Development of an Alternative to the Double Tee Bridge System

Many bridges on the South Dakota local highway system need replacement due to deterioration or increased traffic demands. 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 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. Thus an alternative solution for this problem should be proposed at the design stage to reduce joint movements and increase girder continuity. The solution can be developed as a new connection detail between girders or a more robust precast girder prototype for precast bridges in South Dakota. Bridges on the local system in the State of South Dakota carry millions of dollars of agricultural products to market, as well as tourists, outdoor adventurist, school buses, and everyday travelers. If budgets of local governments cannot increase and the cost of a bridge replacement does not decrease, the only option will be to close bridges, raising the cost of getting products to market will rise and increasing inconvenience to the traveling public. If fewer routes are available due to closed bridges, emergency vehicles will experience increased response times to rural incidents. The number of structurally deficient bridges on the local system only continues to grow due to the cost of replacement and limited local government budgets. These bridges are vital for agriculture and the traveling public and cannot be allowed to close without adverse effects on local communities. An immediate solution is desirable. Due to the poor serviceability performance of longitudinal joints in precast double tee bridge girders on South Dakota roads, an experimental research project, SD2013-01, was conducted at South Dakota State University (SDSU) to investigate the performance of the currently used longitudinal joint detail and to assess the adequacy of a proposed new joint detail for use with double tee girders (Konrad, M. 2014). The study involved fatigue and strength testing of two full-scale specimens, one representing the as-built conditions and the other representing a modified joint detailing. The fatigue load was determined using American Association of State Highway and Transportation Officials (AASHTO) specifications (AASHTO 2012). The modified joint detailing specimen involved overlapping the steel mesh in the joint region of adjacent girders. The grouted joint is 6 inches wide and requires some flat formwork during the placement of the grout. Results from fatigue and strength testing of the as-built and modified specimens revealed that the current joint detailing is severely inadequate if the bridge is to last for 50 years or more, while the modified joint detail provided adequate performance under fatigue loading equivalent to more than 70 years of service. Currently, there is only one supplier for the double tee bridge girder system in South Dakota. Alternative precast concrete and other type bridge systems may prove to provide potential options for local governments when making a bridge type selection based on performance and cost. Therefore, a study is needed to identify potential alternative systems and assess the construction feasibility, structural performance, and durability of those systems that have potential for implementation in South Dakota.

Language

  • English

Project

  • Status: Active
  • Funding: $159999
  • Contract Numbers:

    DTRT13-G-UTC38

  • Sponsor Organizations:

    Research and Innovative Technology Administration

    University Transportation Centers Program
    1200 New Jersey Avenue
    Washington, DC  United States  20590
  • Project Managers:

    Kline, Robin

  • Performing Organizations:

    South Dakota State University, Brookings

    Department of Civil and Environmental Engineering
    P.O. Box 2219
    Brookings, SD  United States  57007
  • Principal Investigators:

    Wehbe, Nadim

  • Start Date: 20150819
  • Expected Completion Date: 20180731
  • Actual Completion Date: 0
  • Source Data: MPC-501

Subject/Index Terms

Filing Info

  • Accession Number: 01579738
  • Record Type: Research project
  • Source Agency: Mountain-Plains Consortium
  • Contract Numbers: DTRT13-G-UTC38
  • Files: UTC, RiP
  • Created Date: Oct 27 2015 5:33PM