SEAWAY STRESSES OBSERVED ABOARD THE GREAT LAKES BULK ORE CARRIER "EDWARD L. RYERSON" (1965-1968)

Over a four-year period from 1965 through 1968, hull bending stress, ship operation, and environmental data were acquired from the S.S. EDWARD L. RYERSON operating in Lakes Michigan, Superior, and the northern end of Lake Huron. The acquired show clearly that wave bending loads of significant magnitude occur only intermittently, in contrast to the situation on ocean-going ships where stresses of varying magnitude are observed almost continuously at sea. This situation reflects the environmental conditions. Furthermore, it is customary for Great Lakes captains to avoid serious storms, when possible, by remaining in port or seeking shelter. In addition to wave-induced bending stresses and changes in static stress experienced during loading and discharging cargo, so-called "springing" stresses are often of significant magnitude. Although the latter phenomenon has been experienced on ocean-going ships, it appears to be of greater relative magnitude here because of the greater flexibility of the typical Great Lakes ore carrier. A series of specific experiments was performed to test the effects of various headings, speeds, and wave conditions on the occurrence and magnitudes of springing stresses. It was concluded that the real source of springing excitation is the general presence, as shown by the wave buoys, of wave energy at such wave lengths and wave frequencies that its combination with vessel speed produces an encounter frequency very close to 3.40 radians per second--the RYERSON's natural first-mode frequency of vibration.

  • Supplemental Notes:
    • Prepared by Task Group HS-1-2 (Wave Loads-Great Lakes Vessels) of the Hull Structure Committee.
  • Corporate Authors:

    Society of Naval Architects and Marine Engineers

    601 Pavonia Avenue
    Jersey City, NJ  United States  07306-2907
  • Publication Date: 1971-5

Media Info

  • Features: References;
  • Pagination: 155 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00043584
  • Record Type: Publication
  • Source Agency: Society of Naval Architects and Marine Engineers
  • Report/Paper Numbers: 2-18 T&R Bulletin
  • Files: TRIS
  • Created Date: Apr 13 1973 12:00AM