Bridge Inspection and Maintenance 1

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Preface to the Third Edition

The book Bridge Inspection and Maintenance was firstpublished in 1988. As this book was very popular amongst fieldengineers, the second revised edition was published in 1996updating the chapter on repairs to concrete bridges.

The third revised and enlarged edition has now beenbrought out to fulfil the continuous demand for the book. Sinceunderwater inspection of bridge is one of the key activities to beundertaken for maintenance of bridge substructure andfoundation, a new chapter on underwater inspection of bridgeshas been included. Two more chapters on non destructivetesting and nemerical rating system for bridges have also been

added to make it more comprehensive.

It is hoped that this booklet will act as a guide for the fieldengineers who are entrusted with the task of inspection andmaintenance of bridges.

Shiv Kumar

DirectorIRICEN, Pune.


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Acknowledgement

The first edition of this book was published in August, 1988 toserve as a guide to the field engineers who are entrusted with thejob of inspection and maintenance of bridges. The second editionwas brought out in December, 1996, which has been very popular

amongst field engineers. The third edition is being brought out tofulfil this continuous demand. While revising the book, new chapterson underwater inspection of bridges and non-destructive testinghave been included to make it more comprehensive. Efforts havebeen made to improve the readability of the book.

It would not be out of place to acknowledge the support andassistance rendered by IRICEN faculty and staff in the above efforts.I am grateful to Shri Ghansham Bansal, Professor/Bridges for proof-

checking of the entire book. I am particularly thankful to Shri PraveenKumar, Professor/Computers who has provided the necessarylogistic assistance for printing of this book.

Above all, the author is grateful to Shri Shiv Kumar, Director forhis encouragement and guidance for improving the publication.

A.K. Yadav

Senior Professor/BridgesIRICEN, Pune


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Preface to the Second Edition

The book Bridge Inspection and Maintenance has beenan useful guide to the Engineers of Indian Railways. The firstedition was published in August, 1988 and was very popularamong the field engineers. This second revised edition hasbeen brought out to fulfil the continuous demand for this book.While revising, the chapter on repairs to concrete bridges hasbeen updated by including the latest techniques on grouting,repairing of spalled concrete, use of polymer based materialsetc. This book also includes the current instructions on bridgeinspection and maintenance of concrete bridges.

I hope the contents of the revised edition will be

implemented by the field engineers during the inspection andmaintenance of Railway bridges, so that our tradition of caringfor bridges with high order of reliability can be kept up. Anysuggestion to improve the book is most welcome.

S. Gopalkrishnan

DirectorIndian Railways Institute of

Civil Engineering, Pune.


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PREFACE

The subject of Inspection and Maintenance ofBridges is of considerable importance to the field officials whoare engaged in this aspect of work of the Civil EngineeringDepartment. Requests for outstation courses conducted by

IRICEN on this subject are frequent and even repetitive, whichis indicative of the need for dissemination of information andexperience on this topic. It is hoped that this booklet will fulfilthis need and be of assistance to field officials in briefing themabout the aspects to be inspected and the corrective action tobe taken.

This book has been prepared by ProfessorK. Ananthanarayanan of this Institute.

If there are suggestions kindly write to the undersigned.

N.K. ParthasarathyDirector

Indian Railways Institute ofCivil Engineering, Pune.


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CONTENTS

CHAPTER - 1 BRIDGE INSPECTION - GENERAL

1.1 Introduction 11.2 Purpose of bridge inspection 2

1.3 Elements of a bridge 2

1.4 Planning the inspection 3

1.5 Schedule of inspection 3

1.6 Preliminary study 4

1.7 Inspection equipments 4

1.8 Safety precautions 7

CHAPTER - 2 DETAILED INSPECTION OF BRIDGES

2.1 Foundations 8

2.1.1 Disintegration of foundation material 8

2.1.2 Heavy localized scour in the vicinity of 10piers/abutments

2.1.3 Uneven settlement 13

2.2 Abutments and piers 14

2.2.1 Crushing and cracking of masonry 14

2.2.2 Weathering 14

2.2.3 Failure of mortar 16

2.2.4 Bulging 16

2.2.5 Transverse cracks in piers 16

2.3 Protection works 17

2.3.1 Flooring 18

2.3.2 Pitching 20

2.3.3 Guide bunds 20

2.3.4 Aprons 22

2.4 Arch bridges 22

2.4.1 Cracks in abutments and piers 25

2.4.2 Cracks associated with spandrel wall 26

2.4.3 Cracks on the face of arch bridge 31


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2.4.4 Cracking and crushing of masonry 32

2.4.5 Leaching out of lime/cement mortar 32in the barrel

2.4.6 Loosening of key stones and voussoirs 32of arch

2.4.7 Transverse cracks in the arch intrados 32

2.5 Bed blocks 34

2.6 Bearings 37

2.6.1 Elastomeric bearings 40

2.6.2 PTFE bearings 41

2.7 Inspection of steel bridges 41

2.7.1 Loss of camber 42

2.7.2 Distorsion 42

2.7.3 Loose rivets 43

2.7.4 Corrosion 44

2.7.5 Fatigue cracks 45

2.7.6 Early steel girders 45

2.8 Inspection of concrete girders 46

2.8.1 Cracking 47

2.8.2 Delamination 48

2.8.3 Scaling 49

2.8.4 Spalling 49

2.8.5 Reinforcement corrosion 49

2.8.6 Cracking in prestressed concrete structures 50

2.8.7 Loss of camber 52

2.8.8 Locations to be specially looked for defect 53

2.9 Track on girder bridges 55

2.9.1 Approaches 55

2.9.2 Track on bridge proper 55

CHAPTER - 3 UNDER WATER INSPECTION OFBRIDGES

3.1 Introduction 583.2 Bridge selection criteria 58


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3.3 Frequency of inspection 59

3.4 Methods of underwater inspection 59

3.4.1 Wading inspection 59

3.4.2 Scuba diving 603.4.3 Surface supplied air diving 62

3.5 Method selection criteria 64

3.6 Diving inspection intensity levels 64

3.6.1 Level I 65

3.6.2 Level II 65

3.6.3 Level III 66

3.7 Inspection Tools 67

3.8 Underwater photography and video equipments 67

3.9 Documentation 67

3.10Reporting 69

CHAPTER - 4 NON DESTRUCTIVE TESTING FORBRIDGES

4.1 Introduction 70

4.2 NDT tests for concrete bridges 70

4.2.1 Rebound hammer 70

4.2.2 Ultrasonic pulse velocity tester 71

4.2.3 Pull-off test 73

4.2.4 Pull-out test 74

4.2.5 Windsor probe 75

4.2.6 Rebar locators 75

4.2.7 Covermeter 76

4.2.8 Half-cell potential measurement 76

4.2.9 Resistivity test 78

4.2.10Test for carbonation of concrete 78

4.2.11Test for chloride content of concrete 79

4.2.12Acoustic Emission technique 79

4.3 NDT tests for masonry bridges 80

4.3.1 Flat Jack testing 80


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4.3.2 Impact Echo testing 80

4.3.3 Impulse Radar 81

4.3.4 Infrared Thermography 81

4.4 NDT tests for steel bridges 814.4.1 Liquid Penetrant Inspection (LPI) 81

4.4.2 Magnetic Particle Inspection (MPI) 82

4.4.3 Eddy current testing 83

4.4.4 Radiographic testing 83

4.4.5 Ultrasonic test

CHAPTER - 5 NUMERICAL RATING SYSTEM

5.1 Introduction 85

5.2 Relevance of numerical rating system 86

5.3 Numerical rating system for Indian Railways 86

5.4 Condition rating number (CRN) 86

5.5 Overall rating number (ORN) 87

5.6 Major bridges 87

5.7 Minor bridges 89

5.8 Road over bridges 89

5.9 Recording in bridge inspection register 89

CHAPTER - 6 MAINTENANCE OF BRIDGES

6.1 Introduction 90

6.2 Symptoms and remedial measures 91

CHAPTER - 7 REPAIRS TO CONCRETE ANDMASONRY BRIDGES

7.1 General 95

7.2 Cement pressure grouting of masonry structures 96

7.2.1 Equipments 96

7.2.2 Procedure 96

7.3 Epoxy resin grouting of masonry structures 100

7.3.1 General 100


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7.3.2 Procedure 101

7.4 Repairs of cracks in reinforced concrete 103and prestressed concrete girders and slabs

7.4.1 General 103

7.4.2 Materials used for filling the cracks 103

7.4.3 Crack injection steps 105

7.4.4 Injection equipments and injection process 106

7.5 Spalled concrete- Hand applied repairs 108

7.5.1 Preparation 109

7.5.2 Choice of material 109

7.5.3 Curing 112

7.6 Guniting 113

7.6.1 Equipments and materials 113

7.6.2 Procedure 114

7.7 Jacketing 116

7.7.1 General 116

7.7.2 Procedure 117

CHAPTER - 8 MAINTENANCE OF STEEL BRIDGES

8.1 Painting of girder bridges 119

8.1.1 Surface preparation 119

8.1.2 Painting scheme as per IRS code 121

8.1.3 Important precautions 122

8.2 Replacing loose rivets 124

8.2.1 General 124

8.2.2 Procedure 125

8.3 Loss of camber 126

8.4 Oiling and greasing of bearings 127

Annexure-A Proforma for Bridge Inspection Registers 128

Annexure-B Elastomeric bearing 135

Annexure-C Teflon or PTFE bearing 137

Annexure-D Guidelines for alloting Condition 139Rating Number (CRN)


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CHAPTER 1

BRIDGE INSPECTION GENERAL

1.1 Introduction

Bridges are key elements of the Railway network because oftheir strategic location and the dangerous consequences whenthey fail or when their capacity is impaired. The fundamentaljustification for a bridge inspection programme lies in theassurance of safety. Timely and economic planning andprogramming of remedial and preventive maintenance and repairwork, or even bridge replacement with the minimum interruption

to traffic are dependent upon detailed bridge inspection. It isparticularly necessary in case of old bridges not designed tomodern loading standards and also whose materials ofconstruction have deteriorated as a result of weathering.

Inspection is aimed at identifying and quantifyingdeterioration, which may be caused by applied loads and factorssuch as deadload, liveload, wind load and physical/chemicalinfluences exerted by the environment. Apart from inspection ofbridge damage caused by unpredictable natural phenomena orcollision by vehicles or vessels, inspection is also needed toidentify or follow up the effect of any built-in imperfections.Inspection can also help to increase life of older bridges. Forexample, there are certain types of deterioration which appearearly in the life of a bridge and which, if not recorded andrepaired promptly, can lead to considerable reduction in thelength of service life of the bridge.


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1.2 Purpose of bridge inspection

Specific purposes of bridge inspection can be identified asdetailed below:

1. To know whether the bridge is structurally safe, and todecide the course of action to make it safe.

2. To identify actual and potential sources of trouble atthe earliest possible stage.

3. To record systematically and periodically the state ofthe structure.

4. To impose speed restriction on the bridge if thecondition/situation warrants the same till the repair/rehabilitation of the bridge is carried out.

5. To determine and report whether major rehabilitation ofthe bridge is necessary to cope with the naturalenvironment and the traffic passing over the bridge.

6. To provide a feedback of information to designers andconstruction engineers on those features which givemaintenance problems.

1.3 Elements of a bridge

Bridge structure is generally classified under two broadcategories:

1. Superstructure

2. Sub-structure

Superstructure consists of all the parts of the bridge that aresupported by the bearings on abutments or piers (e.g. bridgegirders, bridge deck, bridge flooring system etc.).


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Sub-structure consists of all those parts of the bridge, whichtransmit loads from the bridge span to the ground (e.g.abutments, piers, bed blocks, foundations, etc.).

1.4 Planning the inspection

Careful planning is essential for a well-organized, completeand efficient inspection. The bridges over water are inspected attimes of low water, generally after the monsoon. Bridgesrequiring high climbing should be inspected during seasons whenwinds or extreme temperatures are not prevalent. Bridgessuspected of having trouble on account of thermal movementshould be inspected during temperature extremes. The bridges

are inspected starting from foundations and ending withsuperstructures. Planning for inspection must include thefollowing essential steps:

1. Decide the number of bridges to be inspected on aparticular day.

2. Go through the previous inspection reports of thosebridges before starting the inspection.

3. Try to have plans and other details of importantbridges.

4. Plan any special inspection equipments, staging etc.required in advance.

5. Dont rush through the inspection just for completionsake. Remember that you are inspecting the bridge

only once in a year.

1.5 Schedule of inspection

The schedule of inspection for various officials is prescribedin Indian Railways Bridge Manual (IRBM). As per this, all thebridges are to be inspected by PWIs/IOWs once a year beforemonsoon and by AENs once a year after monsoon, andimportant bridges by DENs once a year. All the steel structures


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are inspected by BRIs once in 5 years and selected bridges byBridge Engineers/Dy.CE (Bridges) as and when found necessary.Side by side, the track on the bridge should also be inspectedthoroughly. The bridges that have been referred by AEN/DEN/

Sr.DEN for inspection by a higher authority, should be inspectedby the higher authority in good time. Bridges which are of earlysteel, and bridges which are overstressed should be inspectedmore frequently as laid down vide page 509 of IRBM.

Proforma for Bridge Inspection Register is shown atAnnexure-A.

1.6 Preliminary study

While going for bridge inspection one should be familiar withthe historical data of the bridges i.e.

1. Completion plans, where available

2. Pile and well foundation details

3. Earlier inspection reports

4. Reports regarding the repairs/strengthening carried outin the past.

For major girder bridges, stress sheets are useful.

1.7 Inspection equipments

The following equipments are required for thorough inspectionof the various elements of bridges:

1. Pocket tape (3 or 5 m long)

2. Chipping hammer

3. Plumb bob

4. Straight edge (at least 2 m long)

5. 30 metre steel tape

6. A set of feeler gauges (0.1 to 5 mm)


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7. Log line with 20 kg lead ball (to be kept at bridge site)

8. Thermometer

9. Elcometer

10. Wire brush

11. Mirror ( 10x15 cm)

12. Magnifying glass (100 mm dia.)

13. Crackmeter

14. Chalk, Waterproof pencil, pen or paint for marking onconcrete or steel

15. Centre punch

16. Callipers (inside and outside)

17. Torch light (5 cell)

18. Screw drivers

19. Paint and paint brush for repainting areas damagedduring inspection

20. Gauge-cum-level21. Piano wire

22. 15 cm steel scale

23. Inspection hammer (350-450 gm)

24. Rivet testing hammer (110 gm)

25. Schmidt hammer

26. Concrete cover meter

OPTIONAL (where required)

27. Binoculars

28. Camera


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Depending on the bridge site and the need envisaged duringinspection, some additional equipments that may becomenecessary are listed below:

1. Ladders2. Scaffolding

3. Boats or barges

4. Echo sounders (Fig. 1.1) to assess the depth of water/scour depth

Fig. 1.1 Echo Sounder

5. Levelling equipment (to assess camber)

6. Dye penetration test equipment (to detect cracksspecially in welds)


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1.8 Safety precautions

While inspecting bridges, one should adopt certain safetymeasures which are listed below:

1. Wear suitable dress so that loose ends do not getcaught; too-tight-a-dress may hamper your freemovements.

2. If you normally wear glasses for improving your eyesight, wear them when climbing up or down the sub-structures or superstructures.

3. Keep clothing and shoes free of grease.

4. Scaffolding or platforms should be free from grease orother slippery substances.

5. Scaffolding and working platforms should be ofadequate strength and must be secured againstslipping or over turning.

6. No short cuts, at any cost, should be adopted.


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CHAPTER 2

DETAILED INSPECTION OF BRIDGES

Detailed inspection of a bridge is required to be donestarting from foundation right up to superstructure, including thetrack. Approaches of bridges should also be inspected for scour,settlement etc.

2.1 Foundations

Visual inspection of foundations is difficult in majorityof cases and the behavior of foundations has to be judged

based on observation of exposed elements of bridgestructures. Foundation movements may often be detectedby first looking for deviations from the proper geometry ofthe bridge.

1. Any abrupt change or kink in the alignment of bridgemay indicate a lateral movement of pier (Fig. 2.1).

2. Inadequate or abnormal clearance between theballast wall and end girders are indications ofprobable movement such as leaning, bulging etc.of abutments.

Types of defects in foundation which one should look forduring inspection are discussed below:

2.1.1 Disintegration of foundation material

In many bridges where open foundations are provided, some


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MISALIGNMENT AT PIER

Fig. 2.1 Effect of scour on deep foundation

ELEVATION

PLAN

RIVER FLOW

Bridge Inspection and Maintenance 1

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