PRESTRESSED CONCRETE PRISMS AS REINFORCEMENT FOR CRACK CONTROL

A MEANS OF REINFORCING THE DECK CONCRETE FOR CONTINUITY AND CRACK CONTROL IS "AUXILIARY PRESTRESSING". PART OR ALL OF THE DECK REINFORCEMENT IS REPLACED BY LONG PRECAST PRISMS OF CENTRALLY PRESTRESSED CONCRETE. WHEN THIS IS DONE, LIMITED PAST EXPERIENCE HAS SHOWN THAT THE CAST-IN-PLACE CONCRETE SURROUNDING THE PRECOMPRESSED CONCRETE PRISMS IS RESTRAINED FROM CRACKING. THE STRUCTURE BEHAVES AS THOUGH IT WERE PRESTRESSED. DEFORMED BAR REINFORCEMENT, COMBINATIONS OF DEFORMED BARS AND PRESTRESSED CONCRETE PRISMS, AND OF DEFORMED BARS AND PRESTRESSING STEEL WERE COMPARED IN TESTS OF SEVEN T-BEAMS WITH THREE DIFFERENT SETS OF CROSS SECTIONS. THE PRISMS WERE EITHER 1-1/2 X 1-1/2 IN. OR 2 X 2 IN. IN CROSS SECTION AND CONTAINED EITHER A 0.162-IN. WIRE OR A 1/4-IN. PRESTRESSING STRAND. THE T-BEAMS WERE TESTED IN NEGATIVE MOMENT BENDING OVER A CENTRAL SUPPORT. COMPARISONS WERE BASED ON CRACKING MOMENT, CRACK WIDTH, DEFLECTION, AND ULTIMATE STRENGTH. PRESTRESSED CONCRETE PRISMS PLACED AS PART OF THE REINFORCEMENT IN THE DECK OVER SUPPORTS OF T- BEAMS WERE FOUND IN THE TESTS REPORTED HERE TO ACT AS PRESTRESSING REINFORCEMENT. THE BENDING MOMENT AT FIRST CRACKING WAS INCREASED BY THE PRESENCE OF THE PRESTRESSED CONCRETE PRISMS. THE OVERALL EFFECT WAS SIMILAR TO THAT OF DIRECTLY PRESTRESSING THE DECK CONCRETE. ULTIMATE STRENGTH OF THE SEVEN TEST BEAMS WAS SATISFACTORILY PREDICTED BY EQUATIONS GOVERNED BY YIELDING OF THE FLEXURAL REINFORCEMENT. IT IS BELIEVED THAT THIS NEW TECHNIQUE IS READY FOR FIELD TRIAL.

  • Availability:
  • Supplemental Notes:
    • Vol 14, No 5, PP 14-31, 16 FIG, 4 TAB, 13 REF
  • Authors:
    • Hanson, N W
  • Publication Date: 1969-10

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Filing Info

  • Accession Number: 00209183
  • Record Type: Publication
  • Files: TRIS
  • Created Date: May 19 1970 12:00AM