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CHAPTER 3
Research Findings
This chapter presents the results and findings of the work copy of the survey is presented in Appendix B. Results from the
plan developed by the research team and reported in Chapter 2. questionnaire have been most helpful in seeing how organiza-
In order to keep the size of this report within acceptable tions around the country and beyond have been dealing with
limits, detailed discussions on the material covered in this this issue.
chapter are provided in Appendices B through G, which The research team received 44 responses, which have
are not provided herein (to find Appendices A through G been compiled and summarized in Appendix B. There were
for this report, go to www.trb.org and search for "NCHRP 32 responses from state DOTs, 10 responses from precast
Report 654"). The contents of Chapter 3 and the correspond- concrete producers, 1 response from a consultant, and 1 re-
ing appendices are as follow. sponse from a researcher.
Most responses indicated experience in the design, fabri-
Subtasks and Deliverables Section Appendix cation, or construction of thousands of linear feet of precast/
prestressed concrete girders annually. As anticipated, most state
· National Survey 3.1 B
DOTs deal with I-girders, bulb tees, and box girders. Some also
· Structural Investigation and 3.2 C
stated that they deal with voided slabs, double tees, and--
Full-Scale Girder Testing
among others--inverted tees. Thirty-six respondents, or 82%
· Epoxy Injection Testing 3.3 --
of those who replied, said that they experienced longitudinal or
· Durability Testing 3.4 D and E
diagonal cracks in the webs of the end zones of their girders, but
· Field Inspection of Bridges 3.5 F only eight said they did not encounter the problem. I-girders
· Manual of Acceptance, Repair, 3.6 -- and bulb tees seem to be experiencing the longitudinal crack-
or Rejection ing the most. About half of the responses stated that only 1% to
· Improved Crack Control 3.7 G 10% of their girders experienced cracking, while the other half
Reinforcement Details for stated that cracking occurred in 80% to 100% of their girders.
Use in New Girders Of those who experienced longitudinal web cracking, 56%
· Proposed Revisions to the 3.8 -- do not have any official criteria for classifying it. The others use
AASHTO LRFD Bridge a combination of crack width and crack length. The most preva-
Design Specifications lent answer in the surveys for acceptance/rejection was criteria
based on crack width in the range of 0.006 to 0.025 in. The size
3.1 National Survey of the width determines the need for, and level of, repair. The
literature review shows that cracks that are 0.01 in. wide or
The research team developed a questionnaire to survey ex- smaller can be sealed just by using a brush-on sealant, but cracks
periences regarding longitudinal end zone cracking. It was sent that are in the range of 0.01 to 0.025 in. must be repaired by
to all the state DOTs, other owner agencies, selected bridge con- epoxy injection. Most of these ranges were set for durability
sultants, and precast concrete producers. It was also sent to aspects, to protect the reinforcement from corrosion and the
about 150 PCI bridge product producers, the PCI Committee crack width from growing during freeze and thaw cycles.
on Bridges, the PCI Bridge Producers Committee, and selected Most inspectors stated that routine inspection is used to
Canadian agencies. The questionnaire included surveys on determine the extent of cracking. However, 17 of the 36 who
reinforcement details, strand release process, criteria for repair experienced end zone cracking used crack comparators,
and rejection of cracked members, and repair methods. A shown in Figure 3.1, and 5 used magnifying scopes.
