Effects of increasing the allowable compressive stress at release on the shear strength of prestressed concrete girders.

Details

• Creators:
  Heckmann, Christopher ; Bayrak, Oguzhan
• Corporate Creators:
  University of Texas at Austin. Center for Transportation Research
• Corporate Contributors:
  Texas. Dept. of Transportation. Research and Technology Implementation Office ; United States. Federal Highway Administration
• Subject/TRT Terms:
  • Prestressed concrete
  • Girders
  • Shear strength
  • Compressive strength
  • Prestressed concrete bridges
  • Prestressed concrete
  • allowable compressive stress
  • shear tests
  • diagonal cracking
  • concrete beams
• Publication/ Report Number:
  FHWA/TX-09/0-5197-3
• Resource Type:
  Tech Report
• Geographical Coverage:
  Texas
• Corporate Publisher:
  Texas Department of Transportation. Research and Technology Implementation Office
• Abstract:
  In recent years, several research projects have been conducted to study the feasibility of increasing the allowable ; compressive stress in concrete at prestress transfer, currently defined as 0.60f'ci in the AASHTO LRFD Bridge ; Design Specifications. Increasing the limit would result in many economical and design benefits for the precast ; concrete industry, such as increased span lengths and faster turnover of beams in stressing beds. This research study ; focuses on the effects of increasing the allowable compressive stress at release on the shear strength of prestressed ; concrete members, a topic which has not yet been explored by past research projects. The current experimental work ; is funded under TxDOT Project 5197, which initiated in 2004 at the University of Texas at Austin. ; In the shear performance evaluation, 18 shear tests were performed. In the shear tests, the beams were loaded to fail ; in web-shear, with a shear span to depth ratio of 2.22. The diagonal cracking shears and shear capacities were ; experimentally measured for all specimens tested. All test specimens were TxDOT Type-C highway bridge girders ; (40-inch deep pretensioned I-beams) and were fabricated by three different precast plants in Texas. The compressive ; stress at release for the test specimens ranged from 0.56f'ci to 0.76f'ci. The measured cracking shears and shear ; capacities were compared to the estimated cracking shears and shear capacities, as calculated using ACI 318-08 and ; AASHTO LRFD (2007), and the effects of higher release stresses on shear strength and serviceability were ; evaluated by examining the conservativeness and accuracy of the predictions. Based on the experimental results ; summarized in this report, an increase in the allowable maximum compressive stress in concrete in the end regions ; of prestressed concrete beams at prestress transfer to 0.65f'ci or 0.70f'ci can be justified.
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• Format:
  PDF
• Funding:
  0-5197
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/16779/dot_16779_DS1.pdf
• File Type:
  [PDF - 9.47 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:c61d78cd50d1f1ab203f6580a0763adc9494bf6c074c1a6fe760ebb94ed9115c