NCHRP 18-18 [Final]
Design and Construction of Deck Bulb Tee Girder Bridges with UHPC Connections
| Project Data
||Ohio University |
||Dr. Eric Steinberg |
||Published as NCHRP Research Report 999|
Many state DOTs and the Federal Highway Administration (FHWA) are actively promoting accelerated bridge construction (ABC) to reduce traffic impacts, onsite construction time, environmental impacts, and life-cycle costs. However, the usage of prefabricated deck bulb tee (DBT) girders has been limited to relatively short-span and low traffic bridges because of (1) difficulties in accommodating super-elevation transitions on bridge decks, pier skews, differential camber, and stability; and (2) concerns of long-term performance of connections between DBT girders. For example, skewed DBT girders cause bridge deck profile problems because the cambers in adjacent girders do not "line up," and if diaphragms are used to bring the DBT girders into line, large forces are induced.
For the longitudinal and transvers connections between DBT girders, there are a wide range of potential variables to be considered during design and construction of the connections including connection width, bar size, bar spacing, bar detailing (straight, bent or headed), black or epoxy bars, flange thickness, and closure pour materials. The typical DBT girders connected by longitudinal joints with welded tie and grouted connection are not performing well and are not suitable for long-span DBT girder bridges as the load transfer demand on the connection is high. Addressing these topics and use of ultra-high performance concrete (UHPC) as closure pour materials could result in a dramatic improvement in reliability and economy of DBT girders for ABC.
The objective of this research is to propose draft AASHTO LRFD Bridge Design Specifications and AASHTO LRFD Bridge Construction Specifications for design and construction of DBT girder bridges using UHPC for connection.
Task 1. Conduct a literature review of relevant domestic and international guidelines and specifications. The review should also cover research findings, existing design guidelines, and owner and industry experience.
Task 2. Synthesize the literature review to identify the knowledge gaps for DBT girders design, fabrication, stability, erection, construction, and UHPC connection details. These gaps should be addressed in the final product or in the recommended future research as budget permits.
Task 3. Propose analytical and parametric studies to be executed in Phase II. At a minimum, the studies should consider the following:
a. fabrication, control of camber, stability, and erection of DBT girders using conventional and light weight concrete;
b. effect of span length, girder spacing and skew, diaphragm effects, differential camber, and provisions for bridge widening;
c. connections details between DBT girders and continuity at intermediate piers using UHPC as an option; and
d. live load continuity at the transverse connections between DBT girders and applicability of the AASHTO LRFD Bridge Design Specifications live load distribution factors.
Task 4. Propose a system test to be executed in Phase III. The plan for the system test should be presented in a matrix format and shall include at a minimum:
a. multiple girder lines to verify negative moment continuity at the intermediate pier and to verify longitudinal joints effectiveness with locked-in-stress due to differential camber and live load distribution;
b. different connection details with different UHPC mixes; and
c. service loads, cyclical testing of at least two million cycles, and ultimate strength.
Task 5. Propose areas of the AASHTO bridge design and construction specifications that will require modification or addition.
Task 6. Prepare Interim Report No. 1 that documents Tasks 1 through 5 and provides an updated work plan for the remainder of the research. The updated plan must describe the process and rationale for the work proposed for Phases II through V. This report must be submitted no later than 4 months after contract award.
PHASE II—Analytical and Parametric Studies
Task 7. Execute the analytical and parametric studies according to the approved Interim Report No.1.
Task 8. Finalize the system test work plan and describe how the test results will be utilized to develop the AASHTO specifications.
Task 9. Prepare Interim Report No. 2 that documents Tasks 7 and 8 and provides an updated work plan for Phases III through V. This report must be submitted no later than 9 months after approval of Phase I.
PHASE III—System Test
Task 10. Execute the system test according to the approved Interim Report No. 2. Validate the analytical and parametric studies based on the testing results.
Task 11. Prepare Interim Report No. 3 that documents Task 10 and provides an updated work plan for the remainder of the project. This report must be submitted no later than 12 months after Phase II approval.
PHASE IV—Specifications Development
Task 12. Develop draft proposed modifications to the AASHTO design and construction specifications, and design examples and connection details to demonstrate the application of the proposed specifications, and AASHTO agenda items for the AASHTO Highway Subcommittee on Bridges and Structures. Prepare Interim Report No. 4 that documents Task 12. This report must be submitted no later than 4 months after approval of Phase III.
PHASE V—Final Products
Task 13. Revise the proposed draft AASHTO bridge design and construction specifications, design examples, and connection details after consideration of the panel’s review comments.
Task 14. Prepare final deliverables including: (a) a final report that documents the entire research effort and (b) the proposed draft AASHTO specifications, design examples, and connection details.
STATUS: Final, NCHRP Research Report 999