INSIDE THE DOT
South Dakota Department of Transportation
Precast Bridge Girder Details for Improved Performance
12/2/2013 - 11/30/2015
Many bridges on the local highway system need replacement. Local governments rely on the South Dakota Department of Transportation (SDDOT) to help replace them but, with limited resources, SDDOT can only help replace about 30 bridges statewide each year, causing a backlog of local bridges in need of replacement. The current standard bridge used in these replacements is the double tee precast girder bridge for its relatively low construction cost, outsourced design, and short construction duration. The expected design life of these bridges was 50 to 70 years, but some built less than 40 years ago already need replacement. The most common problem is that longitudinal joints become damaged over time, most likely due to inadequate shear transfer between the girders, allowing water and debris to enter the joints. It is only a matter of time before the joint begins to spall, creating a path for moisture to reach the prestressing steel, initiate corrosion, and degrade the structural capacity of the bridge. It should also be noted that the double tee should to be designed for girder continuity, often achieved by a reinforced concrete overlay or transverse post tensioning. Many local bridges are not designed for girder continuity, however, resulting in longitudinal joint deterioration and a non-redundant structure. Routine maintenance of these bridges does increase the life span, but is not a feasible long-term solution. The amount of routine maintenance required to keep the joints sealed is too costly for local governments. Other methods, such as asphalt overlays, are also expensive and can cause increased damage over time by trapping moisture that eventually reaches the prestressing steel. It is proposed to develop an alternative connection detail between girders or a more robust precast girder prototype for precast bridges in South Dakota that can help minimize girder relative movements.
2 Perform load testing on alternative girder(s) and double tee girder, and compare results.
1 From literature review, determine whether alternatives to the double tee precast girder exist with improved details for shear transfer between longitudinal joints to alleviate joint degradation.
6 If directed by the technical panel, prepare a technical memorandum describing a complete instrumentation, construction, and testing plan for technical panel review.
11 Prepare a final report and executive summary of the reserach methodology, findings, conclusions, and recommendations.
1 Meet with the technical panel to review project scope and work plan.
2 Perform literature review of precast girder technologies with alternative shear transfer at the longitudinal joint.
3 Create and administer survey to other Departments of Transportation to identify other viable precast bridge girder designs.
4 Contact precast companies, describe problems with current design, and inquire about solutions to longitudinal joint details or entire sections.
5 Prepare a technical memorandum and meet with technical panel to discuss the improved joint details and precast girder designs gleaned from literature review, surveys, and precast companies. Based on discussion, technical panel will decide which option(s), if any, require structural testing to compare with the double tee.
7 Upon approval of the plan by the technical panel, proceed with instrumentation and construction of test girders.
8 Perform and provide the technical panel opportunity to observe ultimate and fatigue loading of alternate girder(s) and the traditional double tee girder.
9 Based on the results of testing, compare fatigue and shear transfer characteristics of the double tee and alternative section(s).
10 Develop a recommendation to the SDDOT based on cost and performance of the alternative girders compared to the double tee.
12 Make an executive presentation to the SDDOT Research Review Board at the conclusion of the project.
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