cee 3604 transportation engineering pavement...
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Transportation Engineering (A.A. Trani)
Pavement Design
• The level of service of roads depends not only onnumber of lanes and safety features of the road butalso on the quality of pavements
• Pavement design techniques:
• Flexible and Rigid pavements
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Read Florida DOT Pavement Design Document
Transportation Engineering (A.A. Trani)
Definition of Flexible Pavement Layers
• A typical pavement is made up of multiplelayers
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Definitions• Friction course
• Provides a skid-resistancesurface
• Structural course
• Distributes the traffic loadsto the base course
• Base course
• Supports the structuralcourse and distribute loads tothe stabilization (subgrade)layer
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Transportation Engineering (A.A. Trani)
Types of Pavements
• Flexible pavements
• Rigid pavements
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Source: Encyclopedia Britannica
Transportation Engineering (A.A. Trani)
Flexible Pavements
• Multi-Layered system (3-4 layers)
• Design life is usually 10-20 years
• Unit cost ($2-$3 per square foot according toRO Anderson Engineers, 2017)
• Higher maintenance cost
• Relatively low flexural strength (highdeformation of the sub-grade)
• Better ride quality (no expansion joints)
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Transportation Engineering (A.A. Trani)
Rigid Pavements
• Normally 2-3 layers
• Design life 30-40 years
• Unit cost ($6-$8 per square foot according toRO Anderson Engineers, 2017)
• Lower maintenance cost
• Relatively high flexural strength (lessdeformation of sub-grade)
• Lower ride quality (due to expansion joints)
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Example: Original Airport Pavement for Dulles International Airport (circa 1962)
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Source: Fuselier, Grubs and McQueen, ASCE 2008 Transportation Engineering (A.A. Trani)
Transportation Engineering (A.A. Trani)
Example: New Specification for Airport Pavement at Dulles International Airport (circa 2005)
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18 inches of PCC6 inch Cement Treated Base layer12 inch subgrade Soil (Cement Stabilized)
Transportation Engineering (A.A. Trani)
Why Do some Pavements Have to Be So Complex?
• To support large transportation vehicles (like very large aircraft)
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Airbus A380-800 maximum takeoff mass is around 570 metric tons
Transportation Engineering (A.A. Trani)
AASHTO Equation
• An equation that relates the pavementstructural performance and various operationalfactors such as the vehicle loadings, strength ofroadbed soils and pavement structure
• The American Association of State Highway Officials(AASHTO)
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Transportation Engineering (A.A. Trani)
AASHTO Design Equation Variables
• Accumulated 18-kip Equivalent Single Axle LoadsESAL or ESALD
• Traffic load information used in pavement design
• Traffic levels for ESAL
• Resilient Modulus (MR)
• A measurement of the stiffness of the roadbedsoil
• Reliability (%R)
• Standard Normal Deviate (ZR)
• Reliability (%R) value converted into logarithmicform for calculations purposes
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Transportation Engineering (A.A. Trani)
AASHTO Equation Design Constants
• Standard deviation (So)
• Accounts for variability in traffic load and construction (So = 0.45 typical)
• Current Serviceability Index (PSI)
• A rating of 0 to 5 is used with 5 being the best and 0 being the worst
• Initial Serviceability (PI)
• Terminal Serviceability (PT)
• Change in Serviceability (dPSI)
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Transportation Engineering (A.A. Trani)
AASHTO Design Procedure
• Required Structural Number (SNR)
• “a weighted thickness in inches calculated from traffic load information and roadbed soil stiffness, representing the required strength of the pavement structure”
• The objective of the AASHTO design method is to calculate the value of SNR
• SNR represents the strength of the pavement required to carry the traffic loads down to the road soil layer with adequate serviceability throughout the life cycle of the pavement
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Transportation Engineering (A.A. Trani)
Design Procedure Required Structural Number
• Step 1 - the 18-kip Equivalent Single Axle Loads 18-kip (ESAL's) are obtained from the District Planning Office
• Step 2 - the Resilient Modulus (MR) used to characterize the strength of the roadbed soil is obtained from actual laboratory testing
• Step 3 - A safety factor is applied using a Reliability (%R) value from Table 5.2. Recommended values range from 75 to 99%. A Standard Deviation (SO) of 0.45 is used in the calculation. The Standard Normal Deviate (ZR) is dependent on the Reliability (%R)
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Design Procedure• Most DOTs have produced tables with acceptable values
of SNR for given inputs to the AASHTO Equation (see the Florida manual DOT)
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Layer Calculations
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source: Florida DOT Flexible Pavement Design Manual
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Pavement Design Layer Calculations
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SNc = a1D1+ a2D2 + a3D3+ a4D4
where:SNc= Total calculated strength of all pavement layers (inches or millimiters)a1 = first pavement layer coefficient (dim)D1 = first pavement layer thickness (inches or millimiters)a2,a3 and a4 are coefficients for other layersD2,D3 and D4 are thicknesses forother layers
Transportation Engineering (A.A. Trani)
Layer Coefficients (per Florida DOT Manual)
• “Layer coefficients ( ) have been developed which represent the relative strength of different pavement in materials”
• “The values for these materials are given in Table5.4” of the Florida Pavement Design Manual
• The coefficients presented in this table are basedon the best available data. Future adjustments willbe made to these values by manual revisions shouldresearch or other information dictate”
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source: Florida DOT Flexible Pavement Design Manual
a1,a2,a3 and a4
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Layer Coefficients (Table 5.4)
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Design Examples (Florida DOT Design Manual)
• Page 47 of Florida DOT Flexible Pavement design Manual
• Go to page 64 in the DOT Flexible Pavement Design Manual
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Design Example # 1 (AASHTO Method)
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Design Example # 1 (Florida DOT Design Manual)
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Design Example # 1 (Florida DOT Design Manual)
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Asphalt Concrete Friction Course Selection Chart (Table 4.1)
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Design Example (Initial Step)
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Design Example (Initial Step)
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Design Example (Initial Step)
32source: Florida DOT Flexible Pavement Design Manual
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Design Example Solution
33source: Florida DOT Flexible Pavement Design Manual
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Example of FC-5 Material
Source: Jim Musselman , Florida Department of Transportation
Permeable 3/4 inch layerTexture and aggregates to improve friction and avoid hydroplaning
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Design Example Solution
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Design Example Solution
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source: Florida DOT Flexible Pavement Design Manual
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Design Example Solution
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source: Florida DOT Flexible Pavement Design Manual
For example problem
Transportation Engineering (A.A. Trani)
Structural Numbers for Base Layer
Source: Florida Department of Transportation
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Note that using optionalbase group 10 with astructural course of 5''provides an SN number of 4.09 (versus 4.05 required)
Transportation Engineering (A.A. Trani)
Design Example Solution
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Design Example Solution
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source: Florida DOT Flexible Pavement Design Manual
For example problem
Transportation Engineering (A.A. Trani)
Design Example Solution
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Design Example Solution
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source: Florida DOT Flexible Pavement Design Manual
Transportation Engineering (A.A. Trani)
Typical Cost of Mix Asphalt
Source: Yin and West, 2018 - https://eng.auburn.edu/research/centers/ncat/files/technical-reports/rep18-03.pdf
SMA = Stone Matrix AsphaltSuperpave = Superior Performing Asphalt Pavement
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Transportation Engineering (A.A. Trani)
Virginia Pavement Data
SMA Pavements Superpave Pavements
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Transportation Engineering (A.A. Trani)
Example of Pavement Design Software
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• Uses National Cooperative Highway research Program (NCHRP) Mechanistic-Empirical method
• Calculates pavement responses (stresses, strains, and deflections)
• Includes traffic, climate, and materials parameters
• Hot-mix asphalt (HMA) and Portland Cement Concrete (PCC) pavements
https://www.aashtoware.org/wp-content/uploads/2018/10/Pavement-ME-Design-Brochure-FY-2019.pdf
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Minnesota DOT Software
https://www.dot.state.mn.us/materials/pvmtdesign/software.html
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Airport Pavements
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Note: At rest, ~ 95% of the aircraft weight is on the main landing gear
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Sample Airport Pavement Charts
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Aircraft manufacturersprovide ready-made charts
for quick verification
http://www.boeing.com/commercial/airports
Boeing 777-300ER Taking Off at ChicagoO’Hare Airport
Transportation Engineering (A.A. Trani)
Sample Airport Pavement Charts
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Boeing 777-300ERDimensions in
Airport Design Document
http://www.boeing.com/commercial/airports
Boeing 777-300ER Taking Off at ChicagoO’Hare Airport
Transportation Engineering (A.A. Trani)
Sample Airport Pavement Charts
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Flexible PavementDesign Chart
U.S. Army Corps of Engineers
Design Method (S-77-1):
Source: 777-200LR / -300ER / -Freighter
Airplane Characteristics for Airport Planning
Transportation Engineering (A.A. Trani)
Sample Airport Pavement Charts
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Flexible PavementDesign Chart
U.S. Army Corps of Engineers
Design Method (S-77-1):
Source: 777-200LR / -300ER / -Freighter
Airplane Characteristics for Airport Planning
California Bearing Ratio (CBR)
Flexible Pavement Thickness (inches)
Weight onMain Landing
Gear
Annual Departures
Transportation Engineering (A.A. Trani)
California Bearing Ratio (CBR)
• A measure of the load-bearing capacity (or strength) of natural soil
• Strength of soil compared to crushed California limestone (assumed to have a CBR value of 100)
• CBR is a standard described in ASTM Standard D1883-05 (for laboratory samples)
• D4429 (for soils in the field)
• AASHTO T193
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Check out information in : http://www.pavementinteractive.org/california-bearing-ratio/
Transportation Engineering (A.A. Trani)
Sample Airport Pavement Charts
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Flexible PavementDesign Chart
Portland Cement Association
Design Method
Source: 777-200LR / -300ER / -Freighter
Airplane Characteristics for Airport Planning
Transportation Engineering (A.A. Trani)
Sample Airport Pavement Charts
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Flexible PavementDesign Chart
Portland Cement Association
Design Method
Source: 777-200LR / -300ER / -Freighter
Airplane Characteristics for Airport Planning
Allo
wab
le W
orki
ng S
tres
s (p
si)
Pave
men
t Thi
ckne
ss (
inch
es) Subgrade
StrengthModulus
(lb/cu.inch)
Weight onMain Landing
Gear