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MATRIX ANALYSIS OF HULL NATURAL VIBRATION FREQUENCIES

STUDIO CON MATRICI DELLE FREQUENZE NATURALI DI VIBRAZIONE DELLO SCAFO

A matrix method is explained for the fundamental frequency calculations of hull bending vibrations, including the deflection due to shear force. For this purpose, the differential equation of a variable-section girder was written. This is due to the fact that the equation for a constant section girder, subsequently applied to each section in which the hull is subdivided, does not contain the terms representing the contribution due to the section variation. These terms should be independently considered at each step of the section. If a procedure is adopted in which these terms are neglected, the hull would be considered more stiff than it actually is and higher frequencies would be obtained by calculation. A FORTRAN II source program for the evaluation of the critical frequencies with the corresponding deflection curve and its derivatives is reported, together with the directions for the program operation. This program solves the eigenvalue and eigenfunction calculation problem. The results of some calculations are reported showing the amount of shear force effects when it is properly considered. These results were compared with the ones obtained by other authors employing different methods and with the actual values measured on ships in service. An analysis of these results shows the validity of the matrix method but on the other hand, the fact that the virtual mass coefficients are absolutely inadequate for this purpose, especially when dealing with higher frequencies. The need for directing research towards an adequate study of such coefficients is evident. In Italian

  • Corporate Authors:

    Registro Italiano Navale

    20 Via Vente Settembre
    Genoa,   Italy 
  • Authors:
    • Marsisch, S
  • Publication Date: 1967-3

Media Info

  • Features: Appendices; Figures; Tables;
  • Pagination: 30 p.
  • Serial:
    • Issue Number: 15

Subject/Index Terms

Filing Info

  • Accession Number: 00019320
  • Record Type: Publication
  • Source Agency: Registro Italiano Navale
  • Report/Paper Numbers: Tech Rpt
  • Files: TRIS
  • Created Date: Nov 8 1972 12:00AM