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THE WAVE BENDING MOMENT DISTRIBUTION ALONG THE HULL

L'ANDAMENTO DEL MOMENTO FLETTENTE D'ONDA LUNGO LO SCAFO

The results of theoretical research aimed at determining weight distribution and hull geometry influence on the wave bending moment in confused seas for tankers and bulk carriers was covered in a paper presented at the 7th Symposidm of Naval Hydrodynamics. The results of the research are, in the present work, left out because they have been exhaustively exposed in the quoted paper; it is only worth noting that 3528 calculations of bending moment in confused seas were deemed necessary to perform the systematic research, covering several weight distributions, hull geometries and sea states. Calculations were performed by means of an electronic computer adopting a program worked out by Authors. A formula was finally obtained that furnishes the maximum wave bending moment value along the hull as a function of certain parameters representing hull geometry, weight distribution and sea state. The formula was checked by comparison of its values with those directly computed for a large number of existing ships; the maximum noticed difference was about 4 percent and, therefore, quite acceptable with respect to accuracy granted by the adopted theoretical method. The present paper is partly intended as a completion of the said research, and furnishes some sufficiently detailed information about the distribution of wave bending moment in confused sea along the hull. The results indicate that it does not appear possible to find a sufficiently approximate formula that can effectively replace the arduous direct calculation for determining wave bending moment distribution along the hull, once its maximum value is known. If envelopes are drawn of bending moment distributions relevant to all cases taken into account during the systematic calculation (inner and outer envelope), it may be noted that the distance between the two envelopes is at most equal to 10 divided by 15 percent units aft and 25 divided by 30 percent units forward, the differences ratio being about equal to 2.0. The comparison between the above said envelopes and those obtained with a similar procedure for a great number of existing ships shows that the assumed sample is adequate and significant; nevertheless, the differences might appear to prevent any possibility of applying the envelopes to actual cases. If it is considered that the highest variations are due to different loading conditions (and these generally occur to be very different for each given ship), it can be easily realized that, at an early design stage, the adoption of outer envelope may quickly furnish an idea about wave bending stresses along the hull once maximum wave bending moment is derived from the formula provided in the report. The necessity of working out direct calculations is evident where particular conditions occur. Moreover, it seems that the validity of the results lies within the range of accuracy of the adopted method and for parameter values not far exceeding the considered fields. In English

  • Corporate Authors:

    Registro Italiano Navale

    20 Via Vente Settembre
    Genoa,   Italy 
  • Authors:
    • Merega, F
  • Publication Date: 1968-9

Media Info

  • Features: Figures; Tables;
  • Pagination: 7 p.
  • Serial:
    • Issue Number: 23

Subject/Index Terms

Filing Info

  • Accession Number: 00019325
  • Record Type: Publication
  • Source Agency: Registro Italiano Navale
  • Report/Paper Numbers: Tech Rpt
  • Files: TRIS
  • Created Date: Nov 8 1971 12:00AM