ON THE IMPACT STRENGTH OF SHIPS DUE TO SHIPPING GREEN SEAS

Many serious damages of ship structures in rough seas due to the impacts of shipping green seas, such as cave-in of the forecastle decks and the forward parts of upper decks, buckling of pillars between decks, dropping of hatch covers into holds, collapse of the bridge front walls and the others, have been frequently reported. Corresponding to these important problems, many researches have been made from the view points of manoeuvring and structural seaworthiness, but there is much obscurity in the problems of peak pressures of shipping wave impacts, their durations, the generation mechanism and the elasto-plastic responses of the whole and local structures of ships. The experimental researches on these problems have been made by towing a ship model of wood at various speeds in regular waves of varying height and length in the experimental tank, under the simultaneous observations of wave height at the bow, pitching and heaving motions, shipping wave impact pressures on the deck, longitudinal bending moments and the vibrations of whipping. The obtained results in these studies are summarized as follows: (a) The serious impact of shipping green seas on the forward deck of ship in rough seas is generated by dropping of the piled-up spray and the swelled-up waves and in the condition of scooping waves in the severe pitching motion. (b) The maximum gifle pressure of impact on the forecastle deck can reach 50 ton/sq. m. in the most severe conditions. (c) It must be noticed that the vibratory longitudinal bending stress of whipping due to shipping waves may attain to (40-70) per cent of the dynamically sagging bending stress of the running condition in regular waves.

• Corporate Authors:

  Society of Naval Architects of Japan

  23 Shiba-kotohiracho, Minato-ku
  Tokyo 135,   Japan 
• Authors:
  • Kawakami, M
• Publication Date: 1971

Media Info

• Pagination: p. 1-16
• Serial:
  • Selected Papers, J of Soc of Naval Arch of Japan
  • Volume: 8
  • Publisher: Society of Naval Architects of Japan

Subject/Index Terms

• TRT Terms: Bending; Hulls; Loads; Longitudinal strength; Pitch (Dynamics); Plastic deformation; Waves
• Old TRIS Terms: Hull bending; Wave induced loads
• Subject Areas: Marine Transportation; Vehicles and Equipment;

Filing Info

• Accession Number: 00035096
• Record Type: Publication
• Source Agency: Society of Naval Architects of Japan
• Files: TRIS
• Created Date: Oct 27 1972 12:00AM