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Proposed AASHTO Guides for Bridge Preservation Actions (2020)

Chapter: Chapter 5 - Guides to Preservation

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Suggested Citation:"Chapter 5 - Guides to Preservation." National Academies of Sciences, Engineering, and Medicine. 2020. Proposed AASHTO Guides for Bridge Preservation Actions. Washington, DC: The National Academies Press. doi: 10.17226/26013.
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Suggested Citation:"Chapter 5 - Guides to Preservation." National Academies of Sciences, Engineering, and Medicine. 2020. Proposed AASHTO Guides for Bridge Preservation Actions. Washington, DC: The National Academies Press. doi: 10.17226/26013.
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Suggested Citation:"Chapter 5 - Guides to Preservation." National Academies of Sciences, Engineering, and Medicine. 2020. Proposed AASHTO Guides for Bridge Preservation Actions. Washington, DC: The National Academies Press. doi: 10.17226/26013.
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Suggested Citation:"Chapter 5 - Guides to Preservation." National Academies of Sciences, Engineering, and Medicine. 2020. Proposed AASHTO Guides for Bridge Preservation Actions. Washington, DC: The National Academies Press. doi: 10.17226/26013.
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Suggested Citation:"Chapter 5 - Guides to Preservation." National Academies of Sciences, Engineering, and Medicine. 2020. Proposed AASHTO Guides for Bridge Preservation Actions. Washington, DC: The National Academies Press. doi: 10.17226/26013.
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Suggested Citation:"Chapter 5 - Guides to Preservation." National Academies of Sciences, Engineering, and Medicine. 2020. Proposed AASHTO Guides for Bridge Preservation Actions. Washington, DC: The National Academies Press. doi: 10.17226/26013.
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Suggested Citation:"Chapter 5 - Guides to Preservation." National Academies of Sciences, Engineering, and Medicine. 2020. Proposed AASHTO Guides for Bridge Preservation Actions. Washington, DC: The National Academies Press. doi: 10.17226/26013.
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Suggested Citation:"Chapter 5 - Guides to Preservation." National Academies of Sciences, Engineering, and Medicine. 2020. Proposed AASHTO Guides for Bridge Preservation Actions. Washington, DC: The National Academies Press. doi: 10.17226/26013.
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Page 35
Page 36
Suggested Citation:"Chapter 5 - Guides to Preservation." National Academies of Sciences, Engineering, and Medicine. 2020. Proposed AASHTO Guides for Bridge Preservation Actions. Washington, DC: The National Academies Press. doi: 10.17226/26013.
×
Page 36
Page 37
Suggested Citation:"Chapter 5 - Guides to Preservation." National Academies of Sciences, Engineering, and Medicine. 2020. Proposed AASHTO Guides for Bridge Preservation Actions. Washington, DC: The National Academies Press. doi: 10.17226/26013.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

28 The research team produced a guide to bridge preservation (Bridge Guide) and a guide to bridge deck preservation (Deck Guide). The Bridge Guide is Appendix D, and the Deck Guide is Appendix E of this report. These will be published by AASHTO. Lists of articles for these Guides are presented in this chapter. List of Articles: Guide to Bridge Preservation Actions The numbering shown here matches the numbering of the articles in the Bridge Guide. Chapter 1 Introduction This is a guide to the preservation of highway bridges. Preservation keeps existing bridges in service, keeps load capacities and traffic capacities at design values, and keeps bridges in fair or good condition. 1.1 Content of the Guide The Guide identifies candidates for bridge preservation. It lists actions in bridge preservation. 1.2 Bridge Preservation Programs for bridge preservation are limited in scope to candidate bridges and admissible actions. The limited scope allows programs to deliver actions to protect bridges before defects appear, and to deliver repairs for minor defects before larger defects appear. 1.3 Audience for the Guide The Guide is intended for professional staff in transportation agencies who are engaged in design, maintenance, repair, and replacement of highway bridges. Staff should have a general understanding of principles of asset management and procedures in selection and development of bridge projects. 1.4 Organization The Guide is presented in five chapters, a commentary, and four appendices. 1.5 Sources The information presented in the Guide is collected from publications of bridge owners, publications of the FHWA, and records of bridge maintenance contributed by bridge owners that participated in NCHRP Project 14-36. C H A P T E R 5 Guides to Preservation

Guides to Preservation 29 Chapter 2 Bridge Preservation Chapter 2 presents the concept of bridge preservation and applies the concept to identify candidate bridges and admissible actions. Chapter 2 defines terms in bridge preservation. It also presents a possible organization of agency staff for bridge preservation. 2.1 Bridges, Bridge Components, and Bridge Elements The terms bridge, bridge component, and bridge element are used in the Guide. Definitions of these terms are presented here. 2.2 Concept of Preservation of Highway Bridges Preservation is a program of maintenance for existing bridges that have acceptable condition, capacity, robustness, and durability. Preservation is appropriate for bridges that bridge owners elect to keep in service. 2.3 Bridge Preservation—Definition The term bridge preservation is defined by AASHTO (4) and by the FHWA (20). Definitions are applied as criteria for bridge preservation candidates and for bridge preservation actions. 2.4 Actions in Bridge Preservation Actions are admissible as preservation actions when actions maintain conditions and extend service life. Actions are identified for major components of bridges and for other components of bridges. 2.5 Candidate Bridges. Preservation Population Bridges are candidates for preservation when bridge condition, capacity, robustness, and durability are adequate. Bridges programmed for reconstruction or replacement are not usually candidates for preservation. 2.6 Bridge Preservation Plans Programs for bridge preservation will develop preservation plans for individual bridges or groups of similar bridges. A preservation plan is a statement of the actions and time intervals for actions necessary to preserve the bridge. The plan identifies actions that can be performed together. It also lists costs of actions. The plan states the anticipated year for bridge replacement. 2.7 Agency Organization for Bridge Preservation The preservation of highway bridges should be the responsibility of a Bridge Preservation Engineer supported by a Bridge Preservation Team. Together, these form the Bridge Preservation Staff. Preservation staff plan, manage, execute, and evaluate an agency’s program for bridge preservation. 2.8 Information on Conditions of Bridges and Its Relation to Bridge Preservation Preservation programs need information on the condition of bridges. The Guide recognizes AASHTO’s Manual for Bridge Element Inspection (MBEI) (5) as a detailed national practice for standard information on the condition of bridges. The Guide uses MBEI bridge elements, defects, and condition states. Preservation programs can be executed with various levels of information. All competent assessments of needs for actions at bridges, using MBEI or not, can provide information for successful execution of bridge preservation programs.

30 Proposed AASHTO Guides for Bridge Preservation Actions 2.9 Glossary of Terms in Bridge Preservation Terms in bridge preservation are defined in Appendix D: Glossary of Terms in Bridge Preservation. Chapter 3 Actions in Bridge Preservation Chapter 3 presents actions for the preservation of bridges. Preservation actions are organized by bridge component, activity, and detail. Chapter 3 presents standard tables of information for actions. 3.1 Preservation Actions—Component, Activity, and Detail Preservation actions are named by bridge component and activity. Most actions are further identified by detail. There are eleven bridge components and eight preservation activities. Details attach to individual combinations of component and activity. 3.2 Information on Bridge Preservation Actions Actions in bridge preservation are selected for their effect, their cost, and their duration in service. Standard information is provided for each preservation action. Information on actions in bridge preservation is presented under standard headings: • Basis • Description • Procedure • Context • Effect • Materials • References 3.3 Catalog of Preservation Actions Preservation actions with supporting information are listed in Appendix A: Catalog of Bridge Preservation Actions. Actions are named using the component, activity, detail system. Information on actions is presented under the headings basis, description, procedure, context, effect, materials, and references. Chapter 4 Selection of Actions for Bridge Preservation Chapter 4 presents an approach to the selection of actions for bridge preservation. Actions should be appropriate to needs at bridges and should be cost-effective. Criteria for candidates for bridge preservation, stated in terms of conditions and defects, are presented in the catalog of preservation actions in Chapter 3 and also in Appendix B. In Chapter 4, a method for evaluation of costs and benefits of preservation actions is presented. 4.1 Appropriate Preservation Actions Preservation actions are selected in response to needs at bridges. For cyclic actions, time is a need. If the time since previous application of a cyclic action exceeds the prescribed interval, then there is a need for a new application of the action. For condition-driven actions, defects are needs. Actions are selected to respond to types of defects, to extents and severities of defects, and to materials and forms of bridge components. Actions are mapped to defect types and severity in Appendix B.

Guides to Preservation 31 4.2 Cost-Effective Preservation Actions Bridge preservation is cost-effective if preservation reduces agency costs for bridge service. Agency costs for bridge service are the costs of preservation actions at bridges plus the costs of eventual replacement of bridges. Reduction in agency costs is comparative. Service costs of bridges with preservation are compared with service costs of bridges without preservation. 4.3 Preservation-Cycle Cost Analysis Cost evaluations are made using PCCA. PCCA computes the costs of keeping existing bridges in fair or good condition, and in service at current capacities. The period from initiation of preservation at a bridge to the time of replacement of a bridge is the analysis period. This period is the preservation cycle. When a bridge is replaced, the preservation cycle repeats. 4.4 Steps in PCCA PCCA is performed in the following steps: • Identify the focus of preservation. This is normally an entire bridge but can be a major component: deck, superstructure, or substructure. • List the actions for preservation of the bridge or component. List costs and time intervals for actions. • Estimate the remaining service life of the bridge or component. Estimate remaining service with preservation and without preservation. These two alternatives are compared in PCCA. • Compute annual costs of preservation actions. • Compute annual cost of (future) replacement of the bridge or component. • Compute annual service costs for the preservation alternative and the no-preservation alternative. • Compute the benefit of preservation. 4.5 Examples in Cost Evaluation for Bridge Preservation PCCA is applied in a set of examples in Appendix C: Examples of Cost Evaluation of Bridge Preservation. Examples are as follows: • Preservation plan and PCCA for a prestressed concrete multibeam bridge. • Preservation plan and PCCA for a painted steel multibeam bridge. • Annual budget for preservation of a population of candidate bridges. • Subset PCCA to compare alternatives in preservation of reinforced concrete deck. • Subset PCCA to compare alternatives in preservation of painted steel superstructure. • Sensitivity of outcomes of PCCA. Chapter 5 Implementing a Program for Bridge Preservation Chapter 5 presents steps that bridge owners can follow to adapt the Guide to bridge preser- vation programs at their agencies. 5.1 Overview Bridge owners can adapt the Guide to their own programs for bridge preservation by • Identifying the bridge preservation population. • Establishing a catalog of preservation actions. • Designating staff to execute the preservation program. • Defining the scope of the program and the authority of preservation staff. • Creating and tracking measures of performance of the preservation program. • Allocating resources to the preservation program.

32 Proposed AASHTO Guides for Bridge Preservation Actions 5.2 Bridge Preservation Population The bridges that meet a bridge owner’s criteria for preservation candidates are identified. This is the preservation population. 5.3 Bridge Components, Activities, and Details. Catalog of Actions. Bridge owners will form catalogs of preservation actions. Information for actions will include costs, time intervals, and context for use. Methods, specifications, and qualified materials for actions will be identified. Actions will be stated in terms of existing standards, specifications, qualified materials, and bid items in use at an agency. Special standards, specifications, material statements, and bid items will be developed as needed for preserva- tion actions. 5.4 Bridge Preservation Staff Bridge owners will identify staff positions, new or existing, that will execute the bridge preservation program. Bridge owners will establish qualifications for preservation staff. 5.5 Scope of Program. Authority of Staff. Bridge owners will define the scope of preservation programs and the authority of preserva- tion staff. Policy on the relative roles and responsibilities of headquarter staff and staff in districts will be stated. 5.6 Resources for Preservation Bridge owners will establish budget allocations for preservation programs. Bridge owners will identify the intended uses of budgets. Bridge owners will establish procedures for requests and approvals of expenditures for bridge preservation. 5.7 Monitoring, Evaluation, Updating, and Reporting Bridge owners will establish procedures to measure and evaluate the selection and delivery of preservation programs. Bridge owners will monitor and update costs of preservation actions. Bridge owners will establish procedures for periodic review and update of context for actions and time intervals for actions. Bridge owners will establish measures of performance of bridge preservation programs. Bridge owners will make periodic reports of accomplishments and performance of bridge preservation programs. Bridge owners will develop budgets to support preservation plans of bridges. Appendix A: Catalog of Bridge Preservation Actions Information on actions in bridge preservation is provided in a standard format. The format presents basis, description, procedure, context, effect, materials, and references for each preserva- tion action. Appendix B: Defects and Preservation MBEI defects are mapped to bridge preservation actions. Tables relating defect types and severities to preservation actions help in the selection of actions. Additional element-level defects are proposed in the Guide for use in bridge preservation. These are Guide-developed defects. These defects can provide evidence that preservation actions are needed. These defects identify needs that are not reported by defects of the MBEI.

Guides to Preservation 33 Appendix C: Examples of Cost Evaluation of Bridge Preservation A method for PCCA is introduced. Preservation plans are developed for two bridges. Costs and benefits of bridge preservation are computed. In addition, preservation of bridge deck (only) and of bridge superstructure (only) are considered. Sensitivity of outcomes to changes in costs of actions and intervals for actions is evaluated. A comparison to life-cycle cost analysis is presented. Appendix D: Glossary of Terms in Bridge Preservation A glossary of terms related to bridge preservation and used in the Bridge Guide is provided. List of Articles: Guide to Preservation of Highway Bridge Decks The numbering shown here matches the numbering of articles in the Deck Guide. Chapter 1 Introduction This is a guide to preservation of highway bridge decks. Preservation is a program of treatments applied to bridge decks in service to keep them in good or fair condition. 1.1 Preservation of Bridge Decks Preservation of bridge decks is a program of treatments intended to • Extend service life of bridge decks • Keep bridge decks in fair or good condition • Reduce life-cycle costs 1.2 Preservation Candidates Preservation programs address a defined population of bridge decks. These are bridge decks that meet the criteria in the following: • Work history • Capacity • Robustness • Durability 1.3 Organization of the Guide The Guide is presented in five chapters and five appendices. 1.4 Audience for the Guide The Guide is intended for staff involved in bridge preservation at bridge-owning agencies. 1.5 Related Documents Preservation of bridge decks is related to the design of decks and to the preservation of deck joints. Two AASHTO publications are useful: Guide Specification for Service Life Design of Highway Bridges, which is a guide to design of bridges for 100-year service life (2), and Guide- lines for Maintaining Small Movement Bridge Expansion Joints, which is a guide to maintenance of expansion joints (3).

34 Proposed AASHTO Guides for Bridge Preservation Actions 1.6 Bridge Decks Addressed in the Guide Most of the information in the Guide is for steel-reinforced concrete decks. It does have some information on steel grid decks and timber decks. Chapter 2 Preservation Treatments for Bridge Decks 2.1 Introduction Chapter 2 presents general information on preservation treatments for highway bridge decks. 2.2 Typical Reinforced Concrete Decks of Highway Bridges Typical designs for Portland cement reinforced concrete (PCRC) bridge decks are two mats of steel reinforcement in a cast-in-place PCC slab. Thickness of slab varies with spacing between supporting beams. Spacings of 4 ft to 12 ft with slab thicknesses of 7 in. to 9 in. are common. 2.3 Preservation Treatments for Bridge Decks Preservation treatments are as follows: • Deck cleaning • Surface sealers • Thin polymer overlays • Polyester concrete overlay • Asphalt wearing surface plus waterproofing membrane • PCC overlays • Crack sealing • Deck patching 2.4 Summary of Preservation Treatments for Bridge Decks Treatments can require removal of overlays and compromised concrete and may require additional removals to meet a required roadway grade after treatment. Some treatments require a degree of roughness on surfaces to receive treatment. Treatments can need time to cure after placement. 2.5 Deck Treatments—Appendix A Appendix A: Preservation Treatments for Highway Bridge Decks lists deck treatments and information on treatments. Appendix A has multiple articles. Each article deals with one treatment. 2.6 Treatments in Combination Preservation of a bridge deck can require the use of more than one treatment. An overlay may be installed on a deck in good condition, and few or no repairs to the deck are needed. For a bridge deck in fair condition, repairs must be made before installing an overlay. The repair and the overlay are separate treatments. Chapter 3 Evaluation of Bridge Decks 3.1 Introduction Chapter 3 reviews types of deterioration in bridge decks, together with standard forms of data used to report conditions of bridge decks. Chapter 3 reviews the evaluations needed for decisions in preservation treatments for bridge decks.

Guides to Preservation 35 3.2 Data on the Condition of Bridge Decks Data on the condition of bridge decks include performance measures, NBI condition ratings, element-level condition states, and element-level defects. Data on condition contribute to evaluations of bridge decks and to decisions on preservation treatments for decks. 3.3 Bridge Elements. Element-Level Condition Reports. The AASHTO MBEI defines bridge elements, defects in bridge elements, and condition states for elements and defects. 3.4 Defects and Treatments Defects, by their extent and severity, require remedies either as treatment or as replacement of decks. 3.5 Evaluation of Bridge Decks Evaluation of bridge decks is performed by the following: • Applying selected methods of inspection. • Collecting and analyzing material samples (for selected decks depending on the condition of the deck). • Documenting presence and extent of defects. 3.6 Compromised Area of Bridge Decks The extent of the compromised area of a bridge deck affects decisions to preserve or to replace the deck. Deck area is compromised if the following applies: • A defect is present, or • A deterioration process is active and could cause a defect, or • An agent is present that could initiate a deterioration process. 3.7 Reports Reports of evaluations of bridge decks should include a summary and detailed findings. Chapter 4 Selecting Preservation Treatments for Bridge Decks 4.1 Introduction Chapter 4 presents a process for selecting preservation treatments. Selection of treatment proceeds from the following: • Intended duration of service life (after treatment) • Materials, design, and capacity of existing deck • Deck condition • Service, average daily traffic (ADT), route functional class • Status of the bridge as a candidate for preservation • History of deck treatments 4.2 Preserve or Replace? Deck preservation decisions are affected by bridge preservation decisions. Deck preserva- tion is appropriate only if the bridge will remain in service. If the bridge will be reconstructed or replaced, then the deck is no longer a candidate for preservation.

36 Proposed AASHTO Guides for Bridge Preservation Actions 4.3 Selection of Treatment Data on condition of bridges indicate the types, severities, and extent of deterioration. All are important in selecting preservation treatments. 4.4 Extent of Treatment Treatments such as surface sealing and placement of overlays usually affect the entire deck surface. Other treatments such as spall patching are local and are applied to a limited extent of the deck. 4.5 Selection of Preservation Treatments for Bridge Decks—Appendix C Preservation treatments are triggered by condition or by time interval. Time intervals as triggers for treatment are relevant for decks in good condition and for treatments that are waterproofing or water-restricting. To keep treatments effective, treatments should be renewed without waiting for defects. Chapter 5 Costs and Benefits of Deck Preservation 5.1 Introduction Chapter 5 applies PCCA to evaluate the monetized benefits of deck preservation. The PCCA method is presented in the AASHTO Guide to Bridge Preservation Actions (1). 5.2 Preservation-Cycle Cost Analysis PCCA computes the costs of keeping existing bridge decks in good or fair condition, and in service at current capacities. Costs are evaluated for service life of a bridge deck. Any deck will be replaced eventually. Replacement is sooner if decks are not preserved. Replacement is later if preservation treatments are applied. Costs are incurred when a treatment is applied and when a deck is replaced. Replacement is the last cost in the preservation cycle for a deck. 5.3 Examples in Costs and Benefits of Deck Treatments Examples of computation of costs and benefits of deck treatments are presented as follows: 1. Use of thin polymer overlay on a bridge deck in good condition 2. Re-application of thin polymer overlay on a bridge deck in good condition 3. Use of a PCC overlay on a deck in fair condition 4. Use of a PCC overlay on a deck in poor condition Appendix A—Preservation Treatments for Highway Bridge Decks Appendix A provides information on materials and procedures for preservation treatments for bridge decks. Information is collected from standard specifications of state DOTs and from guide specifications of manufacturers of products for treatments. Each treatment is presented using a set of standard headings. Appendix B—Defects in Highway Bridge Decks Appendix B presents defects in bridge decks with corresponding treatments. Defects are defined in AASHTO MBEI. Defect condition is a local finding based on the severity of the defect. Deck condition is a global finding based on the extent of the defect. Deck program shows treatments and urgency of treatments. On interval indicates that the intended program for deck preservation can continue without change. Now indicates that treatment is needed

Guides to Preservation 37 right away to avert worsening condition. W/repair and other w/ notations indicate that addi- tional work is needed before protective treatment. Appendix C—Selection of Preservation Treatments for Bridge Decks Appendix C provides guidance on selection of preservation treatments for bridge decks with various prior treatments and in various conditions. A bare deck has no prior treatment. A deck with surface sealer has surface sealer already in place when selection of additional treatment is considered. If treatment with surface sealer is selected, this would be the second applica- tion of surface sealer. If treatment with an overlay is selected, this is a change in treatment. Deck with thin polymer overlay already has overlay in place when additional treatment is considered. Thin polymer overlay may be re-applied or other treatment may be selected. Similarly, deck with HMA plus waterproofing membrane and deck with PCC or PCC overlay indicate existing treatments. Actions for decks are identified as Treatments and as Repairs. Treatments are surface sealers and overlays. Treatments protect decks. Repairs are patching and crack sealing. For decks in fair or poor condition, repairs are made in preparation for protective treatment.

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Many transportation departments have significant practical experience with bridge preservation and have developed conclusions regarding the effectiveness of bridge preservation actions based on those experiences. However, limited efforts have been made to identify, measure, evaluate, and document the short- and long-term performance of specific bridge preservation actions.

The TRB National Cooperative Highway Research Program's NCHRP Research Report 950: Proposed AASHTO Guides for Bridge Preservation Actions presents the development of two AASHTO guides for bridge preservation, including a general guide to preservation of highway bridges and a guide to preservation of highway bridge decks.

Supplementary to the report is Appendix B: Summaries of Information from State DOTs.

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