FATIGUE STRENGTH OF STEEL BEAMS WITH WELDED STIFFENERS AND ATTACHMENTS

This research (which is the second phase of a study intended to provide reliable information on fatigue behavior of steel bridge members), and an extensive investigation of fatigue effects in welded steel beams, which formed the basis for recommendations for revision of the fatigue provisions of the AASHP Standard Specifications for Highway Bridges. A hundred and fifty seven steel beams and girders were fabricated and tested to define the fatigue strength of various structural details, including stiffeners and attachments. Stress range was observed for nearly all the variation in cycle life for all stiffener and a attachment details examined in this study. For purposes of design the the fatigue strength of ASTN A514 steel rolled beams was found to be about the same as A36 and A441 steel rolled beams. The stress range-cycle life relationship described the fatigue strength for all three grades of steel. The beam bending stress range at the held toe termination was found to dominate the fatigue strength of full-depth stiffener details welded to the web alone. The bending stress range at the stiffener-to-flange weld defined the strength for stiffeners welded to the web and the flanges. For design purposes, the same fatigue strength values are applicable to transverse stiffeners welded to the web and the tension flange. The allowable bending stress range at the termination of the flange weld toe is the same as for stiffeners welded to the web alone. The magnitude of shear need not be considered when determining the allowable bending stress range for fatigue of full-depth stiffeners welded to the web alone. The welding of transverse stiffeners to the tension flange, the addition of new design categories to the AASHO specifications, fatigue crack growth, and the attachment of diagonal bracing to transverse stiffeners are other aspects which were studied. The empirical exponential model relating stress range to cycle life provided the best fit to the test data. A theoretical stress analysis based on the fracture mechanics of crack growth confirmed the suitability of the empirical regression models. The theoretical analysis also provided a means of rationally explaining the observed behavior and permitted the effect of other variables such as plate thickness and initial crack size to be examined in a rational manner.

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    Transportation Research Board

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  • Authors:
    • Fisher, J W
    • Albrecht, P
    • Yen, B T
    • Klingerman, D J
    • McNamee, B M
  • Publication Date: 1974

Media Info

  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 85 p.
  • Serial:
    • NCHRP Report
    • Issue Number: 147
    • Publisher: Transportation Research Board
    • ISSN: 0077-5614
  • Publication flags:

    Open Access (libre)

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Filing Info

  • Accession Number: 00272109
  • Record Type: Publication
  • Files: TRIS, TRB, ATRI
  • Created Date: Sep 30 1974 12:00AM