FIELD-MEASURED POST-TENSION PRESTRESS LOSS IN STRESS-RELIEVED STRANDS

Four 1/2 inch stress-relieved prestress strands were installed and stressed in an interior bay of each of six post-tensioned box girder highway bridges. The test strands are linearly continuous, unsupported, and ungrouted between the bridge abutments. At each site two were stressed before the structure was stressed and the other two were stressed after. Five of the structures are two-span continuous and one is a single span. The average apparent representative prestress loss after ten years for the 16 two-span test strands jacked to about 70% of 270 ksi and anchored at about was 39 ksi. The projected loss for these strands at 50 years is about 45 ksi. The data pltos show an appreciable amount of scatter, which an only partly be explained by seasonal temperature and humidity variations at the test sites. An additional analysis was made which compares the difference between the apparent and estimated "test strands" losses with the controlling estimated loss for the "working strand" of each structure. The analysis indicates that the minimum single "lump sum" prestress loss value for a current design of these structures would be, on the average, about 34 ksi for a design conservative to ten years and about 40 ksi for a design conservative to 50 years, excluding friction and anchorage. (Author)

  • Supplemental Notes:
    • This study was conducted in cooperation with the Federal Highway Administration, original Study Title: Field Verification of Prestressing Steel Losses.
  • Corporate Authors:

    California Department of Transportation

    Division of Structures Design, 1120 N Street
    Sacramento, CA  United States  95814

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Richardson, J E
  • Publication Date: 1984-6

Media Info

  • Features: Figures; References;
  • Pagination: 156 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00395668
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-CA-SD-84-02 Final Rpt.
  • Contract Numbers: F73SD01
  • Files: TRIS, USDOT, STATEDOT
  • Created Date: Feb 28 1987 12:00AM