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2Statement of the Problem The FHWA and many state DOTs are actively promot- ing accelerated bridge construction (ABC) to minimize construction-related impacts to the traveling public and to enhance work-zone safety. Many successful applications of ABC techniques have been recently realized, largely in regions of low seismic activity. A number of these ABC applications are documented in Connection Details for Prefabricated Elements and Systems, published by FHWA in 2009. However, use of ABC techniques has been more limited in moderate-to-high seismic regions of the country. A key factor in successful implementation of this initiative lies in the con- nections between prefabricated elements. Providing reliable connections to ensure ductile performance is essential to developing designs capable of performing to the specifications required in earthquake-prone areas. Several prefabricated con- nection details used for recent ABC projects in seismic regions hold significant promise for more widespread application, but they have not been fully tested for seismic loading. In addition, by testing these details and developing an improved under- standing of their ultimate performance, these details could be used for potential ABC application throughout the country for other extreme event hazards. The challenge of ABC construction in seismic regions affects at least 36 of the 50 U.S. states, according to the American Association of State Highway and Transportation Officials (AASHTO) seismic design methodology, which is a function of site soil conditions. For sites with the poorest soils, 36 states could have bridges that fall into the moderate-to-high seismic areas (Seismic Zone 2 or higher and Seismic Design Category of B or higher). Therefore, this is a national issue. The sys- tems developed in this research will, of course, be usable in all 50 states. If the connectionsâ constructability properties are outstanding, their use may be economically attractive, even if high connection ductility is not required. The use of ABC is a national initiative and expansion of the use of ABC to seismic zones is necessary to provide the benefits of ABC for all high- way users. Objectives of the Study The scope of the study was generally determined by the tasks identified in the request for proposal (RFP). The following is the task description from the RFP: The objective of this research is to synthesize the available information related to connection details recently used or under development for potential use on ABC bridges with promise for more widespread application in seismic regions. The work should include the following connection categories, and associated com- ponents and systems: ⢠Pile to pile cap connections ⢠Foundation to substructure connections ⢠Substructure to superstructure joints and connections ⢠Connections between column segments ⢠Connection between precast girders and pier diaphragms ⢠Various connection devices and technologies ⢠Superstructure to substructure connection from Self-Propelled Modular Transporters (SPMTs) (Roll-in) technology It is anticipated that the research will encompass at least the following tasks. Task 1. Review relevant literature, specifications, ongoing research findings, current practices and other information can- vassing all engineering and material disciplines to determine the current state of knowledge on connections, and associated components and systems for potential research in each above- mentioned connection category. This information shall be assem- bled from published and unpublished reports, contacts with academia, transportation agencies, industry organizations, and other domestic and foreign sources, bridge owners, precast fabri- cators, contractors, and others. Task 2. Summarize the various connections and joints iden- tified on Task 1. Outline the perceived advantages and disadvan- tages of each respective detail based on constructability, seismic performance, inspectability, and durability. In addition each connection and joint should be assessed for its effect on system performance. Task 3. Identify gaps in validation of the findings in Task 2. C H A P T E R 1 Background
Task 4. Submit a final report describing the entire research project and making suggestions for future research needs. A draft final report is due one month before the contract end date. Organization of the Research Report The report is organized into four chapters. Chapter 1 gives the background for the research project. Chapter 2 summa- rizes the methodology used for information gathering and the approach for the evaluation of connections and bridge systems. The identified connections are characterized and evaluated individually according to the defined evaluation procedure and are presented in the form of separate cut sheets for each con- nection in Appendices A through G. Appendix H provides detailed summaries of connection types, and Appendix I includes the questionnaires that were sent out to support the information gathering. Chapter 3 summarizes the characteristics and evaluations of connection types, expands the seismic performance evalu- ation to entire bridge systems, and presents the identified knowledge gaps. Chapter 4 presents the conclusions and gives suggestions for further research. A 2012 Research Prob- lem Statement to address the identified research needs is given in Appendix J. The overall flow of the report is shown schematically in Figure 1. 3 Chapter 2 Research Approach Chapter 3 Evaluations Chapter 3 Knowledge and Experience Gaps w/ Prioritization Chapter 4 Recommendations Appendices A-G Connection Descriptions Appendix H Detailed Evaluation of Connection Types Appendix I Questionnaire Appendix J Research Problem Statement Figure 1. Report flow chart.
