INVESTIGATION OF DESIGN FACTORS AFFECTING FATIGUE STRENGTH OF REINFORCING BARS--TEST PROGRAM

A comprehensive experimental investigation of the influence of stress range, minimum stress level, bar size, type of specimen, and ASTM grade on the fatigue life of reinforcing bars is described. The experiment included 236 tests carried out on concrete beams, each containing a single straight deformed bar as the main reinforcing element. All the bars came from the same mill of a United States manufacturer. Test specimens simulated conditions found in bridge deck salbs and girders, and in other structures subjected to high amplitude repeated loading. Stress range in the test bars was varied to obtain fatigue fractures between approximately 50,000 and 5,000,000 cycles of applied loading. Minimum stress levels of 6 ksi compression, 6 ksi tension, and 18 ksi tension were investigated. Five bar sizes--Nos. 5, 6, 8, 10 and 11--were included in the experimental program. Tests were carried out on T-beams with the test bar at three different nominal effective depths--6, 10, and 18 in. Grade 40, Grade 60, and Grade 75 bars were tested. Primary emphasis was, however, placed on Grade 60 reinforcement. Evaluation of the test data, including a statistical analysis, is described in a separate paper. Minimum stress level, bar size, and grade of bar were found to have a small effect on the fatigue life. Type of specimen, as measured by the effective depth was not significant. Information on the fatigue strength of bars subjected to stress ranges above their yield stress, and on bars subjected to high stress ranges after having sustained 5,000,000 cycles at a low stress range, was obtained. A stress range of 21 ksi was observed to be a lower bound of all of the test data.

  • Supplemental Notes:
    • Reprinted with permission from "Abeles Symposium: Fatigue of Concrete, SP-41," American Concrete Institute, Detroit, Michigan, 1974.
  • Corporate Authors:

    Portland Cement Association

    5420 Old Orchard Road
    Skokie, IL  United States  60077
  • Authors:
    • Hanson, J M
    • Somes, N F
    • Helgason, T
  • Publication Date: 1974

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 27 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00129381
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Mar 29 1976 12:00AM