ByMr.Surasak Kaewdee

Transportation Engineering

Dr. Kunnawee Kanitpong (Adviser)

Asian Institute of Technology

ANALYSIS OF TRAFFIC LOADING CHARACTERISTICSFOR MECHANISTIC-EMPIRICAL PAVEMENT DESIGN

IN THAILAND

Introduction

Method for the flexible pavement design

1. Empirical Method - based on past experience designs and the data generated from the field tests

2. Mechanistic – Empirical (M-E) Method- based on the use of stress, strain and deflection

analysis to determine the minimum thickness of pavement

Introduction

Disadvantage of the empirical design method.

1. Limited only to certain pavement materials that were developed Limited only one or two pattern.

2. The thickness design of the pavement structure using design charts will have some errors.

Advantage of the M-E design method

1. The design is correct and confident anywhere and any environment condition.

2. Pavements can be designed according to any available materials.

3. The approach can provide any magnitude of wheel loads and frequencies.

4. Pavement can be designed into various patterns.

Limited Traffic Applications

AXLE LOAD REPETITIONS

PA

VE

ME

NT

TH

ICK

NE

SS

PA

VE

ME

NT

TH

ICK

NE

SS

CurrentCurrentDesignsDesigns

Projection AProjection A

> 100 Million

ProjectionProjection B B

Proje

ctio

n

Proje

ctio

n C C

ProjectionProjection B BData Data LimitsLimits

(AASHO (AASHO Road Test)Road Test)

Source: FHWA (2002)

Problem statement

Problem load characterization in Thailand.

1. The count station counts only the number of each vehicle.

2. The Truck factors are always assumed for the new pavement design and the rehabilitated design.

3. The calculation of ESALs does not represent the existing types and categories of vehicles.

4. The new limits of axle load and gross weight for ten wheels standard trucks has been increased from 21 tons to 25 tons.

Objectives of Study

• To classify loading types and configuration for the design.

• To analyze the input data as collected from weigh-in-motion (WIM) for the M-E design method.

• To use the M-E design method by considering the current traffic load in Thailand.

• To develop the guidelines of traffic data collection by using WIM for future use in the design and maintenance of pavements in Thailand.

MethodologyStudy Framework

Conclusions and Recommendation

Conclusions and Recommendation

Collect Traffic Data from WIM Station and Weight control center

Collect Traffic Data from WIM Station and Weight control center

Identify and Understand Load configuration for use in M-E design and maintenance

Identify and Understand Load configuration for use in M-E design and maintenance

Classify groups of vehicles

Classify groups of vehicles

Test LocationTest Location

Traffic Data AnalysisTraffic Data Analysis

Truck Factor and ESAL

Truck Factor and ESAL

Design and Compare pavement structure by using obtainable load parameter in M-E pavement d

esign method

Design and Compare pavement structure by using obtainable load parameter in M-E pavement d

esign method

Determine and Compare thickness of pavement overlay by

M-E method and FWD

Determine and Compare thickness of pavement overlay by

M-E method and FWD

Traffic Loads

Methodology

Test Location

Sikiu (Outbound) WIM Station

Tatamnuk (Inbound) WIM Station

Suwintawong (Inbound) WIM Station

Bang pai (Inbound) WIM Station

Methodology

Weigh-in-motion

• The devices which measure truck weights and axle configuration at highway speeds, are an integral part of the program to provide highway-use data.

Collection traffic data from two locationsWIM stations

Weight Control Center in DOH

Methodology

• Observe from January 2008 to December 2008.• Collect in one direction located at the four selected WIM

stations.• Classify into 13 standard vehicle classes• Select monthly reports; class by hour, class by single axle

weight, class by tandem axle weight and class by tridem axle weight.

• Provide a load interval of each axle group in 2 tons.

Assumption of Data Collection

MethodologyLoad Characterization

Equivalent Axle Load Factor (EALF)

18221

18

log33.4)log(79.4)118log(79.4logt

x

t

t

t GGLLL

W

W

• Defines the damage per pass to a pavement by axle in question relative to the damage per pass of a standard axle load (18-kip, 80-Kn) single-axle load

• The failure criterion for fatigue cracking4

s

x

L

LEALF

Truck factor

)(1

AFpTm

iiif

))(365)()()()()(()( 0 YLDGTTADTESAL f

Equivalent Single Axle Load(ESAL)

The total number of passes of the standard axle load during the design period

m

iiinFESAL

1

The sum of ESALs for all trucks weighed divided by the number of trucks

Traffic Analysis

Comparison of Vehicle Classification in two station types

Count Stations WIM Stations

No. Name Image Class Name Image1 BI+TRI CYCLE

2 MOTORCYCLE 1 Motorcycle

3 CAR < = 7 P2 Passenger Cars

4 CAR > 7

5 LIGHT BUS

4 Buses6 MEDIUM BUS

7 HEAVY BUS

8LIGHT TRUCK(Light Truck or Pick-Up) 3

Single Unit Truck(Two Axle, Four Tire)

9MEDIUM TRUCK(Two-Axle Truck (6 Wheels)) 5

Single Unit Truck(Two Axle, Six Tire)

10HEAVY TRUCK(Three-Axle Truck ,10 Wheels)

6Single Unit Truck(Three Axle)

7Single Unit Truck(Four Axle)

11SEMI TRAILERSemi Trailer (Four or More Axle)

8

Single Trailer(Three Axle)Single Trailer(Four Axle)

9Single Trailer(Five Axle)

10Single Trailer(Six or More Axle)

12FULL TRAILERFull trailer (Four or More Axle)

11Full Trailer(Five Axle)

12Full Trailer(Six Axle)

13Multi-Trailer(Seven or More Axle)

Traffic Data Result and Analysis

Truck Monthly Distributions

Truck Traffic Distribution

Highway number 2 4 304 304

WIM StationSikiu

(Outbound)

Tatamnak

Suwintawong

Bang pai

Data Collection (month) 10 10 12 10Time period Percent of daily truck traffic,%

midnight to 6 a.m. 25.95 15.01 9.32 33.596 a.m. - 10 a.m. 21.35 18.44 17.17 25.6510 a.m. - 4 p.m. 26.15 36.12 36.38 24.834 p.m. - 8 p.m. 13.67 17.05 25.02 6.13

8 p.m. - midnight 12.89 13.38 12.10 9.80

Truck Hourly Distributions

Normalized truck traffic distribution

Traffic Data Result and Analysis

AADT from four WIM stations

Average Annual Daily Traffic (AADT)

AADT on highway number 304 from the permanent count station.

Class of

Veh.

Highway road number

2 4 304 304

WIM StationSikiu

(Outbound)

Tatamnak

Suwintawong

Bang pai

DescriptionAverage Annual Daily Traffic

(AADT)

1 Motorcycle 1,410 399 8 562 Passenger car 2,964 26,878 5,541 14,2554 Bus 56 92 157 467  Single Unit truck        3 Two Axle, Four Tire 174 89 3,038 1,485

5 Two Axle, Six Tire 329 125 552 7746 Three Axle 689 885 324 5767 Four Axle 2 4 1 2  Single Trailer        8 Three and Four Axle 447 178 39 1439 Five Axle 275 280 147 23010 Six or More Axle 182 275 47 86  Full Trailer        

11 Five Axle 150 38 43 10712 Six Axle 43 21 16 49  Multi Trailer        

13 Seven or More Axle 67 34 5 17Summary 5,378 28,900 9,911 18,190

Both directions 10,756 57,800 19,822 36,380

YearTypes of vehicles

TOTAL(AADT)CAR<

=7PCAR>7

PLB MB HB LT MT HT

FULL_TL

SEMI_TL

200612,757 4,427 345 54 723

3,736 2607 2,238 1,235 1,047

29,169total car 17,184

MB+HB 777  

MT+HT 4,845  

FTL+STL 2,282

                   

200710,679 5,519 322 63 596

4,185 2919 2,181 1,522 1,080

29,066total car 16,198

MB+HB 659  

MT+HT 5,100  

FTL+STL 2,602

                   

200814,532 5,951 481 8 796

5,722 2732 1,332 939 684

33,177total car 20,483

MB+HB 804  

MT+HT 4,064  

FTL+STL 1,623

                   

Traffic Data Result and Analysis

Truck Factor

Highway Road number

2 4 304 304

WIM StationSikiu

(Outbound)Tatamnak Suwintawong Bang pai

Data Collection (month)

10 10 12 10

Bus 1.107 0.046 1.094 0.634Single Unit truck         Two Axle, Four Tire 7.343 1.581 8.391 1.404 Two Axle, Six Tire 0.675 0.304 0.416 0.295 Three Axle 0.633 0.319 0.479 0.401 Four Axle 2.566 0.254 0.486 0.710All Single Unit truck 1.624 0.419 6.608 0.897Single Trailer         Three and Four Axle 0.190 0.070 0.908 0.392 Five Axle 1.446 0.629 1.080 1.063 Six or More Axle 1.754 1.029 1.061 0.941All Single Trailer 0.888 0.643 1.047 0.831Full Trailer         Five Axle 3.788 2.642 2.655 3.413 Six Axle 3.649 1.985 2.603 3.237All Full Trailer 3.757 2.412 2.642 3.358Multi Trailer         Seven or More Axle 1.169 1.075 0.510 0.497         All Truck 1.494 0.552 6.053 0.954

Traffic Data Result and Analysis

Equivalent Single Axle Load (ESAL)

Highways number 2 4 304 304

WIM Station Sikiu (Outbound) Tatamnak Suwintawong Bang pai

Vehicle class\ Purpose of design

New designOverlay

pavementNew

designOverlay

pavementNew design

Overlay pavement

New designOverlay

pavement

Bus 451,283 178,079 31,063 12,258 1,257,277 496,128 2,163,153 853,592

Single Unit truckTwo Axle, Four Tire 9,315,766 3,676,051 1,025,209 404,553 186,272,118 73,503,983 15,232,837 6,010,960Two Axle, Six Tire 1,621,052 639,676 278,402 109,859 1,678,906 662,505 1,667,788 658,118Three Axle 3,188,659 1,258,262 2,064,037 814,480 1,134,754 447,780 1,688,090 666,130Four Axle 41,179 16,250 6,853 2,704 4,310 1,701 11,241 4,436Single TrailerThree and Four Axle 620,050 244,675 91,129 35,960 259,857 102,541 409,384 161,545Five Axle 2,910,304 1,148,422 1,284,836 507,003 1,161,966 458,518 1,785,481 704,560Six or More Axle 2,334,745 921,303 2,068,826 816,370 360,825 142,383 594,124 234,444Full TrailerFive Axle 4,159,379 1,641,313 740,775 292,314 843,593 332,886 2,669,148 1,053,260Six Axle 1,150,497 453,992 300,623 118,627 296,830 117,131 1,152,176 454,655Multi TrailerSeven or More Axle 572,606 225,953 268,020 105,762 17,704 6,986 62,732 24,755ESAL Design Traffic 16,478,450 6,502,485 5,099,858 2,012,431 173,959,326 68,645,288 24,692,539 9,743,810

ESAL for new design and rehabilitation of four highways from WIM database

Materials Traffic

Layer Thickness(Structure)

Climate

Analysis Pavement

Compute Damage

ModifyLayer Thickness

Meet Performance Criter

ia?

YES

NO

Design Thickness

INPUT

ANALYSIS

mechanistic-empirical design flowchart

M-E design

Source: Kevin,D (2005)

Pavement Design and Analysis

New Pavement Design

Typical Cross Section of the selected highway number 304

No Layer

Relations between thickness of pavement structure (cm.) and materials of each layer.For ESAL=2.47E+7 (WIM station)

The first pavement structure

The second pavement structure

The third pavement structure

The fourth pavement structure

 

1 PavementAsphalt

Concrete20

Asphalt Concrete

15 PMA 10 PMA 5  

2 Base Soil Cement 20Modified

Crush Rock20 Soil Cement 20

Modified Crush Rock

30  

3 SubbaseSoil

Aggregate20

Soil Aggregate

20Soil

Aggregate20

Soil Aggregate

20  

4Selected Material

Selected Material "A"

15Selected

Material "A"30

Selected Material "A"

20Selected

Material "A"40  

5 Subgrade (CBR=4%) infinite (CBR=4%) infinite (CBR=4%) infinite (CBR=4%) infinite  

Thickness of various new designs

Pavement Design and Analysis

New Pavement Design

Relation between the various pavement structures and allowable ESAL application

•sensitivity of structural responses

Overlay by Falling Weight Deflectometer (FWD) procedure

• Evaluate the physical properties of a pavement.• Determine the requested thickness of the

pavement overlay.

Layer Material TypeThickness

(cm)

Elastic Modulus

(Mpa)

1Existing Asphalt

Concrete10 1,961

2 Soil Cement Base 20 858

3Soil Aggregate Subbase and

Selected Material “A”50 247

4Subgrade (CBR=4%)

infinite 239

Source of Traffic data

YearAverage Overlay

(cm.)

Standard

deviationOverlay

(cm.)

Overlay(cm.)

Count station at Km.17+200

2008 0.8 1.2 2.0

Bang pai WIM station at Km.

6+1922008 0.6 1.1 1.7

Pavement Rehabilitation (Overlay)

Pavement Design and Analysis

Overlay by M-E method

• The thickness of the pavement overlay on this section of highway number 304 is two centimeters.

• The traffic data from the WIM stations are accurate and reliable than the count station.

• The annual truck factors represent the actual truck distributions relating to the current traffic volume.

• The ESAL are determined for each vehicle which is more accurate and reliable.

• Truck distributions are important issues for planning and geometrical purposes.

• The new design by M-E method can design various pavement structures.

• The thickness of overlay design is two centimeters for both FWD and M-E approaches.

Conclusions

Conclusions and Recommendations

Recommendations

• The WIM systems should be calibrated periodically.

• A future study should test the material properties..

• Development of traffic data collection and results by using WIM for future use in the new design and maintenance of pavements in Thailand.

• These traffic data are collected continuously and systematically.

Questions and Comments