This paper gives an account of a hypothesis which states that for an elastic structure, subjected to limited forces which are decreasing or constantly distributed over the structure, the generalised force expression A sub T times F converges towards zero as the number of nodes in the natural mode increases. From this it follows that the summation by the natural mode method needs to be carried out only over a small number of natural modes. It is likely that one can as a rule avoid resonance between disturbance force and natural frequencies, if the structure is not too stiff or the disturbance frequency not too low. The question of the size of the damping is now also of secondary importance. As only a limited number of the lowest natural frequencies need to be included, the cost of finite element calculations can be lowered substantially, in comparison with a conservative calculation where the hypothesis is not taken into account. The hypothesis is illustrated in a simple example for a 135,000-dwt EMV tanker. Agreement with the measured vibrations was within 15-20%. Order from BSRA as No. 48,992.

  • Supplemental Notes:
    • Presented at the 22nd Nordic Ship Technical Conference (NSTM 77) at Lingby in 1977.
  • Corporate Authors:

    Nordic Ship Technical Conference

    Malmo,   Sweden 
  • Authors:
    • Haagen, T
  • Publication Date: 1977-10


  • Swedish

Media Info

  • Pagination: 18 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00182522
  • Record Type: Publication
  • Source Agency: British Ship Research Association
  • Files: TRIS
  • Created Date: Oct 31 1978 12:00AM