Thesis submitted in fulfilment of the requirements for the degree of

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UN! VERSITI TEKNOLOGI MARA

FRACTURE MECHANICS ANALYSIS OF PRESTRESSED CONCRETE RAILWAY

SLEEPERS CONTAINING FIBRES

^j AFIDAH BINTI ABU BAKAR

Thesis submitted in fulfilment of the requirements for the degree of

Doctor of Philosophy Faculty of Civil Engineering

November 2010

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CANDIDATE'S DECLARATION

I declare that the work in this thesis was carried out in accordance with the regulations of Universiti Teknologi MARA. It is original and is the result of my own work, unless otherwise indicated or acknowledged as referenced work.

This thesis has not been submitted to any other academic institution or non- academic institution for any other degree or qualification.

In the event that my thesis is found to violate the conditions mentioned above, I voluntarily waive the right of conferment of my degree and agree to be subjected to the disciplinary rules and regulations of Universiti Teknologi MARA.

Afidah binti Abu Bakar 2002100269

PhD in Civil Engineering Faculty of Civil Engineering

Fracture Mechanics analysis of prestressed concrete railway sleepers containing fibres.

Name of candidate Candidate's ID No.

Programme Faculty Thesis Title

!:iIJ

Signature of Candidate

Date November 2010

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ABSTRACT

) The Malaysian rail industry has developed tremendously over the last decade in order to play a major role in providing better alternative for road users. Taking a cue to future developments, sleeper demand will also increase. However, these prestressed concrete sleepers are mostly prestressed concrete types designed with less emphasis on dynamic irregularities of the train or the rails that generate fatigue loads. Cracks could develop during a train passage which can be a threat to the overall stiffness properties as they can propagate further under repeated loads. By utilising fibres, namely polypropylene as crack arresters, the behaviour of the sleeper would definitely change. Thus the research work presented in this thesis is focused on the performance of fibred prestressed concrete sleeper (HSFRC) under static and fatigue loads.

Preliminary material study was carried out to select a new mix design of high strength concrete containing fibres. A major part of the laboratory investigation covered on the preparation of the sleeper itself and compliance to design requirements. There were no formations of cracks or crack propagations in the sleepers under constant and variable amplitude loads, testifying that fibres were

p

effective in crack resistance. The proposed fibred-sleeper was capable to resist 97% of the yield strength after the occurrence of first crack and has a maximum strength capacity of 36% higher than the non-fibred sleeper (HSC).

The residual strengths at post-fatigue remained almost similar for both types of sleepers depending on the cyclic stress ratios, but failures of the non-fibred sleepers were severe. Analysis sought by Linear Elastic Fracture Mechanics (LEFM) was extended using static test results and found that equivalent fatigue characteristics and life of sleepers had all been improved significantly. These include fracture toughness properties, stress intensities and crack growth rate.

The fibres were effective to control cracks and its life is predicted at 86% more than the non-fibred sleepers.

•r

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ACKNOWLEDGEMENTS

Firstly, I am most thankful to ALLAH, The Most Gracious (Ar-Rahman) and The All Knowing (Al-'Aleem) for giving me the opportunity to seek knowledge in the true sense. I would like to record my gratitude to the Universiti Teknologi Mara, Malaysia for the scholarship that enabled me to pursue the research work; to the Bureau of Research and Consultancy (now known as Research Management Institute) for funding the research grant; and to the Faculty of Civil Engineering for the laboratory facilities provided.

I would like to acknowledge my deepest appreciation and recognize all the contributions of Professor Dr. Hajjah Khafilah Din as my supervisor. Although she went for early retirement, she had continually given her encouragement, criticisms and moral support that I need during the course of the work. A thank you is also due to Professor Dr. Wan Mahmood Wan Abd Majid for his kind assistance.

Writing of the draft was frequently postponed due to health condition that resulted with both minor and major operations. Thus, this thesis would not be completed without the continuous and sincere moral support and understanding from my husband, Haji Azhari Ahmad, my children, Afzal, Azfar and Aqilah;

family members and friends. I would also like to record my appreciation to the laboratory staff, especially to Haji Mat Som Marwi, Ahamad Razman Arshad and Zu Iskandar for their kind assistance; to Mr. Vasanthan for sharing his knowledge on the tensioning works. Only ALLAH rewards them.

Finally this work is also dedicated to the memory of my parents, Haji Abu Bakar Mohamed and Hajjah Maimunah Othman for all their love; Haji Hashim

Mohd Said Abdullah and Haji Abdul Rahim Othman, whom had given me lots of moral guidance and inspiration and all whom had passed away while I was doing the research. May all be rewarded with Jannah.

Afidah binti Abu Bakar, Shah Alain.

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TABLE OF CONTENTS

Page TITLE PAGE

AUTHOR'S DECLARATION ¹¹

ABSTRACT ¹¹¹

ACKNOWLEDGEMENTS iv

TABLE OF CONTENTS ^V

LIST OF TABLES xiii

LIST OF FIGURES xv

LIST OF PLATES xix

NOMENCLATURE xxi

CHAPTER 1: INTRODUCTION

1.1 Background 1

1.2 Problem statement 2

1.3 Significance of study 3

1.4 Objectives of study 3

1.5 Definitions 4

1.6 Scope of works and limitations 5

1.7 Outline of thesis 6

CHAPTER 2: LITERATURE REVIEW

2.1 Overview 8

2.1 .1 Road transportation problems 8

2.1.2 Malaysian rail network 10

2.1.3 Design requirements of the local sleeper 16

2.2 Prestressed concrete railway sleepers 17

2.2.1 Reasons for study 17

lor

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2.2.2 General perspective of railway sleepers 19 2.2.3 Overview on some design standards 27

2.2.4 Design approach 33

2.2.5 Construction of sleeper 41

2.2.6 Fatigue behaviour of sleepers 43

2.2.7 Crack growth in sleepers 44

2.2.8 Fatigue life of sleepers 46

2.2.9 Challenges in production of railway sleepers 46 2.2.10 Proposal of high strength concrete containing

Fibres in railway sleepers 47

2.3 High strength fibre-reinforced concrete (HSFRC) 48

2.3.1 General 48

2.3.2 HSC containing fibres 49

2.3.3 Strength behaviour of HSFRC 58

2.3.4 Choice of concrete material 64

2.4 Fatigue performance 64

2.4.1 Fatigue loading 65

2.4.2 Design approach 66

2.4.3 Fatigue life 67

2.4.4 Fatigue cracking 69

2.4.5 Fatigue failure 70

2.5 Application of Fracture Mechanics 71

2.5.1 Background 71

2.5.2 Concepts of Fracture Mechanics 72

2.5.3 Modes of failure 74

2.5.4 Fracture energy ⁷⁵

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2.5.5 Stress intensity factor 76

2.5.6 Fracture process zone 81

2.5.7 Crack propagation under cyclic loading 81

2.5.8 Measurement of the crack propagation rate 83

2.5.9 Application of Paris Law 85

2.5.10 Fracture mechanics of fibre-reinforced concrete 87

Estimation of fatigue life 89

2.6.1 Damage tolerance assessment 90

2.6.2 Application of Miner's Law 90

2.6.3 Reliability of Miner's Law 91

2.7 Summary of works on railway sleepers 92

CHAPTER 3: EXPERIMENTAL PROGRAMME

3.1 General 96

3.1.1 Assumptions and limitations 97

3.1.2 Methodology 97

3.1.3 Summary of test programme 98

3.2 Equipments and testing machine 100

3.2.1 Prestressing bed and equipments 100

3.2.2 Testing machines 109

3.2.3 Measurement of deflections, strains, crack

lengths and widths 110

3.2.4 Machine performance 110

3.2.5 Identification of components of uncertainty 112 3.3 Preliminary study on strength properties of HSC

containing fibres 113

3.3.1 General 113

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3.3.2 Mix design 114

3.3.3 Preparation of test specimens 116

3.3.4 Analysis of results 117

3.3.5 Conclusions on preliminary works 130

3.3.6 Choice of mix design for actual works 133

3.4 Material study on HSFRC 137

3.4.1 Compressive strength 137

3.4.2 Splitting tensile strength 141

3.4.3 Flexural behaviour 141

3.4.4 Toughness of HSFRC 147

3.4.5 Fatigue behaviour 148

3.5 Summary 154

CHAPTER 4: DESIGN AND PRODUCTION OF PRESTRESSED HSFRC RAILWAY SLEEPERS

4.1 General 156

4.2 Preliminary study on prestressed HSC railway sleepers 157

4.2.1 Description of test specimens 157

4.2.2 Experimental test set-up 158

4.2.3 Deflection and strain measurements 158 4.2.4 Effects of machine control modes 160 4.2.5 Performance of sleeper using UTS machine 162

4.3 Design of HSFRC railway sleepers 163

4.3.1 General description 163

4.3.2 Design calculations 168

4.3.3 Stress distribution 168

4.3.4 Material properties 170

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4.4 Determination of critical locations using Finite

Element Analysis (FEA) 170

4.4.1 General 170

4.4.2 FEA using LUSAS 171

4.4.3 Initial test model 174

4.4.4 FEA of railway sleeper model 176

4.4.5 Summary on FEA 184

4.5 Production of prestressed HSFRC railway sleepers 184

4.5.1 Production process 185

4.5.2 Control measures 192

HR Compliance performance tests 194

4.6.1 General 194

4.6.2 "Type" tests 194

4.6.3 Comparative behaviour of sleepers 203

4.7 Challenges 207

4.8 Summary 208

CHAPTER 5: STRUCTURAL PERFORMANCE TESTS OF SLEEPERS

5.1 General 210

5.2 Static tests on HSFRC railway sleepers 211

5.2.1 Test procedure 211

5.2.2 Crack detection and measurements 211

5.2.3 Parameters of flexural behaviour 212

5.2.4 Determination of crack growth rate 214

5.3 Flexural fatigue tests 214

5.3.1 Determination of load spectra 215

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5.3.2 Constant amplitude load spectra 224

5.3.3 Variable amplitude load spectra 225

5.3.4 Ultimate strength tests and determination of

fracture toughness 226

5.4 Application of fracture mechanics 226

5.4.1 Determination of crack growth rate 227

5.4.2 Estimation of material parameters 228

5.4.3 Stress cycle counting using Reservoir Method 229

5.5 Estimation of life of sleeper 230

5.6 Summary 230

CHAPTER 6: ANALYSIS AND DISCUSSION

6.1 General 231

6.2 Flexural static behaviour of HSFRC sleeper 231

6.2.1 Structural response 231

6.2.2 Cracking behaviour 237

6.2.3 Energy absorption capacity 242

6.2.4 Flexural toughness 243

6.2.5 Comparative behaviour of prestressed

concrete railway sleepers 243

6.3 Fatigue behaviour 249

6.3.1 General 249

6.3.2 Fatigue capacity under constant amplitude loads 249 6.3.3 Fatigue capacity under variable amplitude loads 254 6.3.4 Effect of cyclic loads on static strength 259 6.3.5 General comparison of post fatigue behaviour 261

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6.4 Analysis using Fracture Mechanics 264

6.4.1 General 264

6.4.2 Fracture toughness 266

6.4.3 Stress intensity 266

6.4.4 Crack growth 268

6.4.5 Fracture strength 271

6.5 Estimation of life of sleeper ²⁷⁵

6.6 Summary 277

6.6.1 Effectiveness of HSFRC material in railway sleepers 277

6.6.2 Use of Fracture Mechanics 278

CHAPTER 7: CONCLUSION AND RECOMMENDATIONS

7.1 General 280

7.2 Conclusion 280

7.2.1 Development of new HSFRC material 280 7.2.2 Design and production of railway sleeper

containing fibres 281

7.2.3 Structural behaviour of HSFRC sleepers 282 7.2.4 Fatigue characteristics and life of HSFRC 283

sleeper using LEFM

7.3 Recommendations 284

REFERENCES 287

RELATED STANDARDS! SPECIFICATIONS 302

PUBLISHED AND NON-PUBLISHED WORKS RELATED

TO THE DOCTORAL STUDY 303

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APPENDIX A 304

APPENDIX B 312

APPENDIX C 333

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LIST OF TABLES

Page Table 2.1 Typical dimensions of Malaysian PSC railway sleepers 26 Table 2.2 Comparisons of some railway design standards/ guidelines 28 Table 2.3 Properties and application of cementitious materials 52

Table 2.4 Fibre technical data 56

Table 2.5 Fatigue load spectrum (source: Hsu, 1981) 71 Table 2.6 Summary of works carried out on PSC sleepers 94

Table 3.1 Summary of test programme 99

Table 3.2 Sleeper identification in accordance to type of test 100 Table 3.3 Summary of mix proportions per cubic meter of concrete 116 Table 3.4 Statistical analysis of concrete cubes strength at 28 days 121 Table 3.5 Relationship of splitting tensile and compression

strength at 28 days 123

Table 3.6 Proposed HSFRC mix design 136

Table 3.7 Summary of compressive cube strength tests at various ages 138 Table 3.8 Flexural strength properties of HSFRC beams under 144

four-point bending

Table 3.9 Loading scheme for flexural fatigue tests on HSFRC beams 148 Table 3.10 Summary of fatigue test results of HSFRC beams 149 Table 3.11 Summary of mechanical properties of Grade 60 HSFRC 155

Table 4.1 Test details 157

Table 4.2 Geometrical properties of HSC sleeper 158 Table 4.3 Test data of prestressed HSC railway sleepers due to

control modes 161

Table 4.4 Comparison of railway sleeper geometries 167

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Table 4.5 Table 4.6 Table 4.7 Table 4.8 Table 4.9 Table 5.1 Table 5.2 Table 5.3 Table 5.4 Table 6.1 Table 6.2

Design criteria for HSFRC sleeper Material properties of HSFRC model

Control measures (source: Abu-Bakar and Din, 2008) Compliance type tests summary as to AS 1085-14 (2003) Compliance performance test results

Sleeper identification in accordance to type of test Summary of train loading

Data input for constant amplitude load tests Data input for variable amplitude load tests Summary of static test results of PSC sleepers Regressed relationships of crack lengths to applied static loads

167 173 193 196 206 210 218 222 223 237

242 Table 6.3 Summary of fatigue test results under constant amplitude

load 251

Table 6.4 Summary of fatigue test results under variable amplitude

load 258

Table 6.5 Material properties of PSC sleepers 265

Table 6.6 Summary of overall results 279

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LIST OF FIGURES

Page (a) Malaysian rail network, (b) Close view near Kuala

Lumpur city (source: e-map, JUPEM, 2005)

Rail linkages between Asia and Europe 16 Typical cross-section of a permanent track 20

Connection of rail to the sleeper 21

Plan view of concrete sleepers; (a) Monoblock sleeper, 23 (b) Twin-block sleeper

Pressure distributions under sleeper (Gupta and Gupta,

2003) 34

Wheel load distribution (source: Thun, 2006) 38 Distribution of bond stresses (source: Khrishna Raju,

2007) 42

Definitions associated with fatigue loadings Me Schematic representation of material integrity with respect

to crack lengths 70

Basic fracture modes ⁷⁵

Stress flow-lines for panel in tension (a) without crack;

(b) with crack 76

Crack opening of Mode I 77

Contour integral for a body with crack 79

Definition of CTOD 80

Stress distribution at crack tip and fracture process zone 81 Mechanism of crack growth under cyclic load 82 Failure process and crack growth rate as a function of

stress intensity 84

Figure 2.1

Figure 2.2 Figure 2.3 Figure 2.4 Figure 2.5

Figure 2.6

Figure 2.7 Figure 2.8

Figure 2.13 Figure 2.14 Figure 2.15 Figure 2.16 Figure 2.17 Figure 2.18

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Figure 2.19 Figure 2.20 Figure 3.1 Figure 3.2 Figure 3.3 Figure 3.4

Figure 3.5

Figure 3.8 Figure 3.9 Figure 3.10

Figure 3.11 Figure 3.12 Figure 3.13 Figure 3.14 Figure 3.15 Figure 3.16 Figure 3.17 Figure 4.1 Figure 4.2

Fatigue crack propagation law 85

Fibre bridging mechanism in crack 88

Overall experimental programme 96

Schematic layout of prestressing bed 102

Stress plate 106

Investigation on machine performance: load-deflection response of timber beams using UTM-250T and

UTS-100T test machines 112

28-days strength results of preliminary works on HSC 119 containing polymeric fibres

Effect of volume fibres on flexural strength of HSC beams 128 Influence of silica fume in HSFRC beams containing

0.5% PP fibres (source: Abu-Bakar et al., 2004) 134 Average flexural strengths of HSC beams 135

Development of concrete strength 139

Percentage of strength gain for HSFRC containing 0.5%

PP fibres 140

Load-deflection curves of HSFRC beams 145 Model equation derived from stress-strain relationship 146 Energy absorption capacities of HSFRC beams 147 Relationship of crack length and number of cycles 151 Strain behaviour of HSFRC beams under cyclic loads 151 Crack growth rate as function of stress intensity 153

Linearization of logarithmic plot 154

Rail seat positive moment test set-up 159 Flexural behaviour of HSC sleepers tested using UTM4 and

UTS frames 162

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Figure 4.3 Geometrical dimensions of HSFRC sleeper ¹⁶⁵ Figure 4.4 Tendon profile at rail seat of HSFRC sleeper 166 Figure 4.5 Stress distributions in sleepers 170

Figure 4.6 (a) Isotropic material definition for concrete, (b) local

contact state 172

Figure 4.7 Finite element model of half-beam 175 Figure 4.8 Crack patterns of half beam at (a) 14 kN and (b) 20 kN 176

Figure 4.9 Linear state of HSFRC sleeper 179

Figure 4.10 Prediction of stress development in HSFRC sleeper 182 Figure 4.11 Predicted stress distribution across depth of rail seat 183 Figure 4.12 Predicted strain distribution across depth of rail seat 184 Figure 4.13 Compliance or acceptance type test procedures ¹⁹⁵ Figure 4.14 Performance of railway sleepers after undergoing

compliance repeated load tests 205

Figure 5.1 A general load-deflection curve of HSFRC sleeper 213 Figure 5.2 Example of reservoir cycle counting procedures 229 Figure 6.1 Load-deflection curves for HSFRC sleepers at the rail seats 232 Figure 6.2 Stress-strain curves for HSFRC sleepers at the rail seats 234 Figure 6.3 Typical behaviour of railway sleepers against designed

wheel load 237

Figure 6.4 Flexural crack propagation at rail seat under static load 241 Figure 6.5 Load-deflection relationship of HSC sleepers 245 Figure 6.6 Stress-strain behaviour of HSC railway sleepers 245 Figure 6.7 Normalised stress-strain curves of HSFRC and HSC

sleepers on basis of designed wheel load 247

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Figure 6.10

Figure 6.11

Figure 6.12

Figure 6.13 Figure 6.14 Figure 6.15

Crack growth due to the effect of static load 248 Static load response of prestressed concrete sleepers after subjected to constant amplitude loads 252 Effect of various stress levels on static on post fatigue

loads 253

Static behaviour of HSFRC sleepers after subjected

to VAL 256

Effect of fatigue loads on static behaviour of railway

sleepers 260

Effect of stress level on residual loads 261 Comparative behaviour between sleepers 262 Function of crack propagation rate to stress intensity of

prestressed concrete sleepers 270

Fracture energy in relation to extension of crack length 273 Stress distribution along the crack length 275

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LIST OF PLATES

Plate 3:1 Plate 3.2

Plate 3.3

Plate 3.4 Plate 3.5 Plate 3.6

Plate 3.7

Plate 3.8

Plate 3.9 Plate 3.10

Plate 3.11

Plate 4.1 Plate 4.2 Plate 4.3 Plate 4.4

Page

Overall view of prestressing bed 101

Main jacking equipment system (a) stress plate,

(b) hydraulic jack 105

Locking system during pretensioning; (a) lock ring to maintain tendon location, (b) attachment of ring to the

stress plate 107

Long bolt tied to stress plate 107 End plates; (a) each end of sleeper mould, (b) anchorage end 108 Types of polymeric fibres used in the experimental

programme 115

Typical splitting crack behaviour for Series 1: (a) without fibres, (b) 0.5% PP fibres, (c) 0.5% PL fibres. Note the well-distributed concrete matrices in each specimen upon

broken up 124

Flexural behaviour study of beams containing polymeric

fibres 126

Splitting condition of HSFRC cylinders 141 Typical failure condition of HSFRC beams under

four-point bending 145

Typical crack pattern of HSFRC beams under fatigue loading.

Note the micro-cracks. 150

Tensioning operation 187

Casting operation 188

De-stressing and de-moulding works 190

Curing and stacking of HSFRC sleepers 191

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Plate 4.5 Plate 4.6 Plate 4.7 Plate 4.8 Plate 4.9

Plate 4.10 Plate 5.1

Plate 6.1 Plate 6.2

Plate 6.3 Plate 6.4

Plate 6.5

Test set-up at rail seat 198

Conditions of sleeper just after repeated load test 200 Centre negative bending moment test set-up 201

Development length test set-up 202

Final conditions of HSFRC sleepers after undergoing all

series of compliance type tests 203

Static failure of HSC sleeper after subjected to fatigue loads 204 Fatigue test set-up, with neoprene supports replaced with

plywood strips 215

Typical crack propagation of HSFRC sleeper 239 Crack patterns of HSFRC sleepers at ultimate static

conditions 240 Ultimate conditions of HSC railway sleeper without fibres 246 Failure modes of typical HSFRC sleeper after undergoing

VAL test ²⁵⁷

Static condition of sleepers after subjected to fatigue

loading 263

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NOMENCLATURE

a crack length

C crack growth coefficient in Paris Law CMOD crack mouth opening displacement CTOD crack tip opening displacement da/dN crack growth rate from fatigue test da/dP crack growth rate from static test

deflection

E Elastic or Young's modulus f ultimate strength of concrete

ultimate tensile strength of tendon fpi initial prestress

fpe final prestress

A yield stress

ft stress at the bottom fibres f2 stress at the top fibres

FE Finite Element

g sleeper gauge

G fracture energy

H height of specimen

K stress intensity factor Kc fracture toughness

K1 stress intensity factor for Mode I cracking

Kic critical stress intensity or fracture of toughness at first crack load

LEFM Linear Elastic Fracture Mechanics

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M crack growth exponent in Paris Law

Ii

N number of load cycles

P prestress force

Pu Ultimate load

Py Yield load

PP polypropylene

R stress ratio

stress due to applied static load stress due to applied cyclic load silica fume

maximum stress due to cyclic load minimum stress due to cyclic load yield strength

Poisson's ratio strain

stresses in x, y and z direction respectively width of the section along the crack line

width of sleeper at the bottom of rail seat section width of sleeper at the top of rail seat section geometry correction factor

AA

VI

SF Smax Smin Sy

V

cY, (Ty, Gz

W WB WT Y

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CHAPTER 1

INTRODUCTION

1.1 BACKGROUND

Malaysian roads have seen tremendous increase in the number of road-users, especially in the Klang Valley. Even with the new network of roads and highways, traffic congestions remained and this demands upgrades of the existing railway system as alternative for land transport. As a result, the rail industry has developed tremendously over the last decade with more electrified lines and new light rail transit (LRT) systems are also implemented, but the latter systems are concentrated only within the Klang Valley.

Keretapi Tanah Melayu Berhad (KTMB), a corporatised Government company, has been the nation's major established player in land transportation sector. Its rail network has services throughout the Malaysian peninsular and recognizing there are potentials for further economic growth, large capital investment has been made to develop its established rail infrastructure in order to provide safe, efficient and reliable services (KTMB Annual Report, 2001). Further, infrastructure rehabilitation and enhancement programs are well underway (Briginshaw, 2001). In view of these massive projects, expert technological solutions need to be readily available to check all track designs, products and any related materials; of which sleeper is the interest of this study.

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1.2 PROBLEM STATEMENT

A railway sleeper is a structural element that supports the rails and distributes the loads to the ground via a layer of coarse aggregates known as ballast. In this context, the Malaysian KTMB rail network has been using timber sleepers ever since the beginning of rail system in the country. The first prestressed concrete types were laid in 1982 between Palong and Gemas; near the borders of the southern states of Johore and Negri Sembilan (R. Mohamed, 2003; General Manager of Permanent Way, KTMB; in private communication). These concrete sleepers had replaced most of the timber ones only around Kuala Lumpur to the west, i.e. to Port Kiang, when electrified commuter trains were first introduced in 1995. With the development of a second rail track to Ipoh in the north, and further up to Butterworth, more of these PSC sleepers will replace the existing timber types.

Taking a cue to the future developments in the local rail industry, the numbers of sleeper demand will also increase. Presently, none of the prestressed sleepers had been replaced as usual design life of concrete structures is about fifty years. Although there are no mishappenings on the part of the prestressed concrete sleepers, KTMB is concerned over a case where some newly-laid sleepers along a four-kilometre track in the northern Ipoh to Butterworth Main line cracked soon after installation. The causes of these cracks should be of great concern as there might be due to other problems; with a great possibility of poor mix design or poor production method that led to shrinkage and creep coupled with environmental factors. Internal investigations were carried out by KTMB but no conclusions can be drawn, as there