LABORATORY STUDIES OF PROGRESSIVE BOND FAILURE IN CONTINUOUSLY-REINFORCED CONCRETE SLABS

THIS PAPER REPORTS THE RESULTS OF RESEARCH INITIATED TO DETERMINE A METHOD OF MEASURING BOND FAILURE, TO EVALUATE THE EFFECT OF REPETITIVE VERTICAL LOADS IN PRODUCING PROGRESSIVE BOND FAILURE FROM CRACK TO CRACK IN CONTINUOUSLY -REINFORCED CONCRETE PAVEMENTS, AND TO DETERMINE THE MAGNITUDE AND DISTRIBUTION OF BOND STRESSES IN THE VICINITY OF CRACKS. TO EVALUATE BOND STRESSES NEAR CRACKS AND TO STUDY THEIR CHANGE UNDER REPETITIVE LOADS, A PLASTIC GAGE WAS DEVELOPED TO DETERMINE MINUTE MOVEMENTS OF THE STEEL BAR WITH RESPECT TO THE CONCRETE. THESE MOVEMENTS CHANGE THE RATE OF COMPRESSED AIR FLOW THROUGH THE GAGE, AND LINEAR MOVEMENTS ARE DETERMINED BY MEASURING THE RATE OF AIR FLOW. AN ATTEMPT WAS MADE TO RELATE THESE DIFFERENTIAL MOVEMENTS TO BOND STRESS BY ASSUMING THAT THESE DIFFERENTIAL MOVEMENTS, DIVIDED BY THE DISTANCE BETWEEN PLASTIC GAGES, WERE STRAINS IN THE STEEL. PULL-OUT TESTS ON 9-IN. CONCRETE CUBES WERE USED IN ARRIVING AT A SATISFACTORY SIZE AND CONFIGURATION FOR THE PLASTIC GAGE. CONCLUSIONS REACHED ARE AS FOLLOWS: (1) THE PLASTIC GAGE USED IN CONJUNCTION WITH AN AIR FLOW METER PROVIDES A SIMPLE AND PRACTICAL MEANS OF DETERMINING THE DIFFERENTIAL MOVEMENT OF STEEL BARS WITH RESPECT TO CONCRETE WITHOUT DESTROYING ANY OF THE DEFORMATION ON THE BARS, (2) BOND STRESS AT POINTS WITHIN A REGION OF SLIP MAY GREATLY EXCEED THE AVERAGE BOND STRESS OVER THIS REGION, (3) HEAVY REPETITIVE VERTICAL LOADS INCREASED THE MAGNITUDE OF SLIP IN REGIONS ADJACENT TO CRACKS, BUT BOND STRESSES WERE NOT INCREASED IN THE SAME PROPORTION, (4) SEVEN MILLION REPETITIONS OF HEAVY WHEEL LOADS RESULTED IN SLIP OF LESS THAN 0.002 IN. AT A DISTANCE OF 6 IN. FROM A CRACK, 12 IN. FROM A CRACK THE SLIP WAS ZERO, (5) WHEN CRACKS ARE SPACED MORE THAN 2 FT APART, THE POSSIBILITY OF 9,000-LB TRUCK WHEEL LOADS PRODUCING PROGRESSIVE BOND FAILURE IN CONTINUOUSLY-REINFORCED PAVEMENTS ON MEDIUM PLASTIC SUBGRADES IS PRACTICALLY NONEXISTENT. /AUTHOR/

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 1-15
  • Monograph Title: Rigid pavement design studies 1962
  • Serial:

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Filing Info

  • Accession Number: 00206758
  • Record Type: Publication
  • Files: TRIS, TRB, ATRI
  • Created Date: Jul 29 1994 12:00AM