STRENGTH EFFECT OF CUTTING OFF TENSION BARS IN CONCRETE BEAMS

SIXTY-FOUR CONCRETE BEAMS REINFORCED WITH NO. 8 OR NO. 11 BARS (LARGELY A432) WERE TESTED AS SIMPLE BEAMS. MOST OF THESE HAD BARS CUT OFF AT THE MINIMUM POINT FOR MOMENT OR AT 12D OR 15D BEYOND SUCH POINTS. SOME, FOR COMPARISON, CONTAINED FULL LENGTH BARS OR BARS BENT UP. THE MAJORITY OF THE BEAMS WITH BARS CUT OFF WERE DESIGNED TO BE BALANCED AT ULTIMATE IN FLEXURAL STRENGTH, SHEAR STRENGTH, AND BOND STRENGTH. WITH BARS CUT OFF AND NO REMEDIAL STEPS, ONLY 2 BEAMS OUT OF 33 DEVELOPED THE DESIGN ULTIMATE STRENGTH. THE LOSSES RANGED IN THE ORDER OF 15 TO 25 PERCENT, WITH ONE BEAM SHOWING MORE THAN 40 PERCENT. WITH BARS BENT UP NO DEFICIENCIES OCCURRED. THE ADDITION OF EXTRA STIRRUPS IMPROVED THE WEAK BEAMS, BUT STIRRUP EFFECTIVENESS IN REPLACING STRENGTH WAS ONLY ABOUT HALF THE NORMAL IN THE Y PLANE EVALUATION. DESIGN RECOMMENDATIONS BASED ON THE USE OF THE ACI BUILDING CODE ALLOWABLES FOR BOND AND SHEAR STRESSES ARE MADE FOR BEAMS WITH BARS CUT OFF. DESIGNS SHOULD BE BASED ON A TYPICAL 30 PERCENT LOSS OF SHEAR STRENGTH WHERE BARS CUT OFF, A 20 PERCENT LOSS WHERE HEAVY STIRRUPS ARE ALREADY PROVIDED (RF IN THE Y PLANE APPROXIMATELY EQUALS 130 PSI), AND A 10 PERCENT LOSS FOR SLABS 12 IN. OR LESS IN THICKNESS. IF REMEDIAL STIRRUPS ARE USED, THEY SHOULD PROVIDE AN RF Y IN THE Y PLANE ADEQUATE TO CARE FOR TWICE THE INDICATED SHEAR DEFICIENCY AND IN NO CASE LESS THAN 100 PSI. /AUTHOR/

  • Supplemental Notes:
    • Hpr-1 (6), STATE 80
  • Corporate Authors:

    University of Texas, Austin

    Center for Highway Research, 200 West 21st Street
    Austin, TX  United States  78712

    Texas State Department of Highways & Public Transp

    11th and Brazos Streets
    Austin, TX  United States  78701
  • Authors:
    • Ferguson, P M
    • Husain, S I
  • Publication Date: 1967-6

Subject/Index Terms

Filing Info

  • Accession Number: 00212015
  • Record Type: Publication
  • Source Agency: Bureau of Public Roads /US
  • Files: TRIS, STATEDOT
  • Created Date: Oct 4 1994 12:00AM