ENDURANCE OF A FULL-SCALE PRETENSIONED CONCRETE BEAM

THE BEHAVIOR IS DESCRIBED OF A STRAND REINFORCED PRETENSIONED CONCRETE BEAM UNDER 1,300,000 REPETITIONS OF AN EQUIVALENT STANDARD H20-S16 (36-TON GROSS WIEGHT) TRUCK LOADING, FOR WHICH IT WAS DESIGNED, AND A SUBSEQUENT 100,000 REPETITIONS OF 54 PERCENT DESIGN OVERLOAD. THE BEAM WAS 38 FT. LONG, 36 IN. WIDE, AND 21 IN. DEEP, AND CONTAINED 40 5/16-IN. DIAMETER 7-WIRE STRANDS, WITH A TOTAL STEEL AREA PER BEAM OF 2.25 SQ. IN. SEVEN STATIC TESTS, EACH WITH LOADS RANGING FROM 0 TO 100 PERCENT OF DESIGN LOAD, AND SIX MORE WITH 0 TO 410 PERCENT OF DESIGN LOAD, WERE MADE CONCURRENT WITH THE REPETITIVE LOAD TESTS. THE BEAM WAS ONLY PARTIALLY PRESTRESSED; AT ABOVE 70 PERCENT OF THE DESIGN LOAD THE BOTTOM FIBER CONCRETE STRESSES CHANGED INTO TENSION. CONSEQUENTLY, THE BEAM CRACKED DURING THE FIRST LOADING AND CRACKS OPENED DURING EACH OF THE SUBSEQUENT 1,400,000 LOAD REPETITIONS. THUS, THE TEST IS CONSIDERED MORE SEVERE THAN IF THE BEAM HAD BEEN FULLY PRESTRESSED. NO END SLIP OF STRANDS INDICATING END BOND FAILURE OCCURRED AND THE BONDING OF THE STRAND WAS ENTIRELY SATISFACTORY. THE BEAM DEFLECTED AS PREDICTED; THE DESIGN LOAD REPETITIONS HAD LITTLE EFFECT ON DEFLECTIONS WHICH, HOWEVER, INCREASED 30 PERCENT WITH THE OVERLOAD CYCLES. CONCRETE STRESSES OBSERVED AT RELEASE AND UNDER DESIGN LOAD WERE FOUND TO BE IN SATISFACTORY AGREEMENT WITH CONVENTIONAL COMPUTATIONS. STEEL STRESSES OBSERVED BELOW CRACK OPENING LOAD WERE AS PREDICTED AND COULD BE ESTIMATED WITH SUFFICIENT ACCURACY AT OTHER LOADS. THE PRESTRESS LOSSES WERE SEPARATELY EVALUATED AND COMPARED WITH BEAM BEHAVIOR; LOSSES WERE NOT INCREASED BY THE REPETITIONS OF DESIGN LOAD, AND ONLY SLIGHTLY BY THE OVERLOAD. THE BEAM WAS FINALLY TESTED TO DESTRUCTION; FAILURE BY CRUSHING OF THE CONCRETE OCCURRED AT DEAD LOAD PLUS 4.2 TIMES DESIGN LOAD, INCLUDING 30 PERCENT IMPACT, OR 3.1 TIMES THE DEAD LOAD, LIVE LOAD, AND IMPACT. NO BOND OR STEEL FAILURE OCCURRED. THE BEAM PROVED TO BE STRUCTURALLY SOUND AND ENTIRELY SATISFACOTY FOR ITS USE AS A HIGHWAY BRIDGE MEMBER FOR A LIFETIME OF SERVICE IN A MOST SEVER LOCATION. THE TESTS CONFIRMED THE ADEQUACY OF THE METHODS OF ANALYSIS TO PREDICT BEAM BEHAVIOR. /AUTHOR/

  • Supplemental Notes:
    • Vol 36, pp 103-128, 23 FIG, 5 TAB, 7 REF
  • Authors:
    • Knudsen, K E
    • Eney, W J
  • Publication Date: 1957

Media Info

  • Monograph Title: Proceedings of the Thirty-Sixth Annual Meeting of the Highway Research Board, Washington, D.C., January 7-11, 1957
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00209470
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: May 22 1972 12:00AM