Lecture 18
Rigid Pavement Design
PCA Method
1
PCA Procedure
Reference:
Thickness Design for Concrete Highway and
Street Pavements, Portland Cement Association
1984
2
Design Methods Addresses
• PCC Slab Thickness Regardless of Pavement
Type
• JPCP, JRCP, CRCP
• Joint Design Recommendations
3
PCA Pavement Design
• History
– 1966 and 1984
• Basis - Mechanistic Empirical
– Finite Element Program (JSLAB) used to
determine critical stresses and deflections
– Output coupled with design criteria (fatigue and
erosion)
– Design Criteria based on AASHO Road Test and
Faulting Studies
4
Thickness Design Factors
•
•
•
•
•
•
Doweled Joints: Yes or No
Shoulder Type: PCC or Other
PCC Modulus of Rupture
Subgrade and Subbase Support (k value)
Design Period
Expected Traffic and Load Safety Factor
5
PCC Modulus of Rupture (MR)
• Tensile Strength in Flexure at 28 days under
3rd Point Loading
• ASTM C78
• Note: MR = Sc in AASHTO
6
Subgrade and Subbase Support
• No Subbase
– k = k value of subgrade
• Subbase
– k = a composite k value for the
• subgrade and subbase
– Use Tables 1 and 2
7
subbase-subgrade k
Granular Base
CTB
8
Design Period
• Design Period is synonymous with TrafficAnalysis Period
9
Traffic
• See Traffic Analysis Notes considering
differences:
• Growth Factors (Table 3)
• Lane Distribution (Figure 3)
10
Growth Factors
11
Truck Traffic Distribution
12
Load Safety Factor
Traffic Safety Factor Applied to Axle Loads
Classification
Load Safety Factor
Interstates
1.2
Highway and Arterials
1.1
Roads and Residential Streets
1.0
13
Known Traffic Data
• Complete Calculation of Pavement Thickness
Table
• Assume Thickness
• Perform
– Fatigue Analysis
– Erosion Analysis
14
Calculation of Pavement Thickness
15
Fatigue Analysis
• Without PCC Shoulders
• With PCC Shoulders
16
17
18
19
Erosion Analysis
• Without PCC Shoulders
– Doweled joints or CRCP
– Aggregate interlock joints
• With PCC Shoulders
– Doweled joints or CRCP
– Aggregate interlock joints
20
21
22
23
24
25
26
27
28
29