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5 tions with commentary, the design examples, and the recom- mended integral connection details as appendices. In addition to the inherent limitations of the study tasks, as the work progressed, other limitations to the scope were dictated by the type of connection and type of substructures selected for further study and by the characteristics of the structures analyzed. The system selected for detailed stud- ies and laboratory testing consists of a straight (non-curved) I-girder superstructure connected rigidly to a steel box-beam pier cap that is, in turn, connected integrally to a reinforced concrete single-column pier. All studies assumed that the Figure 1. Concrete pier cap connected integrally to steel column is at mid-width of the bridge and that the bridge is I-girder superstructure. not skewed. Studying this system implies that the following types of structures and structural components were not directly Task 1. Review relevant domestic and foreign practice, per- studied: formance data, research findings, cost comparisons, and other Curved structures, information related to integral connections. This information Multi-column substructures, shall be assembled from technical literature and from unpub- Single-column piers with the column not at mid-width lished experiences of engineers, bridge owners, steel suppli- of the bridge, ers, fabricators, and others. Information on field performance Superstructure girders other than I-girders, is of particular interest. Pier caps other than steel box-beam pier caps, and Skewed superstructures. Task 2. Identify integral connection concepts that enhance bridge performance and economy. Throughout the work, engineering judgment was used, to the extent possible, to extrapolate the research results to Task 3. Based on review and assessment of the findings in cover these types of structures that were not directly covered Task 1 as well as new concepts generated by the research in the study. team in Task 2, recommend concepts to be fully developed, validated, and detailed. Task 4. Prepare a detailed work plan for the remainder of the 1.4 RESEARCH APPROACH project that includes a description of the proposed processes for validating the effectiveness of the integral connection To accomplish the stated objectives of the research and concepts. Estimates of the cost to evaluate each concept shall to cover the work on the tasks of the project, the following be provided. approach was followed: Task 5. Submit an interim report to document Tasks 1 through To gather information on past use and performance of 4 for review by the NCHRP panel. integral pier caps, a questionnaire was prepared and was sent to all AASHTO voting and nonvoting members (i.e., Task 6. In accordance with the approved work plan, con- DOTs in all states and Canadian provinces, as well as duct analytical and/or experimental work to validate the inte- other quasi-governmental authorities such as turnpike gral connections approved by the project panel for further authorities). A slightly modified questionnaire was sent development. to domestic researchers and bridge designers and inter- national bridge designers. The response to the question- Task 7. Based upon the results of Task 6, further develop and naire was used to study the state of the practice of inte- finalize integral connections that will enhance performance, gral connections. economy, and construction ease. In addition to the questionnaire, an extensive litera- Task 8. Develop recommended methodologies, specifications, ture search was performed to identify and review rele- commentary, and design examples. vant past research. Task 9. Submit a final report describing the entire research To identify integral connection concepts that are potential project. Include the recommended methodologies, specifica- candidates for this study, the research team studied the

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6 connection concepts used in the past and developed sev- to simulate the performance under simulated service condi- eral other systems. In total, 14 systems were examined. tions and under cyclic loads to simulate performance during Selection criteria were developed to assist in selecting a seismic events. Load, strain, displacement, and rotation mea- system for detailed studies. The selection criteria were surements were recorded throughout the tests. based on the expected economy, constructability, and The analytical studies were conducted on finite element expected performance of the 14 systems considered. models of both the prototype bridge and the test specimens. Several practicing engineers participated in this process The analytical studies of the prototype bridge were used to and the average of the scores was recorded. The system validate the applicability of some of the existing design pro- with the highest score was selected for further study and visions, which were originally developed for girders sup- was approved by the project Technical Panel. ported on conventional bearings, to girders of structures with Analytical and experimental studies were conducted to integral connections. The analytical studies on the test spec- validate the system approved by the project technical imen computer model were used to determine the anticipated panel for further development. A two-span bridge was forces acting on different components of the laboratory spec- selected as the basis for these studies. Throughout this imens and to validate the modeling technique by comparing the analytical results with the laboratory results. report, this bridge is referred to as "the prototype bridge." The results of the analytical and experimental studies were used to finalize the details of the integral connections and The experimental studies were accomplished by testing to develop design methodologies, specifications, commen- two, one-third-scale models of the pier region of the proto- tary, and a detailed design example based on the proposed type bridge. The specimens were tested under low-level loads specifications.