“Some
Hydro-Structural Aspects of Large Container Ships”
by John Kokarakis
The 8th
technical meeting of the Greek Section for the 2009-10 season was held on
Thursday April 15th at the Maran Auditorium in Athens.
The technical topic
of the evening was related to the hydro-structural aspects of large container
ships and the impact of related phenomena on the design. The topic was
presented by Gijsbert De Jong, in charge of technical developments for this
type of ships at Bureau Veritas. Although, these vessels have suffered a
setback recently, it became clear that research and technical analysis towards
better designs continues. Main hydro-structural phenomena presented were the
whipping and springing. The former is related to the effect of high pressure
loads at the ship ends on the stresses amidships. The later is an offshoot of
the trend for longer and more flexible ships resulting in lowering of the
natural frequencies of bending vibrations. This fact coupled by the increase on
wave encounter speed due to the high speeds of containerships might lead to
resonance effects and induce significant stresses. On the basis of both full
scale measurements and hydro-elastic analysis the effect of stress increases on
fatigue damage were studied. It was concluded by the presenter that for the
cases studied the effect on fatigue damage was up to a 10% increase. Finally,
container lashing analysis was presented as a “base excitation” problem and
there was an interesting discussion on why containers are lost at sea. Coupled
to this effect was the phenomenon of parametric roll which was also analyzed.
The presentation was concluded with a lively and interesting question and
answer session. As always the evening closed with the traditional get together
reception at the hospitable rooms of the Angelikoussis Group of Companies.
from left to right:
V. Dimoulas, G. Andreadis, P. Palaiologou, all three from Bureau Veritas, Piraeus; N. Dionysopoulos, current Membership Chair;
G. De Jong, Author; P. Lalangas, Chair; L. Chahalis, new membership chair ( 2010-12 ); J. Kokarakis, Vice Chair; K. Maounis. Secretary / Treasurer