specification for concrete pavement design. If the Engineer selects an alternate value for Mr, then it must be documented with an explanation.

26. Pavement design for Rigid Pavement 28-day Concrete Elastic Modulus Elastic modulus of concrete is an indication of concrete stiffness. It varies depending on the coarse aggregate type used in the concrete. Although the value selected for pavement design could be different from the actual values, the elastic modulus does not have a significant effect on the computed slab thickness. A modulus of 5,000,000 psi should be used for pavement design. The use of a different value must be documented with an explanation.

27. Pavement design for Rigid Pavement Effective Modulus of Subbase/Subgrade Reaction: k-value The AASHTO guide allows pavement designers to take into account the structural benefits of all layers under the concrete slab. It also allows designers to consider the effect of loss of support of the underlying material due to erosion or deterioration. The slab support is characterized by the modulus of subgrade/ sub base reaction, otherwise known as the k-value. It can be measured in the field by applying a load equal to 10 psi on the subgrade/subbase combination using a 30-inch diameter steel plate. The k-value is then calculated by dividing 10 psi by the measured deflection (in inches) of the layers under the plate.

28. Pavement design for Rigid Pavement Serviceability Indices For concrete pavement design, the difference between the initial and terminal serviceability is an important factor. An initial serviceability value of 4.5 and a terminal serviceability value of 2.5 are to be used in the procedure, which results in a difference of 2.0. Different values, if used, must be documented and justified.

29. Pavement design for Rigid Pavement Load Transfer Coefficient The load transfer coefficient is used to incorporate the effect of dowels, reinforcing steel, tied shoulders, and tied curb and gutter on reducing the stress in the concrete slab due to traffic loading. The coefficients recommended in the AASHTO Guide were based on findings from the AASHO Road Test.

30. Pavement design for Rigid Pavement Drainage Coefficient The drainage coefficient characterizes the quality of drainage of the sub baselayers under the concrete slab. Good draining pavement structures do not give water the chance to saturate the subbase and subgrade; thus, pumping is not as likely to occur.

31. Pavement design for Rigid Pavement Reliability, % The reliability value represents a "safety factor," with higher reliabilities representing pavement structures with less chance of failure. The AASHTO Guide recommends values ranging from 50% to 99.9%, depending on the functional classification and the location (urban vs. rural) of the roadway. If the Engineer decides to use a different value, then it must be documented and justified

32. Pavement design for Flexible Pavement Determine the desired terminal serviceability, pt Convert traffic volumes to number of equivalent 18-kip single axle loads (ESAL) Determine the structural number, SN Determine the layer coefficients, ai Solve layer thickness equations for individual layer thickness

33. Pavement design for Flexible Pavement Variables included in Nomographs Reliability, R Incorporates a degree of certainty into design process Ensures various design alternatives will last the analysis period Resilient Modulus for Roadbed Soil, MR Generally obtained from laboratory testing

34. Pavement design for Flexible Pavement Variables included in Nomographs Effective Modulus of Sub-Grade Reaction, k Sub-base type Sub-base thickness Loss of support Depth to rigid foundation Drainage Coefficient, mi Use in layer thickness determination Applies only to base and sub-base

35. Flexible Pavement – Construction CEE 320Steve Muench

36. Rigid Pavement – Construction Fixed form CEE 320Steve Muench

37. Rigid Pavement – Construction Slipform CEE 320Steve Muench