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3 1.1 Problem Statement Accelerated bridge construction (ABC) utilizes rigorous planning, new technologies, and improved methods to expedite construction. Prefabricated columns and their connections to the adjoining bridge members (cap beams, footings, pile caps, and pile shafts) are the most critical components of ABC in moderate- and high-seismic regions. Recent studies on the seismic performance of various types of ABC column connections have demonstrated the feasibility of ABC in these seismic regions. Some gaps remain. To facilitate utilization of ABC in moderate- and high-seismic regions, seismic design specifications are needed. 1.2 Research Objectives The main objective of NCHRP Project 12-105 was to develop proposed AASHTO displacement- based design and construction specifications for the implementation of ABC column connec- tions in moderate- and high-seismic regions. The project was focused on three types of precast column connections: (1) mechanical bar coupler connections, (2) grouted duct connections, and (3) pocket/socket connections. Five phases encompassing 14 tasks were completed in this project to achieve the aforementioned objective: I. Planning, II. Analytical program, III. Testing program, IV. Specification development, and V. Final products. Interim Report 1 included the activities of Phase I of the project, which comprised Tasks 1â4: 1. Review of the literature, 2. Identification of knowledge gaps, 3. Development of analytical and testing programs, and 4. Preparation of Interim Report 1. As part of Task 1, a survey of state departments of transportation, federal agencies, and consulting engineers was conducted to obtain information about their experience, preferences, and past and future utilization of ABC connections. Interim Report 2 documented the work conducted under Phase II of the project, which comprised Tasks 5â7: 5. Execution of the analytical program according to the approved Task 4 work plan; 6. Finalization of the testing program work plan, including a test matrix and design details; and 7. Preparation of Interim Report 2. C H A P T E R 1 Introduction
4 Proposed AASHTO Seismic Specifications for ABC Column Connections Interim Report 3 presented the details and findings of activities carried out in Phase III, which comprised Tasks 8â10: 8. Execution of the testing program according to the approved Task 7 work plan, 9. Validation of the analytical program on the basis of the testing results, and 10. Preparation of Interim Report 3. Interim Report 4 covered the activities completed in Phase IV of the project, which comprised Tasks 11 and 12: 11. Development of a draft design and construction specifications with connection details, selection criteria, design examples, and acceptance criteria for seismic couplers, and 12. Preparation of Interim Report 4. Phase V comprised Tasks 13 and 14 of the project: 13. Updating of the proposed guidelines and the design examples on the basis of the project panelâs comments, and 14. Preparation of this final report, which documents the work of the 13 previous tasks. 1.3 Organization This report is organized into six chapters and four appendices, as follows: Chapter 1. Introduction, Chapter 2. State-of-the-Art Literature Review, Chapter 3. Experimental Programs, Chapter 4. Analytical Programs, Chapter 5. Proposed Specifications and Examples, and Chapter 6. Summary and Conclusions. Appendix A. Survey of State Departments of Transportation, Appendix B. Proposed AASHTO/ASTM Standard Test Method for Bar Couplers, Appendix C. Proposed AASHTO Specifications for ABC Columns, and Appendix D. Detailed Design Examples. Chapter 1 summarizes the projectâs objectives. Chapter 2 presents a review of the state-of-the-art of precast column connections suitable for bridge columns. The findings of the experimental work performed under this project are presented in Chapter 3. Chapter 4 describes the analytical studies done and the use of the test data collected in the project and from previous studies to verify the pro- posed design methods. Chapter 5 briefly discusses the methodology used to develop design and con- struction guidelines for precast bridge columns, and Chapter 6 presents a summary and conclusions. The four appendices to this report are not printed herein but can be downloaded from the TRB website (trb.org) by searching for âNCHRP Research Report 935â. Appendix A summarizes the findings of the survey conducted to collect data on the current and future use of ABC column technologies in the United States. Appendix B presents the proposed standard testing method for mechanical bar splices in the format and language of AASHTO/ASTM documents. Appendix C presents the proposed design and construction guidelines for the three types of precast column connections approved by the project panel. This appendix, which was prepared in the AASHTO format and language, can be incorporated into the current edition of the AASHTO Guide Speci- fications for LRFD Seismic Bridge Design (AASHTO 2014) as Appendix C. Appendix D provides step-by-step examples to illustrate the application of the proposed guidelines. 1.4 References AASHTO. (2014). AASHTO Guide Specifications for LRFD Seismic Bridge Design. American Association of State Highway and Transportation Officials, Washington, D.C.
