esign purposeof pavement - faculty server...
TRANSCRIPT
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
PURPOSE OF PAVEMENT• Protect the subgrade from excessive
permanent deformation• Resist loss of structural capacity from
fatigue produced by repeated traffic loads
• Provide adequate serviceability to users, without repair, for a given period of time
from Johnson (SCDOT)
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
FLEXIBLE PAVEMENT DESIGN PRINCIPLES
Design the pavement thick enough to ensure the strength of the subgrade
is not exceeded for the loads to which it will be exposed.
When a pavement is too thin the strength of the subgrade is
exceeded and the pavement experiences high strain causing it to
fatigue and eventually fail.
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
From Ohio DOT
FLEXIBLE PAVEMENT DESIGN PRINCIPLES
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
PAVEMENT BASICS
From FHWA NHI-05-037
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
PAVEMENT BASICS
from FHWA NHI-05-037
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
PAVEMENTBASICS?
from FHWA NHI-05-037
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
PAVEMENT BASICSDESIGN FACTORS
• Traffic Loading (heavy trucks)• Soil Subgrade Strength• Pavement Materials Characteristics
(strengths of materials comprising the pavement build-up)
• Environmental Conditions (Its effect on soil and pavement material strength)
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
PAVEMENT DESIGN METHODSSEVERAL DESIGN METHODS EXIST:
• American Association of State Highway and Transportation Officials (AASHTO 1972)
• American Association of State Highway and Transportation Officials (AASHTO 1993)
• Mechanistic-Empirical Pavement Design Guide (MEPDG) (NCHRP 1-37A)
• Various State DOT Procedures• Others (Asphalt Institute)
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHODBased on empirical models drawn from field
performance data measured at the AASHO road test in the late 1950’s.
http://www.pavementinteractive.org/article/AASHO-Road-Test/
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
DESIGN CONSIDERATIONS• Pavement Performance• Traffic• Roadbed Soil• Materials of Construction• Environment• Drainage• Reliability• Life Cycle Costs (& Shoulder Design)
AASHTO 1993 METHOD
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHOD
SN is the OUTPUT!
DESIGN EQUATION
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHOD
Where:a = Structural Number CoefficientD = Depth (i.e. thickness) (in inches)m = Drainage Coefficients1 = Surface, 2 = Base, 3 = Subbase
STRUCTURAL NUMBER (SN) EQUATION
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993
METHODSTRUCTURALNUMBER (SN)
A2 COEFFICIENTCORRELATIONS
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHODSTRUCTURAL NUMBER (SN) COEFFICIENTS
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHODSTRUCTURAL NUMBER (SN) m COEFFICIENTS
from FHWA NHI-05-037
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHOD
Where:ADTO = Average daily traffic at the start of the design periodT = Percentage of trucks in the ADTTf = Truck factor, or the number of 18 kip ESALs per truckG = Traffic growth factorD = Directional distribution factorL = Lane distribution factorY = Design period in years
W18 (ESAL) EQUATION
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHODW18 (ESAL) CALCULATIONS
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHODW18 (ESAL) Calculations
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHODW18 (ESAL)
CALCULATIONS
http://www.paiky.org/technical-resources/paiky-esal-calculator/
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHOD
RELIABILITY - OVERALL STANDARD DEVIATION (S0)
From FHWA NHI-05-037
For flexible pavements, values for S0typically range between 0.35 and 0.50, with a value of 0.45 commonly used for design.
RELIABILITYDesign reliability is defined as the probability that a pavement section will perform satisfactorily over the
design period. It must account for uncertainties in traffic loading, environmental conditions, and construction
materials.
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHODSTANDARD NORMAL DEVIATE (ZR)
From FHWA NHI-05-037
Step 1 – Determine Recommended Reliability
Level
Step 2 – Determine ZR using Recommended
Reliability Level
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHOD
From FHWA NHI-05-037
SERVICEABILITY (PSI)
Where:p0 = Initial Serviceability Index corresponds to road conditions immediately after construction. Typical value is 4.2.pt = Terminal Serviceability Index (i.e. the lowest serviceability that will be tolerated before rehabilitation or reconstruction becomes necessary). 2.5 recommended for major highways.
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHODSUBGRADE RESILIENT MODULUS (MR)
Correlations between resilient modulus and various material strength and index properties (from FHWA NHI-05-037)
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
AASHTO 1993 METHOD
SUBGRADE RESILIENTMODULUS (MR)
Typical Values (from NCHRP 1-37A, 2004)
Revised 03/2015
ENGN.4010 ENGINEERING CAPSTONE DESIGNFLEXIBLE PAVEMENT DESIGN
GENERAL DESIGN PROCEDURE1. Determine the analysis period.2. Evaluate the design traffic (W18).3. Determine the design reliability factors.4. Determine the allowable serviceability loss due to
traffic.5. Evaluate the subgrade resilient modulus MR.6. Solve Design Equation for the required overall
Structural Number.7. Calculate SN from various pavement options*
(iterative process).
AASHTO 1993 METHOD
* Might have Minimum Pavement Thickness requirements!