Pavement Design - II.pdf

Pavement Design Guest Lecturer Dr. Sirous Alavi, P.E. SIERRA TRANSPORTATION ENGINEERS, INC. 1005 Terminal Way, Suite 125 Reno, Nevada 89502

Topics „

Introduction – Design Factors – Pavement Types

„

Fundamentals of Pavement Design – AASHTO – Asphalt Institute

FUNDEMENTALS

Types of Design

State-of-Practice State-of-the-Art

Empirical

MechanisticMechanistic Empirical

1

FUNDEMENTALS

Mechanistic-Empirical (M-E) Design „

Primary advantage is the consideration of the state of stress

HMA Base Subbase Subgrade Soil

FUNDEMENTALS

Mechanistic-Empirical (M-E) Design „

Establishes connection between distress and distress mechanism

FUNDEMENTALS

Mechanistic-Empirical (M-E) Design Accounts for new materials, traffic loads, and construction procedures „ All design features affecting pavement performance considered „ Relies more on fundamental engineering mechanics „ Primary focus on pavement performance „

2

FUNDEMENTALS

Mechanistic-Empirical (M-E) Design „ „

1993 AASHTO Guide Design Variables – – – – – –

Time Traffic Reliability Environment Serviceability Structural Number

FUNDEMENTALS

Mechanistic-Empirical (M-E) Design

FUNDEMENTALS

AASHTO Design „ Time

Constraints

– Performance Period „ Refers

to the time that an initial pavement structure will last before rehab

– Analysis Period „ Refers

to the period of time that any design strategy must cover

3

FUNDEMENTALS

AASHTO Design „

Traffic – Equivalent Single Axle Load (ESAL) „ Converts

wheel loads of various magnitudes and repetitions to an equivalent number of "standard" or "equivalent" loads based on the amount of damage they do to the pavement

FUNDEMENTALS

AASHTO Design „

Equivalent Axle Load Factor (EALF) – Damage per pass to a pavement by the axle in question relative to the damage per pass of a standard axle load – Depends of type of pavements, thickness or structural capacity and terminal conditions

FUNDEMENTALS

EALF Table for Flexible Pavement, Single Axle & pt of 2.5 Pavement Structural Number (SN) Axle Load (kips) 2 4 6 8 10 12 14 16

1

2

3

4

5

6

0.004 0.003 0.011 0.032 0.078 0.168 0.328 0.591

0.004 0.004 0.017 0.047 0.102 0.198 0.358 0.613

0.003 0.004 0.017 0.051 0.118 0.229 0.399 0.646

0.002 0.003 0.013 0.041 0.102 0.213 0.388 0.645

0.002 0.002 0.010 0.034 0.088 0.189 0.360 0.623

0.002 0.002 0.009 0.031 0.080 0.176 0.342 0.606

4

FUNDEMENTALS

AASHTO Design „

m

„

i =1

„

ESAL = ∑ Fi ni

m = number of axle load groups Fi = the EALF for the ith axle load group ni = number of passes of the ith axle load group

FUNDEMENTALS

200X AASHTO Design Guide „ „

„

No more ESALs Traffic input – Vehicle type (number of axles) – Axle weight Quantity and quality of raw traffic data similar to that used to compute ESALS – Consistent with FHWA Traffic Monitoring Guide

FUNDEMENTALS

Traffic Hierarchical Input Levels

Input Level

Input Values

Knowledge of Parameters

1

Site specific WIM & AVC

Good

2 3

Regional Default WIM & AVC, Vehicle Counts National Default WIM & AVC, Vehicle Counts

Modest Poor

5

200X AASHTO Design Guide Load Spectra – Axle weight frequencies for each common axle combination (e.g. single axle, tandem axle, tridem axle, quad axle).

800

700

600

Number of Axles

FUNDEMENTALS

„

500

400 300

200

100

0 0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

55000

60000

65000

70000

75000

80000

Axle Load (lbs)

FUNDEMENTALS

AASHTO Design „

Reliability - Incorporating some degree of certainty into the design process to ensure that various design alternatives will last the Analysis Period Recommended Level of Reliability Functional Classificaiton

Urban

Rural

Interstate Arterials Collectors Local

85 - 99.9 80 - 99 80 - 95 50 - 80

80 - 99.9 75 - 95 75 - 95 50 - 80

FUNDEMENTALS

AASHTO Design „ Environmental

– Temperature „ Stresses

induced by thermal action „ Changes in creep properties „ Effect of freezing and thawing of subgrade

– Rainfall „ Penetration

of surface water into underlying

materials

6

FUNDEMENTALS

AASHTO Design „ Serviceability

– Initial serviceability index is function of pavement type and construction quality – Terminal serviceability index is lowest index that will be tolerated before rehab, resurfacing, or reconstruction

SURFACE (AC)

AASHTO Design

BASE

FUNDEMENTALS

SUBBASE (OPTIONAL)

„

Structural Number

SUBGRADE

– mi = drainage coefficient for layer i – a1, a2, a3 = layer coefficient representative of surface, base, and subbase course, respectively – D1, D2, D3 = thickness representative of surface, base, and subbase course, respectively

SN = a1D1 + a2 D2 m2 + a3 D3 m3

FUNDEMENTALS

AASHTO Design Example „ Ridgeview

Dr. Rehabilitation

– 20-year flexible pavement analysis period – Low volume road with limited growth potential

7

NAM ED

M PLU

VIEW

COPPER POINT

R IDGE

AS

FUNDEMENTALS

C OPP

ER PO INT

COPPER POINT

GREEN RANCH

V GE IE W

D ME TA

ADO W HEIG

IN VIS

WINDY M

MOU N TA

NS CR EE

HTS

GREEN RA NCH

RID

NA UN

RIDGEVIEW

UM PL

W VIE GE

AS

RID COPPER

„ Traffic

– 72-hour vehicle counts were conducted directionally at three locations within the project boundaries using machine traffic counters – Manual classification counts were conducted at the machine count locations to “calibrate” the machine count data and categorize into the FHWA 13 vehicle classification scheme

Vehicle Classification

FUNDEMENTALS

AASHTO Design Example

8

Adjusted Traffic Volumes and Vehicle Classification Year 2005 Through 2010 Road Segment:

Ridgeview Drive @ Plumas Street Class 1

EB

Class 2

% Volume

WB

Volume

Class 3

Class 4

Class 5

Class 6 0.15

Class 9

Total

43.64

54.11

0.35

1.60

0.15

100

1132.30

1404.00

9.10

41.60

3.90

3.90

2594.8

43.29

54.11

0.70

1.60

0.15

0.15

100

1123.20

1404.00

18.20

41.60

3.90

3.90

2594.8

%

5189.6 Road Segment:

Class 1

FUNDEMENTALS

Total ADT

Ridgeview Drive @ Mountain Vista Way

EB

Class 2

%

43.44

Volume WB

Class 3

823.65

54.11 1026.00

Class 4

Class 5

0.45

1.60

8.55

30.40

Class 6 0.20

Class 9

Total

0.20

100

3.80

3.80

%

42.94

54.11

0.95

1.60

0.20

0.20

100

Volume

814.15

1026.00

18.05

30.40

3.80

3.80

1896.2

1896.2

3792.4

Total ADT

Adjusted Traffic Volumes and Vehicle Classification Year 2011 Through 2025 Road Segment:

Ridgeview Drive @ Plumas Street Class 1

EB

% Volume

WB

% Volume

Class 2

Class 3

Class 4

Class 5

43.94

54.11

0.35

1.60

1140.10

1404.00

9.10

41.60

43.59

54.11

0.70

1.60

1131.00

1404.00

18.20

41.60

Class 6

Class 9

0.00

0.00

0.00

0.00

Total 100 2594.8 100 2594.8 5189.6

Road Segment:

Total ADT

Ridgeview Drive @ Mountain Vista Way Class 1

EB WB

Class 2

Class 3

Class 4

Class 5

%

43.84

54.11

0.45

1.60

Volume

831.25

1026.00

8.55

30.40

%

43.34

54.11

0.95

1.60

Volume

821.75

1026.00

18.05

30.40

Class 6

Class 9

0.00

0.00

0.00

0.00

Total 100 1896.2 100 1896.2 3792.4

Total ADT

AASHTO Design Example FUNDEMENTALS

Compute ESALs using EALFs from AASHTO Tables in Appendix D „ Assumptions „

– Typical axle weights for each vehicle class – SN of 3.0 – pt of 2.5

WB Daily ESALs

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

WB Yearly ESALs

Cumulative ESALs

Plumas

Mountain Vista

Plumas

Mountain Vista

Plumas

Mountain Vista

90 90 90 90 90 90 75 75 75 75 75 75 75 75 75 75 75 75 75 75 75

81 81 81 81 81 81 66 66 66 66 66 66 66 66 66 66 66 66 66 66 66

33,031 33,031 33,031 33,031 33,031 33,031 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362 27,362

29,487 29,487 29,487 29,487 29,487 29,487 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963 23,963

33,031 66,062 99,093 132,124 165,155 198,187 225,548 252,910 280,271 307,633 334,994 362,356 389,717 417,079 444,441 471,802 499,164 526,525 553,887 581,248 608,610

29,487 58,973 88,460 117,947 147,433 176,920 200,882 224,845 248,807 272,770 296,732 320,695 344,657 368,620 392,582 416,545 440,507 464,470 488,432 512,395 536,357

9

FUNDEMENTALS

AASHTO Design Example „

Materials – R-value data was collected at five sample locations (8, 7, 10, 20, 8) – Resilient Modulus (MR) relationship

R-value ≤ 20 MR = 1000 + 555 x R-value (psi)

Parameter Design Life, years Traffic (ESALs), W18 Reliability, R (%)

Average 20 610,000 80%

Standard Deviation (New Construction), So

0.45

Subgrade R-value

10.60

Subgrade Resilient Modulus, MR (ksi)

6.9

Initial Serviceability, P0

4.2

Terminal Serviceability, Pt

2.5

Modulus of Elasticity for New AC (ksi)

350

Layer Coefficient for New Plant Mix Surface (AC), a1

0.39

Layer Coefficient for Gravel Base, a2

0.14

Layer Coefficient for Subbase (Borrow), a3

0.08

Drainage Coefficient for AC layer, m1

1.0

Drainage Coefficient for Base layer, m2

1.1

Drainage Coefficient for SB layer, m3

1.1

SN ≈ 3.1

10

AASHTO Design

SURFACE (AC) BASE

FUNDEMENTALS

SUBGRADE

„

Assume D values for surface and base – Asphalt is 4 inches – Base is 10 inches

„

Calculate SN - Is it acceptable?

SN = a1D1 + a2 D2 m2 SN = 0.39 × 4.0 in + 0.14 × 10 in × 1.1 SN = 3.1

Topics „

Introduction – Design Factors – Pavement Types

„

Fundamentals of Pavement Design – AASHTO – Asphalt Institute

FUNDEMENTALS

Asphalt Institute (AI) Design „

Determine minimum thickness of asphalt layer that will adequately withstand the stresses that develop for two strain criteria – Vertical compressive strain at surface of subgrade – Horizontal tensile strain at bottom of asphalt layer

11

Asphalt Institute (AI) Design FUNDEMENTALS

Wheel load

P0 P1

P1 SUBGRADE

Stress distribution within different layers of the pavement structure

General form of stress reduction

Asphalt Institute (AI) Design FUNDEMENTALS

Wheel load

SUBGRADE

Tension Compression

FUNDEMENTALS

Asphalt Institute (AI) Design „

20% Fatigue

Design Criteria – Fatigue „ Nf

= allowable number of load repetitions = dynamic modulus „ ∈t = horizontal tensile strain at the bottom of the asphalt layer „ Assumes asphalt volume of 11% and air void volume of 5% „ |E*|

Nf = 0.0796(∈t)-3.291 |E*|-0.854

12

FUNDEMENTALS

Asphalt Institute (AI) Design „

0.5 inch

Design Criteria – Permanent Deformation „ Nd

= allowable number of load repetitions = vertical compressive strain on the surface of the subgrade

„ ∈c

Nd = 1.365 x 10-9 (∈c)-4.477

FUNDEMENTALS

Asphalt Institute (AI) Design „

Five main steps 1. 2. 3. 4.

Select or determine input data Select surface and base materials Determine minimum thickness required Evaluate feasibility of staged construction and prepare plan, if necessary 5. Carry out economic analyses

NAM ED

M PLU

VIEW

COPPER POINT

R IDGE

AS

C OPP

ER PO INT

IE W

TA

ADO W HEIG

IN VIS

WINDY M

MOU N TA

NS CR EE

HTS

GREEN RA NCH

V GE

D ME

RIDGEVIEW

COPPER POINT

GREEN RANCH

RID

NA UN

FUNDEMENTALS

UM PL

W VIE GE

AS

RID COPPER

13

FUNDEMENTALS

Asphalt Institute (AI) Design Example Gross „

Select or determine input data – Traffic Characteristics – ESALs similar to AASHTO

WB Daily ESALs

2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Axle Load (kips) 1 2 4 6 8 10 12 14 16

WB Yearly ESALs

Single Tandem Tridem Axles Axles Axles 0.00002 0.00018 0.00209 0.0003 0.01043 0.001 0.00030 0.0343 0.003 0.001 0.0877 0.007 0.002 0.189 0.014 0.003 0.360 0.027 0.006 0.623 0.047 0.011

Cumulative ESALs

Plumas 2

Plumas 2

Plumas 2

118 118 118 118 118 118 72 72 72 72 72 72 72 72 72 72 72 72 72 72 72

43,110 43,110 43,110 43,110 43,110 43,110 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197 26,197

43,110 86,221 129,331 172,441 215,552 258,662 284,859 311,057 337,254 363,451 389,649 415,846 442,043 468,241 494,438 520,635 546,833 573,030 599,227 625,425 651,622

FUNDEMENTALS

Asphalt Institute (AI) Design Example „ Select

or determine input data

– R-value data was collected at five sample locations (8, 7, 10, 20, 8) – Resilient Modulus (MR) relationship MR = 1155 + 555 x R-value (psi)

14

FUNDEMENTALS

Asphalt Institute (AI) Design Example „ Select

surface and base materials

– Asphalt concrete surface or emulsified asphalt surface – Asphalt concrete base, emulsified asphalt base, or untreated aggregate base

FUNDEMENTALS

Asphalt Institute (AI) Design Example „

Determine minimum thickness required – Obtained by computer program – Entering the appropriate table or chart „ Assume

10 inch untreated aggregate base MR of 7 psi „ Design ESAL of 655,000 „ Subgrade

6.5 inch

15

FUNDEMENTALS

Asphalt Institute (AI) Design Example „ Evaluate

feasibility of staged construction and prepare plan, if necessary – Used when adequate funds are not available to construct the pavement to the “required” depth

FUNDEMENTALS

Asphalt Institute (AI) Design Example „ Carry

out economic analyses

– Evaluate alternative designs based on the type of pavement, type of materials used, whether or not staged construction is used, etc.

FUNDEMENTALS

Questions

16