Rc4300 Bridge Repair Manual

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Issue A Australian Rail Track CorporationRevision 1 This document is uncontrolled when printedMarch 2006 Page 1 of 245

Engineering Practices ManualCivil Engineering

Bridge Repair Manual

RC 4300

Issue A, Revision 1March 2006


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Engineering Practices ManualCivil Engineering RC 4300Bridge Repair Manual


Contents

Part 1 General .................................................................................................................8

1. Introduction ............................................................................................................9

1.1. The purpose of this manual ...................................................................................... 9

1.2. Nature of the repair procedure..................................................................................9

1.3. Who should use this manual?................................................................................... 9

1.4. Aims of repair procedures....................................................................................... 10

1.5. The structure of this manual ................................................................................... 10

1.6. Format for repair procedures ..................................................................................10

2. Selecting repair actions ....................................................................................... 11

2.1. Introduction............................................................................................................. 11

2.2. Procedure for selecting repair action ...................................................................... 12

2.3. Testing for and measuring defects.......................................................................... 14

2.4. Engineering assessments.......................................................................................15

2.5. Avoiding recurrence of defects ...............................................................................16

2.6. Steel repair issues ..................................................................................................16

2.7. Concrete repair issues............................................................................................ 18

2.8. Masonry repair issues ............................................................................................18

3. Health and Safety .................................................................................................18

3.1. General ..................................................................................................................18

3.2. Work Safety............................................................................................................19

3.3. Public safety...........................................................................................................20

3.4. Health..................................................................................................................... 20

3.5. First aid ..................................................................................................................21

3.6. Cleaning up ............................................................................................................ 21

3.7. Removal of lead based paints ................................................................................22

Part 2 Steel Repairs....................................................................................................... 23

4. Introduction to standard steel repairs ................................................................24

4.1. Introduction............................................................................................................. 24

4.2. Selecting the appropriate repair procedure .............................................................24

4.3. Sub-procedures......................................................................................................24

4.4. Avoid welding ......................................................................................................... 24

4.5. Drawings ................................................................................................................25

4.6. Repair materials .....................................................................................................25

4.7. Health and safety.................................................................................................... 25


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4.8. References .............................................................................................................25

5. Sub-procedures....................................................................................................26

5.1. Arresting corrosion (Sub-Procedure) ......................................................................26

5.2. Removing rivets and replacing with bolts (Sub-procedure) ..................................... 275.3. Patch painting (including surface preparation) ........................................................ 30

5.4. Filling voids (Sub-procedure).................................................................................. 33

5.5. Sealing interfaces (Sub-procedure) ........................................................................ 35

6. Repairing corroded flanges and webs of girders............................................35

6.1. Repairing flange corrosion in riveted girders...........................................................35

6.2. Repairing flange corrosion in rolled or welded girders ............................................39

6.3. Repairing web corrosion near bottom flange angles in riveted girders .................... 416.4. Repairing webs with localised corrosion .................................................................45

6.5. Repairing corroded bottom flanges of jack arch bridges ......................................... 47

7. Repairing stiffeners, bracing connections and bearings ..................................51

7.1. Relief of corrosion site at the base of intermediate web stiffeners........................... 51

7.2. Repairing intermediate and bearing web stiffeners with localised corrosion............55

7.3. Repairing bearing web stiffeners with localised corrosion at base of outstand leg ofstiffener ..................................................................................................................61

7.4. Relief of corrosion site at the base of splayed angle bearing end stiffeners ............627.5. Repairing corrosion at bottom flange bracing connection........................................64

7.6. Replacing bearing plates ........................................................................................ 68

7.7. Repairing cracked and broken wind brace welded connections ..............................73

8. Repairing fatigue damage.................................................................................... 74

8.1. Intercepting fatigue cracks...................................................................................... 74

8.2. Repairing fatigue cracks at connections of coped I-sections................................... 76

9. Repairing impact damage .................................................................................... 78

9.1. Description of Defect ..............................................................................................78

9.2. Engineering Discussion .......................................................................................... 79

9.3. Sub-procedures required ........................................................................................ 79

9.4. Procedure outline ...................................................................................................80

10. Repairing stepways and footways structures .................................................... 87

10.1. Repairing steel risers and stringers in stepways ..................................................... 87

10.2. Repairing corroded angle colums ...........................................................................93

10.3. Repairing corroded 4-angle colums ........................................................................ 96

11. Complete replacement of members ..................................................................102


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11.1. Replacing members or elements of riveted members ........................................... 102

12. Introduction ........................................................................................................ 105

12.1. General ................................................................................................................ 105

12.2. Health and safety.................................................................................................. 10512.3. References ........................................................................................................... 105

13. Deterioration of concrete...................................................................................105

13.1. Factors affecting deterioration .............................................................................. 105

13.2. Causes of deterioration ........................................................................................ 106

14. Types of defects .................................................................................................113

14.1. Introduction........................................................................................................... 113

14.2. Cracking ............................................................................................................... 113

14.3. Spalling ................................................................................................................ 116

14.4. Scaling .................................................................................................................117

14.5. Delamination ........................................................................................................ 118

14.6. Leaching............................................................................................................... 118

14.7. Rust stains............................................................................................................119

14.8. Honeycombing ..................................................................................................... 119

14.9. Dampness ............................................................................................................ 120

14.10. Leaking joints................................................................................................... 120

14.11. Breaking up of repairs...................................................................................... 120

15. Assessment of deterioration ............................................................................. 120

15.1. General ................................................................................................................ 121

15.2. Assessment procedures ....................................................................................... 121

15.3. Other detection methods ...................................................................................... 123

16. Repair materials..................................................................................................123

16.1. Introduction........................................................................................................... 123

16.2. Material properties................................................................................................ 124

16.3. Types of Repairs ..................................................................................................124

16.4. Questions to consider before choosing a repair material ...................................... 137

17. Repair options ....................................................................................................139

17.1. Establish need for repairs..................................................................................... 139

17.2. Repair options ...................................................................................................... 139

17.3. Selection of repair methods ..................................................................................139

18. Introduction to concrete repair procedures .....................................................14018.1. General ................................................................................................................ 140


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18.2. Repair methods ....................................................................................................140

18.3. Sub-procedures....................................................................................................140

18.4. Steps in repair work.............................................................................................. 140

19. Sub-procedures.................................................................................................. 14119.1. Removing damaged concrete (sub-procedure)..................................................... 141

19.2. Removing concrete at joints (Sub-procedure).......................................................143

19.3. Cleaning concrete substrate for patch repairs and re-casting (sub-procedure) ..... 145

19.4. Cleaning Concrete Surface for Overlays...............................................................145

19.5. Cleaning reinforcement (Sub-procedure).............................................................. 146

19.6. Adding reinforcement (Sub-procedure)................................................................. 146

19.7. Applying bonding coat to concrete (Sub-procedure) .............................................147

19.8. Coating reinforcement (Sub-procedure)................................................................ 14819.9. Formwork for re-casting concrete (Sub-procedure)............................................... 148

19.10. Curing (Sub-procedure) ...................................................................................149

19.11. Surface preparation for external coatings (Sub-procedure) ..............................150

20. Repairing cracks................................................................................................. 151

20.1. Types of cracks ....................................................................................................151

20.2. Repair methods for cracks.................................................................................... 151

20.3. Cracks that should be repaired.............................................................................152

20.4. Epoxy injection ..................................................................................................... 153

20.5. Grouting ............................................................................................................... 154

20.6. Routing and sealing.............................................................................................. 155

20.7. Drilling and plugging ............................................................................................. 156

20.8. Stitching ............................................................................................................... 157

20.9. Adding reinforcement ........................................................................................... 158

20.10. Surface treatments........................................................................................... 160

20.11. Flexible sealants for live cracks........................................................................ 161

21. Patch repairs....................................................................................................... 163

21.1. Engineering discussion......................................................................................... 163

21.2. Repair procedure with cement-sand mortars ........................................................ 163

21.3. Repair procedure with polymer modified cementitious mortars............................. 164

21.4. Repair procedure with epoxy mortars ................................................................... 164

22. Recasting with concrete .................................................................................... 165

22.1. Engineering discussion......................................................................................... 165

22.2. Concrete mix design.............................................................................................16622.3. Repair procedures ................................................................................................168


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22.4. Replacing bearing pads........................................................................................169

23. Repairs for corrosion ......................................................................................... 170

24. Sprayed concrete ............................................................................................... 170

24.1. Repair procedure.................................................................................................. 171

25. Protective coatings ............................................................................................ 172

25.1. Engineering Discussion ........................................................................................ 172

25.2. Repair procedure for chloride build up ..................................................................173

25.3. Repair procedure for carbonation ......................................................................... 174

26. References.......................................................................................................... 175

27. Introduction to masonry repairs........................................................................ 179

27.1. General ................................................................................................................ 179

27.2. Health and safety.................................................................................................. 179

27.3. Acknowledgements .............................................................................................. 179

28. Deterioration of Masonry ...................................................................................179

28.1. Causes of deterioration ........................................................................................ 179

29. Types of defects .................................................................................................182

29.1. Cracks ..................................................................................................................182

29.2. Fretting .................................................................................................................18329.3. Spalling ................................................................................................................ 183

30. Assessment of deterioration ............................................................................. 183

30.1. General ................................................................................................................ 183

30.2. Assessment procedure......................................................................................... 183

31. Repair materials..................................................................................................185

31.1. General ................................................................................................................ 185

31.2. Function of mortar ................................................................................................185

31.3. Problems with strong mortars ...............................................................................185

31.4. Importance of lime in mortars ...............................................................................186

31.5. Basic principles ....................................................................................................186

32. Methods of repair ............................................................................................... 186

32.1. General ................................................................................................................ 186

32.2. Steps in repair work.............................................................................................. 187

32.3. Strength and stability............................................................................................ 187

32.4. Repairs of cracks.................................................................................................. 18732.5. Fretting .................................................................................................................189


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32.6. Impact damage..................................................................................................... 191

32.7. Corrosion of embedded iron or steel..................................................................... 191

32.8. Miscellaneous repairs...........................................................................................191

Appendix A Repair materials...................................................................................... 193

Appendix B Guidelines for Management of Lead Paint on Steel Structures ...........196

Appendix C Guidelines for welding old steels .......................................................... 231

Appendix D Techniques for removing rivets using oxy-fuel equipment ................. 244


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Part 1General


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1. Introduction

1.1. The purpose of this manual

The purpose of this manual is to describe and detail standard repair procedures fordefects commonly found in bridges owned and maintained by ARTC. Both newprocedures and those that have been previously used successfully on ARTC'sbridges are included.

Several advantages result from standardising repair procedures:

The standard repair procedures included have been developed to be bothstructurally sound and practically achievable. Adherence to standard repairprocedures reduces the incidence of inappropriate and ineffective repairsand repairs that have adverse effects on the bridge.

Repairs will be undertaken in a consistent fashion throughout ARTC, whethercarried out by day labour or under contract.

The engineering input into detailing sound repairs is minimised andduplication of effort in developing repair procedures is avoided.

The cumulative knowledge and experience gained in carrying out repairs canbe incorporated into the repair procedures and details. This is an effectivemeans of passing on the knowledge.

Relevant engineering information about the repair procedures is included in

the manual to assist those responsible for selecting appropriate repair action.

1.2. Nature of the repair procedure

The repair procedures given are generic in nature; that is, they apply to a range ofsimilar solutions, with varying member size, position and arrangement. As such it isnot possible to completely detail the repair. Additional information such as the sizeand connections of strengthening elements and their precise position needs to besupplied to enable the repair to be completed.

Notwithstanding the above, guidelines for the selection of size, position andconnections of strengthening elements etc, are given wherever possible to minimise

the amount of engineering input required. Such guidelines are often conservativeand savings may be made in materials and labour requirements for the repair if theengineering details of the repair are determined by design for the specific case athand. The savings may be significant and worthwhile if the extent of repair is great.

1.3. Who should use this manual?

This manual should be used by those responsible for:

selecting repair actions for bridges;

implementing repairs either using day labour or under contract;

inspecting repair work carried out by either day labour or


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contractors;

carrying out routine or special maintenance on bridges that have beenrepaired.

1.4. Aims of repair procedures

The aim of the repair procedures is to restore the strength and serviceability of thebridge structure, either to the "as new" condition, or to the condition that is requiredfor current or envisaged use.

In developing repair details the normal design practices, as specified in theAustralian Bridge Design Code, are applied. It is reasonable that there will be thesame level of confidence in the repaired bridge as in a new structure. For steelstructures, the fatigue life of the repaired bridge should not be less than the life thatwould have remained had the defect not occurred.

Some of the repair procedures, such as concrete etching, aim to restore the originalintegrity of the member. Other repairs, typically when used in steel structures, aim tocompensate for the defect by the attachment of additional structural elements.

A few procedures that are included are not repairs as such, but rather actions thatcan be taken to reduce or arrest further deterioration of the structure, or make thestructure easier to maintain.

1.5. The structure of this manual

The manual is divided into five parts.

Part 1 provides an introduction to the manual, discusses the process ofselecting repair actions and presents information on environmentalsafety and occupational health as related to bridge repairs.

Part 2 covers standard repairs to steel bridges.

Part 3 covers standard repairs to concrete bridge superstructures andsubstructures.

Part 4 covers repairs to masonry.

Part 5 covers repairs to timber bridges. (not yet written)

Additional information such as specifications for repair materials and furthertechnical information are included in the Appendices.

1.6. Format for repair procedures

Each repair procedure is presented in a consistent format comprising the followingparts.

1. Description of defect.

2. Description of repair.= A brief statement describing the form of the repair.


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3. Engineering discussion.= A discussion of engineering aspects of the repair.

4. Sub-procedures required.

5. Procedure outline.= The main steps in implementing the repair are described. This is to beread in conjunction with drawings detailing the repair. Separate procedureoutlines may be given for different cases.

6. Alternative details.= Describes possible alternatives to part, or all, of the repair.

7. Action to avoid recurrence.= Describes action that can be taken to avoid or minimise recurrence of thedefect.

8. Special considerations and effects of repair.= Describes special considerations required, such as traffic restrictions, oreffects of the repair on the structure.

9. Follow-up inspection and testing.= Indicates requirements for follow-up inspection or testing to confirm theongoing performance of the repair.

10. Drawing List.= Lists the drawing(s) that describe and detail the repair.

Some of these parts are omitted if they are not relevant.

2. Selecting repair actions

2.1. Introduction

The aim of repairing a bridge is to extend its life. It is most important that the repairactions selected satisfy this aim at a cost commensurate with the benefits derived.Inappropriate repair action may actually reduce the life expectancy of a bridge. It isalso possible that money spent on extensive and costly repair will not extend the lifeof the bridge significantly and would be better put towards a new bridge.

Selection of appropriate maintenance, rehabilitation and replacement (MR & R)actions for a bridge is part of the function of a Bridge Management System. Theprinciples of Life Cycle Costing are applied in Bridge Management Systems todetermine the optimum MR & R strategy that will result in minimum annual cost ofproviding a bridge at a site.

If a Life Cycle Costing analysis cannot be carried out, the next best thing is todetermine the appropriate repair action by applying a process of logical assessmentto the bridge as a whole.

Section 2.3 below presents a series of questions to be considered in the process of

selecting appropriate repair action.


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2.2. Procedure for selecting repair action

In determining the appropriate repair action to be carried out on a bridge, thefollowing questions should be answered:

2.2.1 What is the nature, severity, location and extent of each defect?

To enable a considered logical assessment of repair actions, full data about eachdefect must be known and recorded from site inspections, measurements andtesting. Clause 2.3 deals with testing for and measurement of defects.

2.2.2 Is a repair to restore full strength necessary?

The underbridge, overbridge, footbridge or stepway may have been designed with aload capacity greater than currently required or envisaged. In this case the strengthreduction caused by the defect may be acceptable.

Even if the full design load capacity is needed, a small overstress say 10% -resulting from the defect can usually be accepted.Some elements may be able to tolerate considerable deterioration before repair orstrengthening is needed. For example, the full flange area of a rolled girder may notbe necessary near the end of a span where the bending moment is small.

The necessity for and extent of a repair should be determined, where appropriate,by a full engineering assessment. The time and effort required for such a task maybe repaid by minimising the extent of repairs needed or by determining that therepairs are not structurally necessary. Clause 2.5 discusses the role of engineeringassessments.

If it is found that repair or strengthening is not needed, then the only actionrequirement is to protect the structure from further deterioration.

The serviceability requirements, particularly fatigue in steel, should be considered ina similar manner to strength.Note that a repair may be warranted to improve the appearance of a bridge, even ifit is not structurally essential.

2.2.3 Is a standard repair procedure available for each defect?

It is not normally appropriate to repair one defect in a bridge if other signifiantdefects are left unrepaired because satisfactory or cost effective repair procedures

are not available.

It should be confirmed that a standard repair procedure envisaged is actuallyappropriate to the defect. The engineering discussion accompanying each repairprocedure will describe where the procedure should and should not be used.

2.2.4 What is the total cost of repairing all defects?

The total cost of repairing all defects in a bridge, even if only determined crudely,should be estimated and compared with the expected benefits. The benefits areusually either extending the life of the bridge or eliminating an immediate dangeroussituation. The costs of any track possessions etc. that are required should be

included.

If the costs of repair are substantial and the repairs are non-urgent for safety, then it


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may be better to replace the bridge and divert repair funds to more appropriatecases.

The initial cost estimate will be a factor in deciding if a detailed engineeringassessment is worthwhile. When the total cost is high say more than 5% to 10% of

the bridge replacement cost -a detailed engineering assessment must be carriedout. The extent of repair is likely to be minimised as are sizes and numbers ofconnections for strengthening elements.

2.2.5 How significant will the repair be in extending the life of the bridge?

The proposed repair may not provide value for money if the life of the bridge is notextended because of other factors.

Most steel bridges have a finite life, governed by fatigue of the steelwork. It may notbe appropriate to spend large amounts of money on repairs if the bridge is near theend of its predicted fatigue life. Replacement is probably a better option.

In concrete structures, defects such as corrosion of reinforcement may not beapparent at the present time, but the effects may show up in the form of concretecracking and spalling in the near future. It may not be appropriate to spend moneyon repairing some localised defects if much more extensive defects are likely toshow up in the near future. Investigation by specialists into the complete structuremay be warranted prior to undertaking costly repairs of concrete.

As another example, the benefits of repairing corroded bottom flanges of jack archbridges may not be certain because the condition of the remainder of the steelsection is usually not known. The effort in repairing the bottom flange would bewasted if the top flange and web were also severely corroded.

2.2.6 Can the cost of the repair be justified on the basis of benefits derived?

The answer to this question will normally be evident from the answers to questions2.2.2 to 2.2.5. For some bridges there may be additional factors that influence thedecision on whether to implement a particular repair.

Taking advantage of planned track possessions may often be a significant factor indeciding whether to implement a repair or not. In many repairs, particularly smallerones, the cost of the track possession is the major component. If the repair can becarried out under a possession provided for other reasons, the actual cost of therepair drops significantly for the same benefit. A repair that could not normally be

justified on a cost/benefit basis may become cost effective as a result.

2.2.7 Is a detailed engineering assessment needed?

The reasons for, and benefits of, an engineering assessment are discussed in Part 2Section 2.4 of this manual. The decision to undertake an engineering assessmentwill be based on the cost of the assessment versus the possible benefits.

A longer lead time to implement a repair will usually be required if an engineeringassessment is to be undertaken.

2.2.8 Has partial replacement of the bridge been considered?

As an alternative to repairing defects or strengthening members, considerationshould be given to partial replacement of the structure.


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This may involve merely replacement of damaged bracing members, stiffeners,stringers, cross girders etc. up to complete replacement of main girders.

The decision will be based on time, cost and effectiveness of the repair compared tothat of a complete replacement. If the effectiveness or life expectancy of repairs or

strengthening is limited, then complete replacement of an element may be a betteroption, particularly if the cause of the defect can be eliminated at the same time.

2.2.9 Will the repair have any adverse effects on the structure?

Consider any adverse effects that the repair may have on the performance of thebridge.

Will traffic clearances be reduced?

Will the structure become more vulnerable to damage or deterioration?

Will other potential defects be hidden by the repair?

2.3. Testing for and measuring defects

2.3.1 General

As stated in 2.2.1 above, it is necessary to determine the nature, severity, extentand location of defects to determine appropriate repair actions. Most defects areinitially detected by visual inspection. The severity, extent and location aredetermined by subsequent measurements and tests.

2.3.2 Measuring section loss in steel

In steel structures, corrosion of steel leading to a loss of section is a common defect.Measurements are to be taken to determine the thickness of remaining sound steelfor comparison with the original thickness. All loose rust and corrosion product mustbe removed at the point of measurement to allow an accurate reading. Verniercalipers or preferably a micrometer should be used to obtain accuratemeasurements to at least an accuracy of 0.25mm.

The number and location of measurements required will depend on the defect underconsideration. Usually the minimum requirement is to measure the remaining cross-sectional area of an element (flange, web, stiffener) at the location of the greatest

corrosion loss and location of greatest stress.

2.3.3 Testing for and measuring cracks in steel

Although many cracks in steel can be detected by visual inspection, it is usuallynecessary to use techniques such as magnetic particle testing to determine theexact extent of cracks. This is particularly important in mapping fatigue cracks wherethe end point must be found.

Examination for cracks and other defects in new welds will require the use of non-destructive techniques such as ultrasonic or X-ray examination.

Further discussion of N-D examination methods is beyond the scope of this manual,but reference is made to the appropriate Australian Standards.


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2.3.4 Observation under load

The severity of some defects is best determined by observing the structure duringthe passage of a heavy load. Loose rivets and bolts may be detected by thismeans. The behaviour of girder bearing plates and bed plates under load will aid in

determining the necessity for repair or replacement.

2.3.5 Detecting defects in concrete

While most defects in concrete, such as cracking, spalling and rust staining aredetected by visual examination, the likelihood of further deterioration can bedetermined using specialist testing techniques. Tests to determine extent ofcarbonation, chloride penetration, cover to reinforcing etc. can be carried out todetermine the life expectancy of concrete. As outlined above, this information isuseful in planning the long term maintenance and repair strategy for a concretestructure.

Refer to Part 3 of this manual, dealing specifically with concrete repairs, for moreinformation on testing of concrete.

2.4. Engineering assessments

An engineering assessment or investigation into a proposed repair must be carriedout and is essential to determine the appropriateness of the repair and the repairdetails. The engineering assessment is based on measured and recorded defectsfound on the bridge during inspections, the structural drawings of the bridge and theload capacity requirement of the bridge.

The aims of an engineering assessment are to:

determine the effect of the defects on the strength of the structure,

determine the effects of the defects on the serviceability of the bridge,including its fatigue performance,

determine or confirm that each proposed standard repair is both necessaryand suitable to address the defect,

determine the extent of all the required repairs,

determine the engineering details of the repairs where required these includeplate sizes, fastener sizes and types, new connection details etc.

A detailed engineering assessment is not always required. The repair proceduresinclude, where possible, guidelines for determining the above data, albeit adopting aconservative approach. A detailed engineering assessment is required where theestimated total cost of repairs is more than 5% to 10% of the replacement cost ofthe structure. In such cases, the cost of the investigation could be more than savedin the reduced extent of repair.


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2.5. Avoiding recurrence of defects

In conjunction with carrying out the repairs, action should be taken where possible toavoid recurrence of the defects. This has been considered in devising repairprocedures. To protect against recurrence of the defect, the original cause must be

known and eliminated where possible.

The causes of defects are often built into the structures and are difficult to eliminate.Deterioration of concrete, for example, due to insufficient cover to reinforcing or poorconcrete compaction, cannot be easily addressed. Details in steel structures whichare prone to corrosion because of collection of water and dirt cannot be readilyeliminated without changing the structure significantly.

Often the only effective means of avoiding recurrence of the defect is preventivemaintenance of the structure to remove dirt and debris and to maintain the integrityof the paint system.

Where possible galvanised strengthening or replacement elements should be usedto ensure long term corrosion protection with minimum maintenance requirements.The standard repair procedures specify galvanised elements where possible.

2.6. Steel repair issues

2.6.1 Methods of connection

In addressing defects in steel bridges resulting from steel corrosion, it is clearly notpossible to reinstate the steel to its original condition. Similarly, restoring physicallydamaged steel to its original condition is often difficult. Most repairs therefore involvefitting new steel elements to compensate for the reduction in strength or

serviceability caused by the section loss.

The two standard methods of connecting new elements are welding and mechanicalfastenings (bolts etc.). Of the two, mechanical fastenings have the least potentialproblems although welding is usually easier and cheaper. Mechanical fastenershave been adopted as the standard method in all steel repair procedures.

The two main potential problems with field welded connections are:

1. satisfactory welds may be difficult or impossible to achieve in steels of older

bridges because of their metallurgical properties; and

2. the fatigue life of the structure may be adversely affected by welding. Theeffect may be severe.

Refer to 2.6.2 and 2.6.3 below.

Connection by welding can only be permitted if satisfactory welds are proven to beachievable and any effects on fatigue life are acceptable. Most standard repairs,detailed with bolted connections, can be readily adapted for welded connections.

2.6.2 Weldability of steel

While modern steels can be readily repaired by welding using appropriateprocedures, the steels found in older steel bridges are often considered "not


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weldable" or very difficult to weld because of their metallurgical properties. The highsulphur and phosphorous contents largely contribute to difficulty in welding.

Unfortunately, it is not possible to classify steels as weldable or "not weldable"based on their age. From the 1940's to the 1960's some imported steels were from

plants producing steels designed to be weldable, while others were from plantsproducing unweldable steels.

It is essential that, where a welded repair is proposed on steels of unknownweldability, the steels be tested to determine whether or not they are weldable bynormal welding procedures. The necessary tests can be carried out by NATA

Accredited Laboratory.

It is sometimes technically possible to achieve satisfactory welds in older style (non-weldable) steels, but only by careful adherence to particular welding proceduresdesigned for such steels. A high level of operator skill and good welding conditionsare required. Unfortunately, most steel repairs must be carried out in conditions

which are anything but conducive to good welding.

Appendix C provides details of techniques for welding so-called "nonweldable"steels. The information is intended for accredited welders/boilermakers alreadyskilled in normal welding techniques. If such welding is attempted, it is essential tocarry out test welds to confirm that acceptable results can be achieved under siteconditions. It is also necessary to carry out non-destructive testing of the completedwelds to confirm their integrity.

Also, careful consideration must be given to the ramifications of a failed attempt at awelded repair on "non-weldable" steels. The cost of undoing the damage may be

significantly greater than if a bolted connection repair had been carried out.

2.6.3 Effect on fatigue life

As in the design of new steel bridges, the details of welded connections used insteel repairs may have an effect on the fatigue life of a bridge. Although theremaining life of a bridge that has been in service for many years is not expected tobe as great as a new bridge, it is best to avoid any repair actions that wouldadversely affect fatigue life. This is particularly so if viable bolted connectionalternatives are available.

Properly maintained riveted girder bridges with low stress levels may never fail by

fatigue. Repairs involving welded connections on such bridges often set a finitefatigue life and so should be avoided.

If a welded repair is proposed, it should always be accompanied by an engineeringassessment of the effect on the fatigue life of the weldment. The AREA Manual forRailway Engineering should be used to assess the effects. The proposed weldedrepair should only be implemented if the effects on fatigue life are acceptable.

2.6.4 Redundancy of riveted girders

Riveted girders, comprising multiple elements for flanges, have beneficialredundancy that should not be removed by the repair process. Redundancy means

that if one of the plate or angle elements of a flange fails, say by a fatigue crack, thewhole girder will not immediately fail as the fatigue crack cannot propagate to otherelements. Inspection can detect the failed component for repair prior to complete


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failure of the girder. The stress levels in the uncracked elements obviouslyincrease, causing overstress and reducing the overall fatigue life, but the situation isbetter than in welded or rolled girders where a crack in a flange can quicklypropogate all the way through the section, leading to collapse.

The elements of riveted girder flanges must not be joined by welding as this wouldcreate paths to allow fatigue cracks to propagate from one element to another.

Redundancy is of particular benefit in bridges of a considerable age because itprovides a degree of protection against sudden failure. The redundancy must bepreserved.

2.7. Concrete repair issues

The most important issue in the repair of any structure is to ensure adequatestrength and stability at all times. This is particularly relevant in repair to reinforcedconcrete elements where significant areas of concrete are to be removed. In such

cases the strength or stability of the structure with the concrete removed should bechecked by a structural engineer before commencing repairs. Also, load restrictionsshould be applied and the structure temporarily supported as necessary.

The repair of concrete structures requires a knowledge of the following issues:

1. Types of defects which can occur due to deterioration, e.g. cracks, spalls,delamination, scaling, honeycombing etc.

2. Causes of deterioration, e.g. chloride penetration, carbonation, alkali -aggregate reaction, shrinkage and thermal effects, foundation movements

etc.3. Test methods for assessing the severity of deterioration.4. Selection of appropriate repair materials, from ordinary Portland cement to

synthetic polymers, resins and acrylics according to particularrequirements of a repair project.

5. Selection of appropriate repair procedure.

Part 3, Concrete repairs, contains detailed discussion of all the above issues.However, it does not include complex and advanced repair methods such ascathodic protection, re-alkalisation etc., which should only be entrusted toorganisations specialising in this work.

Also, the repair methods are for reinforced and plain concrete only, not prestressedconcrete.

2.8. Masonry repair issues

The repairs of masonry structures generally involve the same issues as for concretestructures. Methods and materials for masonry repairs are included in Part 4.

3. Health and Safety

3.1. General

For the protection and safety of workmen, public and environment, safe workpractices are essential on every work site. The following safety aspects are


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common to most types of ARTC work and must be considered prior tocommencement of any construction or repair project:

Work safety

Public safety

Environmental safety Health

Health and safety have a high priority at all times during field operations. Allstatutory rules and regulations under various Occupational Health and Safety Actsand safety practices detailed in ARTCs Safety Management System are forguidance in planning for safety at all the worksites. Commonsense should be usedin anticipating the particular safety requirements for each and every project to beundertaken.

3.2. Work Safety

Work safety must be planned ahead. Before commencing work the supervisorneeds to attend to the following:

1. Familiarise yourself with full requirements of the repair work includingformwork, falsework, demolition, repair materials, repair method, and safetyrequirements of handling repair materials and equipment.

2. Arrange personnel who are skilled in the particular type of repair.

3. Ensure that all tools, plant and equipment are available and in good workingorder.

4. Arrange all repair materials including materials necessary for cleaning toolsand plant after completion of work.

5. Arrange safety harnesses, clothing, footwear, gloves, ear muffs, eyeprotection glasses, masks, helmets, welding shields, and any other itemsnecessary for personal safety of the workers. Supply washing soap, towelsand barrier creams for worker hygiene.

6. Identify and locate all the utilities existing at site, such as water, sewerage,electricity, signals, communications, gas etc. If any utilities are affected by

work take measures in advance to protect them or get them relocated asnecessary through appropriate authorities. If any risk is foreseen, inform theauthorities to stand by for any emergencies.

7. Ensure that first aid equipment is available at site and that at least one of thepersonnel at site holds a valid qualification for giving first aid.

8. If necessary, plan and arrange for standby oxygen administering equipmentand fire-extinguishers. Under such circumstances workers should be trainedbeforehand in how to use them.

9. All work must be carried out in well ventilated and well lit areas. If necessarymake prior arrangements for exhaust fans and artificial lighting.


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10. If scaffolding and falsework are required for supporting the structure, arrangethis to be designed by qualified structural engineers. Erection and stability offalsework must be supervised by qualified technical persons.

11. Persons who are not qualified for carrying out a particular task or operating a

particular equipment must not be allowed to do that task or operate theequipment.

12. Generally, all the work should be carried out as per industry's normalstandards of practice and/or in compliance with the Australian Standards.

13. All repair work using proprietary materials must be carried out strictlyaccording to the manufacturer's printed instructions. The manufacturer'sproduct data sheets for health and safety precautions must be carefully readand followed.

3.3. Public safety

There are legal obligations to take all necessary precautions and adequatemeasures for safety of public in and around the working area. The following stepsshould be taken to safeguard the public against any injury, loss of life or property:

1. Attend immediately to any damage and deterioration which may cause lossof strength and stability of a structure and thereby may result in injury, loss oflife or property to public.

2. Take steps to support the structure against instability and collapse, as wellas protect the adjacent properties, plant and utilities from possible damage.

3. Until the structure is made safe, close off access to it and prohibit its use by

the public by setting up suitable fences and barriers. With the assistance ofpolice and Road and Traffic

Authority arrange to divert the pedestrian and vehicular traffic by alternativeroutes. Provide warning signs and hazard lights as necessary to caution thepublic of danger.

4. During progress of the work, take all necessary precautions to safeguard thepublic from suffering excessive hardship and inconvenience which may becaused by equipment, materials and procedures. Minimise noise, dust,flooding, blowing of sand and grit in blasting operations, toxic fumes, debrisand so on.

5. At the completion of the repairs, clean up all dirt and debris, remove all plant,equipment and materials and restore the facility to public.

Caution:

In construction and repair work on railway sites, use is frequently made ofexplosives, detonators and hazardous materials. The issue and use of suchmaterials must be strictly controlled. Particularly, all explosives and detonators mustbe accounted for in order to prevent their falling into hands of children andundesirable elements. Many a loss of life and limb has been caused by detonators

picked up by children and adolescents and used for "fun".

3.4. Health

All personnel engaged at a work site must be protected against sickness andpersonal injury caused by work conditions, repair materials and methods of repair.

Accidents, injury and sickness can be minimised by taking the following precautions:


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1. Do not work in unventilated or poorly ventilated areas. Many repairmaterials and procedures give off unpleasant vapours or toxic fumes thatcan cause nausea or breathing difficulties. If necessary, wear respiratormasks. Do not smoke while working, as you may inhale vapours and

fumes too.2. Handling of polymers, epoxies, acrylics and other cementitious materials

often causes skin and eye irritations. Before mixing and using thesematerials, read all label warnings on the packages as well as themanufacturers product literature and follow the handling instructionscarefully. Avoid physical contact with the materials by wearing protectiveclothing, shoes, gloves and protective eye wear at all times.

3. Apply protective barrier cream on exposed skin. (However, do not usebarrier creams as substitute for protective clothing).

4. If any material comes into contact with skin or enters the eyes, give first aidimmediately, as described herein later.

5. If overalls or inside of shoes and gloves become contaminated, remove

them as soon as practicable and replace them with clean ones.6. Wash thoroughly with warm soapy water before eating, drinking or smoking

and after finishing work.

3.5. First aid

The following first aid procedures should be followed:

EyesIf any material enters the eyes or irritation persists, hold eyes open, flush with lowpressure water for at least 10 minutes and seek immediate medical aid.

SkinIf skin contact occurs, remove contaminated clothing and wash skin thoroughly withwarm soapy water. If irritation persists or skin rashes or allergic responses such aswheezing and swelling occur, seek immediate medical aid.

InhalationPersonnel affected by inhalation of vapour etc. should be removed from thecontaminated area into fresh air. Apply artificial respiration if not breathing and seekimmediate medical aid.

Ingestion

Immediately rinse the mouth repeatedly with water. If swallowing occurs, do notinduce vomiting. Drink plenty of water and seek immediate medical aid.

FireUse a fire extinguisher appropriate to the type of burning material. Avoid breathingproducts of combustion.

3.6. Cleaning up

All leaks or spillages should be cleaned up as they occur and before they set. Thematerial should be soaked up in suitable absorbents such as dry sand or sawdust,or swept up if it is powdered material. The material should be disposed of quickly

and safely into waste drums.


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Tools and equipment can be cleaned with proprietary solvents or warm water anddetergent before the adhesive has had time to set.

3.7. Removal of lead based paints

The large majority of rail bridges are primed with red lead primer. Lead in any formis toxic to humans and animals when ingested or inhaled.

Particular attention therefore must be paid to environmental safety and worker andpublic health and safety in the process of removing lead based paints. Reference ismade to Appendix B containing the "Guidelines for Management of Red Lead Painton Steel


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Part 2

Steel Repairs


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4. Introduction to standard steel repairs

4.1. Introduction

Part 2 of this manual gives details of standard repair procedures for defectscommonly occurring in steel bridges and other structures within the ARTC system.Documenting standard repair procedures assists in ensuring that common defectsare repaired in a consistent and structurally satisfactory manner by both ARTC staffand sub-contractors.

It must be emphasised that the information given on each repair is not a fullspecification (in the contractual sense) but a description of the form of the repair andthe steps required to implement the repair for each generic type of defect.

Additional information, such as size and thickness of plates, numbers andarrangement of new bolts, extent of repair etc. must be determined by anengineering assessment and provided to the repairer in conjunction with information

in this manual. Guidelines for determining this additional information are given withthe procedure, where possible.

4.2. Selecting the appropriate repair procedure

Chapter 2 of Part 1 deals with selecting the appropriate repair actions or strategiesfor the bridge, looking at it as a whole. Reference is made to that section.

Because of the generic nature of some of the repair procedures given, it is alsonecessary to ensure that the procedure proposed is appropriate and applicable forthe particular defect. Careful engineering assessment of the defects, on a case bycase basis, is strongly recommended to assist in ensuring that the appropriate repairprocedure is selected.

Discussion of the engineering considerations of each repair is given within theprocedure. Where appropriate, the discussion includes guidelines for determiningthe necessity for the repair based on the severity of the defect.

4.3. Sub-procedures

Some actions in the repair process are common to more than one repair procedure.For example, the process of replacing a rivet with a high strength bolt is to becarried out in many of the repair procedures. These actions or sub-procedures are

described and detailed in Chapter 5.2. Required sub-procedures are referred to inthe main repair procedures.

4.4. Avoid welding

The repair procedures presented generally use bolted connections instead of sitewelding for the following reasons:

High quality site welds are difficult to achieve.

Many of the repairs are to be carried out on old bridges in which the steelsare considered unweldable.

The addition of weldments to members with calculable stresses can oftenreduce the fatigue life significantly.


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Welded repairs can remove or reduce the inherent structural redundancy ofbuilt up riveted sections.

Alternative connection details involving site welding may be possible butshould only be implemented after:

carrying out a full engineering investigation of the effects on strength, fatiguelife and degree of redundancy; and

determining by analysis and tests that site welding the existing steels isachievable and practicable.

Refer to Chapter 2 of Part 1 for more information on the suitability of site weldedrepairs.

4.5. Drawings

Each repair procedure is detailed on one or more drawings. It is envisaged thatthese drawings, together with the text of the procedure outline and the additionalinformation from the engineering assessment referred to in 4.1, will provide all theengineering detail required by site personnel to implement the repair.

As the drawings often include several alternative details, instructions on whichalternative to use may also be required.

4.6. Repair materials

In the repair procedures, repair materials are referred to by their generic name.

Specific brand and material names of epoxies, paints etc. are usually avoided asavailability may vary from time to time and new, superior materials may becomemore appropriate. Lists of suitable brand and material names are given in Appendix

A, together with the specifications for standard repair materials such as steel andhigh strength bolts.

Where new steel parts are to be fitted as part of the repair, it is generallyrecommended that those parts be galvanised. Use of galvanised steel can reducelong term maintenance requirements and minimise the amount of on-site paintingrequired. Where the appearance of galvanised steel is not acceptable, and paintingover galvanised surfaces is impractical, the steel parts may be painted instead usingone of the high quality paint systems used in bridge repainting. Refer to sub-

procedure 5.3 for further information.

4.7. Health and safety

Attention is drawn to Chapter 3 of Part 1 on "Health and Safety" which highlights theprecautions required when handling specialised and hazardous materials duringmaintenance and repair work.

4.8. References

The following references were used in the preparation of Part 2 -Steel Repairs.

1. Australian Bridge Design Code

2. AREA Manual for Railway Engineering


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3. AS4100-1990 Steel Structures

4. AS1252-1983 High Strength Steel Bolts with Associated Nuts andWashers for Structural Engineering.

5. Bridge Fatigue Guide - Dr J W Fisher - AISC New York 1977

6. Guidelines for Evaluation and Repair of Damaged Steel BridgeMembers - National Co-operative Highway Research Program Report271.

7. Importance of Redundancy in Bridge - Fracture Control. R R P Sweeny- Canadian National Railways.

5. Sub-procedures

5.1. Arresting corrosion (Sub-Procedure)

5.1.1 Description of action

Any action that will prevent further deterioration and loss of section in steel due tocorrosion.

5.1.2 Engineering discussion

Arresting of corrosion may be the only repair action that is required or possible for abridge, or it may be required in conjunction with other repair actions. The mosteffective method of arresting corrosion is abrasive blast cleaning followed by the

correct application of a high quality paint system and its ongoing maintenance.

If that form of corrosion arrest is appropriate, refer to sub-procedure 5.3, patchpainting, for information on preparing for and carrying out patch painting. Note thatthe use of so called "rust converters" prior to painting is not permitted.

In addition to painting, action can be taken to avoid conditions which promotecorrosion. Action to avoid collection and entrapment of water may be worthwhile. Insome locations, holes may be drilled to allow water to drain away. Voids anddepressions which catch water may be filled with epoxy. Epoxy fillers may also beused to profile a surface to promote free drainage of water. Advice on appropriateepoxies should be sought from the recognised manufacturers. Epoxies should bedurable, paintable, and should bond adequately to the substrate. Epoxy with someflexibility may be appropriate for the purpose described.

Denso Tape covering of steel elements may be a suitable alternative to painting.Denso tape could be used at the interface between concrete and steel or timber andsteel. These locations are typically difficult to protect by painting. The interfacebetween steel beams and other metal elements such as steel decking may betreated similarly.

One advantage of Denso tape is that the amount of surface preparation required isminimal. All that is usually required is the removal of loose rust, dirt, paint etc. from

the surfaces. The primers and fillers can then be applied.


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Guidance on the appropriate Denso Tape treatment and its correct applicationshould be sought from the manufacturer.

Caution:

Corrosion protection systems such as Denso Tape wrapping and epoxy filling may

hide critical defects such as fatigue cracks. Such defects may be difficult to detectduring normal inspections and may result in collapse of the structure.Corrosion protection systems such as these should not be used on fatigue-criticalelements unless appropriate procedures to regularly check for and detect cracks areimplemented.

5.1.3 Procedure

Prepare for and apply Denso Tape, epoxy fillers etc. in accordance with themanufacturer's recommendations.

Where patch painting is to be used for corrosion arrest, refer to sub-procedure 5.3.

5.1.4 Materials

Refer to the manufacturers of Denso Tape systems and epoxy resins for advice onsuitable materials for each particular case.

5.1.5 Alternative details

None

5.2. Removing rivets and replacing with bolts (Sub-procedure)


This sub-procedure covers the removal of existing rivets and replacement with highstrength friction grip bolts and also installation of new high strength bolts. Often thebolts also attach new steel elements.

5.2.2 Procedure:

5.2.2.1 Remove one head of the rivet:

To remove rivet heads, one of three methods are usually used:

cutting using oxy-fuel equipment;

grinding off all or part of the head; or

drilling through the centre of the rivet head.

Oxy-fuel cutting:

Because of the possibility of creating heat affected zones in tension regions ofmain members and adversely affecting their fatigue life, avoid using oxy-fuelcutting to remove the head except where it is adjacent to:

1. any steel that is to be removed and discarded as part of the repair process;

2. intermediate web stiffeners; or


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3. minor bracing members that are not subject to dynamic or cyclic loading.

Do not allow the oxy flame or molten steel to touch any other steel elementexcept those listed above.

In cases 2) and 3) above, where the steel adjacent to the rivet head is to remainin place, take care to avoid or minimise flame effects on that steel, to leave a neathole for installation of the bolts.

If the use of oxy-fuel cutting cannot be avoided in cases other than those above,take great care to avoid flame effects on the adjacent steel. Any flame affectedsteel around the hole must be completely removed by reaming prior to installingthe bolt.

Grinding:

If removing the head by grinding, it is only necessary to remove the portion of thehead outside the shank diameter.

Take care to avoid creating grooves and indentations in steel that is to remain inplace. If such indentations and grooves occur, remove them by grinding thesurface smooth after removing the rivet.

Where large numbers of rivets are to be removed, consideration should be givento procuring a grinding bit such as a broaching bit which, when positionedcentrally on the domed head will grind away material outside the shank diameter.

Drilling:

Rivet heads may be removed by drilling along the axis of the rivet with a drillingbit larger in diameter than the shank.

5.2.2.2 Remove the rivet

After the head of the rivet has been removed, force the remaining part out of thehole by punching or using hydraulic rams etc. The rivets are often not easilyremoved by punching because of deformation of the shaft in slightly misalignedholes.

Alternatively, remove the rivet head and shank and prepare the hole to acceptthe new bolt in one operation by drilling all the way through the rivet. The drill bitsize must be slightly larger than the rivet hole size and must be of a size to suitinstallation of a high strength bolt.

First drill a small hole through the rivet. Where the remainder of the rivet cannotbe removed by the above means, it is permissible to burn a hole through thecentre of the shank using oxy-fuel equipment to assist in the removal process.

As stated above, extreme care is required to avoid any flame effects on thesurrounding steel. This operation is only to be carried out by experiencedoperators. Any flame-affected areas of steel must be completely removed byreaming the hole prior to installing the bolt.

Refer to Appendix D for further information on techniques and equipment for saferemoval of rivets using oxy-fuel and other equipment.


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5.2.2.3 Prepare the hole for the bolt:

Prepare the hole to accept the bolt by reaming out the hole to the requireddiameter, then removing burrs etc. at the edge of the hole and creating a smooth,

level surface on both sides for bedding the washer and bolt head. Grinding, wirebrushing and scraping may be used.

The hole diameter after reaming must be no more than 2 mm larger than thediameter of the bolt to be installed unless a plate washer is to be installed inaccordance with detail A on Fig 5.2.1. In the latter case the hole diameter maybe up to 10 mm greater than the bolt diameter.

Use reaming to remove any areas of steel around the hole that have beenflame affected during the removal of the rivet.

The minimum and maximum edge distances and spacings for new bolt-holes in

existing or new steel are to comply with the requirements of the Australian BridgeDesign Code.

5.2.2.4 Install the bolt:

Install the replacement bolt in accordance with the following specification. Table5.2.1 specifies minimum replacement bolt sizes. The arrangement for oversizeholes is shown in Detail A of Fig 5.2.1.

Specification for New or Replacement Bolts

1. All bolts are to be high strength structural bolts of grade 8.8 to AS 1252,

fully tensioned to AS 4100 as a friction joint. Tension is to be controlled byload indicating washers or turn of nut method.

2. Swage bolts installed in accordance with the manufacturer's instructions,may be used as an alternative.

3. All bolts, nuts and washers are to be galvanized.4. Swage bolts, pins and washers are to be galvanised and the steel surface

exposed after separation of the pintail is to be painted.5. Nominal maximum hole diameter to be the diameter of the fastener +2mm

unless plate washers, as illustrated in Detail A are used, unless otherwisespecified for swage bolts.

6. For each standard rivet size the minimum size of replacement bolt to give

equivalent shear capacity is given in Table 5.1. Larger bolts may be used.7. For Huck BOM blind fasteners, sufficient room must be available on theblind side to accommodate the expanded head. Refer to Detail B.

Rivet size Bolt size

8.8 T/F

Huck Bolt

C50L

Huck-Fit

Grade 10.9

Huck

BOM

3/4 M20 3/4 20mm 3/4

7/8 M24 7/8 22mm -

1 M27 1 27mm -


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Table 5.1 Minimum replacement bolt sizes

If Huck bolts are used, the HUCK-FIT fastening system is recommended as the pinsare available in standard metric sizes including non-preferred sizes (M20, M22,M24, M27 etc.). The HUCK-FIT system allows fit up and snug tightening of bolts

prior to tensioning. Huck bolts are to be installed in accordance with themanufacturers instructions.


If there is only access to one side of plates to be bolted, use Huck BOM blindfasteners, installed in accordance with manufacturers instructions. Use galvanisedBOM fasteners. Make sure there is adequate room for the enlargement of the blindside head. Refer to detail B in Fig 5.1.

Note that Huck BOM fasteners are not friction grip connectors and may not besuitable for all situations. Bolt slip may occur to the limit of the hole clearance. Slipcan be minimised by drilling close tolerance holes (19 to 20mm for as shown in

Fig 5.1.

A similar blind fastener for high strength friction grip applications is available fromHuck on special order. It is known as the USBB (Ultra Strength Blind Bolt). Usethese fasteners when blind friction grip connections are essential.

5.3. Patch painting (including surface preparation)(Sub-procedure)


Patch painting is required in conjunction with steel repair as a corrosion protection

system for new and existing steel in the vicinity of the repair, and to restore auniform appearance to the bridge.


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Patch painting to arrest corrosion may be the only form of repair required.

This sub procedure only covers painting to small areas where hand and power toolpreparation is the only feasible method.

Large areas, where the cost of abrasive blast cleaning can be justified, should bepainted in accordance with ARTCs standard practices.


Paint systems for patch painting should ideally have the following characteristics:

Formulated to provide good adhesion and protection to poorly prepared steelsurfaces (hand or power tool preparation).

Formulated to bond to sound existing paints of the types typically found onbridges.

High build, single coat systems to minimise total painting time

(i.e. adequate film thickness applied in one coat). Available in a large range of colours to blend with colour of existing paint and

avoid the necessity for a colour matched top coat.

Able to bond adequately to galvanised steel.

Suitable for top coating where a top coat is required.

Leading paint manufacturers have paint systems with most of the abovecharacteristics. One system specifically developed for this application is a two partsurface tolerant epoxy mastic.

ALKYD systems are not suitable for application to galvanised surfaces because the

long term bond cannot be guaranteed. Where galvanised parts have been fitted aspart of the repair and the selected patch paint system is not suitable for galvanisedsurfaces, the following options exist:

1. Leave the galvanised surface unpainted. Painting is normally onlynecessary to achieve a uniform appearance with the rest of the steel.

Or2. Use different single coat systems for galvanised and ungalvanised surfaces.

Systems for galvanised surfaces are readily available. Galvanised parts canbe painted prior to installation.Or

3. Apply the standard single coat patch paint to ungalvanised surfaces then

apply a suitable top coat to both galvanised and patch painted surfaces. Topcoat systems suitable for such situations are available.Or

4. Paint new steel parts instead of galvanising them. Use the patch paintsystem on site or, where parts can be prepainted, use the paint systemadopted for repainting of bridges. Abrasive blast cleaning is required for thelatter.

The minimum surface preparation for small areas is usually specified by paintmanufacturers as hand or power tool cleaning to AS 1627.7 or 1627.2 Class 2. The

Australian Standard referred to provides a full description of the methods andequipment to be used and the quality of surface finish required.

For rough surfaces, such as the surface of site fillet welds, special preparation andapplication procedures are required. Unless precautions are taken, the paint


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thickness on sharp ridges will be considerably less than the minimum required andpremature breakdown of the paint system may occur.

5.3.3 Procedure

5.3.3.1 Prepare the surface

For normal steel surfaces

Prepare the surfaces for painting in accordance with therecommendations of the paint manufacturer for the paint system to beapplied. Hand or power tool cleaning to AS1627.7 or AS1627.2 Class 2 isthe minimum requirement.

For rough surfaces

Remove sharp ridges and deep narrow grooves or pits from the steel

surface by power grinding. Alternatively, for the surface of site fillet welds,fill the surface to a smooth even finish using epoxy resin fillers such asthose used for void filling described in 5.4.

Where the depth of the roughness is less than 0.5mm, an adequate anddurable paint system can be achieved without the above surface levellingby applying multiple coats of the paint. Each coat is to be no more thanthe maximum film thickness recommended by the manufacturer. Enoughcoats are to be applied so that the minimum required dry film thickness(typically 150 microns) is achieved at all sharp ridges.

For galvanised surfaces

Prepare the galvanised surface for painting in accordance with the paintmanufacturers recommendations. Coating manufacturers usuallyrecommend degreasing and abrasion, acid etching or pretreatment withetch (wash) primers prior to painting. Light abrasive blast cleaning (brushblasting) is the most reliable means of achieving satisfactory coatingadhesion. However, where light abrasive blast cleaning is impractical dueto the small areas involved, power wire brushing/hard scouring withaluminium oxide impregnated nylon pads to remove the shiny patina onnew galvanised steelwork and the white soluble zinc salts on old(weathered) galvanised steelwork is preferred to acid etching orpretreatment with etch primer.

5.3.3.2 Apply the paint

Mix the paint components and apply in accordance with the manufacturersinstructions. The paint should be applied immediately after surface preparation,preferably within 4 hours, and certainly on the same day. The minimum total dryfilm thickness of the system should not be less than 125 micrometres.

5.3.4 Repair materials

Paint systems suitable for patch painting are listed in Appendix A. They are typically

2 part epoxy based, high build systems.



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None.

5.4. Filling voids (Sub-procedure)


When new steel plates or sections are fitted to existing steel as part of repairprocedures, voids may be created, usually as a result of the existing steel beingheavily corroded or pitted. The voids may need to be filled with epoxy resin for oneor both of the following reasons.

1. To preclude the ingress of air and moisture which would lead to furthercorrosion, and/or

2. To provide a smooth, level surface on to which the new steel elements canbe fitted. Engineering discussion


Where the latter is the reason for void filling, the epoxy filler is often structural. Itmay be required to resist the compressive forces created by the tensioning of boltsor, in the case of bearing plates, transfer bearing forces.

The necessity for void filling depends on the severity of corrosion and uniformity andgeneral profile of the corroded surface (after preparation). If the surface is uniformlypitted so that the surface remains generally flat and steel attachments

Rc4300 Bridge Repair Manual

Documents

repair procedures

repair actions

rc4300 bridge repair

bridge repair manualissue

steel repair issues

concrete repair issues

masonry repair issues

engineering assessments