FRACTURE RESISTANCE OF FATIGUE CRACKED WELDED DETAILS

Fatigue cracks in welded details can initiate brittle fracture at low temperatures. Rolled steel beams of A36 steel and welded beams of the same size made of A441 steel with large fatigue cracks were tested at low temperatures. With some exceptions each beam was loaded repeatedly to a predetermined bending moment. This moment was arbitrarily chosen between 0.28 and 0.85 times the moment corresponding to start of yielding. If five cycles of loading at the selected test temperature did not cause fracture, the test temperature was lowered for another five cycle trial. Material characterization data, obtained with compact tension tests, Charpy V-Notch tests and tensile coupon tests were compared with the test results from the beam tests. All except one of the A36 steel beams fractured at temperatures below -140 deg F (-95 deg C). The cracked cross sections resisted bending moments between 0.43 times and 0.87 times the plastic moment. The A441 steel beams fractured at temperatures below -110 deg F (-79 deg C). The cracked cross-sections resisted bending moments between 0.20 times and 0.43 times the plastic moment. Brittle fracture of the compact tension specimens and also of the beams usually occurred after yielding of the ligament. The estimates of K at fracture of the beams were generally larger than the K values obtained using fracture test specimens. This is partially due to the relatively small thickness of the flange which produced plane-stress conditions. The full plastic moment of the precracked section at the critical temperature could never be reached before fracture occurred. The yield moment of the precracked section could only be reached in a few cases. (FHWA)

  • Supplemental Notes:
    • From the study "High Cycle Fatigue of Welded Bridge Detials".
  • Corporate Authors:

    Lehigh University

    Fritz Engineering Laboratory
    Bethlehem, PA  United States  18015

    Pennsylvania Department of Transportation

    P.O. Box 2926
    Harrisburg, PA  United States  17120

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Authors:
    • Hausamann, H
    • Roberts, R
    • Irwin, G R
    • Fisher, J W
  • Publication Date: 1980-3

Media Info

  • Pagination: 89 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00319780
  • Record Type: Publication
  • Source Agency: Federal Highway Administration
  • Report/Paper Numbers: FHWA-PA-72-3-11, FCP 45F2-212
  • Contract Numbers: 72-3
  • Files: TRIS, USDOT, STATEDOT
  • Created Date: Mar 12 1981 12:00AM