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28 pavement design

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flexible pavment design

flexible pavment design


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  • INSERT SLIDE HERE TO SHOW THE FORMULA AND HOW TO CALCULATE
  • Transcript

    • 1. Pavement Design CE 453 Lecture 28
    • 2. Objectives
      • Understand and complete ESAL calculation
      • Know variables involved in and be able to calculate required thickness of rigid and flexible pavements
    • 3. AASHTO Pavement Design Method Considerations
      • Pavement Performance
      • Traffic
      • Roadbed Soil
      • Materials of Construction
      • Environment
      • Drainage
      • Reliability
      • Life-Cycle Costs
      • Shoulder Design
    • 4.
      • Two Categories of Roadway Pavements
      • Rigid Pavement
      • Flexible Pavement
      • Rigid Pavement Typical Applications
      • High volume traffic lanes
      • Freeway to freeway connections
      • Exit ramps with heavy traffic
    • 5.
      • Advantages of Rigid Pavement
      • Good durability
      • Long service life
      • Withstand repeated flooding and subsurface water without deterioration
    • 6.
      • Disadvantages of Rigid Pavement
      • May lose non-skid surface with time
      • Needs even sub-grade with uniform settling
      • May fault at transverse joints
      • Requires frequent joint maintenance
    • 7. Flexible Pavement Typical Applications
      • Traffic lanes
      • Auxiliary lanes
      • Ramps
      • Parking areas
      • Frontage roads
      • Shoulders
    • 8.
      • Advantages to Flexible Pavement
      • Adjusts to limited differential settlement
      • Easily repaired
      • Additional thickness added any time
      • Non-skid properties do not deteriorate
      • Quieter and smoother
      • Tolerates a greater range of temperatures
    • 9.
      • Disadvantages of Flexible Pavement
      • Loses some flexibility and cohesion with time
      • Needs resurfacing sooner than PC concrete
      • Not normally chosen where water is expected
    • 10. Basic AASHTO Flexible Pavement Design Method
      • Determine the desired terminal serviceability, p t
      • Convert traffic volumes to number of equivalent 18-kip single axle loads (ESAL)
      • Determine the structural number, SN
      • Determine the layer coefficients, a i
      • Solve layer thickness equations for individual layer thickness
    • 11. Basic AASHTO Rigid Pavement Design Method
      • Select terminal serviceability
      • Determine number of ESALs
      • Determine the modulus of sub-grade reaction
      • Determine the slab thickness
    • 12. 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
    • 13. Variables included in Nomographs
      • Effective Modulus of Sub-Grade Reaction, k
        • Considers:
          • Sub-base type
          • Sub-base thickness
          • Loss of support
          • Depth to rigid foundation
      • Drainage Coefficient, m i
        • Use in layer thickness determination
        • Applies only to base and sub-base
        • See Tables 20.15 (flexible) and 21.9 (rigid)
    • 14.
    • 15.
    • 16. Other Growth Rates
      • Multiple payment compound amount factor, with i = growth rate
      • G = [(1+i) n -1]/i
    • 17.
    • 18.
    • 19.
    • 20.
    • 21.
    • 22.
    • 23.
    • 24.
    • 25.
    • 26.
    • 27. Flexible Pavement Design
      • Pavement structure is a multi-layered elastic system, material is characterized by certain properties
        • Modulus of elasticity
        • Resilient modulus
        • Poisson ratio
      • Wheel load causes stress distribution (fig 20.2)
        • Horizontal: tensile or compressive
        • Vertical: maximum are compressive, decrease with depth
        • Temperature distribution: affects magnitude of stresses
    • 28. Components Sub-grade (roadbed) course: natural material that serves as the foundation of the pavement structure Sub-base course: above the sub-grade, superior to sub-grade course Base course: above the sub base, granular materials such as crushed stone, crushed or uncrushed slag, gravel, and sand Surface course: upper course of the road pavement, should withstand tire pressures, resistant to abrasive forces of traffic, provide skid-resistant driving surface, prevent penetration of surface water 3 inches to > 6 inches
    • 29. Economic Analysis
      • Different treatments results in different designs
      • Evaluate cost of different alternatives
    • 30. Sensitivity Analysis
      • Input different values of traffic volume
      • Compare resulting differences in pavement
      • Fairly significant differences in ADT do not yield equally significant differences in pavement thickness
    • 31. OTHER ISSUES
      • Drainage
      • Joints
      • Grooving (noise vs. hydroplaning)
      • Rumble strips
      • Climate
      • Level and type of usage
    • 32. FAILURE EXAMPLES
      • Primarily related to design or life-cycle, not construction
      • All images from Distress Identification Manual for the Long-Term Pavement Performance Program , Publication No. FHWA-RD-03-031, June 2003
    • 33. FATIGUE CRACKING
    • 34. RUTTING
    • 35. SHOVING
    • 36. PUMPING
    • 37. EXAMPLES
      • http://training.ce.washington.edu/wsdot/modules/09_pavement_evaluation/09-7_body.htm
      • http://training.ce.washington.edu/wsdot/modules/09_pavement_evaluation/09-8_body.htm