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3C h a p t e r 1 Second Strategic highway research program Background The Second Strategic Highway Research Program (SHRP 2) was authorized by Congress to address some of the most pressing needs related to the nationâs highway system: the high toll taken by highway deaths and injuries, aging infra structure that must be rehabilitated with minimum dis ruption to users, and congestion stemming both from inadequate physical capacity and from events that reduce the effective capacity of a highway facility. SHRP 2 is divided into four areas: ⢠Safety: to study the interaction between human and high way safety and comprehend the interaction among various factors involved in highway crashes, such as driver, vehicle, and infrastructure, and to develop effective solutions; ⢠Renewal: to develop technologies and solutions to support the systematic rehabilitation of highway infrastructure in a way that is rapid, presents minimal disruption to users, and results in longÂlasting facilities; ⢠Reliability: to develop basic analytical techniques, design procedures, and institutional approaches to comprehend ing and addressing such areas as crashes, work zones, spe cial events, inclement weather, and improving travel time reliability; and ⢠Capacity: to develop transportation planning that more accurately integrates economic, community, and environ mental considerations into highway capacity. The overall objective of SHRP 2 highway renewal is to achieve renewal that is performed rapidly, causes minimum disruption, and produces longÂlived facilities. A related objec tive is to achieve such renewal not just on isolated, high profile projects, but consistently throughout the nationâs highway system. problem Statement Bridge service life has been at the forefront of bridge ownersâ concerns for several years, particularly in the form of growing fiscal needs for bridge maintenance. As bridge maintenance costs increase, available funds for new facilities and for upgrad ing existing facilities become more difficult to budget. Bridge maintenance and repair affect mobility and contribute to traffic interruption. Bridge owners are spending significant portions of their annual budgets on maintenance and repair. Enhancing the service life of existing and new bridges will enhance mobil ity and reduce the maintenance and repair costs of bridges. Providing safety for the public by having adequate strength for constructed facilities has been the cornerstone of the framework used by engineers during bridge design. This phi losophy has served the building industry well, where most structural elements are protected from weather elements. Over the years, the design for strength has been polished, streamlined, and perfected. In the case of bridges, however, the structural elements are subject to various environmental and traffic loads. The majority of maintenance and repair actions for bridges are created by service lifeârelated factors. The design for service life is currently approached in a hap hazard manner. Various specifications provide design and detailing provisions to address historically observed bridge service life challenges. However, there is a need to develop a service life design approach for bridges that is systematic, for mal, and coherent. The design for service life of bridges should be approached in the same manner as that used for strength. research Objectives The overall objective of the SHRP 2 renewal program is to achieve renewal that is performed rapidly, causes minimum traffic disruption, and produces longÂlived facilities. As part of this objective, the R19A project calls for strategies to develop Background
4highÂperforming bridges by identifying the problematic areas and providing solutions at the bridge system, subsystem, and component levels. The knowledge gained through this effort must be communicated with bridge professionals in ways that can be implemented in practice. Specific objectives of the project included ⢠Identifying the problems that have historically limited the service life of bridges and, while learning from bridges of all span lengths, concentrating on bridges with maximum span lengths of 300 ft; ⢠Developing promising concepts that can enhance the service life of bridges, performing proof of concept tests, and making specific recommendation for future research by others; and ⢠Communicating the results with the bridge community. Scope of Study The research focused on developing a systematic, compre hensive, and coherent approach for design of bridges for ser vice life. The research team explored various approaches for design for service life and identified the elements of a system atic approach, as well as ways of presenting 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 systematic approach for design for service life was identifying the problems that have historically limited the service life of bridges. Several surveys and literature searches were conducted to identify current service life challenges. For select and highÂpriority service life challenges, potential solutions were identified and proof of concept tests were carried out. project Outcome The body of knowledge developed during the project was summarized in the main project deliverable, the Design Guide for Bridges for Service Life (the Guide), which provides a sys tematic and comprehensive approach for designing bridges for service life. The main objective of the Guide is to provide information about, and define procedures for, systematically designing both new and existing bridges for service life and durability. The ini tial approach to designing for service life is to provide a body of knowledge relating to bridge durability under different expo sure conditions and constraints and to establish an array of options capable of enhancing service life relative to those condi tions. However, the philosophy used in the Guide could also be used to establish a plan for designing a specific bridge for service life by customizing certain steps within the framework. Included in the Guide are 11 chapters, each devoted to par ticular bridge elements, components, subsystems, or systems. Collectively, these chapters provide a basis for approaching service life design in a logical, systematic manner.
