SHEAR STRENGTH OF PRESTRESSED CONCRETE I-BEAMS

THE FIRST PHASE OF THE PROJECT WAS A STUDY OF THE FLEXURAL BEHAVIOR OF A PRESTRESSED CONCRETE BRIDGE BEAM. IT APPEARS FROM THIS STUDY AND OTHER INVESTIGATIONS THAT THE FLEXURAL CHARACTERISTICS OF PRESTRESSED BEAMS ARE WELL UNDERSTOOD AND CAN BE PREDICTED WITH REASONABLE ACCURACY. THE SECOND PHASE WAS A STUDY OF THE SHEAR STRENGTH OF PRESTRESSED CONCRETE I-BEAMS. THE TERM "SHEAR STRENGTH" IS SUBJECT TO VARIED DEFINITIONS. IN THIS PAPER SHEAR STRENGTH IS DEFINED AS THE LOAD AT WHICH A SUDDEN DIAGONAL CRACK COMPLETELY TRAVERSES THE WEB OF THE BEAM. THE REGION IN WHICH THE CRACK OCCURS IS SUBJECT TO DIRECT AND SHEARING STRESSES ON ITS VERTICAL PLANES, PRODUCING TENSILE STRESSES ON THE INCLINED FAILURE PLANE. A THEORY OF FAILURE FOR CONCRETE UNDER COMBINED STRESS IS NECESSARY FOR THE RATIONAL SOLUTION OF THE PROBLEM OF SHEAR STRENGTH. OF THE MANY THEORIES ADVANCED FOR FAILURE OF CONCRETE UNDER COMBINED STRESS ONLY ONE WAS CONSIDERED. GRASSAM HAS SUGGESTED A MODIFIED MAXIMUM TENSILE STRESS THEORY IN WHICH ACCOUNT IS TAKEN OF SOME PLASTICITY WITHIN THE CONCRETE. ARBITRARILY TAKING AS THE FAILURE STRESS THE MEAN OF THE STRESSES WOULD CAUSE FAILURE UNDER THE ASSUMPTION OF ELASTICITY AND PLASTICITY, HIS TEST RESULTS SHOWED SATISFACTORY AGREEMENT WITH THE THEORY. HE ALSO SUGGESTS THAT AN ARBITRARY VALUE OF CRITICAL TENSILE STRESS EQUAL TO 1.2 TIMES THE TENSILE STRENGTH WILL FIT THE RESULTS FOR A COMBINED STRESS CONDITION. THE RESULTS IN THIS PAPER SHOULD BE CONSIDERED PRELIMINARY IN NATURE, BECAUSE THE INFORMATION FROM ONLY FOUR TEST BEAMS IS INCLUDED. THREE I-BEAMS IN WHICH REINFORCEMENT WAS OMITTED FROM THE SHEAR SPANS WERE TESTED. HOWEVER, 2-FT OVERHANGS WITH WEB REINFORCEMENT WERE INCLUDED ON EACH BEAM SO THAT THE FULL PRESTRESS FORCE WOULD BE DEVELOPED OUTSIDE THE SHEAR SPAN. THE ONLY VARIABLE INTRODUCED IN THE THREE WAS THE LENGTH OF THE SHEAR SPAN. THESE THREE BEAMS WERE FABRICATED IN A COMMERCIAL PRESTRESS PLANT. THE FOURTH BEAM WITH WEB REINFORCEMENT THROUGHOUT ITS ENTIRE LENGTH WAS FABRICATED IN THE IOWA ENGINEERING EXPERIMENT STATION LABORATORY. THE DEPTH AND THE CROSS-SECTION OF THE FOURTH BEAM VARIED SLIGHTLY FROM THE FIRST THREE BEAMS. /AUTHOR/

  • Supplemental Notes:
    • Vol 37, pp 106-118, 10 FIG, 2 REF
  • Authors:
    • Hulsbos, C L
  • Discussers:
    • Schupack, M
  • Publication Date: 1958

Media Info

  • Monograph Title: Proceedings of the Thirty-Seventh Annual Meeting of the Highway Research Board, Washington, D.C., January 6-10, 1958
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00209473
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Oct 3 1971 12:00AM