The New Handbook of Conventional Maintenance Practices for Railway Bridges

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1 The New Handbook of Conventional Maintenance Practices for Railway Bridges Prepared by D. Tingley Ph.D., P.Eng. Sub-Chairman of the Committee established to develop a new Handbook of Conventional Maintenance Practices Development Committee, Committee 10 Abstract The Railway Bridge Inspection Handbook seminar series conducted by Committee 10 members has been attended by close to 750 people over the years. It has received high praise and has been very successful. During the delivery of these seminars it has become apparent that there is significant interest in a new Handbook of Conventional Maintenance Practices for Railway Bridges and a subsequent seminar series utilizing this new handbook. Students of the inspection seminars constantly asked for ideas and recommendations for ways to deal with typical railway bridge maintenance issues. These requests and interest has led to Committee 10 members creating a new Handbook of Conventional Maintenance Practices. Structures Committee approved the concept of this new Handbook of Conventional Maintenance Practices for Railway Bridges in June of This article discusses the new handbook content and seeks to review the important points covered. There are three sections contained in the handbook including timber, concrete and steel. The timber section discusses substructure restoration including pile posting techniques; pile bent partial and full framing. In addition pumping pile solutions are presented along with cap replacement strategies. Superstructure maintenance methods are also discussed including chord ply replacement, stringer replacement and methods of upgrading practices for these maintenance procedures such as slope cutting notches. In the concrete bridge maintenance section such topics as crack abatement and repair, tension face spalling and delamination repair are discussed. Further, replacement of degraded reinforcing steel and restoring continuity is discussed. Reactive aggregate repair methods are discussed and proper adhesion methods for patch repair are covered. In the steel section important topics such as bottom flange angle splice change, crack arrest and rivet replacement are discussed. AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 1/18 92 AREMA 2016

2 CONVENTIONAL MAINTENANCE PRACTICES HANDBOOK BACKGROUND Wood, steel and concrete are used to construct bridges. Once bridges made with Timber (Figure 1), Concrete (Figure 2), or Steel (Figure 3), are constructed, they become subject to environmental conditions such as the most corrosive natural abundant substance on the planet water. Figure 1 Timber Bridge Figure 2 Concrete Bridge AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 2/18 AREMA

3 Figure 3 Steel Bridge Water in all its states has detrimental effects on bridges, especially railway bridges as they are open to the environment. Water affects all of our building materials including steel, concrete, and wood through moisture content and contact propagating the growth of entropic life and oxidation. In the case of timber, the combination of moisture content in excess of 22% by weight, common oxygen level of the atmosphere of over 21%, and an ambient temperature range between 35 F to 120 F allows decay to proceed with subsequent loss of structural section. Decay was the primary cause of the loss of pile strength shown below (Figure 4). Figure 4 Degraded Timber Pile at waterline AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 3/18 94 AREMA 2016

4 PURPOSE The purpose of this handbook is to provide a reference for railway bridge maintenance personnel charged with the responsibility of maintaining and retrofitting railway bridges. An excellent inspection handbook has already been issued and many inspection seminars have been delivered by experienced railway industry people. After inspections, maintenance is the next major event to take place. The natural evolution of committee 10 is a handbook for the implementation of proper maintenance and repair to extend the life of the aging infrastructure. It is possible to slow down degradation and extend the life of a structure through proper inspections, maintenance of elements subjected to wear, and retrofitting or replacing those elements which no longer provide a functional service to extend the life of the whole structure without a total bridge replacement. This saves money in many ways and improves the bridges performance. For example, railway bridges subject to degradation due to water influences can have their functional and economic lives extended by years or decades through the proper identification of the water exposure, collection points, and scouring flow that have detrimental effects. Migrating streams or rivers can erode embankments causing track to slough laterally and into the river (Figure 5) Figure 5 Eroded Track embankment While other topics precede the chapters for timber, concrete, and steel, the core of the handbook focuses on these materials. Most railroad bridges are a hybrid of these three materials. There are very few bridges which consist of a single material in either timber or concrete. Timber and concrete bridges use steel either through reinforcing or connections. Steel bridges are usually supported by concrete footings or piers (Figure 6). AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 4/18 AREMA

5 Figure 6 Combination Steel and Concrete Piers and Abutments The three material sections will review the various conditions of degradation caused by outdated or ineffective past maintenance practices and provide examples of recommended practices for restoration of the degraded structure. For ease of reference from the handbook, the three basic building materials are isolated into their own chapters. Each chapter covers the advance signs of material degradation and then discusses conventional techniques to retrofit, refurbish, and/or restore the affected elements that have been structurally compromised, such that speed and tonnage must be reduced or the bridge must be closed. This Conventional Maintenance Practices Handbook will not purport to have the only answer to elemental degradation in a bridge structure but will instead provide conventional practices that the reader will find helpful as they develop their own solutions to bridge degradation problems. When major bridge elements have deteriorated the capital costs of replacement of the bridge are often not available. This handbook provides helpful methods of restoring and maintaining the bridge with limited funding. The application of recommended practices outlined in the new Handbook will assist railway bridge owners in the application of conventional maintenance through retrofit, refurbishment, restoration, and/or elemental replacement. This will extend the life of the asset allowing for the strategic allocation of funding for complete replacement of those structures which are really beyond their useful lives. The objective of the Bridge Inspection Handbook and this Handbook of Conventional Maintenance Practices for Railway Bridges is assist the bridge maintenance personnel in recognizing defects in the bridges and the development of a restoration strategy for elements which no longer serve their useful purpose. This allows for a conventional, industry accepted, way of extending the life of these AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 5/18 96 AREMA 2016

6 assets. Figure 7 Bridge defect not picked up by Inspections or through maintenance Recommended practices for such retrofits which restore the structural integrity of the bridge will be discussed. One of the main objectives of the handbook is to provide a higher level of quality and consistency in railway bridge maintenance and restoration works. This handbook can t replace the need for site specific engineering and management of the restoration process but does provide for the use of recognized and accepted methods for bridge restoration/maintenance. This event should never happen under any circumstances without proper inspections and maintenance so that collapses like shown in the photo below can be avoided (Figure 7). The final decisions on the load carrying capabilities of any restoration or replacement strategy used in a railway bridge must always be the responsibility of the bridge engineer. Such decisions are to be based on the material capacity parameters, quantifiable field measurements, observations under load, operational considerations, good engineering judgment, proper application of analytical methods, and proper engineering design. This handbook serves to assist the engineer in his/her work of restoring/maintaining a railway bridge by providing ideas and concepts that represent conventional practices with regard to some of the more conventional or common maintenance/restoration activities. In each chapter of the handbook, there are details provided on each of the restoration/maintenance methods discussed. The intricacies of each recommended practice will be outlined. These topic lists are by no means complete or all inclusive. Over the course of time additional topics will be added to the handbook. This Conventional Maintenance Practices Handbook will provide detailed descriptions of deteriorations for each material, how to identify them, and then line item steps/methods to extend the useful life of the infrastructure. For AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 6/18 AREMA

7 example the piers of the bridge shown below were suffering from delamination of the concrete cover extensively exposing the reinforcing to the environment. Under loading, such a condition could result in compression bulging of the reinforcing leading to progressive collapse. These repairs and retrofits upgraded the bridge and extended the useful life of the concrete. Similarly the results for the steel superstructures can be the same when repairs, retrofits, refurbishments, and replacements are applied to the steel elements (Figure 8). TIMBER Figure 8 Bridge with restored concrete piers This chapter discusses the salient topics of pile postings, pumping piles, bent framing, lateral framing restoration, cap repairs and retrofits, chord retrofits and reinforcements, stringer replacements and retrofits. In later editions more recommended practices will be introduced to the chapter. For the posting of piles, there will be several types discussed, such as full postings. First, the pile needs to be cut down to bright wood (exposed full section wood with no decay) (Figure 9). Then if required, a shear pin is inserted (Figure 10) and once the posting is inserted, rotation splines are cut in the four quadrants of the pile (Figure 11). Splines are glued into place and fish plates are installed for the completed posting (Figure 12). AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 7/18 98 AREMA 2016

8 Figure 9 Pile cut to bright wood Figure 10 Shear Pin 1 AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 8/18 AREMA

9 Figure 11 Rotation Spline cut Figure 12 Splines glued, fish plates installed Other postings include segmental postings, Dutchman patch postings, or posting sleeves. Each type will address the component pieces of the postings and preparation of the un-posted portions of the pile to remain. Depending upon the specific situation, components consist of rotation splines, shear pins, fish plates, and reinforcement wraps. For the Dutchman s patch and piles with side degradation repairs, the timber segments and/or full diameter inserts will be presented. Every posting type, with the various methods of the installation will be clearly described. Pumping piles have but four major causes attributed to them; geologic, at or below ground damage, construction errors, and design flaws. Geologic causes are such things as unforeseen soft strata under the pile tip, flowing strata caused by adjacent excavations or bank sloughing, or localized sloping substrata, eccentricity due to tip slipping on supporting strata, or overweight due to earthen fill. Damage at or below ground surface might be due to the breaking of pile, decay due to lower ground water level, marine borer and insect attack or corrosion, or impact. Construction issues could be due to an inadequate driving formula, hammer size (too heavy, damaged driving or light, insufficient depth of penetration), concrete degradation due to reactive aggregate, vibrations causing lateral or vertical movement, or damage to the driven casing. Design flaws could be inaccurate soil classification, misinterpretation of applied loads, or tension failure of concrete pile due to a lack of reinforcement. The treatment of each situation is explained in relation to the engineering, options available, and methods of restoration techniques that may be employed. In the repair of these pumping piles, the ripple effect of the differential settlements into other elements, such as adjacent pilings, caps, and continuous chords, are addressed. AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 9/ AREMA 2016

10 Substructure pile bents framing, due to decay or excessive movement causing mis-alignment (Figure A of Figure 13), is discussed. A technique is discussed that involves the use of framing comprised of either partial or full framing (Figure B of Figure 13). When to use either type, and how to configure them will be illustrated and explained Figure A Twisted Bent due to differential sediment Figure B Bent Frame Replacement Figure 13 Full Bent Framing Repair and replacement of sashes, wales, and cross-braces of the bents are described, detailed and illustrated as to the use of notches and packers. Cap replacement strategies are discussed regarding not only the overstressing of the system, but also the ripple effect caused by pumping piles. Piles which drop out of the load path due to pumping will cause an increase in the shear span within the cap and cause high shear stresses. Cap replacement methods are discussed including those methods that consist of removing the tie deck (Figure A of Figure 14) and jacking the span up off the existing cap with the old cap removed and the new installed (Figure B of Figure 14). A new Tie Deck is installed to complete the work. Figure A Removing the Tie Deck to enable cap replacement Figure B Jacked span with new cap installed Figure 14 Cap Replacement AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 10/18 AREMA

11 Within the superstructures of the timber bridges, the chapter discusses the causation of chord failures through shear overstressing of continuous chord plies and the differential stiffness as the plies splice across bent caps. Restoration methods and solutions to this predicament are presented and illustrated. Techniques such as chord reinforcement and balanced shear strengthening are also discussed. Topics such as the complexity of replacements versus the speedy installation of reinforcing schemes when timing does not allow for bridge shutdown are discussed. Maintaining grade is always of major concern. The proper way to fashion notches and slope cutting to prevent loss of structural section will be reviewed in detail. Application of notches and orientation of included knots is addressed as to size, location of, and position when hidden by treatment. Methods such as kerf cutting to provide for even shrinkage and minimal checking of timber elements are discussed. AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 11/ AREMA 2016

12 CONCRETE In this chapter, the loss of structural sections due to cracking, delamination of the reinforcement cover, and steel reinforcement corrosion due to this cover loss, water intrusion, or reactive aggregate are discussed. Each situation is diagnosed with proper solution methods being presented. In the case of cracking, the causes of these will be delineated, such as freeze/thaw, flexural, impact or overstressing. Advanced methods of arresting cracks, including epoxy injection and cathodic protection, are presented both for identification and treatment. The processes that lead to these degradations and solutions for repair are also discussed. Cathodic Protection systems is fully explained, the components of the various types of repairs is outlined, and the installation of these components described. Restorations through epoxy injections, shotcrete, and crack abatement techniques are articulated on the basis to restore the structural integrity of these elements. Methods of arresting the effects of reactive aggregates will be addressed. Descriptions of the types of reactions from these aggregates, such as alkali-silica and alkali-carbonate reactions, how they affect the concrete, corrode the reinforcement, and lead to delamination (Figure 15), spalling (Figure 16), and map cracking (Figure 17). Figure 15 Delamination in a concrete pier AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 12/18 AREMA

13 Figure 16 Spalling in a concrete pier Figure 17 Map cracking due in a concrete cap due to reactive aggregate AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 13/ AREMA 2016

14 Restoration of reinforcement continuity problems are discussed in depth along with methods for retrofitting the bars and restoration of the protective cover. Difficulties with regard to adherence of patch repairs and cover restorations to the base elements necessary to restore the longevity of the bridge elements are discussed. AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 14/18 AREMA

15 STEEL This steel section will begin with discussion of loose, severely rusted, or sheared rivets and the proper techniques of their removal. Replacement and strengthening strategies are articulated such as bolt replacement, the proper tightening techniques by turn-of-the-nut, snug-tight, and pretensioning methods, and plate restoration through welding, to name a few. Important topics such as a bottom flange angle splice change is discussed. Bottom flange angle splicing involves the removal of the fasteners and then the corroded steel flange angles (Figure 18). New steel is added (Figure 19) and fasteners are installed and properly tightened in accordance with RCSC Section 8 (Figure 20) for the finished product (Figure 21). Figure 18 Fastener and flange removal in a steel composite I Section AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 15/ AREMA 2016

16 Figure 19 New Steel is positioned for bolting in a steel composite I Section Figure 20 Fastener Tightening AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 16/18 AREMA

17 Figure 21 Angle Flange finished product The topic of crack identification through the use of dye-penetrates (Figure 22) and the method of drilling the ends to arrest (Figure 23) them will be discussed along with other arresting strategies of welding and patching is also addressed. Figure 22 Dye Penetrant exposes extent of cracking AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 17/ AREMA 2016

18 Figure 23 Hole drilling to arrest the crack in a steel section. Other methods of retrofitting, repairing and restoration strategies are provided. A section on web loss due to corrosion and conventional methods and techniques to repair and restore the structural section are discussed. Frozen bearings, rockers, sliders, and pins with discussions in the types and workings of each and the best practices to the restoration of their designed functioning are explained. Corrosion of the steel through standing water, drainage channeling, or salts etching are illustrated and verbalized as to rust packs related to loss of section, complete disintegration of structural elements, and loss of connection fasteners and material. Repair methods for restoration of these situations is explained including strengthening strategies. AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 18/18 AREMA

19 CONCLUSION Mitigation of risk is at the root of design, inspection, and maintenance of railway bridges. In design, there are numerous texts, AREMA chapters, standards, and handbooks written to spell out the methods and techniques to employ. When bridge personnel conduct railway bridge inspections, there are numerous recommended lists of data to gather, non-destructive testing tools to use, testing and performance standards to follow, and AREMA s Bridge Inspection Handbook to provide guidance. The Inspection Handbook lays out the processes, levels of review, specific areas to concentrate effort, and systematic methods of recording the findings to provide a clear report of a bridges in situ condition. The logical progression of events after a thorough inspection has been completed is effective maintenance and restoration to keep the railway bridge in good working order. This involves the correct repair of degraded elements, restoration of deteriorated assemblages, and replacement of severely dilapidated critical members in an effective and economical fashion. Many solutions are available to bridge engineers to restore or maintain bridge elements. There are very few publications that bring together conventional maintenance/restoration practices in a way that can be utilized effectively by bridge engineers and maintenance personnel. The Handbook of Conventional Maintenance Practices for Railway Bridges will become that publication. It will give designers, inspectors, and maintenance of way personnel the tools to effectively maintain and refurbish bridge elements thereby increasing the longevity of bridge assets. AREMA COMMITTEE 10 HANDBOOK OF CONVENTIONAL MAINTENANCE PRACTICES PAGE 19/ AREMA 2016

20 Handbook of Conventional Maintenance Practices for Railway Bridges TIMBER STEEL CONCRETE The three main building materials for railway bridges require inspection and maintenance to continue to provide valuable services. AREMA

21 THIS CAN BE PREVENTED With the right tools... With the right tools... With the right tools... The right tool... A HANDBOOK The right tool... A HANDBOOK On Conventional Maintenance Practices Three chapters treating timber, steel, & concrete On Conventional Maintenance Practices Three chapters treating timber, steel, & concrete 112 AREMA 2016

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23 HANDBOOK HANDBOOK HANDBOOK HANDBOOK HANDBOOK HANDBOOK 114 AREMA 2016

24 HANDBOOK HANDBOOK HANDBOOK HANDBOOK HANDBOOK HANDBOOK BOTTOM FLANGE ANGLE SPLICE CHANGE AREMA

25 HANDBOOK HANDBOOK Remove rivets and replace with bolts. Mark where to cut. HANDBOOK HANDBOOK Remove Steel Replace Steel HANDBOOK HANDBOOK 116 AREMA 2016

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