FATIGUE STRENGTH OF COMPOSITE BEAMS WITH A REDUCED NUMBER OF SHEAR CONNECTORS IN HIGHWAY BRIDGES

THE 1961 EDITION OF THE AASHO BRIDGE SPECIFICATIONS BASED ITS DESIGN REQUIREMENTS FOR SHEAR CONNECTORS ON STATIC AND CYCLIC LOAD TESTS WHICH, WHILE INCLUDING A LIBERAL SAFETY FACTOR, DID NOT INVESTIGATE THE FATIGUE STRENGTH OF THE CONNECTORS. AN INVESTIGATION, BASED ON THE ASSUMPTION THAT THE REQUIRED NUMBER OF CONNECTORS SHOULD BE A FUNCTION OF THE EXPECTED FATIGUE LIFE OF THE STRUCTURE, HAS BEEN CONDUCTED BY PLOTTING STRESS AGAINST NUMBER OF CYCLES IN STATIC DYNAMIC TESTS. THE COMPOSITE BEAMS WERE OF THE TYPE 8WF 17 (ASTM A36 STEEL); SHEAR CONNECTORS 0.5 INCH IN DIAMETER WERE PLACED IN CONCRETE SLAB 30 INCHES THICK WITH A CYCLINDER STRENGTH OF 3000 PSI. SERIES A AND B BEAMS WERE DESIGNED FOR A REPETITION OF 500,000 CYCLES AT A RATE OF 100 CYCLES/ MINUTE, SERIES A HAVING A SAFETY FACTOR OF 1.4 AND SERIES B ONE OF 1.0. SERIES C BEAMS WERE DESIGNED TO THE 1961 ASSHO SPECIFACTIONS. IN EACH SERIES THREE BEAMS WERE TESTED CYCLICALLY, WHILE THE FOURTH WAS TESTED STATICALLY. FATIGUE FAILURE IN THE CYCLIC TESTS PROVED TO BE PROGRESSIVE, OCCURRING IN SIX PHASES. COMPOSITE ACTION IS EFFECTIVE LONG AFTER THE INITIAL CRACK OF THE CONNECTORS EVEN THOUGH CONTINUED CYCLING WILL EVENTUALLY LEAD TO COMPLETE FAILURE. THE RESULTS OF THE ULTIMATE LOAD TESTS CONFIRM PREVIOUS REPORTS THAT THE 1961 SPECIFICATIONS ARE TOO CONSERVATIVE WITH RESPECT TO THE NUMBER OF CONNECTORS REQUIRED FOR STATIC LOADINGS.

  • Supplemental Notes:
    • 38 Pp, 10 FIG, 10 REF
  • Corporate Authors:

    North Carolina State University, Raleigh

    Raleigh, NC  USA  27695
  • Authors:
    • Uyanik, M E
    • Jetter, F R
  • Publication Date: 1970-7

Subject/Index Terms

Filing Info

  • Accession Number: 00209358
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Dec 28 1970 12:00AM