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13 CHAPTER 2 Research Approach The research team developed and executed the following details, strand release process, criteria for repair and rejection approach to achieve the project objectives listed in Chapter 1: of cracked members, and repair methods. The national sur- vey and its results are provided in Appendix B. Also, a sum- Literature search: The research team searched the litera- mary of the survey results is presented in Chapter 3. ture looking for performance criteria and data of prestressed Required tasks: Based on the information collected from girders where end zone cracking was reported. The search the literature review and analysis of the national survey included national and international resources such as jour- results, the research team identified the following set of nal papers and reports published in the past 60 years. Also, issues that, if addressed, would help establish procedures the search tried to collect information on any acceptance or for the acceptance, repair, or rejection of precast/prestressed rejection measures developed for prestressed girders with concrete girders with end zone cracking. These issues are end zone reinforcement. The research team found that most 1. Effect of end zone cracking on structural capacity, dura- of the available measures are related to flexural cracks in bility and aesthetics of prestressed concrete girders. conventionally reinforced beams. Very few publications that 2. Improvement of the current design of end zone reinforce- deal with end zone cracking of prestressed bridge girders ment to reflect recent usage of high-strength concrete and were available. The literature search showed that there is high levels of prestress. no unified approach or set of criteria that is available and 3. Methods and material of end zone crack repair, if widely accepted by highway authorities in the United States. required. The majority of publications on end zone cracking agreed Work plan: To investigate these issues, the research team that crack width is the best measure that can be used to developed the following work plan. The plan has four Task develop practical acceptance/rejection criteria. 6 subtasks of the project, as shown in Table 2.1. A set of National survey: After searching the literature, and due to questions were developed to be answered by each subtask. the lack of information on polices used by precast produc- Details of work in each subtask including results and con- ers and highway authorities regarding acceptance/refusal clusions are presented in Chapter 3. of girders with end zone cracking, the research team devel- Project deliverables: After the subtasks listed in Table 2.1 oped a national survey to collect information on the expe- were conducted and the results were analyzed, the research rience regarding longitudinal end zone cracking. The team developed national survey was sent to all of the state DOTs, other 1. A user's manual for acceptance criteria and repair materi- owner agencies, selected bridge consultants, and precast als and methods. concrete producers. It was also sent to about 150 PCI bridge 2. Improved crack control reinforcement details for use in product producers, the PCI Committee on Bridges, the PCI new girders. Bridge Producers Committee, and selected Canadian agen- 3. Proposed revisions to the AASHTO LRFD Bridge Design cies. The questionnaire included questions on reinforcement Specifications.

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14 Table 2.1. Questions and corresponding work-plan subtasks developed to reach project objectives. Questions Work-Plan Subtasks 1. Does end zone cracking 1. Structural Investigation and Full-Scale Girder Testing negatively affect the Analysis of previous work, identification of influencing flexural and shear parameters, and determination of potential structural effect of capacities of prestressed end zone cracking led to the design and testing of eight full-scale girders? girders. 2. Do variations of the end Two girders were fabricated in each of four states: FL, TN, zone reinforcement VA and WA. Shear capacity, flexural capacity, and variations of details have significant end zone reinforcement details were included. These details effect on the number, included LRFD recommendations, proposed detail, and, if width, and pattern of end available, local practices. zone cracks? 2. Epoxy Injection Testing Two 12-ft long specimens were fabricated by Concrete 3. If epoxy injection is used Industries (CI), Lincoln, NE, as part of an NU 1350 (53-in. deep) to repair end zone bridge girder production. The first specimen was fabricated with cracking, can repair only shear reinforcement and no additional end zone restore the tensile reinforcement. The second specimen was fabricated with a capacity of the cracked different method of end zone reinforcement at each end (LRFD concrete? method and the proposed method). 4. Is epoxy injection The specimens were repaired using epoxy injection by CI capable of completely staff using the procedure from PCI's Manual for the Evaluation filling the crack through and Repair of Precast, Prestressed Concrete Bridge Products the width of the web? (11). Sections of the web at the ends were saw cut, visually examined, and structurally tested. 3. Durability Testing 5. If repair is required, what This testing was conducted in three stages. In Stage I, 60 repair method and 4 8-in. concrete cylinders were fabricated and sealed using five material should be used? commercial sealants. ASTM D6489-99 Specification, Water 6. Should the end zone Absorption Test of Hardened Concrete Coated with Water surface be sealed with a Repellant. surface sealant regardless Sealant effectiveness was evaluated. The best performing of whether cracks are sealants were selected for further testing. required to be filled with In Stage II, 49 prisms were fabricated with preformed cracks a patching material? ranging in width from 0.007 to 0.054 in. The results of Stage II were verified through a series of tests on 69 prisms in Stage III. 4. Field Inspection of Bridges 7. Does the width of end The research team developed criteria for bridges to be zone cracking change inspected. Two states (Nebraska and Virginia) were targeted. with time? Several bridges were inspected in each state. The inspection 8. If end zone cracking is process included detected at the precast Collection of reports of inspection conducted at the plant. plant and no repair was Examination of the report and identification of repair method conducted, do these and material. cracks lead to corrosion Collection of inspection reports of the bridges in service. of the strands and bars, or Visits by the research team of the bridges under study. The delamination of the inspection included observation of crack growth since concrete? production and of signs of reinforcement corrosion and concrete delamination.