Mechanistic-Empirical Pavement Design Guide

Tommy Nantung INDOT Research and Development Division

February 13, 2014

Pavements are designed to fail

(in a predictable way)

Performance vs. Design Life

From AASHTO 1993

Designer enters a trial design for a given set of site conditions

Design software analyzes the trial design and predicts performance

Design may be modified until agency performance requirements are met

MEPDG Procedure

It means, there is no unique solution

Pavement Design

“Practical” pavement design tool for practitioners

Pavement Analysis

Pavement analysis

Materials acceptance

Pavement performance analysis

Others

Academic exercise

MEPDG as a Tool

Chicken

Correct traffic data

Egg

Local calibration

Which one is first?

Pavement ME

Climate Traffic

Materials

Structure

Distress Response

Time

Damage

Damage

Accumulation

MEPDG – DARWin-ME – Pavement ME

M-E Design Process

Input Data

Environmental

Effects Model

Pavement

Response

Model(s)

Distress

Models

Material Characterization Models

Performance

Predictions

Traffic Model

User’s Decisions Inputs

General Traffic Climate Structure

Selection of Trial Design

Structural Responses (s, e, d)

Calibrated Damage-Distress Models Distresses Smoothness

Performance Verification Failure criteria

Design Reliability

Design Requirements

Satisfied? No

Feasible Design

Rev

ise

tria

l des

ign

Damage Accumulation with Time

Yes

Ottawa, IL

AASHO Road Test Location

Field Performance - The LTPP Study

Rigid Pavement Principle

Importance of Traffic

d ec Which criterion? (they don’t all give the same result!)

What is an ESAL? (based on serviceability)

et, or st

Traffic Input – No More ESALs

Number of axles by:

• Axle type

• Truck type

• Axle load interval

Effects of Climatic Conditions

0

10

20

30

40

50

60

70

3.4 3.6 3.8 4.0 4.2 4.4 4.6

28-day PCC modulus of elasticity, million psi

Perc

en

t sla

bs c

rack

ed

Illinois

Southern

California

17 million trucks (31 million ESALs)

9.5-in slab; 15-ft joint spacing; 4-in CTB

28-day PCC MR = 700 psi

α = 6 x 10-6

/°F

Combined Effects of αPCC and EPCC

0

5

10

15

20

25

30

35

40

45

28-day Epcc = 3.6 million psi 28-day Epcc = 4.2 million psi

Pe

rce

nt

sla

bs

cra

ck

ed

α = 5.5 x 10-6 /°F

α = 6.0 x 10-6 /°F

Incremental Damage Calculation

Time, years

Traffic

PCC Strength

Base Modulus

Subgrade

Modulus

CTB

Time

increment

2 8 6 4 0

Stress and Strain in Rigid Pavement

Curling stress

Stress and Strain in Rigid Pavement

Curling stress

Base

Subgrade

Critical stress region at

bottom of slab

JPCP Bottom-up Cracking

(Mid-slab Load + Positive Curl/Warp Condition)

Base

Subgrade

Critical stress

region at top of slab

JPCP Top Down Cracking

(Joint Load + Negative Curl/Warp Condition)

Critical Loading Condition

Outside Lane

Shoulder

Direction of traffic

Critical location (bottom of slab)

Bottom-up cracking

Critical Bottom-up Stresses

Critical Loading Condition

Outside Lane

Shoulder

Direction of traffic

Critical location (top of slab)

Top-down cracking

Critical Top-down Stresses

Top of slab (crack initiation)

JPCP Top-down Cracking

Design Guide uses Gain Curves to estimate the values of structural properties at any time during the design life for use in mechanistic damage analysis.

Concrete Properties

Concrete

IRI

Mid-slab cracking

Faulting

Asphalt

IRI

Fatigue cracking

Asphalt rutting

Total rutting

Top down cracking

Influence of Traffic to Performance

Ride Quality

(“Little Book”, 1998)

Speed = 80 km/h

(Vertical Distance)

Horizontal Distance

0

1

2

0.01 0.1 1 10 100

Wavelength, m

Gain

International Roughness Index (IRI)

Joint Faulting in JPCP

Transverse Cracking in JPCP

Punchout in CRCP

Importance of Traffic

The most single parameter that influences the pavement design

Traffic in Pavement ME

Effects of Axle Weight

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80

Tandem axle load, kips

Re

ma

inin

g T

raff

ic,

%

0%

1%

2%

3%

4%

5%

6%

7%

8%

9%

10%

Da

ma

ge

Co

ntr

ibu

tio

n,

%< 5% of traffic

35% of total damage

Top-down cracking

Problems in Traffic Data

Truck Class Distribution

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00

C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C0

Truck Class

Tru

ck V

olu

me

(%)

Unclassified trucks

Planning data: 126,005 AADT WIM actual data: 101,199 AADT

Traffic Data Analysis

Truck Weight Road Groups

Indiana has 56 WIM sites, 7 more to come Provide files for:

Monthly Adjustment Factor Vehicle Class Distribution Hourly Distribution Axle Load Distribution

Groups A for AADTT = 1 to 3,000 B for AADTT = 3,001 to 6,000 C for AADTT = 6,001 to 20,000 D for AADTT > 20,000

Default Traffic Load Spectra

Parameter Input Level 1 Input Level 3

AADTT, (Seasonal)

Segment specific Not Required

Truck type distribution

Segment specific, AVC

Default – TTC

Axle weight distribution

Segment specific, WIM

Default – TTC

AADT Not Required Segment specific, counts

% Trucks Not Required Segment specific, counts

• Tire Pressures • Axle Configurations • No. of Axles per Truck Type

Hourly Distribution of Trucks

Influences the curling

Traffic Wander

x

Direction of traffic

Pavement Shoulder

x

Direction of traffic

Pavement Shoulder

Typical Values X (mean) = 457 mm (18 in) X (SD) = 254 mm (10 in)

Used to calculate pavement responses & the number of axle load applications over a point for predicting distress & performance Mean wheel location Standard deviation Design lane width

Chicken Correct traffic data

Egg Local calibration

Which one is first if your traffic data is not correct?

Design Features

As a last resort to reduce the pavement curling stress

INDOT suggestions

15, 16, 17, and 18 feet

Calculate it based on cost savings

Thickness versus D1 joint costs

Outside Lane

Shoulder

Direction of traffic

Critical location (top of slab)

Joint Spacing

Slab width is assumed 12 feet

Slab width can be 12 to 14 feet

Influence the thickness <10 inches

The paint stripe is painted at 12 feet width

Pavement ME can be used to design pavement <12 feet, adjust the traffic wander

Widened slab

Requires correct input of Load Transfer Efficiency (LTE)

Monolithically placed and tied with deformed bars traffic lane and shoulder

50 to 70% LTE

Separately placed and tied with deformed bars traffic lane and shoulder

30 to 50% LTE

Tied Concrete Shoulder

PCCP Materials

Mix Property Inputs

Inputs for concrete mix Cement type

Type I or Type II or Type III (select from list)

Cement content Definition: Weight of cement per cubic yard of

concrete

Water-cement ratio Definition: Ratio of water to cement by weight

Aggregate type Mineral composition of aggregate (select from list)

Input

Level

1 2 3

Mix Property Inputs, cont.

Inputs for concrete mix

Used to predict concrete set temperature

Input values

Project-specific inputs

Typical value is agency-specific

Input

Level

1 2 3

Mix Property Inputs, cont.

Shrinkage inputs

Ultimate shrinkage

Definition: Shrinkage predicted at a relative humidity of 40%

Either user inputs or program calculates

Reversible shrinkage

Definition: Percentage of ultimate shrinkage that is reversible

Typical value: 50%

Input

Level

1 2 3

Mix Property Inputs, cont.

Shrinkage inputs, cont.

Time to develop 50 percent of ultimate shrinkage

Typical value: 35 days

Curing method

Curing compound (mostly)

Wet curing

Input

Level

1 2 3

Strength Property Inputs

Level 1 and 2: Inputs at 7, 14, 28, 90 days, and strength ratio at 20 years

* Required only for CRCP design

Level 3: Inputs @ 28 days

**Require either f’c, or Mr, or E and f’c, or E and Mr

Input

Level

Compressive Strength

(f’c)

Modulus of Elasticity

(E)

Modulus of Rupture

(Mr)

Tensile Strength

(ft) *

1

2

3**

Strength Property Inputs, cont.

Compressive strength, f’c

Definition: Axial stress at failure under compressive load

Test: ASTM C 39

Typical value: 4,500 psi

Input

Level

1 2 3

Strength Property Inputs, cont.

Elastic modulus, E

Definition: Ratio of stress to strain when the material is elastic

Indicator of deformation characteristics of the material

Test: ASTM C 469

Typical value: 4,200,000 psi

Input

Level

1 2 3

Strength Property Inputs, cont.

Modulus of rupture, Mr

Definition: Bending stress in concrete at failure (under flexural loads)

Indicator of tensile strength

Test: ASTM C 78

Typical value: 700 psi

Input

Level

1 2 3

“Life is like a box of chocolates, you never know what you will get next.”

Coefficient of Thermal Expansion

Coefficient of Thermal Expansion

Crushed Stone #8

Drainage Layer

Granular Stone #53

Separation Layer

Soil Treatment

Subgrade Soil

Particle-Size Analysis (ASTM D 422)

0

10

20

30

40

50

60

70

80

90

100

0.010.1110100

Sieve Opening (mm)

Pe

rce

nt

Pa

ssin

g (

%)

3in 2in 1in 3/4in No.4 No.40 No.200No.8

p200

D60

p4

Input

Level

1 2 3

Atterberg Limits (ASTM D 4318)

Plasticity Index = Liquid Limit - Plastic Limit

Input

Level

1 2 3

Moisture-Density Relationship

110

114

118

122

126

130

5 6 7 8 9 10 11 12 13 14 15

Gravimetric Moisture Content (%)

Dry

Un

it W

eig

ht

(pc

f)

wopt

gdmax

Input

Level

1 2 3

(ASTM D 698, D1557)

Resilient Modulus

(NCHRP 1-28A, AASHTO T307)

IRI issue in smoothness model (empirical)

IRI = IRII + 0.8203*cracking + 0.4417*Spalling +

1.4929*Faulting + 25.24*SF

Where:

IRII = Initial IRI

SF = Site Factor = AGE*(1 + FI)(1 + P0.075)/106

AGE = pavement age, yr FI = Freezing index, oC days P0.075 = percent subgrade material passing 0.075-mm sieve

Continuously Reinforced Concrete Pavement

Continuously Reinforced Concrete Pavement

Continuously Reinforced Concrete Pavement

Results

Results

Sensitivity

Parameter Roughness Faulting Percent Slabs

Cracked

Level 3

Modulus of Rupture S NS VS

Compressive Strength S NS VS

Level 2

Compressive Strength S NS VS

20-year/28-day Ratio S NS VS

Level 1

Modulus of Rupture S NS VS

Modulus of Elasticity S NS VS

20-year/28-day Ratio S NS VS

Sensitivity

Parameter Roughness Faulting Percent Slabs

Cracked

Permanent Curl/Warp Effective Temperature Difference

VS VS VS

Joint Spacing VS VS VS

Dowel Bar Diameter MS MS NS

Pavement Thickness S MS VS

Poisson’s Ratio MS MS S

Coefficient of Thermal Expansion

VS VS VS

Thermal Conductivity S MS VS

Pavement Design

“Practical” pavement design tool for practitioners

Constructability matters, 0.5 inch precision is excellent

Pavement Analysis

Materials acceptance

Pavement performance analysis

Others

Academic exercise

High precision to 0.01 inch

MEPDG as a Tool

Questions???