On January 4, 1978, major cracks were discovered in three adjacent rigid steel frames supporting an elevated curved section of the Dan Ryan Rapid Transit. Visual inspection of the cracks and subsequent microscopic examination of the fracture surfaces established that the fractures started at the welded junction of the bottom flange of girders that pierced the side plates of the frame. Fatigue crack growth was found in the junctions. Weld quality was poor, partly as a result of the geometry of the joint. However, the notch from the rough flame-cut slot was determined to be sufficient to initiate the fatigue cracking. Physical tests were made to determine the appropriate stress intensity factor for the steel. These tests verified that the critical combination of a severe defect, high stress concentration, and cold temperature, was sufficient to cause the fractures. (TRRL)

  • Supplemental Notes:
    • MFPG Failure Prevention in Ground Transport Systems, Proceedings of the 31st Meeting of the Mechanical Failures Prevention Group.
  • Corporate Authors:

    National Bureau of Standards

    Gaithersburg, MD  United States 
  • Authors:
    • Hanson, J M
  • Publication Date: 1982-10

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 00391528
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: Jan 30 1985 12:00AM