28 Pavement Design presentation of runway.ppt
- 1. 1 Pavement Design CE 453 Lecture 28
- 2. 2 Objectives Understand and complete ESAL calculation Know variables involved in and be able to calculate required thickness of rigid and flexible pavements
- 3. 3 AASHTO Pavement Design Method Considerations Pavement Performance Traffic Roadbed Soil Materials of Construction Environment Drainage Reliability Life-Cycle Costs Shoulder Design
- 4. 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. 5 Advantages of Rigid Pavement Good durability Long service life Withstand repeated flooding and subsurface water without deterioration
- 6. 6 Disadvantages of Rigid Pavement May lose non-skid surface with time Needs even sub-grade with uniform settling May fault at transverse joints
- 7. 7 Flexible Pavement Typical Applications Traffic lanes Auxiliary lanes Ramps Parking areas Frontage roads Shoulders
- 8. 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. 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. 10 Basic AASHTO Flexible Pavement Design Method 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
- 11. 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. 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. 13 Variables included in Nomographs Effective Modulus of Sub-Grade Reaction, k • Considers: 1. Sub-base type 2. Sub-base thickness 3. Loss of support 4. Depth to rigid foundation Drainage Coefficient, mi • Use in layer thickness determination • Applies only to base and sub-base • See Tables 20.15 (flexible) and 21.9 (rigid)
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- 26. 26 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
- 27. 27 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
- 28. 28 Economic Analysis • Different treatments results in different designs • Evaluate cost of different alternatives
- 29. 29 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
- 30. 30 OTHER ISSUES Drainage Joints Grooving (noise vs. hydroplaning) Rumble strips Climate Level and type of usage
- 31. 31 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. 33 RUTTING
- 34. 34 SHOVING
- 35. 35 PUMPING