FATIGUE TESTS OF TWO PRESTRESSED CONCRETE I-BEAMS WITH INCLINED CRACKS

RESULTS OF TESTS ON TWO PRESTRESSED CONCRETE I-BEAMS SUBJECTED TO AN OVERLOAD OF SUFFICIENT MAGNITUDE TO CAUSE DIAGONAL TENSION INCLINED CRACKING AND SUBSEQUENTLY SUBJECTED TO REPEATED LOADS OF LESSER MAGNITUDE ARE REPORTED. HOT-ROLLED DEFORMED NO. 3 BARS AT A CONSTANT SPACING WERE USED FOR VERTICAL STIRRUP REINFORCEMENT. THE WEB REINFORCEMENT RATIO, BASED ON THE WEB WIDTH, WAS 0.61 PERCENT IN THE FIRST BEAM AND 0.46 PERCENT IN THE SECOND BEAM. CONCRETE STRENGTH WAS APPROXIMATELY 7,500 PSI. BOTH BEAMS WERE INITIALLY SUBJECTED TO A SYMETRICAL TWO- POINT LOADING OF APPROXIMATELY 77 PERCENT OF THE ULTIMATE FLEXURAL CAPACITY OF THE SECTION. THIS LOADING, ON A SHEAR- SPAN-TO-EFFECTIVE-DEPTH RATIO OF 3.39, WAS SUFFICIENT TO CAUSE DIAGONAL TENSION CRACKING IN BOTH SHEAR SPANS OF BOTH BEAMS. THE WEB REINFORCEMENT IN BOTH BEAMS HAD PROVEN TO BE SUFFICIENT IN OTHER STATIC TESTS TO DEVELOP THE FLEXURAL CAPACITY, ALTHOUGH IT WAS 57 PERCENT IN THE FIRST BEAM AND 43 PERCENT IN THE SECOND BEAM OF THAT REQUIRED BY AASHO SPECIFICATIONS. CYCLIC LOADING WAS SUBSEQUENTLY APPLIED UNTIL FAILURE OCCURRED. DEFLECTION, DIAGONAL CRACK WIDTH, AND CONCRETE STRAINS WERE MEASURED IN STATIC TESTS CONDUCTED AT VARIOUS INTERVALS DURING THE CYCLIC LOADING. THE FIRST BEAM FAILED IN FATIGUE OF THE PRESTRESSING STRAND AND THE SECOND IN FATIGUE OF THE STIRRUPS. A METHOD USED TO PREDICT FATIGUE LIFE, ASSUMING THAT FAILURE OCCURS IN THE STRAND, PROVIDED GOOD CORRELATION WITH RESULTS OF THE FIRST TEST. CRITERIA ARE DISCUSSED FOR JUDGING IF A PRESTRESSED BEAM WITH DIAGONAL TENSION CRACKING IS CRITICAL IN FATIGUE. /AUTHOR/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 14-30
  • Monograph Title: Bridges and structures
  • Serial:

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Filing Info

  • Accession Number: 00207715
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Apr 1 1994 12:00AM