FATIGUE ANALYSIS OF SHIP STRUCTURE. PART II: CRAB-EYE TYPE SLOT

Fatigue failure in the vicinity of the slotted parts of transverse web frames is an important problem in ship structure analysis. As the transverse web frame of large ships usually has numerous slotted parts, damage in this area can critically affect the strength of the ship. Nippon Kokan has carried out a series of small-scale fatigue tests of a slotted-part model of the transverse structure of a 130,000-ton tanker. The results confirmed that the so-called "crab-eye" construction exhibits excellent fatigue strength. Accordingly, a full-scale model fatigue test was conducted in order to compare the fatigue strength between the "crab-eye" type slot and conventional type slot and to determine the effect of a back bracket and/or collar plate. Fatigue crack initiation and propagation were observed under a constant load of 75 tons. Static stress distributions were measured by rosette strain gauges and also calculated by a finite-element method. It was confirmed that the crab-eye type is largely superior to the conventional type both in crack initiation life and crack propagation life. The results of this test have revealed various problems, especially those associated with welding, that had not been shown by the smallscale tests. Crack propagation is sometimes delayed or accelerated by the redistribution of stresses in the structure, which may result in the initiation of new cracks, simultaneous growth of cracks or variations of compliance in different structural members.

  • Corporate Authors:

    Nippon Steel Corporation

    345 Park Avenue, 41st Floor
    New York, NY  United States  10022
  • Authors:
    • Kawahara, M
    • Satoh, H
  • Publication Date: 1977-4

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Filing Info

  • Accession Number: 00310900
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: May 7 1980 12:00AM