Matakuliah
Tahun
: S0753 – Teknik Jalan Raya
: 2009
Pavement Design
Session 09-12
Contents
• Pavement Classification
• Load & Stress Distribution
•Load Analysis
•Pavement design for Rigid Pavement
•Pavement Design for Flexible Pavement
•Overlay
•Pavement Construction
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Pavement Classification
Classification :
1.Flexible Pavement
2.Rigid Pavement
3.Composite
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Flexible Pavement
Those which are surfaced with
bituminous / asphalt
materials. These types of pavements
are called "flexible" since the total
pavement structure bends or
deflects due to traffic loads. A flexible
pavement structure is generally
composed of several layers of materials
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Flexible Pavement
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Types of Flexible Pavement
Dense-graded
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Open-graded
Gap-graded
CEE
7 320
Steve Muench
Rigid Pavement
Rigid pavements. Those which are surfaced with
portland cement concrete
(PCC). These types of pavements are called
"rigid" because they are substantially stiffer than
flexible pavements due to PCC's high stiffness.
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Rigid Pavement
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Types of Rigid Pavement
• Jointed Plain Concrete Pavement (JPCP)
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CEE 320
10
Steve Muench
Types of Rigid Pavement
• Continuously Reinforced Concrete Pavement
(CRCP)
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CEE 320
11
Steve Muench
Photo from the Concrete Reinforcing Steel Institute
Rigid Pavement
JOINT
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Composite
•
Composite. Those which are surfaced with portland
cement concrete (PCC) and bituminous / asphalt
materials as
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overlay construction
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Load & Stress Distribution
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Flexible Pavement
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Load & Stress Distribution
P ( Load )
Surface
Base
Subbase
Subgrade
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Flexible Pavement
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Load & Stress Distribution
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Rigid Pavement
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Load & Stress Distribution
P ( Load )
Surface
Subbase or base
Subgrade
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Rigid Pavement
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Pavement Design
• Several typical methods
– Design catalog
– Empirical
• 1993 AASHTO method
– Mechanistic-empirical
• New AASHTO method (as yet unreleased)
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Design Catalog
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Example design catalog from the Washington Asphalt
Pavement Association (WAPA) for residential streets
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Empirical
• 1993 AASHTO Flexible Equation
 PSI 
log 10 

4.5  1.5 

log 10 W18   Z R  S o  9.36  log 10 SN  1  0.20 
 2.32  log 10 M R   8.07
1094
0.40 
SN  15.19
• 1993 AASHTO Rigid Equation







PSI




log 10 

0.75

Sc Cd  D  1.132 
 4.5  1.5   4.22  0.32 p  log 
log 10 W18   Z R  S o  7.35  log 10 D  1  0.06 

t
10
1.624 107



1


8.46

18
.
42
D  1
 D 0.75 



215
.
63
J

0.25 
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

20
E



 c k  



  



Terms – Flexible
• W18 (loading)
– Predicted number of ESALs over the pavement’s life.
• SN (structural number)
– Abstract number expressing structural strength
– SN = a1D1 + a2D2m2 + a3D3m3 + …
• ΔPSI (change in present serviceability index)
– Change in serviceability index over the useful pavement life
– Typically from 1.5 to 3.0
• MR (subgrade resilient modulus)
– Typically from 3,000 to 30,000 psi (10,000 psi is pretty good)
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Terms – Rigid
• D (slab depth)
– Abstract number expressing structural strength
– SN = a1D1 + a2D2m2 + a3D3m3 + …
• S’c (PCC modulus of rupture)
– A measure of PCC flexural strength
– Usually between 600 and 850 psi
• Cd (drainage coefficient)
– Relative loss of strength due to drainage characteristics and the total
time it is exposed to near-saturated conditions
– Usually taken as 1.0
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Terms – Rigid
• J (load transfer coefficient)
– Accounts for load transfer efficiency
– Lower J-factors = better load transfer
– Between 3.8 (undoweled JPCP) and 2.3 (CRCP with tied shoulders)
• Ec (PCC elastic modulus)
– 4,000,000 psi is a good estimate
• k (modulus of subgrade reaction)
– Estimates the support of the PCC slab by the underlying layers
– Usually between 50 and 1000 psi/inch
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Pavement design for Rigid Pavement
The following input variables are needed for the AASHTO rigid
pavement design procedure:
•¨ 28-day Concrete Modulus of Rupture, psi¨ 28-day
•Concrete Elastic Modulus, psi¨
•Effective Modulus of Subbase/Subgrade Reaction, pci¨
•Serviceability Indices
•¨ Load Transfer Coefficient
•¨ Drainage Coefficient ¨
•Overall Standard Deviation
•¨ Reliability, %¨
•Design Traffic,
•18-kip Equivalanet Single Axle Load (SEAL).
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Pavement design for Rigid Pavement
28-day Concrete Modulus of Rupture, Mr
The Mr of concrete is a measure of the
flexural strength of the concrete as
determined by breaking concrete beam test
specimens. A Mr of 620 psi at 28 days should
be used with the current statewide
specification for concrete pavement design. If
the Engineer selects an alternate value for
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Mr, then it must be documented with an
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Pavement design for Rigid Pavement
28-day Concrete Elastic Modulus
Elastic modulus of concrete is an indication of
concrete stiffness. It varies depending on the
coarse aggregate type used in the concrete. Although
the value selected for pavement design could be
different from the actual values, the elastic modulus
does not have a significant effect on the computed slab
thickness. A modulus of 5,000,000 psi should be used
for pavement design. The use of a different value must
be documented with an explanation.
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Pavement design for Rigid Pavement
Effective Modulus of Subbase/Subgrade
Reaction: k-value
The AASHTO guide allows pavement designers to take
into account the structural benefits of all layers under
the concrete slab. It also allows designers to consider
the effect of loss of support of the underlying material
due to erosion or deterioration.
The slab support is characterized by the modulus
of
subgrade/ sub base reaction, otherwise known as
the k-value. It can be measured in the field by applying27a
load equal to 10 psi on the subgrade/subbase
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Pavement design for Rigid Pavement
Serviceability Indices
For concrete pavement design, the
difference
between the initial and terminal
serviceability is an important factor. An initial
serviceability value of 4.5 and a terminal serviceability
value of 2.5 are to be used in the procedure, which
results in a difference of 2.0. Different values, if used,
must be documented and justified.
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Pavement design for Rigid Pavement
Load Transfer Coefficient
The load transfer coefficient is used to incorporate the
effect of dowels, reinforcing steel, tied
shoulders, and tied curb and gutter on
reducing the stress in the concrete slab due to
traffic loading. The coefficients recommended in the
AASHTO Guide were based on findings from the AASHO
Road Test.
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Pavement design for Rigid Pavement
Drainage Coefficient
The drainage coefficient characterizes the
quality of drainage of the sub base layers
under the concrete slab. Good draining pavement
structures do not give water the chance to saturate the
subbase and subgrade; thus, pumping is not as likely to
occur.
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Pavement design for Rigid Pavement
Reliability, %
The reliability value represents a "safety
factor," with higher reliabilities representing
pavement structures with less chance of failure.
The AASHTO Guide recommends values
ranging from 50% to 99.9%, depending on the
functional classification and the location (urban
vs. rural) of the roadway. If the Engineer decides
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to use a different value, then it must be
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Pavement design for Flexible Pavement
• 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
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Pavement design for Flexible Pavement
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
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Pavement design for Flexible Pavement
Variables included in Nomographs
Effective Modulus of Sub-Grade
Reaction, k
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
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Flexible Pavement – Construction
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CEE 320
35
Steve Muench
Rigid Pavement – Construction
Fixed form
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CEE 320
36
Steve Muench
Rigid Pavement – Construction
Slipform
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CEE 320
37
Steve Muench