pavement design session 09-12 matakuliah: s0753 – teknik jalan raya tahun: 2009
TRANSCRIPT
Pavement DesignSession 09-12
Matakuliah : S0753 – Teknik Jalan RayaTahun : 2009
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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 Pavement2.Rigid Pavement3.Composite
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Flexible PavementThose 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 which can accommodate this "flexing".
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Flexible Pavement
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Types of Flexible Pavement
Dense-graded
Open-graded Gap-gradedCEE 320
Steve Muench
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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)
CEE 320Steve Muench
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Types of Rigid Pavement• Continuously Reinforced Concrete Pavement
(CRCP)
Photo from the Concrete Reinforcing Steel Institute
CEE 320Steve Muench
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Rigid Pavement
JOINT
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Composite
• Composite. Those which are surfaced with portland cement concrete (PCC) and bituminous /
asphalt materials as overlay construction
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Load & Stress Distribution
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Load & Stress Distribution
Surface
Base
Subbase
Subgrade
P ( Load )
Flexible Pavement
Bina Nusantara University 16Rigid Pavement
Load & Stress Distribution
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Surface
Subbase or base
Subgrade
P ( Load )
Rigid Pavement
Load & Stress Distribution
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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
Example design catalog from the Washington Asphalt Pavement Association (WAPA) for residential streets
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Empirical• 1993 AASHTO Flexible Equation
• 1993 AASHTO Rigid Equation
07.8log32.2
1
109440.0
5.15.4log
20.01log36.9log 10
19.5
10
101810
RoR M
SN
PSI
SNSZW
25.075.0
75.0
10
46.8
7
10
101810
42.1863.215
132.1log32.022.4
1
10624.11
5.15.4log
06.01log35.7log
kE
DJ
DCSp
D
PSI
DSZW
c
dctoR
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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, MrThe 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 Mr, then it must be documented with an explanation.
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Pavement design for Rigid Pavement
28-day Concrete Elastic ModulusElastic 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-valueThe 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 applying a load equal to 10 psi on the subgrade/subbase combination using a 30-inch diameter steel plate. The k-value is then calculated by dividing 10 psi by the measured deflection (in inches) of the layers under the plate.
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Pavement design for Rigid Pavement
Serviceability IndicesFor 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 CoefficientThe 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 CoefficientThe 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 to use a different value, then it must be documented and justified
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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 Soil, MR•Generally obtained from laboratory testing
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Pavement design for Flexible Pavement
Variables included in Nomographs
Effective Modulus of Sub-Grade Reaction, kSub-base typeSub-base thicknessLoss of supportDepth 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
CEE 320Steve Muench
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Rigid Pavement – Construction
Fixed form
CEE 320Steve Muench
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Rigid Pavement – ConstructionSlipform
CEE 320Steve Muench