Presentation is loading. Please wait.

Presentation is loading. Please wait.

Pavement Design CE 453 Lecture 28.

Similar presentations

Presentation on theme: "Pavement Design CE 453 Lecture 28."— Presentation 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

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, 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 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, mi Use in layer thickness determination Applies only to base and sub-base See Tables (flexible) and 21.9 (rigid)













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 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 Economic Analysis Different treatments results in different designs
Evaluate cost of different alternatives

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 OTHER ISSUES Drainage Joints Grooving (noise vs. hydroplaning)
Rumble strips Climate Level and type of usage

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 , June 2003





Download ppt "Pavement Design CE 453 Lecture 28."

Similar presentations

Ads by Google