CAIRO UNIVERSITY FACULTY OF ENGINEERING PUBLIC WORKS DEPARTMENT 4 th Year Civil Engineering Highway Engineering Course 2008-2009 Structural Design of Pavements Lecturer Dr. Eng. Omar Osman Asst. Professor of Highway & Airport Engineering Faculty of Engineering, Cairo University
Structural Design of Pavements II- Rigid Pavements - Materials - Stresses - Design Methods
Pavement Types -Flexible -Rigid
Factors Influencing Pavement Design/Performance
Critical Concrete Pavement Responses: Distresses Faulting Cracks Corner Breaks Joint Failure
RIGID PAVEMENT TYPES a) Simply Reinforced b) doweled c) plain d) skewed joints
JOINT TYPES Expansion: Doweled Contraction: Keyed Construction: Doweled Construction:
JOINT TYPES
STRUCTURAL SYSTEM
STRUCTURAL SYSTEM SUBGRADE SUPPORT Modulus of Subgrade Reaction: k (pci)
STRUCTURAL SYSTEM Radius of Relative Stiffness [25~98 inch] [8~24 inch] [0.15] [50~500 pci] [4,000,000 psi]
STRESSES IN RIGID PAVEMENTS Temperature: Warping Stresses
Temperature: Warping Stresses [0.000005] [2~3 ºF/inch]
Temperature: Warping Stresses
STRESSES IN RIGID PAVEMENTS Temperature: Friction Stresses [1.5]
Temperature: Friction Stresses Slab Length
STRESSES IN RIGID PAVEMENTS Loading Wheel Loads & Stresses
STRESSES IN RIGID PAVEMENTS Loading Cases
STRESSES IN RIGID PAVEMENTS Loading Stresses
STRESSES IN RIGID PAVEMENTS Loading Stresses
PCA Design Method Design Considerations: Flextural Strength of Concrete Subgrade & Subbase Support Traffic Load Design Procedure: Finite-element analysis: Stresses & Deflections Fatigue analysis (crack initiation) Erosion analysis (Pumping, Faulting)
PCA Design Method Flextural Strength of Concrete (modulus of rupture) ASTM C78 Third-point method P L / (w d 2 )
PCA Design Method Subgrade Characterization
PCA Design Method Subbase Support: Correction of Modulus of sub grade reaction (K) associated with agg. subbase thickness.
PCA Design Method Traffic Axle configuration and loads: Classes & Counts Load factors Interstate: 1.2 Arterial: 1.1 Local access: 1.0
PCA Design Method Fatigue analysis To limit fatigue cracking (initiation of first crack) Determine equivalent stress associate with sub grade reaction and pavement thickness Determine stress ratio = equivalent stress/mor Determine allowable number of stress application at the given axel load and stress ratio Repeat for all axel loads Calculate the % fatigue life used for each applied load. The sum for all loads must be less then 100%. Erosion analysis Basically the same method is used as in the fatigue analysis. Limiting corner deflections is the target.
PCA Method Fatigue Analysis, Equiv. Stress; No Shoulder
PCA Method Fatigue Analysis, Equiv. Stress; With Shoulder
PCA Method Fatigue Analysis, Allowable Repetitions
PCA Method Erosion Analysis, Erosion Factor; Doweled No Shoulder
PCA Method Erosion Analysis, Erosion Factor; Agg Interlock No Shldr
PCA Method Erosion Analysis, Erosion Factor; Doweled & Shoulder
PCA Method Erosion Analysis, Erosion Factor; Agg Interlock & Shldr
PCA Method Erosion Analysis, Allowable Repetitions No Shoulder
PCA Method Erosion Analysis, Allowable Repetitions With Shoulder
PCA Method Thickness Design Example