cee 3604 transportation engineering pavement...

Transportation Engineering (A.A. Trani)

CEE 3604 Transportation Engineering

Pavement Design

1


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

2

Read Florida DOT Pavement Design Document


Definition of Flexible Pavement Layers

• A typical pavement is made up of multiplelayers

3

source: Florida DOT Flexible Pavement Design Manual


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

4


Types of Pavements

• Flexible pavements

• Rigid pavements

5

Source: Encyclopedia Britannica


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)

6


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)

7

Example: Original Airport Pavement for Dulles International Airport (circa 1962)

8

Source: Fuselier, Grubs and McQueen, ASCE 2008 Transportation Engineering (A.A. Trani)


Example: New Specification for Airport Pavement at Dulles International Airport (circa 2005)

9

18 inches of PCC6 inch Cement Treated Base layer12 inch subgrade Soil (Cement Stabilized)


Why Do some Pavements Have to Be So Complex?

• To support large transportation vehicles (like very large aircraft)

10

Airbus A380-800 maximum takeoff mass is around 570 metric tons


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)

11


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

12


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)

13


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

14


AASHTO Design Equation

15


AASHTO Design Procedure (per Florida DOT Manual)

16


Design Periods (Florida DOT Design Manual)

17


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)

18


Design Procedure• Most DOTs have produced tables with acceptable values

of SNR for given inputs to the AASHTO Equation (see the Florida manual DOT)

19


Layer Calculations

20



Pavement Design Layer Calculations

21

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


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”

22


a1,a2,a3 and a4


Layer Coefficients (Table 5.4)

23



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

24


Design Example # 1 (AASHTO Method)

25



Design Example # 1 (Florida DOT Design Manual)

26



27




28



Asphalt Concrete Friction Course Selection Chart (Table 4.1)

29


Design Example (Initial Step)

30




31




32source: Florida DOT Flexible Pavement Design Manual


Design Example Solution

33source: Florida DOT Flexible Pavement Design Manual


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

33a



34




35




36


For example problem


Structural Numbers for Base Layer

Source: Florida Department of Transportation

36a

Note that using optionalbase group 10 with astructural course of 5''provides an SN number of 4.09 (versus 4.05 required)

atrani

Highlight

atrani

Highlight



37




38


For example problem



39




40



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

40a


Virginia Pavement Data

SMA Pavements Superpave Pavements

40b


Example of Pavement Design Software

40c

• 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


Minnesota DOT Software

https://www.dot.state.mn.us/materials/pvmtdesign/software.html

40d


Airport Pavements

41

Note: At rest, ~ 95% of the aircraft weight is on the main landing gear


Sample Airport Pavement Charts

42

Aircraft manufacturersprovide ready-made charts

for quick verification

http://www.boeing.com/commercial/airports

Boeing 777-300ER Taking Off at ChicagoO’Hare Airport



43

Boeing 777-300ERDimensions in

Airport Design Document

http://www.boeing.com/commercial/airports

Boeing 777-300ER Taking Off at ChicagoO’Hare Airport



44

Flexible PavementDesign Chart

U.S. Army Corps of Engineers

Design Method (S-77-1):

Source: 777-200LR / -300ER / -Freighter

Airplane Characteristics for Airport Planning



45


U.S. Army Corps of Engineers

Design Method (S-77-1):



California Bearing Ratio (CBR)

Flexible Pavement Thickness (inches)

Weight onMain Landing

Gear

Annual Departures


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

46

Check out information in : http://www.pavementinteractive.org/california-bearing-ratio/



47


Portland Cement Association

Design Method





48


Portland Cement Association

Design Method



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

cee 3604 transportation engineering pavement...

Documents