ACQUISITION AND ANALYSIS OF ACCELERATION DATA

As part of a broad investigation with the objective of developing information on extreme values of load conditions to which cargo might be subjected, seven accelerometers and and unmanned recording system were installed aboard a dry cargo vessel on regular North Atlantic service, and data were obtained over a period of 15 months. The immediate purpose was to establish the basis for prediction of extreme values of acceleration which would be encountered by cargo in the vessel over long periods of time. The data acquisition system operated satisfactorily for slightly less than 14 of 15 round-trip voyages, or an efficiency of approximately 90%. Analysis was based on data accumulated for 30 minutes every four hours representing a total of over 8000 hours of ship operating time of which 6200 hours were in the open ocean. Analysis of wave-induced accelerations using a special purpose probability analyzer resulted in a maximum observed acceleration (bow, vertical) of 1.76 g's peak-to-peak. This value is within 6% of the predicted value for the same circumstances. Slamming or pounding combined with other phenomena resulted in higher frequency accelerations (in the range of 10 cps) in excess of 3.0 g's peak-to-peak. Contrary to expectations, the peak accelerations observed under conditions of "slam" or "pound" were largely the result of hull vibrations of a high mode, and were apparently excited in part by the second order of propeller blade excitation.

  • Corporate Authors:

    Lessells and Associates, Incorporated

    Boston, MA  USA 

    Ship Structure Committee

    National Academy of Science, 2101 Constitution Avenue, NW
    Washington, DC  USA  20418
  • Authors:
    • Bailey, F C
    • Fritch, D J
    • Wise, N S
  • Publication Date: 1964-2-17

Media Info

  • Features: References;
  • Pagination: 65 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00331937
  • Record Type: Publication
  • Source Agency: Ship Structure Committee
  • Report/Paper Numbers: SSC-159 Prog Rpt.
  • Contract Numbers: NObs-88451
  • Files: TRIS
  • Created Date: May 21 1981 12:00AM