EFFECT OF INTERNAL AND EXTERNAL CONSTRAINTS ON THE SHEAR AND BOND STRENGTH OF PRECAST PRESTRESSED CONCRETE GIRDERS

In computing the shear strength of prestressed concrete girders, the AASHTO Bridge Design Specification includes the lack of full effective prestress in the transfer zones adjacent to the ends of the girder. In comparison with earlier design specifications, this results in reduced computed contribution of concrete to the shear strength of the girder in these regions, and a greater computed weight of transverse reinforcement. This is in contrast to the fact that shear failure of prestressed concrete girders has not been a problem in Florida. One possible way to reduce the computed required weight of transverse reinforcement would be to reduce the transfer length. With this in mind, a series of 12 scale model pretensioned test girders were fabricated and loaded to failure in the structural laboratory. All girders were identical, except that in an attempt to reduce transfer length, the test girders incorporated various anchorage devices at the ends of the prestressing strand. Devices were either cast into the girder above the support, or placed externally, bearing against the end of the girder, and included spring loaded chucks, plain chucks with and without bearing plates, steel twists wound around the strand, epoxy-filled tubes, and sizeable bearing plates with chuck-type wedges. Girders were loaded to failure under a concentrated load, placed so as to induce a strut and tie failure mechanism at the end regions of the girders. Transverse reinforcement was omitted between the load and the support, providing a measure of the contribution of the concrete to the shear strength of the girder. Internally placed devices had little effect on either the measured transfer length or the shear strength of the girders. However, improved transfer length and higher shear strengths, along with improved load-deflection ductility were achieved when spring loaded chucks were placed externally, bearing against the ends of the test girders, and 3 ft (915 mm) to 6 ft (1829 mm) of strand adjacent to ends of the girder were debonded from the concrete by enclosing them in steel sleeves.

• Corporate Authors:

  University of Florida, Gainesville

  Department of Civil Engineering, P.O. Box 116580
  Gainesville, FL  United States  32611-6580

  Florida Department of Transportation

  Haydon Burns Building, 605 Suwanee Street
  Tallahassee, FL  United States  32301

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Lybas, J M
  • Fagundo, F E
  • Cook, R A
  • Hoffman, V L
• Publication Date: 1998-7

Language

• English

Media Info

• Features: Appendices; Figures; Photos; References; Tables;
• Pagination: 227 p.

Subject/Index Terms

• TRT Terms: Anchorages; Ductility; Girders; Load tests; Prestressed concrete; Scale models; Shear strength; Transverse reinforcement; Weight
• Uncontrolled Terms: Prestressing strands; Transfer length
• Subject Areas: Bridges and other structures; Design; Highways; I24: Design of Bridges and Retaining Walls;

Filing Info

• Accession Number: 00760587
• Record Type: Publication
• Report/Paper Numbers: WPI 0510774,, Final Report,, State Job 99700-3341-010
• Contract Numbers: BA-494
• Files: TRIS, USDOT, STATEDOT
• Created Date: Mar 30 1999 12:00AM