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.
1The design of bridges for service life is gaining importance as limited resources demand enhanc- ing the service life of existing and new bridges. The cost of addressing service life issues at the design stage is significantly lower than the cost of taking maintenance and preservation actions while a bridge is in service. Currently, design for service life is approached by using individual strategies aimed at enhancing the service life of a particular problematic bridge element that has historically limited a bridgeâs service life. However, design for service life must be approached in a systematic manner using a general framework that is applicable for all bridges, while also allow- ing for specifics that are unique from one bridge to another. These unique differences are neces- sary because design for service life is a context-sensitive problem requiring consideration of local experiences, practice, and owner preferences. The main objective of the Second Strategic Highway Research Program (SHRP 2) Project R19A, Bridges for Service Life Beyond 100 Years: Innovative Systems, Subsystems, and Components, is to develop approaches to service life design for existing and new bridges. The main product of this project is the Design Guide for Bridges for Service Life (the Guide), which is now available through TRB (http://www.trb.org/Design/Blurbs/168760.aspx). The objective of the Guide is to provide information about and define procedures for system- atically designing for service life and durability for both new and existing bridges. The Guide includes new concepts and approaches that offer improvements to current practice and have the potential to enhance the service life of bridges. Its approach to design for service life is to provide a body of knowledge relating to bridge durability under different exposure conditions and con- straints and to establish an array of options capable of enhancing service life. A solution for a particular service life issue is highly dependent on many factors that vary from location to loca- tion and state to state, because a solution depends on local practices and preferences. Conse- quently, use of the Guide is not intended to dictate a unique solution for any specific service life problem or to identify the best and only solution. Rather, it equips the reader with a body of knowledge for developing specific solutions best suited to stated conditions and constraints. This final report details the steps used in the development of the Guide. It also provides results from extensive individual research efforts that have led to the development of new details and concepts that can mitigate factors that have historically limited the service life of bridges. In the course of developing the Guide, the research team explored various approaches for design for service life and identified the elements of a systematic approach, as well as ways to present the information in a transparent form that could be used by bridge owners and lead to development of bridges with enhanced service life. An important aspect of developing a system- atic approach for design for service life was identifying the problems that have historically lim- ited the service life of bridges. Several surveys and literature searches were conducted to identify current service life challenges. For select and high-priority service life challenges, potential Executive Summary
2solutions were identified and proof of concept tests were carried out. The entire body of knowl- edge developed during the project was summarized in the Guide. Tasks within the project were divided into Phase 1 and Phase 2. During Phase 1 of the project, steps were undertaken to identify problems, the state of the practice, and technological gaps. The outcome of Phase 1 was a scope of work intended to address a select number of the identified technological gaps and to develop an outline of a methodology that could lead to the design of bridges for service life. Phase 2 consisted of conducting the scope of work identified in Phase 1 and developing a methodology to design bridges for service life. Chapter 2 of the Guide describes the efforts undertaken to identity the service life challenges. The results of efforts to identify the research needs and challenges with respect to service life are provided in Chapter 3. These are nine main categories: concrete durability; bridge decks; substructure; bearings; expansion joints, joints, and jointless bridges; fatigue and fracture; struc- tural steel corrosion protection; steel bridge systems; and concrete bridge systems. A literature search and other related tasks were conducted to identify topics needing research with respect to design of bridges for service life. Those service life issues requiring further research were divided into three categories. Research topics in Category 1 and 2 were selected for proof of concept testing within the R19A project. Category 1 topics were the highest priority and received the greatest efforts. A list of Category 1 and 2 research topics is summarized in Chapter 3 (Table 3.12). A list of Category 3 research topics recommended to be carried out by others is provided in Appendix A. Category 1 and 2 research topics are further divided into four major categories: joints, bear- ings, enhancing corrosion resistance of concrete bridges, and bridge decks. Category 1 and 2 research topics required conducting 14 research studies. Chapter 3 provides a brief look at the objectives, scope, results, and recommendations resulting from these 14 indi- vidual studies. Providing the full details of all these topics would make this final report unwieldy; therefore, references to theses, dissertations, and published papers are provided for those inter- ested in obtaining additional information. These individual research topics resulted in the devel- opment of new details and concepts, some with associated design provisions. Some of these details and design provisions are listed in the appendices of this report, and some of the developed information is listed in the Guide. For example, the results of the efforts leading to the develop- ment of complete design provisions for jointless bridges are provided in Chapter 8 of the Guide. Select information from the 14 research studies plus the results of other efforts undertaken within the project form the body of knowledge incorporated in the Guide for design of existing and new bridges for service life.
