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BEHAVIOR OF AASHO ROAD TEST BRIDGE STRUCTURES UNDER REPEATED OVERSTRESS

EIGHTEEN SLAB AND BEAM BRIDGES WERE SUBJECTED TO ROAD TRAFFIC AT THE AASHO ROAD TEST. EACH TEST BRIDGE WAS ASSIGNED ONLY ONE TYPE OF TRUCK. EIGHT BRIDGES HAD SINGLE-AXLE AND 10 BRIDGES HAD TANDEM-AXLE VEHICLES OPERATING OVER THEM. TO DETERMINE THE COMBINED CUMULATIVE EFFECTS OF TIME AND TRAFFIC, A NUMBER OF MEASUREMENTS AND OBSERVATIONS WERE MADE ON BRIDGES WITH NO LOAD OTHER THAN THEIR WEIGHT. STRAIN MEASUREMENTS, DEFLECTION MEASUREMENTS, DETERMINATION OF THE DEGREE OF CRACKING OF CONCRETE BEAMS, MEASUREMENTS OF LONGITUDINAL AND TRANSVERSE SLAB PROFILES AND CONDITION SURVEYS WERE USED. ADDITIONAL MEASUREMENTS ON UNLOADED STRUCTURES INCLUDED THE STRAINS CAUSED BY SLAB WEIGHT AND THOSE CAUSED BY VARIATIONS IN TEMPERATURE. THE BRIDGE BEAMS WERE INSTRUMENTED FOR MEASURES OF TRANSIENT STRAINS AND DEFLECTIONS CAUSED BY VEHICLES. THE TRANSIENT DEFLECTIONS WERE MEASURED AT MID-SPAN OF ALL BRIDGES. THE STRAINS WERE MEASURED AT THE ROLLED SECTIONS OFF THE ENDS OF COVER PLATES, AT MID-SPAN AND AT OTHER LOCATIONS. THE ACCUMULATION OF VEHICLE TRIPS WITH TIME ARE SHOWN ON A GRAPH. ENVIRONMENTAL CONDITIONS AT THE TEST ROAD WERE OBSERVED AT A CENTRALLY LOCATED WEATHER STATION. FATIGUE STRENGTH OF THE STEEL BRIDGES WITH PARTIAL-LENGTH COVER PLATES WAS FOUND TO BE IN AGREEMENT WITH LABORATORY TESTS. MAJOR YIELDING WAS FOUND TO OCCUR WITH THE FIRST FEW HUNDRED VEHICLE PASSAGES. THE MAXIMUM STRESSES IN PRE-STRESSED BEAMS OCCURED IN MID-SPAN. NONE OF THE PRESTRESSED CONCRETE BRIDGES FAILED DURING THE PERIOD OF REGULAR TEST TRAFFIC OR THE ACCELERATION FATIGUE TESTS. THREE OF THE PRESTRESSED BRIDGES WERE SUBJECTED TO 1.5 MILLION CYCLES OF STRESS WITHOUT ANY INDICATION OF FATIGUE FAILURE OF THE PRESTRESSING WIRE OR STRAND. THE APPLIED LOAD CYCLE SHOWN HAD NO APPRECIABLE EFFECT ON THE CRACKING OF THE CONCRETE. MAJOR CRACKING FOUND IN THE PRESTRESSED BEAMS WAS BECAUSE APPLIED STRESSES EXCEEDED THE TENSILE STRENGTH OF THE CONCRETE. THE MAXIMUM STRESSES OCCURRED NEAR MID-SPAN IN THE REINFORCED CONCRETE BEAMS. THE INVESTIGATION OF REINFORCED CONCRETE BRIDGES WAS CONCERNED MAINLY WITH THE FATIGUE BEHAVIOR OF THE DEFORMED BARS AND THE EFFECT OF REPEATED STRESSING ON THE WIDTH AND SPACING OF TENSILE CRACKS. THE FATIGUE BEHAVIOR OF THE DEFORMED BARS SHOWS THAT THE BAR DEFORMATIONS INFLUENCED THE FATIGUE STRENGTH AS IF FATIGUE FRACTURES FORMED AT THE DEFORMATIONS. ALL 4 REINFORCED BRIDGES SURVIVED THE PERIOD OF REGULAR TEST TRAFFIC DURING WHICH OVER 556,000 TRIPS OF THE TEST VEHICLE WERE MADE OVER EACH BRIDGE. NO SATISFACTORY CORRELATION WAS FOUND BETWEEN THE STRESS CYCLES AT WHICH CRACKS WERE FIRST NOTICED IN THE CONCRETE OF INDIVIDUAL PRESTRESSED BEAMS AND AVAILABLE LABORATORY DATA FOR THE FATIGUE STRENGTH OF PLAIN AND CONCRETE BEAMS.

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  • Supplemental Notes:
    • pp 19-51, 48 FIG, 10 TAB, 6 REF Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
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  • Authors:
    • Fisher, J W
    • Viest, I M
  • Conference:
  • Publication Date: 1962

Media Info

  • Monograph Title: THE AASHO ROAD TEST - PROCEEDINGS OF A CONFERENCE HELD MAY 16-18, 1962, ST. LOUIS, MISSOURI
  • Serial:

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Filing Info

  • Accession Number: 00209219
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Aug 26 1970 12:00AM