Shear Tests on High-Strength Prestressed Bulb-Tee Girders: Strengths and Key Observations

Although a prestressed concrete section cast with high-strength concrete (HSC) can support larger loads or span longer distances in comparison to the same section cast with normal-strength concrete, current AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications limit the cylinder compressive strength of concrete to 10 ksi (69 MPa) due to a lack of experimental evidence to justify the use of higher strength concretes. This paper summarizes results from a study on the HSC limits of shear design provisions that was part of a larger project aimed at permitting the use of concrete strengths much higher than 10 ksi. To examine the 10 ksi (69 MPa) limit for shear design, ten 52 ft (16 m) long and 73 in. (1.8 m) deep prestressed concrete bridge girders were load tested to failure in shear. The primary test variables were concrete strength, 10 to 18 ksi (69 to 124 MPa); maximum design shear stress, 0.7 to 2.5 ksi (5 to 17 MPa); strand anchorage details (straight, unbonded, and draped); and end reinforcement detailing (bar size, spacing, and level of confinement). A total of 20 tests were conducted to evaluate various combinations of the most critical mechanisms of shear resistance. The results from this research, along with those from other experimental test programs of the project, indicate that the limit on the compressive strength of concrete can be raised safely from 10 to 18 ksi.

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  • Authors:
    • Kuchma, Daniel
    • Kim, Kang Su
    • Nagle, Thomas J
    • Sun, Shaoyun
    • Hawkins, Neil M
  • Publication Date: 2008-5

Language

  • English

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  • Accession Number: 01104864
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jul 18 2008 10:40AM