stab1975 glasgow
TRANSCRIPT
All rights reserved.
No part of this publication may be
reproduced, stored in a retrieval system, or
transmitted
photocopying, recording, or otherwise,
and Naval Architecture, University of Strathclyde,
Glasgow^ Scotland®
Department of Shipbuilding
About The Confe rence
Programme and Timetable
List Of Delegates
Survey Of Delegates' Opinion on Stability C . KUO O f A. W . GORDON
Opening Address — Si r Samuel Curran, F.R.S. (Principal of
University of Strathclyde)
H. BIRD O f A. Y. ODABASI
1.2 Stability of
1.4 Rational Stability Criteria and the Probability of Capsizing
L. KOBYLINSKI
2.1 Environmental Conditions Relevant to the Stability of Ships in Waves — J.A. EWING
2.2 Experimental Study on Lateral Motions of Ship in Waves , H. F U J I I O f T. TAKAHASHI
2.3 Experimental Technique for
Research Institute
Y. TAKAISHI
2.4 A Scale Model Investigation of the Intact Stability of
Towing and Fishing Vessels —
2.5 Safety of a Vessel in Beam Sea J. DUDZIAK
3.1 An Analytical Study of the Mechanism of Capsizing -J.WELLICOME
3.2 Application of the Fokker-Planck Equation to the Study of the Mean and Variance—
M.R. HADDARA
3.3 On Capsizing of Ships in Irregular Seas — W. ABICHT
3.4 On the Statistical Precision of Determining the Probability of Capsizing in Random
Seas S. KASTNER
3.5 Methods for Estimating the Ship's Stability in Irregular Seas J. K. BORODA Y '
E.P. NIKOLAE V
4.1
The Ultimate Half Roll K. KURE O f C . J . BANG
4.2 Capsize Experiment of Box shaped Vessels — S.
4.3 Ship Capsizing in Heavy Seas -/.R. PAULLING, O.H. OAKLEY •
P.D. WOOD
4.4 Hydrodynamic Forces and Moments Acting on Two Dimensional Asymmetrical
Bodies
of a Side Trawler — A. MORRAL
5.1
Long
Term
5.2 Application of
Stability C .
of
5.5 On Dangerous Situations Fraught with Capsizing V.S. DORIN, E.P.
NIKOLAE V
Authors Index
capsizing have always been of utmost
importance to seafarers and to naval architects. In simple terms,,
stability determines the safety
understanding
stability concept. It has become over more necessary to study
the stability of ships
and ocean vehicles in
a
hydrodynamics and statistics, but a proper physical understanding of
all the phenomena involved,
effort, and the
adaptation that follows, has been devoted only to limited aspects
of
attempted
to
of
it has become
essential to establish a means of communication between those actively
involved in
findings,
a) to provide an
operation, research or regulatory purposes to discuss the
available
results can be applied in pratice,
The Conference programme was divided into five
separate sections to
future direction
Experiments^ Theoretical Studiesj Correlation of Theory and Experimentj
and Application of Research Findings. The final programme item was a
"Quiz Session on Stability" in which Conference participants had
an
opportunity to question directly a panel of experts from shipbuilding^
shipping, regulatory bodies, research and education,
I am very fortunate that in making up t l i ' e programme
I have received
the technical backing from Professor S» Motoro, Department of Naval
Architecture, University of Tokyo, Japan; Mr. J.A.IL Paffett of Ship
Division,
Germanyi and
Mathematics, University
England, I offer them my sincere thanks.
¥e are grateful too to the U e K » Departments of Industry and Trade for
the support they have given
us
are also due
to Miss. Ja Chamber's, Secretary to the Conference and others in the
Department of Shipbuilding and Naval Architecture who» in their
different ways, contributed to the success of the Conference,
namely;
Dr. K » J . MacCallum, Dr. A.Y. Odabasi, Mr. S.P. Grieve, Mr. G. Hearn,
Mr* R » Oskan, Mr. Jo Frank and Miss,
G. Short,
Richmond Street,
F . R , S , ,
University of Strathclyde,
, N. Bell
Future"
Safety Concepts"
2.2
2.3
2.4
2.5
Paffett (Ship Division, N ^ P r L s )hair ans Mr» J
2.1
Fujii, I I » and
1930 RECEPTION AND BUFFET GIVEN BY BURMAH OIL COMPANY
in the Assembly Hall,
Coffee
3.3
Abicht, ¥. (Germany)
"On
(U,S.S,R. )
Stability in Irregular Seas"
4.1
1530
1600
4.2
4.3
4.4
4.5
"The
and
Wood,
P.D. (U.S.A.)
Kobayashi,
1900 for
1300
-1130
Criteria in a Random Seaway"
5.2 Kuo, C.
"Application of Dynamic Systems
Stability"
Coffee
Chairmans Professor M. Meek (Ocean Fleets Limited,
and Visiting- Professor)
Mr, A,M. Spassky (iMCO Secretariat)
Mr. S. MacDonald (Royal National Lifeboat
Institution)
Tea
ADAMS, Mr. R.,
Ocean Fleets Limited
ANDERSSON, Mr. B.,
Sikob Limited, Sweden
BATES,
BECK¥ITH, Mr. L,, Lloyd*s Register of Shipping
BELL, Mr. N. , Department of Ti-ade , London
BIRD,
BORSUM, Mr.
BRAMDT, Professor H., Technical University of Berlin
BRIDGE,
C.
Board
COSTA, Mr. A.,
of Trade, London
D.
BERN,
DORIN, Dr. VaSs, Krylov Research
Institute, Leningrad
E.
EL-BADAN, Mr, A o, University of Strathclyde
EVANS, Mr. J«,Marine Engineers Review
EVANS, Mr. K.G,, Ministry of
Defence, Bath
Institute of Oceanographic Sciences
FAIRLIE-CLARKE, Dr.A.Ca, Brown Brothers & Company Limited
FERGUSON, Mr, V,, Scott Lithgow Limited, Port Glasgow
FOSTER, Mr.
G.
GILFILLAN, Mr. A.W., Y-AED Limited
GLADISH,
Mr.
London
GULIEV,
Professor
L. Meyer
GREENIIOV, Mr. P., Ocean Routes Limited
University of Strathelyde
8
Association
JOHNSOM,
KAPLAN, Dr. Pa, Oceanics Incorporated
KARLSEN, M , So, The Ship
Research Institute of Norway
KASTNER, Dr. So, Technical
KRAPPINGER, Professor 0 » , Hamburg University and Hamburg
Ship Model
KUO, Professor G » , University of Strathelyde
KURE,
LLOYD, Dr, AaRsJaM,^ Admiralty
MACCALLUMg Dr.
MCNAUGHT, Mr» D.,
MARTENS, Mr. P « , A.S. Mjellem and
Karlsen Limited
MASUDA, Mr. Ye, Nippon Kaiji Kjokai
MEEK, Professor M o ,
Company
DE,
Guard^ U.S..A.
MONKS, Mr. A.H., Ministry of Defence
MORRALL, Dr» A » , National Physical Laboratory
MORRISON,
Tokyo,
Japan
NIELSEN, Mr. G » , Danish Shipowners* Association
NIKOLAEV, Dr. I « P « , Krylov Research Institute, Leningrad
NUMATA, Mr. E., Stevens Institute
of
ODABASI, Dr» A » Y . , University
of Strathelyde
PEACH, Mr a
S.
SCATCHARD,
of Trade, London
SPASSKY, Mr. AeM., IMCO, London
SPURLOCK, Mr. DoJ,,, Natural Env-i
romnent Research Council
STRACHAN^ Mrs. J., Fishing News, Peterhead
SUHRBIER^ Mr, K ^ R ^ , Vosper Thornycroft Limited
SUTHERLAND, Mr. e , White Fish Authority, Scotland
T»
Institute
TANAKA,
Mrs
F»
TEMPLE, Mr, P » A ^ , P & 0 S^N. Company
THODE, Mr., H» , Vorband der Deutschen Schiffbauindustrie e.,V.
TOBIN, Mr« J«F.K., Lloyd's Register
of Shipping
TSUCHIYA, Mr, T « , Fishing Boat Laboratory, Tokyo
U.
VINJE,
¥,
AB. Sweden
WELLICOME, Dr. J « , University of
Southampton
WILLIAMS, Mr. R o T s , Cammell Laird Shipbuilding
WINXLE, Mr. I » E » , The Northern Ireland Polytechnic
Z,
tinguished experts from aJ 1 over the world to a
particular
3n this case the location vas the University of Strathclyde,
Glasgow and the subject
purposes
eve] for
(b) To facilitate the use
of
encourage the practical application of the
rosulLs.
was
the
ono roof to examine stability. The opportunity Lhus presented
to elicit the
opinions of su^h a group was too good to miss
and thjs brief report comments on the methods adopted and the
results achieved in a delegate
survey. The organisers would
like to thank the delegates for taking time to answer their
quesTJons and it is hoped that tlicy wil3 find Lhe results or
Lho findings to
2. £ii2 IL.I.2--AlJ-l ^ --A ^
It was decided thaL
uhe use of two soJf completion question-
naires, one to be adminisbored at the opening session and one
on the final day, would permit a
study of current opinion to-
gether wi bh an inclinaUon of
how,
t l i e nain a i ms of
the ques Lionnairos were to establish the
views of par LieLpants upon
the existing methods of dealing
with stabji-i ty and the areas of
f c h e subject Lo which they be~
lievod future
and
nrcspoc Lively to thj s report* Their design kept s-imple
with respondents required either to tick relevant items or to
rabo
various
given
attempts
jnformatlon as possible from a limited number of questions which
may
language difficulties often encountered at international con-
ferences .
As
24 hours to complete
the first questionnaire but only a matter of minutes to com-
plete the second,
Of the eleven questions in the opening questLonnaIre
four were
wibh methods of ImprovLng these criteria, one on the importance
of various factors for a fresh approach to stabjiity,
one on
studies and two on the participants* interests in ship and
ocean vehicle stability.
these
to tw o
of these latter two
•was to establish whether
participants * views on the methods for
improving the treatment of intact stability
and on the direc-
The analyses
straight
percentage
of relative importance
ng system was also applied. Thus, in addition
to a direct
to a
second and
1 to
possible* It
more
percentage firsL choice comparison.,
3. STOIMARY OP CONCLUSIONS
and we have
These are as follows?
tne existing stability
unsatisfactorys
2
) 2E
ro
om
2
n
.£S
Opinions wcic* &pl JI on the be&t way of inproving the treat-
ment of in LacL sLability, The rank order ot comments varied
little over f c h e two questJonnairos with approximately one
third requesting cri ten a and a quarter the develop-
men f c of a fresh lioafcment. 4& > the
Jattoi could presurnabJy
conclusions
factor rating
in that f c h e req esb for the
development of
a fresh treatment gained 20 more support in the second
quosfcionna]re whereas
h)
research were seen a f c > s ~
effects of waves,
A1.1 the other li&tod research areas attracted some support
but perhaps the i i i o s L surpri-s ing
feature was the
wind effects",
about what to do
6) J^^ht^ngArm^^rve^
hy^o of respondents foil
that
the
rit ri based on "Lhc use of the various features
of
the
acceptable method for
4i' > quasi-st ti effects
effects.
93
question on meta-
centn c hei ht (Gil) of which a .large majority (60'/J of al
respondents, 80 of
sidered
remainder thought tha itwas not unportant as long as
ithad a psiti value. O the 72^/0 who answered the ques-
ti
0
'3) Dual Criteria
The suggestion tha
The two nost important factors ina new approach to stab-
ilit rit ri
ictyto apply inpractJce* The fact that Lhose could be
conflicting requirements is
rai of a theoret caL
base to new crit ri itappears tha tliore was
sonc con-
JO) Sei
incorporated motion characteristics was required to s
tab-
i1
dLroct transfer of
e\.isLing shp
crit ri and
a furt r 3% required direct tr sf r wthm -nor m fi
ca fc ions•
3l) Future Conference
91 of respondents favoured a furt r conference on ti
topic -^-n or before 197
1
said "no" or
aspects of
to be
the opport-
un tyJt gave Lo keep up bo date i- th various research
studies (55 ) and the op rtunt to meet olier partLea-
pan ts (23 ).
93 respondents ( 6 < - ^ or
pre-cn'nfp'ronce nuestJ onna-i re and 1- 7 (64 )
the
post-conference
one. The sli tl lower response rate inthe second case was
due to some delegates hangto leave erl . For sef
con-
plotaon
hgh
wore designed to elicit the principal reason for the respond-
ents Interest
and their area of work. It
had been hoped that these could have been used in the analyses
of
responses
to
would have on responses.
ively low numbers involved, this
form of error tabulatjon
that
However, to illustrate the
were as
esting and, to a crt extent, puzzli pattern which was
probably due to the r stri ti construction of the
qucst-
jonna-i re which had not allowed for explanatory remarks. The
results were as followst"
i) IIeet the practical needs
ii) Prove unsatisfactory
100
b) The present criteria based on the use of the various
features
method for incorporating?-
i) Static effects
ii) Quasi-static effects
iji) Dynanic effects
opinion
agreeing
41
7
— z
100
been
the 49 vho find the existing methods
unsatisfactory in
all of them unsatis-
factory but only certain parts if the responses to the second
question are to be compatable. Similarly, 15^> of the respond-
ents who either lacked
answer the first question
second.
vcre notable in that 25 and 2 Q
c
ondcnLs feit unable to
respondents thought that
a know]edge
whereas
wao not important
a positive value.
of the 72'/o of
m were
72
Thus 300 mii and noro accounted for 7 6 of respondents who fet
able to answer the question.
,. .
need to have one
design purposes
was need fox'
fet
i rporai otion characteristics was required to stablity
rit ri of semi-submersibles. Only
2% supported the use of
xisti ship
y/J
could be used.
^mp^ovemcntofthoT'reatmentofTntactS^a^
This question was asked inboth the questionnaires and the
answers in tlie first instance inrank order of the number of
mentions to t e firat questionnaire wore as follows I -
1st 2nd
u On
33°^
practical data
21 17
24^>
ri ti arm curve
note that the onyitem
t ri ". he
which t l i e
"collection and analysis of more practical data" losts
The
"extensive training of
masters and operators" which dropped by ^O^o and the 10 of
total responses this represented was gained
in
equal
arm curve" and various
The effects of the conference proceedings themselves had app-
arently nade themselves felt. By roworki-ng the percentages on
„
1. Bettor stability criteria 33
2. Develop fresh treatment 22
3» C o l l e c t and analyse more practical data 19
4. Extensive training of
masters and operators 15
6. Others ^ JisJi
second questionnaire is due to fresh ideas being suggested
which djd noL fit in witlx f c h e five
groups
nor"
Re1ati^e^^npo_tanco^of^ractors_inRe^^
Again the same question was repeated in both questLonnaires
witli respondents being asked to rate the relative importance
of possible areas for further research on intact stability.
On a percentage
fo1 lows;-
1 2
experience and feed- 17
5« Pducation oC slu p masters
and operators 9
6. bcaled model
(The percentages were rounded off and thus not all columns
total 100)
in tlie changes
although based on the
However, when the responses were weighted 3? 2, 1 for
f-irst
different picture emerged^
£~— H2 -.
1.
EFFocts
2 "'.later on deck 2 3 3
3. DcveJoping Fresh
experience, etc. 3 =
6. Vind errocts 6
7. Lducat-Lon, etc. 7
On Frequency or nonbJon thcroFore tho "orrocts or waves" took
prcccdonco on the "development or fresh methods" which gained
considerable support "in the post-conForcnce quest i onna-re,
3ndood i
t was ths swing win ch deposed "water on deck" Froi
second posi "felon to
positions
Tn the end L scolded sarcr to conclude tha irrespective oF
which way tliodata were analysed there were
bliroc
groups in
descend-ing order of prior-ity frori the delegates po t oF view.
Group J ^^FFoc i/s oF waves and Developing Fresh notliods, etc,
Group
2 Vatcr on deck, Gathering oF Ful 3 scale experience,
c Ic.
Vind cFFects and
Tie Fact tha "wind cFFects" rated so lowly occasioned soiie
surprise as tho importance oF these eFFects js g r l rccog-
n
Ged.
t so 1 i
ILs ra iii", as a possible research area
Js nob Fu3 1y apprcc i ? fed.
i.o^at vc^nnorLancc^oF ractors^^^
On tlie Fst quest orna re doJogatcs were asl>-od uo rate jnorder
oF iriportanco Lo blion
any rTcsh s Lab
be developed could lie
a porccn Pg^ baGcd o-i F^ rsL rospo isc uho
rab;ngs we "e aa Fo11ows;-
1. Sinpl
inFluoncing Factors as poss'ble
5. Be
changed places
To file
imi i ti ated observer Lhose result scorned to show a
cerLa n degree oF
rac bors cons Lderc^d tlio i
ore
ajid tlius tlie loss s 1 '
ip 1 c to apply ' i practice.
Si u 1 < - i - > ? 1 y
a
basis and if there are theories
in existence which are incapable
of implementation in practice,
they should be discarded
and tho response pattern may
have been d - i
dated by the restrictive
nature of the qucs tionnaJ re* This docs not appear very probable
as space was left for respondents to write
in other factors and
been made on both questionnaires and
none is
most
studi es 55
3. Able to use knowledge gained 1^ 1
4. Opportuniby f c o take part in discussion 4
5.
in further comments mostly favourable.
The maJor criticism was that papers should have been d i - s t r i bubed
well in advance of the
actua] conference* Tn
seems conimon to all conferences, it
proved inpossible to receive al l tho papers in. tine for printing
and prior d i stribut i - o n . Two papers
arrived only ten days before
tho conference commenced. The point has
been
was no need for any
further conference
on tills top-ic, 35^/0 of the respondents requested a follow-up in
1977, 56 in 3973 and only 9 after 1978.
I^tTO^al^St^bilTtyOriteria
The fjnal quest-ion asked delegates
whether they
in the near future. ^ h ^ o said they
wore, 30*^ said they were not
and, 16' did not known IIany of
the negative respondents indi~
no to f c h e
"near" future
and not
of
CK/JC
C K u o BSc Ph D F R I N A
Professor o f S h i p b u i l d i n g an d N a v a l Architecture
Department of Shipbuilding and
Dear Participant,
(a) To provide an , opportunity at
international
further
systematic manner, we are
your help in carrying
you to
complete two
short questionnaires.
The first is with this letter and as we plan to
provide a of
during Conference, we
questionnaire as
27th March, 1975 will be incorporated in the
proceedings.
of will on your full co-operation
and we you will give us your full support so that the survey can
provide useful information.
T_JJNVERSIY_F_STR CDE
25th-27th MARCH. 1975
appropriate)
stability
Not enough information to form
an opinion.
ship stability criteria which is
b t t , s o d on the use of the various features
of
D
Not enough information to express an opinion
( - • ) Do you regard a knowledge of the magnitude of matacentric height
(GM) as
j j
very important
i——I
has a positive
other, please specify
(4) For a ship with length less than 100 m, which of the following
minimum metacentric heights do you think is realistic?
10 mm 100 mm 200 mm 300 mm more than 300 mm
D
APPENDIX I
(5) Do you think there is a need to have one stability
criteria for
Yes / No
(6) Which approach do you regard as the best way of improving our
treatment
arm curve
Others, please
specify
(7) In a successful fresh stability criteria, how do y ou regard the
relative importance of the following factors?
(Please rate, 1. 2, 3, etc. and where you feel two
or more
Easy for design purposes Simple to apply in practice
Be theoretically based
influencing
sem-submersibles should
the existing ship stability criteria with refinements
D
(9)
would you rate relative of
the following possible
research
(Please rate. 1, 2, 3, etc. you two or more topics
are of equal
with equal ratings).
experiments
of
scale
Developing fresh that would
Design Operation
Others,
please
specify
AT GAINING GENERAL TRENDS)
(1)
If there is to bp another Conference devoted to intact and damaged
stability in
the future, do you think it should take place in
1977 1978
No for any further Conference
(2) What aspect of this Conference have you found to be most satisfying?
Able to meet other participants
Able to up to date with
the various research studies
Other, specify
regard as the
Better stability criteria
Develop fresh treatment
Collect more practical
you now rate as the relative importance of the following
possible for further studies on
intact stability?
Wind
Scaled model
Education of
ship operators
APPENDIX II
(5) Are you more hopeful that a rational stability criteria for ships
will now emerge in
AT
you who have come to
attend this International Conference
±s to ' b e the stability of ships and ocean
vehicles, I think it is
a very appropriate occasion for me
to address a Few renarks to the company because it gives me
an
the Anderson Building of the Universi ty of Strathclyde and
to wish the Conference every success but to
say at the same
applied sciences and in the problems
of
Industry.
sponsored
this
Con-
well-being of
in the United Kingdom,
The university traces bade its foundation to 1796 and the man
on whose idea the University was founded, Professor John
Anderson FRS, was passionately interested in the collaboration
of universities
Revolution^
tackling the problem and trying to make the universities of
his
a large number of his
friends, most of them concerned with business in one way
or
name and one
stature. The second member of
staff was Birkbeck himself who
left the Institute in. the
early 1800*s whose work in London led to the founding
of what is now Birkbeck
College, Without doubt it was not
a philosophy which was
among academics of Andersen*s
time and indeed it was a philosophy that has not been popular
until very recent times. This is
really
why,
in
the history of the Institution, it was
not
would be a University in its own right and one
concerned very
The University has over 8,000 students §, nearly
2,000
postgraduate work and
postgraduate work, Tt is important
to stress that part-time
complement because it shows that
there continues to the pre-
sent day a great range of links between .Indus try, Commerce
and the Universifcy and that these links result
in
flexibility
study and research for higher degrees.
It is more than 100 years since applied mathematics and some
of the engineerxng subjects were recognised in the establish-
ment of Chairs in the Tnsticution and indeed this year sees
• us celebrating the Centenary of the
of
the
Chair
in MathematJ c - s . Applxed Maths has been pursued long
before that date® A of you
here • w i . l l no doubt
be
and some
It
is
difficult to find sufficient resources in universities
in these txmes it is to be regretted that one of
our more
a
abandoned
by
thoroughly applied study,
When costs dominate the scene then it is time to use our
intelligence to the maximum possible extenta
" W e in the U » K »
lack today in money matters but while saying this I would
stress one thing, with due deference
to those of you from
overseas,
capa-
city to think and not markedly on an ability to spend, al-
though at
conferences such as
their
ideas and no conference could be more timely than the
one that
you
sections
Others cover Environ-
lation of Theory and Experiment, and Application of Research
Findings.
part of the oceans de~
serves close study in all of the fields that are listed and
I
do
ference will be well rewarded and
that some worthwhile con-
supporting
team have laid the foundation for a most worth-
while meeting of about 150 of you from a great variety of
countries.
The name Strathclyde, meaning the Valley of the Clyde, was
not chosen by accident because for
many
inter-
building
people in this
subject of your Conference
any time in the
Past ,
Future"
1.2 Krappinger,0. ( G e r m a n y ) "Stability of Ships Modern
Safety Concepts"
1.4 Kobylinski,L. (Poland)
'Rational SablityCriteria and
Probability of Capsizing"
cluding ships, are designed, produced
an d operated to fulfil specific func-
tions efficiently and safely., In that
respect the stability of their motions
can b e of crucial importance
and
it
to review the past and the present
knowledge
of past developments we have concen-
trated on concepts
rather than math-
account of
formative® We have also tried to
highlight the state of the art by
distinguishing between different theor-
special
place
the conclusion that the existing cri-
teria are not adequate both from
theoretical
on the
suitable respectively for the ship
master and for the approving authority®
In preparing this study we have used
all the material available to us and
even with such incomplete information
it has
interest of
to quote
We could not obtain or refer to
all of the numerous contributions
from USSR, East European countries,
and Japan, either because they were
not available, or were in a lang-
uage that the authors could not
understand® Thus, w e will be de-
lighted to hear more about the con-
tributions from those parts of the
world®
the
relating to damage stability as this
would open up a much w ider field®
In avoiding discussion of those
problems, however, we are fully
aware
criteria,
M E N T S
The development of ship stability
theory has had
complete® Throughout this period,
paper we shall classify them in
three
groupst
stability in still water
of ship motions
This classification is arb-
helps
us
atically,
can be
of stability, and
entative quantity,
Certainly the
The principal in
the metacentric radius, B l l ^ as the
ratio of waterplane moment of inertia,
I, to the
which was
used as
•where 1-03 is the •vertical coordinate of
the centre of
the v ti coordinate of the centre
of gr t . The ri i lever was
approximated by GZ = G-M
radians« •
culations of the ri i levers which
•was given as
emerged wedge,
tical distance between the centre of
buoyancy and the centre of gravity,
V
introduced
which
quasi-
under the influence of some potential
external forces and expressed this
work
as the inequality J ""[(e-) - M ]] > 0
o
righting and heeling moments, res-
pectively, and " ^ is the
ing motion.
architects, his principle has not
been developed further till the last
decadeo
other
possibility of applying
expression
ing
by
influence of the variation of right-
ing moment
others. This latter improvement
shall dis-
Simultaneous
ships in
motion itself.
Again we
may summarize
pression for rolling motion in reg-
ular beam seas, by assuming
that
the
length,
not alter the wave form. In 1874,
he also introduced the damping effect
by using the best empirical damping
as
dn
number of oscillations,
mined from experiments, (8).
In 1896 and
an d the theory of rolling was further
developed on the basis of what is
knowi as the Froude-Krylov hypothesis®
Manning, (ll), included the influence
of ship's speed and wave direction by
introducing the period of wave encount-
er while the various other aspects
of
rolling
(l6), Uysell (I?)?
and many others®
their
stability
19th century AaM.
body® This study, however,
stability understanding® Though it
was quite correct vhat
whole capsizing event is a dynamical
event because statical states of
equil~
possible influences of nonlinear
Baumann (23),
analysing
ship
motions
(28),
in the study of nonlinear ship rolling.
Later
developments in the state of art.
The final group of studies were aim-
ed at determining a
criteria. It is known that load
line
but the real efforts for establishing
rules in ship stability came after
l870»
"Captain", capsized and this
ing of the 20th
because of a
to
at
tried. Here we summarize
judging the stability was the initial
metacentric height® In the beginning
of the 20th century,
metacentric
height
his com-
the righting moment
arm» Some of the proposed minimum
GM values
c^ is the block coefficient and
A
ship,
k
in the
for good
B R = GZ , _ + BG sin-^- „ As will be
i- fT • W
equa-
curve as well as various heeling
moments®
Parallel
itial
metacentric
This
but it proved unsuccessful in prac-
tice due to various shortcomings.
The use of the righting arm curves
for judging stability was first pro-
posed by Reed, (32)® Nevertheless
the use
of this
stability criterion was in frequent
use
in
the
up to a of 10
on in
motacentric height*
GZ > 0.14 E 20
^ '3 5
ttte Vy . defined
li
openingsji an e of heel for shfti
of cargo ^
rit ri ,, i ud the IMCO crit ri
d)
also as a stablityCT-lterd one
In1913» Benjamn (3 )» Hs pro-
posal at r compa iig ci l r ntunber
of vessels which operated siiccessf'ullya
lie to the cone 1 •usio-'i i the
mn um dyna cal le-ve-r i »irer%
1)
2)
ing- anges Later Ben.]amri, h sef,
modified hsproposal offered a
he proposed a J m t angle arxl i-equired
tha tlie
must be equivalent to or gz'eater than
the oF tlieloia-1 work
force and
eng-ers on board.
In1939» Raliola, i hd s Pli«D», t sis,
(37)? made a si fl contri uti
towards ach-ieving- wcJrlcable stablity
eFfective
»nd.§, •wa.'veSf ana
ntud of GZ value the
corresponding were suffi t
stablityof considered
by Steel,
fclio nature of the cargo,
"Yamag-ata, in1959, (-40)
Japan® The approach, sim-
dytiainic st blit crit ri
for
dyna c
at the 1mk an e which the
lowest of -8m , fl an e
or 35 degrees,
displ.aceme.at considered® lie con-
t ri the
shp at r the
for the of gyrations
Maritime Consultative Organisation)
Thomson and Tope, (44), more gener-
ally® The outcome of the studies were
certain recommendations for judging
little difference from Rahola's
later.
Later
results
tinues and
follow-
ection and Grim, (20), and Wendel,
(45)? were the pioneers of these new
developments» They both introduced
with time
way, but used
idea was not new» Pollard
and Dudebout,
Here we shall summarize
of con-
Wendol's approach®
Statistical analysis
30 and
Inspired
group of naval
ility condition
of the ship®
wave geo-
ship length. It was pointed out
that the worst condition arises when
the crest is
impose a
allowing
sinkage
effect, e»g. the effect of orbital
motion of water particles,
(49)» Upahl, (50)5 and many others.,
In 1952,
Grim dealt
where I is the virtual
mass moment of
inertia about the
in
frequency, t
angle of rolla By
Mathieu*s equation, he pointed out the
possible instability regions® In
where
The
the stability
forms the basis of the majority of
today*s
research activities®
(23),
and
Rosenberg, (25), indicated possible
work tried to discover some unstable
regions from the results of Hil s
equation®
liThile
of
St» Denis's
introduction of
ject, Cartwright
and Rydill, (28),
Kato et® al», (56), presented an ex-
perimental study for irregular wind
and wave conditions® The study car-
ried out in Japan
by a group of
(see Figiire 3), De Jong, (6l), in
his Ph.D. dissertation tried to solve
the problem
Planck-Kolg-omorov equation and defined
of threshold crossing* Similar
theoretic-
ally
and
features
to-
of
the
determined
the
approximation
way or
com-
putation.
(67 ) » have been further
tributions
which
will cover the grounds which were left
open by us and moreover will contribute
towards a
judging the
tions or recommendations is fairly
ob-
task
con-
ditions, environmental
from
a
the case one would
or an oversimplified
the problem,
column in Table 1» it will
be
appar-
perienced
in
of dis-
more Important, from the latter®
Furthermore, there is invariably a
good deal of speculation about
cases
the above sample®
a clear-cut case of inadequate stab-
ility
illustrated by the
deemed inadequate (e»g® by IMCO stan-
dards), absence of a
what sea conditions might
those
ships
learned from
preferred simplicity and
ility
all the proposals
today we may meet three main groups
of criteria in assessing the stability
of ships, (43), (68),
mulae
teria are
for
ility
ical evaluation of minimum
pillar diagram
plied by many
ation of heeling levers for
comparison
shall summarise the last two methods
of assessing the stability»
IIICO requirements on statical
cargo ships, G i l ^, Os 35 metre
for
timber
axi um vue
radians at ^-= 30°.
ynamcal lever ^ Og09
-0 = 30'' must be greater
than
Additionally, for passenger
less than
h) During the
10" under the xnfluencc of the
moment
Vo is the service speed, L is
the waterline length, T is t l i e
draft,
gravity»
IIICO rec-
those obtained by Rahola (see Figure
1),
a proposal submitted to IMCO
by the
M is calculated by
metre)
is the projected lateral area above
the effective waterline, and Z is
the distance between the centre of
the projected lateral area
is first necessary to calculate the
amplitude of rolling -^ by the for-
mula
and 7^
diagram, the capsizing moment is
II A .0 II
(tonne metre) I I = A . BC
sil be followed Fur 8,
As,
txxo^o T ^ O C ^ ^
only- £i firs
Although altesi'nat.i've proposals
i i usi'v ®
up a
isti of
Those than
examples that IMCO z'ecommend-
fi t to pi'-crvde
basic reasons causing
Q fnPySd€
where .necessary (see Appen-
part .in
chapter's, the stablit of
curve wii is
detormined froni the
and by hypo t i wind and wave
forces •which, are a.ssu.raed
to the st blit of a. conse.r'vatx've
•system,, As a nura, of
•fche "fcliGor'y o x " * oxd3.Ila. '"y diffGr'Bii'fcis.l
if isno
her e li i'
hl appreciating value of prac-
ti exper'ience and accepting
we to dra.-w at ti to
the f l wn aspect»
tlia
of
on
g
a
ap»
justified,
d) The especially of
so-called "existing" ships are
neglected®
statistical weight
so obtained not
executing
certain
oscillatory
to introduce them into
GZ-"^ ¥hile this is
cover
thought to be exceptional cases*
3) There is a dangerous
tendency to
common with ships so far as the
stability of motion is concerned.
They certainly make their maxi-
mum rotational motions about one
of the principal
axes for which
ertia is minimum, and considering
the large asymmetric superstruc-
•with one of the symmetry axes for
the underwater part« Furthermore,
on
made
mathematically, see for example
(74), (75)» no stability criteria
For
ment on current criteria is on
their
•without any
no
incorporate the stability criteria
ational zones and seasons•
plies with the IMCO recommendations
and this is the final word to be
said a Thus, in that respect^
no
ships and floating offshore structures.
According to the general trend these
activities^ we may examine them in
certain groups.
The first
by
corrections.
attempts are made
insufficient to provide safety
ing structures and the studies
carried out may yield trivial res-
ults» if the motion dynamics are not
considered.
fluence of following and quartering
seas, mostly from a statical point of
view* The aim of these studies is
to devise
a ship under the action
of assumed
useful results, it will
statical q uantities® The difference
between the statical and the dynam-
ical uses are best illustrated in
Figure 9®
histories in case, even loss
in restoring moment does not give
a significant
has been
in
length,
tions of motione
relate
timate goal of this
the ship*s stability from its
motions
the stability of ships®
There are nevertheless, certain
broader
naval
remarks;
mathematical
outcomes
before®
be applied in practice* In that respect
we
1)
practice although
sidered first;
inition of stability in of
motion char-
a yield only a point on a
are
stabili ty in order
relations between the
seem to
be of
we -wish to achieve progress in
the practical application
message clear" and precise by
emphasising the
In the authors* opinion, the use
of somewhat more sophisticated
difficult provided
terpreted, Application in con-
philosophy,
types of cargo appear to be ig-
nored in some of the theoretical
studies, although in
vital
Bulk Cargoes introduced by IMCO
(78), as a
making some modifications and
of lost
of fishing vessel casualties
of vessel which has
at
sea
take manoeuvres, in order
it is necess-
ulations for fishing vessels.
ship masters are not always able
to
ascertain
on stability theory and
time.
easily and quickly used by
ship
of Trade, (79)• Since it
establish very
simple stability
ditions^ it is
desirable to dev-
an d on e for designers and approv-
ing
to play®
so-called
5?
products
ships and
urgent especially for masters of
small ships®
the role of maintenance and survey in
order to keep the standard of stab~
ility and seaworthiness at its in-
tended lovole
co-operation between the Marine
at the Department of Shipbuilding
and IIaval Architecture, University of
Strathclyde®
Ship
support«
ments"
(1796)
(1850)
the Statical and Dynamical
Stabilities of a Ship"
Ships of Small Initial Stab-
ility"
Trans INA (l8bl)
8) Froude, W.
of Ships"
this
motion"
Trails,
INA
(1896)
Krylov,
"A
Principles of Naval Architecture,
Vol. II, SNAIIE (1939)
Trans, IWA (l909)
13) Lewis, F,M,
ing a Vibrating Ship"
Trans. SNAHE (l933)
16) ¥atenabe, Y »
of Rolling-"
in the Free Surface of a Fluid"
Quarterly J» of
liech, and Appl«
Russian) (l954)
Trans. I A (l925)
R,M.
26) St» Denis, M® and Pierson^ WaJe
"On the Motions
"The Rolling
Ships
Sicherheit des Schiffes
"Hilfsbuch fttr den Schiffbau"
der Schiffe"
Schiffbau (l913)
Ships"
Trans, INA (l95l)
39) Steel, H.E.
"The Stability of Fishing
J®£o
"International Considerations
of Intact
Stability Standards"
"Theorie du Navire"
Vol^ III Paris
nd Seefischy F«
Yu, I.
Dept
of
Any
Course
i
54) Kerwin, J,E.
"Notes on Rolling
"On the Stability of Ship Motion
in Regular Oblique ¥aves"
K,
Irregular Wind ¥aves"
"Wageningen.
(1957
s
57)
Irregular Waves"
Random Seas"
•UJiregelHiassiger langlaufender
in
PhD Dissertation, Delft (l970)
(1971)
Maxima of Ship Rolling"
65) Odabasi,
A^Y.
Naval
IIydrome
66) Kuo,
Vehicles Stability"
ing
and
Naval
Uni-
Dna k
Delegation
inoAccount Simultaneious ¥nd
and Wave Action"
(lI/TAygaz ^ H i -tixperiment
Private co unication (l974)
"At rn i Approaches to
Shp
(1974)
Cargoes"
(1972)
Lines of
Special Purpose
1 2 to
of the
for these criteria,
(ES»IV)) their relevance to cas-
ualty experience*
A Hoc ¥oridLng Group's
material other basi information
application.
CURRENTLY PUBLISHED IN THE
mended by I1ICO as adopted inthe
Assembly Resolution A 167 (ES I ),
promulgated
in1968,
SB
1
2« ffSSX-.P -J- S
0
.IZlST'
and
ulations to ships of various types and
the extent to which they apply to exist"
ing
requirements relevant to non-passenger
not
considered
in
special stab-
dredgers,
bulk cargoes such
other deck cargoes® Additionally allow-
ances to be made for ice
accretion
are
not
drilling rig supply ships which have
additional problems (now under
and pipe
trap sea water,
Numerous Notices
relevant to stability
567?
1
Sablit is to be adequate to wt
stand an ovrtur moment due to
wind of maxi um veoct 100 knots®
Area under ri i moment
curve should
excess
moment
less than 35 »
(Construction and Survey) Regulations
rec-
ject isundesirable and we would rec-
ommend pubi i of a comprehensive
manual which could
be developed from
item 2 above,
<t>
q•d Mri h4* 11
•r irt .rt M P •r ®
8
B
•r g r a,odo
-P. p i •ti4»
tae.ooo'a ocaja
^+>"d
•riOBtBtt' CJart' M
i-l<+»(a+» dHTlfl
«+»Sal •S t--ri
Oj -l 0-PPh gfi {>,
ir>
tr>
r-l
0
1A
0
op s his ^S
•<s So ® p o® +>
O h ®
fi r-1
® T 0 - •r (>»
h B.ti-P h-i-P
2
g
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^® 02 Q> 0>
r-( <H rf h P<
"C <U 0 <U 0
h .r- j> a bO
$ 0) 01 al 0 H
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+'1-1 ® u ) t >
+ 0) P< <U r< &)
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&
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cni-i o o i c r i ^ S i n h & P i So
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p ) 0 + » ^ g c t 6 ® o i a T 3 o P < H + ' ' " M
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CO
l-
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a
40° (m
"Waves
^(c.577^+0.244 •&
1 INTRODUCTION
architecture and shipbuilding
initiated big changes in this
field; Sails and oars,
of propulsion were gradually
solely used for the
iron
overcome the confinements which
navigators experienced since the
to be unlimited,
troubles left? but they were
con-
sidered
as
euphoria that progress
problems was characteristic of
with respect to safety problems.
The goal was not less
than perfect
thought
relevant
does
problems still means
not
ship
an
proposed to judge
following
tion.
investigate the balance of righting
and heeling moments (1), (2), (3).
for the ship in following waves
as
mean
crest
is used.
rolling motion and the dynamic effect
of gusts. The
alteration of righting
well as heeling ipoments (beside
that from wind) are
the ship
righting
the
many
include
Last but not least the IMCO criterion
(the principle of which is
a very
If a naval architect who tries
to find
ships safe against or if
an administrator who for
other methods they
satisfied with the IMCO criterion.
Other specialists promote the
method on which
the IMCO criterion
think
underlying the weather criterion.
of similar kind) gives the impression
that only much more sophisticated
methods
disposal of naval
of a comprehensive safety concept
which allows us to explain explicitly
the significance of physical facts
in the context of safety.
In order
cept" and to demonstrate that it
comprises more than even perfect-
"knowledge of
in connection with capsizing I will
indicate some relevant ideas,
as well as lacking reliability of
large electronic
systems induced
generally
accepted
more
approach the
which
different safety provisions. As
such it aids much
to economic object of the
overall mortality rate.
t h a t - a ship is safe against capsi-
zing, the following steps would be
necessary :
dimensional j i t
will
3. Integration over the probblit
stri ti mentioned under
capsizing.
procedure isvery simple. thn
two wllbe done during
But if it
would bo possible,the ''
Itwould
no
1
L
ake
nucl. ? ••
use
to dpm Mi pL'-ibability ari
t-hen to chooso tha^-
rbtraril .An opt-irnization (which
rates, economic aspects etc.) wnald
b inorder.
nol be much easier t-han the deter-
ination of tho probablity tt-s^lf.
'Ihe case indicated above isnot
unique.
+ - T - I P optiirum solution of complex
problems is
information and relationships in
optimum solution and t°attempt
to make relevan
idea
relevant details good enough" in
our context.
of each
capsized during a turning
or under the action of following
increase of heel or after increa-
sing
"good
a ship can withstand static heeling
moments which are likely to occur
during its life time,. Other "good
enough details" might be based on
the fact that a shi > should not cap-
size under the simultanious action
of waves and wind. Depending on
the relative direction of waves
and wind we
is
heeled by wind and
regard to the forementioned examples
of "safety details".
models on
It would be practically impos-
sible to establish a model
for
a certain
approximately.
to a certain set of situations
depends respectively on
conditional probability that
the assumed set of situations)
is not known explicitly it
good enough to assume such
values of wind forces, wave
heights
ships
random scatter of the real, but
unknown conditional probability
the assumed set of
of this scatter. But I do not think
it of much practical relevance.
For each ship one of the safety de-
tails mentioned above will dominate.
In general it will be the same de-
tail for
^ - Y P Q - Therefore, it could be useful
to try to define the range - ex-
pressed
dominates. But it
tence of such a dominating safety
detail that it provides a stability
criterion which is generally validr
It is obvious from the literature
that experts more often discuss
the advantages of a
Because
reach agreement how to formulate
safety requirements. It is hoped
that
in
the
tool to stability problems
are given in (6)
only
relevant.
It
would
criterion to deal with the
two last mentioned
Jahrbuch STG p.609
2) Boie, C.;
3) Arndt. B.;
5)
unre el a/3igen Seegang.
Safpty of Fshinc,
to the
a func-
properties, and
eral areas for new
determined by the shape
of the dis«f
This geometrical relationship
ternal forces^ and variations in
loading® Finally, the high seas
locations visited must be considered
in order to determine the maximum
EXPOSURE to sea or weather forces
that the ship is expected to en-
counterg Only with a great deal of
pure good fortune can any of these
three
to
of the
complete, requires
to
mine
or come to rest at a calculated heel
angle. Until recently, governments
bility only as a means
of protecting
ed innocent of a knowledge of the
sea
sea)®
necessity, been rather rigidly hand-
led on passenger ship design in
order
evacuation
out heeling
ments should be able to state the
goal of the ship design in
a manner
begun
to
environment® Shipping firms have
tecting the large investment in men
and materials which goes
accident
is
sidered by the
of safety expected,
Maritime Consultative Organisation
(IMCO) -will be mentioned
which holds responsibility for devel-
oping marine criteria satisfactory to
all nations* To date, in approximate-
ly fifteen years of activity, IMCO
has
criteria for
Inter ational Load Line Convention
extended the stability assumptions of
the
ista«tions party
•with full stability information.
In the late l
bility criteria for ships less than
100 m in
another recommended standard
cargo
carried®
date has
ent solutions. Mot
sels is being challenged
m
this writer» s
exper-
ly development,
so will he lp
cross-purposes.
ing) the search for proper marine stab-
ility criteria can be quickly established
by reciting a few recent casualties
taiown to the author which can serve
as examples* Names
and flags of
pleted, Additionally^ we can examine
the physical differences in the
newer
evaluation®
small ferryboat
allowed on
ship carrying
ial disappeared
half-day from safe harbor® This
of bulk
¥ithin the past year, a small coastal
cargo ship approximately 60 m long
was loaded with a cargo of bulk
sugar
was not completely dry, and it began
to shift as soon as the ship
got to
but only
to
land that it was able to put it in to
shoreo It was deliberately grounded
on a beach to keep it from turning
over.
the sugar
scopic cargo,
to
The vessel
low side tank due to the steady off-
centre pull of
the liquid dumped before resuming the
t o w < »
the horsepower of the former
one^ it
turned itself
new HP developed a heeling action so
quickly that it completely surprised
the experienced captain, who did not
reduce the
ship from capsizing®
water®
duces a virtual loss of meta-
centric height*
deck
it
ship (usually for small ships)„
Occasionally, we
a free surface,
Sometimes, an examination of
_goj_u^on, but a mixture of
two
li-
is in-
reduc-
come to mind regarding
last-minute attempt to avoid
sinks 9 capsizes, o is beached to pre-
vent sinking. At this
accidents only on ^a^ss^enger__y,e^^eJ_Sa
(NOTE The 1973 Pollution
So much for known
stability
ocean systems which will become the
need of the future«
stability
lifting heavy and relatively large ob-
jects at ,s_ea. This causes a loss of
stability while the object is
suspended
and adding or subtracting the
weight
ental shelf exploration systems has
changed the naval
or 15-ton lift at sea to the daily
loading
or
offloading
has
many
If the lift
de-
load may develop dynamic forces great-
er than the factor of safety used in
initial d®sign» Further
ture of the lifting
a new way to transport the world's
goods» but also a new way to spread
the loading diagram
ship, d<ack loading was
usually reser-
routes, ex-
con-
con-
weigh-
to obtain the same average (KG)
loca-
But
what
gyradius
sumptions governing rolling motion?
still
in the cycle due to seaway action?
Thus far,
necessary to offer
guidance or limit"
ing criteria,, The
average Centre of
The
newer
ising bulkhead valves® It seems evid-
ent that if all such valves were left
open, an unsatisfactory condition of
stability would exist. How many valves
can be
This author
has ever been investigated,
to leaving port, the Master should
know the extent of stability degrad&qu
reproduced, stored in a retrieval system, or
transmitted
photocopying, recording, or otherwise,
and Naval Architecture, University of Strathclyde,
Glasgow^ Scotland®
Department of Shipbuilding
About The Confe rence
Programme and Timetable
List Of Delegates
Survey Of Delegates' Opinion on Stability C . KUO O f A. W . GORDON
Opening Address — Si r Samuel Curran, F.R.S. (Principal of
University of Strathclyde)
H. BIRD O f A. Y. ODABASI
1.2 Stability of
1.4 Rational Stability Criteria and the Probability of Capsizing
L. KOBYLINSKI
2.1 Environmental Conditions Relevant to the Stability of Ships in Waves — J.A. EWING
2.2 Experimental Study on Lateral Motions of Ship in Waves , H. F U J I I O f T. TAKAHASHI
2.3 Experimental Technique for
Research Institute
Y. TAKAISHI
2.4 A Scale Model Investigation of the Intact Stability of
Towing and Fishing Vessels —
2.5 Safety of a Vessel in Beam Sea J. DUDZIAK
3.1 An Analytical Study of the Mechanism of Capsizing -J.WELLICOME
3.2 Application of the Fokker-Planck Equation to the Study of the Mean and Variance—
M.R. HADDARA
3.3 On Capsizing of Ships in Irregular Seas — W. ABICHT
3.4 On the Statistical Precision of Determining the Probability of Capsizing in Random
Seas S. KASTNER
3.5 Methods for Estimating the Ship's Stability in Irregular Seas J. K. BORODA Y '
E.P. NIKOLAE V
4.1
The Ultimate Half Roll K. KURE O f C . J . BANG
4.2 Capsize Experiment of Box shaped Vessels — S.
4.3 Ship Capsizing in Heavy Seas -/.R. PAULLING, O.H. OAKLEY •
P.D. WOOD
4.4 Hydrodynamic Forces and Moments Acting on Two Dimensional Asymmetrical
Bodies
of a Side Trawler — A. MORRAL
5.1
Long
Term
5.2 Application of
Stability C .
of
5.5 On Dangerous Situations Fraught with Capsizing V.S. DORIN, E.P.
NIKOLAE V
Authors Index
capsizing have always been of utmost
importance to seafarers and to naval architects. In simple terms,,
stability determines the safety
understanding
stability concept. It has become over more necessary to study
the stability of ships
and ocean vehicles in
a
hydrodynamics and statistics, but a proper physical understanding of
all the phenomena involved,
effort, and the
adaptation that follows, has been devoted only to limited aspects
of
attempted
to
of
it has become
essential to establish a means of communication between those actively
involved in
findings,
a) to provide an
operation, research or regulatory purposes to discuss the
available
results can be applied in pratice,
The Conference programme was divided into five
separate sections to
future direction
Experiments^ Theoretical Studiesj Correlation of Theory and Experimentj
and Application of Research Findings. The final programme item was a
"Quiz Session on Stability" in which Conference participants had
an
opportunity to question directly a panel of experts from shipbuilding^
shipping, regulatory bodies, research and education,
I am very fortunate that in making up t l i ' e programme
I have received
the technical backing from Professor S» Motoro, Department of Naval
Architecture, University of Tokyo, Japan; Mr. J.A.IL Paffett of Ship
Division,
Germanyi and
Mathematics, University
England, I offer them my sincere thanks.
¥e are grateful too to the U e K » Departments of Industry and Trade for
the support they have given
us
are also due
to Miss. Ja Chamber's, Secretary to the Conference and others in the
Department of Shipbuilding and Naval Architecture who» in their
different ways, contributed to the success of the Conference,
namely;
Dr. K » J . MacCallum, Dr. A.Y. Odabasi, Mr. S.P. Grieve, Mr. G. Hearn,
Mr* R » Oskan, Mr. Jo Frank and Miss,
G. Short,
Richmond Street,
F . R , S , ,
University of Strathclyde,
, N. Bell
Future"
Safety Concepts"
2.2
2.3
2.4
2.5
Paffett (Ship Division, N ^ P r L s )hair ans Mr» J
2.1
Fujii, I I » and
1930 RECEPTION AND BUFFET GIVEN BY BURMAH OIL COMPANY
in the Assembly Hall,
Coffee
3.3
Abicht, ¥. (Germany)
"On
(U,S.S,R. )
Stability in Irregular Seas"
4.1
1530
1600
4.2
4.3
4.4
4.5
"The
and
Wood,
P.D. (U.S.A.)
Kobayashi,
1900 for
1300
-1130
Criteria in a Random Seaway"
5.2 Kuo, C.
"Application of Dynamic Systems
Stability"
Coffee
Chairmans Professor M. Meek (Ocean Fleets Limited,
and Visiting- Professor)
Mr, A,M. Spassky (iMCO Secretariat)
Mr. S. MacDonald (Royal National Lifeboat
Institution)
Tea
ADAMS, Mr. R.,
Ocean Fleets Limited
ANDERSSON, Mr. B.,
Sikob Limited, Sweden
BATES,
BECK¥ITH, Mr. L,, Lloyd*s Register of Shipping
BELL, Mr. N. , Department of Ti-ade , London
BIRD,
BORSUM, Mr.
BRAMDT, Professor H., Technical University of Berlin
BRIDGE,
C.
Board
COSTA, Mr. A.,
of Trade, London
D.
BERN,
DORIN, Dr. VaSs, Krylov Research
Institute, Leningrad
E.
EL-BADAN, Mr, A o, University of Strathclyde
EVANS, Mr. J«,Marine Engineers Review
EVANS, Mr. K.G,, Ministry of
Defence, Bath
Institute of Oceanographic Sciences
FAIRLIE-CLARKE, Dr.A.Ca, Brown Brothers & Company Limited
FERGUSON, Mr, V,, Scott Lithgow Limited, Port Glasgow
FOSTER, Mr.
G.
GILFILLAN, Mr. A.W., Y-AED Limited
GLADISH,
Mr.
London
GULIEV,
Professor
L. Meyer
GREENIIOV, Mr. P., Ocean Routes Limited
University of Strathelyde
8
Association
JOHNSOM,
KAPLAN, Dr. Pa, Oceanics Incorporated
KARLSEN, M , So, The Ship
Research Institute of Norway
KASTNER, Dr. So, Technical
KRAPPINGER, Professor 0 » , Hamburg University and Hamburg
Ship Model
KUO, Professor G » , University of Strathelyde
KURE,
LLOYD, Dr, AaRsJaM,^ Admiralty
MACCALLUMg Dr.
MCNAUGHT, Mr» D.,
MARTENS, Mr. P « , A.S. Mjellem and
Karlsen Limited
MASUDA, Mr. Ye, Nippon Kaiji Kjokai
MEEK, Professor M o ,
Company
DE,
Guard^ U.S..A.
MONKS, Mr. A.H., Ministry of Defence
MORRALL, Dr» A » , National Physical Laboratory
MORRISON,
Tokyo,
Japan
NIELSEN, Mr. G » , Danish Shipowners* Association
NIKOLAEV, Dr. I « P « , Krylov Research Institute, Leningrad
NUMATA, Mr. E., Stevens Institute
of
ODABASI, Dr» A » Y . , University
of Strathelyde
PEACH, Mr a
S.
SCATCHARD,
of Trade, London
SPASSKY, Mr. AeM., IMCO, London
SPURLOCK, Mr. DoJ,,, Natural Env-i
romnent Research Council
STRACHAN^ Mrs. J., Fishing News, Peterhead
SUHRBIER^ Mr, K ^ R ^ , Vosper Thornycroft Limited
SUTHERLAND, Mr. e , White Fish Authority, Scotland
T»
Institute
TANAKA,
Mrs
F»
TEMPLE, Mr, P » A ^ , P & 0 S^N. Company
THODE, Mr., H» , Vorband der Deutschen Schiffbauindustrie e.,V.
TOBIN, Mr« J«F.K., Lloyd's Register
of Shipping
TSUCHIYA, Mr, T « , Fishing Boat Laboratory, Tokyo
U.
VINJE,
¥,
AB. Sweden
WELLICOME, Dr. J « , University of
Southampton
WILLIAMS, Mr. R o T s , Cammell Laird Shipbuilding
WINXLE, Mr. I » E » , The Northern Ireland Polytechnic
Z,
tinguished experts from aJ 1 over the world to a
particular
3n this case the location vas the University of Strathclyde,
Glasgow and the subject
purposes
eve] for
(b) To facilitate the use
of
encourage the practical application of the
rosulLs.
was
the
ono roof to examine stability. The opportunity Lhus presented
to elicit the
opinions of su^h a group was too good to miss
and thjs brief report comments on the methods adopted and the
results achieved in a delegate
survey. The organisers would
like to thank the delegates for taking time to answer their
quesTJons and it is hoped that tlicy wil3 find Lhe results or
Lho findings to
2. £ii2 IL.I.2--AlJ-l ^ --A ^
It was decided thaL
uhe use of two soJf completion question-
naires, one to be adminisbored at the opening session and one
on the final day, would permit a
study of current opinion to-
gether wi bh an inclinaUon of
how,
t l i e nain a i ms of
the ques Lionnairos were to establish the
views of par LieLpants upon
the existing methods of dealing
with stabji-i ty and the areas of
f c h e subject Lo which they be~
lievod future
and
nrcspoc Lively to thj s report* Their design kept s-imple
with respondents required either to tick relevant items or to
rabo
various
given
attempts
jnformatlon as possible from a limited number of questions which
may
language difficulties often encountered at international con-
ferences .
As
24 hours to complete
the first questionnaire but only a matter of minutes to com-
plete the second,
Of the eleven questions in the opening questLonnaIre
four were
wibh methods of ImprovLng these criteria, one on the importance
of various factors for a fresh approach to stabjiity,
one on
studies and two on the participants* interests in ship and
ocean vehicle stability.
these
to tw o
of these latter two
•was to establish whether
participants * views on the methods for
improving the treatment of intact stability
and on the direc-
The analyses
straight
percentage
of relative importance
ng system was also applied. Thus, in addition
to a direct
to a
second and
1 to
possible* It
more
percentage firsL choice comparison.,
3. STOIMARY OP CONCLUSIONS
and we have
These are as follows?
tne existing stability
unsatisfactorys
2
) 2E
ro
om
2
n
.£S
Opinions wcic* &pl JI on the be&t way of inproving the treat-
ment of in LacL sLability, The rank order ot comments varied
little over f c h e two questJonnairos with approximately one
third requesting cri ten a and a quarter the develop-
men f c of a fresh lioafcment. 4& > the
Jattoi could presurnabJy
conclusions
factor rating
in that f c h e req esb for the
development of
a fresh treatment gained 20 more support in the second
quosfcionna]re whereas
h)
research were seen a f c > s ~
effects of waves,
A1.1 the other li&tod research areas attracted some support
but perhaps the i i i o s L surpri-s ing
feature was the
wind effects",
about what to do
6) J^^ht^ngArm^^rve^
hy^o of respondents foil
that
the
rit ri based on "Lhc use of the various features
of
the
acceptable method for
4i' > quasi-st ti effects
effects.
93
question on meta-
centn c hei ht (Gil) of which a .large majority (60'/J of al
respondents, 80 of
sidered
remainder thought tha itwas not unportant as long as
ithad a psiti value. O the 72^/0 who answered the ques-
ti
0
'3) Dual Criteria
The suggestion tha
The two nost important factors ina new approach to stab-
ilit rit ri
ictyto apply inpractJce* The fact that Lhose could be
conflicting requirements is
rai of a theoret caL
base to new crit ri itappears tha tliore was
sonc con-
JO) Sei
incorporated motion characteristics was required to s
tab-
i1
dLroct transfer of
e\.isLing shp
crit ri and
a furt r 3% required direct tr sf r wthm -nor m fi
ca fc ions•
3l) Future Conference
91 of respondents favoured a furt r conference on ti
topic -^-n or before 197
1
said "no" or
aspects of
to be
the opport-
un tyJt gave Lo keep up bo date i- th various research
studies (55 ) and the op rtunt to meet olier partLea-
pan ts (23 ).
93 respondents ( 6 < - ^ or
pre-cn'nfp'ronce nuestJ onna-i re and 1- 7 (64 )
the
post-conference
one. The sli tl lower response rate inthe second case was
due to some delegates hangto leave erl . For sef
con-
plotaon
hgh
wore designed to elicit the principal reason for the respond-
ents Interest
and their area of work. It
had been hoped that these could have been used in the analyses
of
responses
to
would have on responses.
ively low numbers involved, this
form of error tabulatjon
that
However, to illustrate the
were as
esting and, to a crt extent, puzzli pattern which was
probably due to the r stri ti construction of the
qucst-
jonna-i re which had not allowed for explanatory remarks. The
results were as followst"
i) IIeet the practical needs
ii) Prove unsatisfactory
100
b) The present criteria based on the use of the various
features
method for incorporating?-
i) Static effects
ii) Quasi-static effects
iji) Dynanic effects
opinion
agreeing
41
7
— z
100
been
the 49 vho find the existing methods
unsatisfactory in
all of them unsatis-
factory but only certain parts if the responses to the second
question are to be compatable. Similarly, 15^> of the respond-
ents who either lacked
answer the first question
second.
vcre notable in that 25 and 2 Q
c
ondcnLs feit unable to
respondents thought that
a know]edge
whereas
wao not important
a positive value.
of the 72'/o of
m were
72
Thus 300 mii and noro accounted for 7 6 of respondents who fet
able to answer the question.
,. .
need to have one
design purposes
was need fox'
fet
i rporai otion characteristics was required to stablity
rit ri of semi-submersibles. Only
2% supported the use of
xisti ship
y/J
could be used.
^mp^ovemcntofthoT'reatmentofTntactS^a^
This question was asked inboth the questionnaires and the
answers in tlie first instance inrank order of the number of
mentions to t e firat questionnaire wore as follows I -
1st 2nd
u On
33°^
practical data
21 17
24^>
ri ti arm curve
note that the onyitem
t ri ". he
which t l i e
"collection and analysis of more practical data" losts
The
"extensive training of
masters and operators" which dropped by ^O^o and the 10 of
total responses this represented was gained
in
equal
arm curve" and various
The effects of the conference proceedings themselves had app-
arently nade themselves felt. By roworki-ng the percentages on
„
1. Bettor stability criteria 33
2. Develop fresh treatment 22
3» C o l l e c t and analyse more practical data 19
4. Extensive training of
masters and operators 15
6. Others ^ JisJi
second questionnaire is due to fresh ideas being suggested
which djd noL fit in witlx f c h e five
groups
nor"
Re1ati^e^^npo_tanco^of^ractors_inRe^^
Again the same question was repeated in both questLonnaires
witli respondents being asked to rate the relative importance
of possible areas for further research on intact stability.
On a percentage
fo1 lows;-
1 2
experience and feed- 17
5« Pducation oC slu p masters
and operators 9
6. bcaled model
(The percentages were rounded off and thus not all columns
total 100)
in tlie changes
although based on the
However, when the responses were weighted 3? 2, 1 for
f-irst
different picture emerged^
£~— H2 -.
1.
EFFocts
2 "'.later on deck 2 3 3
3. DcveJoping Fresh
experience, etc. 3 =
6. Vind errocts 6
7. Lducat-Lon, etc. 7
On Frequency or nonbJon thcroFore tho "orrocts or waves" took
prcccdonco on the "development or fresh methods" which gained
considerable support "in the post-conForcnce quest i onna-re,
3ndood i
t was ths swing win ch deposed "water on deck" Froi
second posi "felon to
positions
Tn the end L scolded sarcr to conclude tha irrespective oF
which way tliodata were analysed there were
bliroc
groups in
descend-ing order of prior-ity frori the delegates po t oF view.
Group J ^^FFoc i/s oF waves and Developing Fresh notliods, etc,
Group
2 Vatcr on deck, Gathering oF Ful 3 scale experience,
c Ic.
Vind cFFects and
Tie Fact tha "wind cFFects" rated so lowly occasioned soiie
surprise as tho importance oF these eFFects js g r l rccog-
n
Ged.
t so 1 i
ILs ra iii", as a possible research area
Js nob Fu3 1y apprcc i ? fed.
i.o^at vc^nnorLancc^oF ractors^^^
On tlie Fst quest orna re doJogatcs were asl>-od uo rate jnorder
oF iriportanco Lo blion
any rTcsh s Lab
be developed could lie
a porccn Pg^ baGcd o-i F^ rsL rospo isc uho
rab;ngs we "e aa Fo11ows;-
1. Sinpl
inFluoncing Factors as poss'ble
5. Be
changed places
To file
imi i ti ated observer Lhose result scorned to show a
cerLa n degree oF
rac bors cons Lderc^d tlio i
ore
ajid tlius tlie loss s 1 '
ip 1 c to apply ' i practice.
Si u 1 < - i - > ? 1 y
a
basis and if there are theories
in existence which are incapable
of implementation in practice,
they should be discarded
and tho response pattern may
have been d - i
dated by the restrictive
nature of the qucs tionnaJ re* This docs not appear very probable
as space was left for respondents to write
in other factors and
been made on both questionnaires and
none is
most
studi es 55
3. Able to use knowledge gained 1^ 1
4. Opportuniby f c o take part in discussion 4
5.
in further comments mostly favourable.
The maJor criticism was that papers should have been d i - s t r i bubed
well in advance of the
actua] conference* Tn
seems conimon to all conferences, it
proved inpossible to receive al l tho papers in. tine for printing
and prior d i stribut i - o n . Two papers
arrived only ten days before
tho conference commenced. The point has
been
was no need for any
further conference
on tills top-ic, 35^/0 of the respondents requested a follow-up in
1977, 56 in 3973 and only 9 after 1978.
I^tTO^al^St^bilTtyOriteria
The fjnal quest-ion asked delegates
whether they
in the near future. ^ h ^ o said they
wore, 30*^ said they were not
and, 16' did not known IIany of
the negative respondents indi~
no to f c h e
"near" future
and not
of
CK/JC
C K u o BSc Ph D F R I N A
Professor o f S h i p b u i l d i n g an d N a v a l Architecture
Department of Shipbuilding and
Dear Participant,
(a) To provide an , opportunity at
international
further
systematic manner, we are
your help in carrying
you to
complete two
short questionnaires.
The first is with this letter and as we plan to
provide a of
during Conference, we
questionnaire as
27th March, 1975 will be incorporated in the
proceedings.
of will on your full co-operation
and we you will give us your full support so that the survey can
provide useful information.
T_JJNVERSIY_F_STR CDE
25th-27th MARCH. 1975
appropriate)
stability
Not enough information to form
an opinion.
ship stability criteria which is
b t t , s o d on the use of the various features
of
D
Not enough information to express an opinion
( - • ) Do you regard a knowledge of the magnitude of matacentric height
(GM) as
j j
very important
i——I
has a positive
other, please specify
(4) For a ship with length less than 100 m, which of the following
minimum metacentric heights do you think is realistic?
10 mm 100 mm 200 mm 300 mm more than 300 mm
D
APPENDIX I
(5) Do you think there is a need to have one stability
criteria for
Yes / No
(6) Which approach do you regard as the best way of improving our
treatment
arm curve
Others, please
specify
(7) In a successful fresh stability criteria, how do y ou regard the
relative importance of the following factors?
(Please rate, 1. 2, 3, etc. and where you feel two
or more
Easy for design purposes Simple to apply in practice
Be theoretically based
influencing
sem-submersibles should
the existing ship stability criteria with refinements
D
(9)
would you rate relative of
the following possible
research
(Please rate. 1, 2, 3, etc. you two or more topics
are of equal
with equal ratings).
experiments
of
scale
Developing fresh that would
Design Operation
Others,
please
specify
AT GAINING GENERAL TRENDS)
(1)
If there is to bp another Conference devoted to intact and damaged
stability in
the future, do you think it should take place in
1977 1978
No for any further Conference
(2) What aspect of this Conference have you found to be most satisfying?
Able to meet other participants
Able to up to date with
the various research studies
Other, specify
regard as the
Better stability criteria
Develop fresh treatment
Collect more practical
you now rate as the relative importance of the following
possible for further studies on
intact stability?
Wind
Scaled model
Education of
ship operators
APPENDIX II
(5) Are you more hopeful that a rational stability criteria for ships
will now emerge in
AT
you who have come to
attend this International Conference
±s to ' b e the stability of ships and ocean
vehicles, I think it is
a very appropriate occasion for me
to address a Few renarks to the company because it gives me
an
the Anderson Building of the Universi ty of Strathclyde and
to wish the Conference every success but to
say at the same
applied sciences and in the problems
of
Industry.
sponsored
this
Con-
well-being of
in the United Kingdom,
The university traces bade its foundation to 1796 and the man
on whose idea the University was founded, Professor John
Anderson FRS, was passionately interested in the collaboration
of universities
Revolution^
tackling the problem and trying to make the universities of
his
a large number of his
friends, most of them concerned with business in one way
or
name and one
stature. The second member of
staff was Birkbeck himself who
left the Institute in. the
early 1800*s whose work in London led to the founding
of what is now Birkbeck
College, Without doubt it was not
a philosophy which was
among academics of Andersen*s
time and indeed it was a philosophy that has not been popular
until very recent times. This is
really
why,
in
the history of the Institution, it was
not
would be a University in its own right and one
concerned very
The University has over 8,000 students §, nearly
2,000
postgraduate work and
postgraduate work, Tt is important
to stress that part-time
complement because it shows that
there continues to the pre-
sent day a great range of links between .Indus try, Commerce
and the Universifcy and that these links result
in
flexibility
study and research for higher degrees.
It is more than 100 years since applied mathematics and some
of the engineerxng subjects were recognised in the establish-
ment of Chairs in the Tnsticution and indeed this year sees
• us celebrating the Centenary of the
of
the
Chair
in MathematJ c - s . Applxed Maths has been pursued long
before that date® A of you
here • w i . l l no doubt
be
and some
It
is
difficult to find sufficient resources in universities
in these txmes it is to be regretted that one of
our more
a
abandoned
by
thoroughly applied study,
When costs dominate the scene then it is time to use our
intelligence to the maximum possible extenta
" W e in the U » K »
lack today in money matters but while saying this I would
stress one thing, with due deference
to those of you from
overseas,
capa-
city to think and not markedly on an ability to spend, al-
though at
conferences such as
their
ideas and no conference could be more timely than the
one that
you
sections
Others cover Environ-
lation of Theory and Experiment, and Application of Research
Findings.
part of the oceans de~
serves close study in all of the fields that are listed and
I
do
ference will be well rewarded and
that some worthwhile con-
supporting
team have laid the foundation for a most worth-
while meeting of about 150 of you from a great variety of
countries.
The name Strathclyde, meaning the Valley of the Clyde, was
not chosen by accident because for
many
inter-
building
people in this
subject of your Conference
any time in the
Past ,
Future"
1.2 Krappinger,0. ( G e r m a n y ) "Stability of Ships Modern
Safety Concepts"
1.4 Kobylinski,L. (Poland)
'Rational SablityCriteria and
Probability of Capsizing"
cluding ships, are designed, produced
an d operated to fulfil specific func-
tions efficiently and safely., In that
respect the stability of their motions
can b e of crucial importance
and
it
to review the past and the present
knowledge
of past developments we have concen-
trated on concepts
rather than math-
account of
formative® We have also tried to
highlight the state of the art by
distinguishing between different theor-
special
place
the conclusion that the existing cri-
teria are not adequate both from
theoretical
on the
suitable respectively for the ship
master and for the approving authority®
In preparing this study we have used
all the material available to us and
even with such incomplete information
it has
interest of
to quote
We could not obtain or refer to
all of the numerous contributions
from USSR, East European countries,
and Japan, either because they were
not available, or were in a lang-
uage that the authors could not
understand® Thus, w e will be de-
lighted to hear more about the con-
tributions from those parts of the
world®
the
relating to damage stability as this
would open up a much w ider field®
In avoiding discussion of those
problems, however, we are fully
aware
criteria,
M E N T S
The development of ship stability
theory has had
complete® Throughout this period,
paper we shall classify them in
three
groupst
stability in still water
of ship motions
This classification is arb-
helps
us
atically,
can be
of stability, and
entative quantity,
Certainly the
The principal in
the metacentric radius, B l l ^ as the
ratio of waterplane moment of inertia,
I, to the
which was
used as
•where 1-03 is the •vertical coordinate of
the centre of
the v ti coordinate of the centre
of gr t . The ri i lever was
approximated by GZ = G-M
radians« •
culations of the ri i levers which
•was given as
emerged wedge,
tical distance between the centre of
buoyancy and the centre of gravity,
V
introduced
which
quasi-
under the influence of some potential
external forces and expressed this
work
as the inequality J ""[(e-) - M ]] > 0
o
righting and heeling moments, res-
pectively, and " ^ is the
ing motion.
architects, his principle has not
been developed further till the last
decadeo
other
possibility of applying
expression
ing
by
influence of the variation of right-
ing moment
others. This latter improvement
shall dis-
Simultaneous
ships in
motion itself.
Again we
may summarize
pression for rolling motion in reg-
ular beam seas, by assuming
that
the
length,
not alter the wave form. In 1874,
he also introduced the damping effect
by using the best empirical damping
as
dn
number of oscillations,
mined from experiments, (8).
In 1896 and
an d the theory of rolling was further
developed on the basis of what is
knowi as the Froude-Krylov hypothesis®
Manning, (ll), included the influence
of ship's speed and wave direction by
introducing the period of wave encount-
er while the various other aspects
of
rolling
(l6), Uysell (I?)?
and many others®
their
stability
19th century AaM.
body® This study, however,
stability understanding® Though it
was quite correct vhat
whole capsizing event is a dynamical
event because statical states of
equil~
possible influences of nonlinear
Baumann (23),
analysing
ship
motions
(28),
in the study of nonlinear ship rolling.
Later
developments in the state of art.
The final group of studies were aim-
ed at determining a
criteria. It is known that load
line
but the real efforts for establishing
rules in ship stability came after
l870»
"Captain", capsized and this
ing of the 20th
because of a
to
at
tried. Here we summarize
judging the stability was the initial
metacentric height® In the beginning
of the 20th century,
metacentric
height
his com-
the righting moment
arm» Some of the proposed minimum
GM values
c^ is the block coefficient and
A
ship,
k
in the
for good
B R = GZ , _ + BG sin-^- „ As will be
i- fT • W
equa-
curve as well as various heeling
moments®
Parallel
itial
metacentric
This
but it proved unsuccessful in prac-
tice due to various shortcomings.
The use of the righting arm curves
for judging stability was first pro-
posed by Reed, (32)® Nevertheless
the use
of this
stability criterion was in frequent
use
in
the
up to a of 10
on in
motacentric height*
GZ > 0.14 E 20
^ '3 5
ttte Vy . defined
li
openingsji an e of heel for shfti
of cargo ^
rit ri ,, i ud the IMCO crit ri
d)
also as a stablityCT-lterd one
In1913» Benjamn (3 )» Hs pro-
posal at r compa iig ci l r ntunber
of vessels which operated siiccessf'ullya
lie to the cone 1 •usio-'i i the
mn um dyna cal le-ve-r i »irer%
1)
2)
ing- anges Later Ben.]amri, h sef,
modified hsproposal offered a
he proposed a J m t angle arxl i-equired
tha tlie
must be equivalent to or gz'eater than
the oF tlieloia-1 work
force and
eng-ers on board.
In1939» Raliola, i hd s Pli«D», t sis,
(37)? made a si fl contri uti
towards ach-ieving- wcJrlcable stablity
eFfective
»nd.§, •wa.'veSf ana
ntud of GZ value the
corresponding were suffi t
stablityof considered
by Steel,
fclio nature of the cargo,
"Yamag-ata, in1959, (-40)
Japan® The approach, sim-
dytiainic st blit crit ri
for
dyna c
at the 1mk an e which the
lowest of -8m , fl an e
or 35 degrees,
displ.aceme.at considered® lie con-
t ri the
shp at r the
for the of gyrations
Maritime Consultative Organisation)
Thomson and Tope, (44), more gener-
ally® The outcome of the studies were
certain recommendations for judging
little difference from Rahola's
later.
Later
results
tinues and
follow-
ection and Grim, (20), and Wendel,
(45)? were the pioneers of these new
developments» They both introduced
with time
way, but used
idea was not new» Pollard
and Dudebout,
Here we shall summarize
of con-
Wendol's approach®
Statistical analysis
30 and
Inspired
group of naval
ility condition
of the ship®
wave geo-
ship length. It was pointed out
that the worst condition arises when
the crest is
impose a
allowing
sinkage
effect, e»g. the effect of orbital
motion of water particles,
(49)» Upahl, (50)5 and many others.,
In 1952,
Grim dealt
where I is the virtual
mass moment of
inertia about the
in
frequency, t
angle of rolla By
Mathieu*s equation, he pointed out the
possible instability regions® In
where
The
the stability
forms the basis of the majority of
today*s
research activities®
(23),
and
Rosenberg, (25), indicated possible
work tried to discover some unstable
regions from the results of Hil s
equation®
liThile
of
St» Denis's
introduction of
ject, Cartwright
and Rydill, (28),
Kato et® al», (56), presented an ex-
perimental study for irregular wind
and wave conditions® The study car-
ried out in Japan
by a group of
(see Figiire 3), De Jong, (6l), in
his Ph.D. dissertation tried to solve
the problem
Planck-Kolg-omorov equation and defined
of threshold crossing* Similar
theoretic-
ally
and
features
to-
of
the
determined
the
approximation
way or
com-
putation.
(67 ) » have been further
tributions
which
will cover the grounds which were left
open by us and moreover will contribute
towards a
judging the
tions or recommendations is fairly
ob-
task
con-
ditions, environmental
from
a
the case one would
or an oversimplified
the problem,
column in Table 1» it will
be
appar-
perienced
in
of dis-
more Important, from the latter®
Furthermore, there is invariably a
good deal of speculation about
cases
the above sample®
a clear-cut case of inadequate stab-
ility
illustrated by the
deemed inadequate (e»g® by IMCO stan-
dards), absence of a
what sea conditions might
those
ships
learned from
preferred simplicity and
ility
all the proposals
today we may meet three main groups
of criteria in assessing the stability
of ships, (43), (68),
mulae
teria are
for
ility
ical evaluation of minimum
pillar diagram
plied by many
ation of heeling levers for
comparison
shall summarise the last two methods
of assessing the stability»
IIICO requirements on statical
cargo ships, G i l ^, Os 35 metre
for
timber
axi um vue
radians at ^-= 30°.
ynamcal lever ^ Og09
-0 = 30'' must be greater
than
Additionally, for passenger
less than
h) During the
10" under the xnfluencc of the
moment
Vo is the service speed, L is
the waterline length, T is t l i e
draft,
gravity»
IIICO rec-
those obtained by Rahola (see Figure
1),
a proposal submitted to IMCO
by the
M is calculated by
metre)
is the projected lateral area above
the effective waterline, and Z is
the distance between the centre of
the projected lateral area
is first necessary to calculate the
amplitude of rolling -^ by the for-
mula
and 7^
diagram, the capsizing moment is
II A .0 II
(tonne metre) I I = A . BC
sil be followed Fur 8,
As,
txxo^o T ^ O C ^ ^
only- £i firs
Although altesi'nat.i've proposals
i i usi'v ®
up a
isti of
Those than
examples that IMCO z'ecommend-
fi t to pi'-crvde
basic reasons causing
Q fnPySd€
where .necessary (see Appen-
part .in
chapter's, the stablit of
curve wii is
detormined froni the
and by hypo t i wind and wave
forces •which, are a.ssu.raed
to the st blit of a. conse.r'vatx've
•system,, As a nura, of
•fche "fcliGor'y o x " * oxd3.Ila. '"y diffGr'Bii'fcis.l
if isno
her e li i'
hl appreciating value of prac-
ti exper'ience and accepting
we to dra.-w at ti to
the f l wn aspect»
tlia
of
on
g
a
ap»
justified,
d) The especially of
so-called "existing" ships are
neglected®
statistical weight
so obtained not
executing
certain
oscillatory
to introduce them into
GZ-"^ ¥hile this is
cover
thought to be exceptional cases*
3) There is a dangerous
tendency to
common with ships so far as the
stability of motion is concerned.
They certainly make their maxi-
mum rotational motions about one
of the principal
axes for which
ertia is minimum, and considering
the large asymmetric superstruc-
•with one of the symmetry axes for
the underwater part« Furthermore,
on
made
mathematically, see for example
(74), (75)» no stability criteria
For
ment on current criteria is on
their
•without any
no
incorporate the stability criteria
ational zones and seasons•
plies with the IMCO recommendations
and this is the final word to be
said a Thus, in that respect^
no
ships and floating offshore structures.
According to the general trend these
activities^ we may examine them in
certain groups.
The first
by
corrections.
attempts are made
insufficient to provide safety
ing structures and the studies
carried out may yield trivial res-
ults» if the motion dynamics are not
considered.
fluence of following and quartering
seas, mostly from a statical point of
view* The aim of these studies is
to devise
a ship under the action
of assumed
useful results, it will
statical q uantities® The difference
between the statical and the dynam-
ical uses are best illustrated in
Figure 9®
histories in case, even loss
in restoring moment does not give
a significant
has been
in
length,
tions of motione
relate
timate goal of this
the ship*s stability from its
motions
the stability of ships®
There are nevertheless, certain
broader
naval
remarks;
mathematical
outcomes
before®
be applied in practice* In that respect
we
1)
practice although
sidered first;
inition of stability in of
motion char-
a yield only a point on a
are
stabili ty in order
relations between the
seem to
be of
we -wish to achieve progress in
the practical application
message clear" and precise by
emphasising the
In the authors* opinion, the use
of somewhat more sophisticated
difficult provided
terpreted, Application in con-
philosophy,
types of cargo appear to be ig-
nored in some of the theoretical
studies, although in
vital
Bulk Cargoes introduced by IMCO
(78), as a
making some modifications and
of lost
of fishing vessel casualties
of vessel which has
at
sea
take manoeuvres, in order
it is necess-
ulations for fishing vessels.
ship masters are not always able
to
ascertain
on stability theory and
time.
easily and quickly used by
ship
of Trade, (79)• Since it
establish very
simple stability
ditions^ it is
desirable to dev-
an d on e for designers and approv-
ing
to play®
so-called
5?
products
ships and
urgent especially for masters of
small ships®
the role of maintenance and survey in
order to keep the standard of stab~
ility and seaworthiness at its in-
tended lovole
co-operation between the Marine
at the Department of Shipbuilding
and IIaval Architecture, University of
Strathclyde®
Ship
support«
ments"
(1796)
(1850)
the Statical and Dynamical
Stabilities of a Ship"
Ships of Small Initial Stab-
ility"
Trans INA (l8bl)
8) Froude, W.
of Ships"
this
motion"
Trails,
INA
(1896)
Krylov,
"A
Principles of Naval Architecture,
Vol. II, SNAIIE (1939)
Trans, IWA (l909)
13) Lewis, F,M,
ing a Vibrating Ship"
Trans. SNAHE (l933)
16) ¥atenabe, Y »
of Rolling-"
in the Free Surface of a Fluid"
Quarterly J» of
liech, and Appl«
Russian) (l954)
Trans. I A (l925)
R,M.
26) St» Denis, M® and Pierson^ WaJe
"On the Motions
"The Rolling
Ships
Sicherheit des Schiffes
"Hilfsbuch fttr den Schiffbau"
der Schiffe"
Schiffbau (l913)
Ships"
Trans, INA (l95l)
39) Steel, H.E.
"The Stability of Fishing
J®£o
"International Considerations
of Intact
Stability Standards"
"Theorie du Navire"
Vol^ III Paris
nd Seefischy F«
Yu, I.
Dept
of
Any
Course
i
54) Kerwin, J,E.
"Notes on Rolling
"On the Stability of Ship Motion
in Regular Oblique ¥aves"
K,
Irregular Wind ¥aves"
"Wageningen.
(1957
s
57)
Irregular Waves"
Random Seas"
•UJiregelHiassiger langlaufender
in
PhD Dissertation, Delft (l970)
(1971)
Maxima of Ship Rolling"
65) Odabasi,
A^Y.
Naval
IIydrome
66) Kuo,
Vehicles Stability"
ing
and
Naval
Uni-
Dna k
Delegation
inoAccount Simultaneious ¥nd
and Wave Action"
(lI/TAygaz ^ H i -tixperiment
Private co unication (l974)
"At rn i Approaches to
Shp
(1974)
Cargoes"
(1972)
Lines of
Special Purpose
1 2 to
of the
for these criteria,
(ES»IV)) their relevance to cas-
ualty experience*
A Hoc ¥oridLng Group's
material other basi information
application.
CURRENTLY PUBLISHED IN THE
mended by I1ICO as adopted inthe
Assembly Resolution A 167 (ES I ),
promulgated
in1968,
SB
1
2« ffSSX-.P -J- S
0
.IZlST'
and
ulations to ships of various types and
the extent to which they apply to exist"
ing
requirements relevant to non-passenger
not
considered
in
special stab-
dredgers,
bulk cargoes such
other deck cargoes® Additionally allow-
ances to be made for ice
accretion
are
not
drilling rig supply ships which have
additional problems (now under
and pipe
trap sea water,
Numerous Notices
relevant to stability
567?
1
Sablit is to be adequate to wt
stand an ovrtur moment due to
wind of maxi um veoct 100 knots®
Area under ri i moment
curve should
excess
moment
less than 35 »
(Construction and Survey) Regulations
rec-
ject isundesirable and we would rec-
ommend pubi i of a comprehensive
manual which could
be developed from
item 2 above,
<t>
q•d Mri h4* 11
•r irt .rt M P •r ®
8
B
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tae.ooo'a ocaja
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i-l<+»(a+» dHTlfl
«+»Sal •S t--ri
Oj -l 0-PPh gfi {>,
ir>
tr>
r-l
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0
op s his ^S
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fi r-1
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40° (m
"Waves
^(c.577^+0.244 •&
1 INTRODUCTION
architecture and shipbuilding
initiated big changes in this
field; Sails and oars,
of propulsion were gradually
solely used for the
iron
overcome the confinements which
navigators experienced since the
to be unlimited,
troubles left? but they were
con-
sidered
as
euphoria that progress
problems was characteristic of
with respect to safety problems.
The goal was not less
than perfect
thought
relevant
does
problems still means
not
ship
an
proposed to judge
following
tion.
investigate the balance of righting
and heeling moments (1), (2), (3).
for the ship in following waves
as
mean
crest
is used.
rolling motion and the dynamic effect
of gusts. The
alteration of righting
well as heeling ipoments (beside
that from wind) are
the ship
righting
the
many
include
Last but not least the IMCO criterion
(the principle of which is
a very
If a naval architect who tries
to find
ships safe against or if
an administrator who for
other methods they
satisfied with the IMCO criterion.
Other specialists promote the
method on which
the IMCO criterion
think
underlying the weather criterion.
of similar kind) gives the impression
that only much more sophisticated
methods
disposal of naval
of a comprehensive safety concept
which allows us to explain explicitly
the significance of physical facts
in the context of safety.
In order
cept" and to demonstrate that it
comprises more than even perfect-
"knowledge of
in connection with capsizing I will
indicate some relevant ideas,
as well as lacking reliability of
large electronic
systems induced
generally
accepted
more
approach the
which
different safety provisions. As
such it aids much
to economic object of the
overall mortality rate.
t h a t - a ship is safe against capsi-
zing, the following steps would be
necessary :
dimensional j i t
will
3. Integration over the probblit
stri ti mentioned under
capsizing.
procedure isvery simple. thn
two wllbe done during
But if it
would bo possible,the ''
Itwould
no
1
L
ake
nucl. ? ••
use
to dpm Mi pL'-ibability ari
t-hen to chooso tha^-
rbtraril .An opt-irnization (which
rates, economic aspects etc.) wnald
b inorder.
nol be much easier t-han the deter-
ination of tho probablity tt-s^lf.
'Ihe case indicated above isnot
unique.
+ - T - I P optiirum solution of complex
problems is
information and relationships in
optimum solution and t°attempt
to make relevan
idea
relevant details good enough" in
our context.
of each
capsized during a turning
or under the action of following
increase of heel or after increa-
sing
"good
a ship can withstand static heeling
moments which are likely to occur
during its life time,. Other "good
enough details" might be based on
the fact that a shi > should not cap-
size under the simultanious action
of waves and wind. Depending on
the relative direction of waves
and wind we
is
heeled by wind and
regard to the forementioned examples
of "safety details".
models on
It would be practically impos-
sible to establish a model
for
a certain
approximately.
to a certain set of situations
depends respectively on
conditional probability that
the assumed set of situations)
is not known explicitly it
good enough to assume such
values of wind forces, wave
heights
ships
random scatter of the real, but
unknown conditional probability
the assumed set of
of this scatter. But I do not think
it of much practical relevance.
For each ship one of the safety de-
tails mentioned above will dominate.
In general it will be the same de-
tail for
^ - Y P Q - Therefore, it could be useful
to try to define the range - ex-
pressed
dominates. But it
tence of such a dominating safety
detail that it provides a stability
criterion which is generally validr
It is obvious from the literature
that experts more often discuss
the advantages of a
Because
reach agreement how to formulate
safety requirements. It is hoped
that
in
the
tool to stability problems
are given in (6)
only
relevant.
It
would
criterion to deal with the
two last mentioned
Jahrbuch STG p.609
2) Boie, C.;
3) Arndt. B.;
5)
unre el a/3igen Seegang.
Safpty of Fshinc,
to the
a func-
properties, and
eral areas for new
determined by the shape
of the dis«f
This geometrical relationship
ternal forces^ and variations in
loading® Finally, the high seas
locations visited must be considered
in order to determine the maximum
EXPOSURE to sea or weather forces
that the ship is expected to en-
counterg Only with a great deal of
pure good fortune can any of these
three
to
of the
complete, requires
to
mine
or come to rest at a calculated heel
angle. Until recently, governments
bility only as a means
of protecting
ed innocent of a knowledge of the
sea
sea)®
necessity, been rather rigidly hand-
led on passenger ship design in
order
evacuation
out heeling
ments should be able to state the
goal of the ship design in
a manner
begun
to
environment® Shipping firms have
tecting the large investment in men
and materials which goes
accident
is
sidered by the
of safety expected,
Maritime Consultative Organisation
(IMCO) -will be mentioned
which holds responsibility for devel-
oping marine criteria satisfactory to
all nations* To date, in approximate-
ly fifteen years of activity, IMCO
has
criteria for
Inter ational Load Line Convention
extended the stability assumptions of
the
ista«tions party
•with full stability information.
In the late l
bility criteria for ships less than
100 m in
another recommended standard
cargo
carried®
date has
ent solutions. Mot
sels is being challenged
m
this writer» s
exper-
ly development,
so will he lp
cross-purposes.
ing) the search for proper marine stab-
ility criteria can be quickly established
by reciting a few recent casualties
taiown to the author which can serve
as examples* Names
and flags of
pleted, Additionally^ we can examine
the physical differences in the
newer
evaluation®
small ferryboat
allowed on
ship carrying
ial disappeared
half-day from safe harbor® This
of bulk
¥ithin the past year, a small coastal
cargo ship approximately 60 m long
was loaded with a cargo of bulk
sugar
was not completely dry, and it began
to shift as soon as the ship
got to
but only
to
land that it was able to put it in to
shoreo It was deliberately grounded
on a beach to keep it from turning
over.
the sugar
scopic cargo,
to
The vessel
low side tank due to the steady off-
centre pull of
the liquid dumped before resuming the
t o w < »
the horsepower of the former
one^ it
turned itself
new HP developed a heeling action so
quickly that it completely surprised
the experienced captain, who did not
reduce the
ship from capsizing®
water®
duces a virtual loss of meta-
centric height*
deck
it
ship (usually for small ships)„
Occasionally, we
a free surface,
Sometimes, an examination of
_goj_u^on, but a mixture of
two
li-
is in-
reduc-
come to mind regarding
last-minute attempt to avoid
sinks 9 capsizes, o is beached to pre-
vent sinking. At this
accidents only on ^a^ss^enger__y,e^^eJ_Sa
(NOTE The 1973 Pollution
So much for known
stability
ocean systems which will become the
need of the future«
stability
lifting heavy and relatively large ob-
jects at ,s_ea. This causes a loss of
stability while the object is
suspended
and adding or subtracting the
weight
ental shelf exploration systems has
changed the naval
or 15-ton lift at sea to the daily
loading
or
offloading
has
many
If the lift
de-
load may develop dynamic forces great-
er than the factor of safety used in
initial d®sign» Further
ture of the lifting
a new way to transport the world's
goods» but also a new way to spread
the loading diagram
ship, d<ack loading was
usually reser-
routes, ex-
con-
con-
weigh-
to obtain the same average (KG)
loca-
But
what
gyradius
sumptions governing rolling motion?
still
in the cycle due to seaway action?
Thus far,
necessary to offer
guidance or limit"
ing criteria,, The
average Centre of
The
newer
ising bulkhead valves® It seems evid-
ent that if all such valves were left
open, an unsatisfactory condition of
stability would exist. How many valves
can be
This author
has ever been investigated,
to leaving port, the Master should
know the extent of stability degrad&qu