Proceedings of the 3rd International Conference on Stability of Ships and Ocean Vehicles, Volume II, Addendum 2, Gdansk, Poland, September 22-26, 1986, STAB'86

giurd

gnternational

amference

on

Stability

of

Ships

and

Ocean

_Vehicles

Volume

_II

dfriclenclum

ADDENDUM 2

P1986

-

3

STAB

_'a

22-26

September

₁₉₈₆

gdarisk-9oland

CONTENTS

Page

An attempt of summary

'3

Welcome by Prof. L.KobyliAski 6

Introductory address by Prof. Ch.Kuo ₇ The final programme of the Conference 11

The closing speech by Prof. L.KobyliAski 19

Panel Discussion I:°Outline of Research Programme

Aimed at Stability Criteri,p _21, - Research and development needs for stability

criteria by A.Morrall 22

- Stability criteria - Safety of a vessel by

T.Nedrelid 28

- Contribution by 0.Krappinger. 30

- Comments to his paper by J.Witiniewski ₃₄

Panel Discussion II: Relationship between Stability

Requirements and Design ₃₆

-

Discussion

00000

37

-

Contribution by S.Kastner

_4o

-

Contribution by J.Stasiak 0 42 - Contribution by J.Dudziak

₄₅

-

Contribution by W.Abicht

04,6440

₅₁ - Contribution by A.N.Kholodilin 52

Discussion on: EXPERIMENTAL STUDY ON PURE LOSS

OF STABILITY IN REGULAR AND IRREGULAR

. FOLLOWING SEAS

54

-

Contribution by 0.Krappinger

₅₄

Contribution by P.Blume - Contribution by W.A.Cleary

₅₅

-

Contribution by E.A.Dahle

₅₆

-

Contribution by D.Vassalos ... 56

-

Contribution by S.hastner

₅₇

Discussion on: AN EXPERIMENTAL TECHNIQUE FOR

IN-VESTIGATION INTO PHYSICS OF SHIP

CAPSIZING 61

Contribution by P.Blume ... ... 61 Discussion on: PROBABILITY OF NON-CAPSIZING OF A SHIP

AS A MEASURE OF HER SAFETY 62

Contribution by N.Umecla 62

Author's reply by W.Blooki ... ... 62

Discussion on: THREE DIMENSIONAL NUMERICAL SIMULATION

OF GREEN WATER ON DECK 65

Contribution by M.S.Pentazopoulos 65

Discussion

on:

NUMERICAL CALCULATION OF FORCES AND

MOMENTS DUE TO FLUID MOTIONS IN TANKS

AND DAMAGED COMPARTMENTS 66 Contribution by M.S.Pantazopoulos 66 Discussion on: THE APPLICATION OF SHIP

STABILITY CRITERIA

BASED ON ENERGY BALANCE 70

Contribution by H.E.Guldhammer 70

Disoussion on: THE EFFECTS OF DECK WETTING ON THE

STA-BILITY OF SHIPS IN BEAM SEAS 72

Contribution.by S.Ch.Duru 72

Discussion on: SUBDIVISION STANDARD AND DAMAGE STABI-LITY FOR DRY CARGO SHIPS BASED ON THE .

PROBABILISTIC CONCEPT OF SURVIVAL 74 Contribution by M Paw/owski 4

Author's reply. by M.Sigurdsen; S,Rusaas ...

75

Discussion on: BSRA TRAWLER SERIES STABILITY IN

LONGITU-DINAL WAVES

77

Contribution by J.Wi4niewski

... eeas ...

41.40etoo.

77

Discussion on: SOME ASPECTS OF SEAKEEPING FOR SMALL

SHIPS

... se.o60.a

...

..*01104..

79

Contribution by H.S6cling

79

Author's reply by

N.R.Kholodilin; V.K.Ti-ouninv

An ATTEMPT of SUMMARY

This is the last volume of the Proceedings connected with

the STAB

'86

_{Conference. Previously vol. I and vol. II and the} supplement to the vol. II were already issued.

Now, the report from the conference discussion is presented

.together

with all

_{contributions and remarke submitted by the}

participants in writing. From formal point

of

view it is also

an intention of the organizers to summari'ie the Conference by this volume. The essential

_{achievementiiof.}

_{the Conference - that}

is a contribution to the improvement of research _{and projects} connected with stability - will be rather estimated in _future

discussions

_{in various circles, mainly at the /MO Subcommittee} SLF and at the next STAB '90 Conference _{in Naples.}

The importance of the Conference _{will also be reflected 412 the}

initiation of some research works and in _{the application of}

their results into practice. Thus the

full

_{appreoiation of the} STAB _{86 is .a long process in which the contributions in this}

volume are

merely the beginning of it.

The STAB '86, held in Gdarisk, gathered

99

representatives from

Universities, Research Centres, Shipyards, Maritime

Administra-tions, Shipowners and Classification Societies from 15 countries

particularly 'from: Australia /1/, Bulgaria /2/, Denmark /2/, Federal Republic of Germany

/10;

_{United Kingdom and IMO /9/,}

German

Democratic

_{Republic /1/, Italy}

/4/,

_{Japan /12/,}

Nether-lands /1/, Norway /6/, _{Poland /34/, Sweden /4/, TUrkeV}

/1/,

United

States of

_America

/9/

_{and USSR}

/3/.

The meetings during the Conference consisted of 12 plenary

ses-sions and 2 discussion

_panels.

The plenary sessions were divided, as follows: Theoretical Studies,

Stabili,y and De,n,

- Stability

of Special Ships Types,

Stability of Semi-submersibles, Experiments with Models,

Stability in Operation,

Other'Problems"- mainly Damaged

Stability.

During these sessions e52 papers

of

72 acoepted and published in

,vol, I and'II!were presented and discussed.

The discussion

panele,

were connected with:

Outline of Research Programme Aimed at

Stability Criteria

Relationehip:betWeett

Stability Requirements and Design

The Conference reveals some progress in

theoretical works,

_

In the. submitted 'paper's Some new solutions of nonlinear

mathe-matical expressions of ship motions as well as a 'probabilistic

Concept

of,the.safety of ships against capsizing are

presented.

'In few papers aomeeXperimental reaults where

the

model 'tests

weredireoted

for Checking computer results

are

presented. In

aonwpapers the

experimental procedure is the fundamental ,basis employed for solving the problem of-Ship

stahility.

Among the *latter papers it 'seems

that

the

Most

important are these, which enable some stability criteria for modern cargo ships to be drawn to make them more.saie at sea. These new

cri-teria would supplement the IMO

criteria, originally set up for

cargo ships under 100 metres in

length.

The problems of stability criteria

still

remains open. In this field the Conference has shown again unsatisfaetory progress.

It seems that

this is

mainly due to the lack of the possibility for applying the very -sOfisticated mathematioal ideas

into

prac-tice,

Very complicated problems associated with ship service and

par-.

ticulary the so called Human raptor are the main obstecles here. The Conference emphasized the view that in spite of the

'refi-rement

of

pure stability from technical point Of view it is al-. so necessary.to improve the information provided to the ship

NMI

master and concerning dynamical properties of his ship. it

se-ems that'aqch information is the most effective way for

incre-asing the safety of a ship at see, where the ship can be treated'

-in terms of technical and economic cybernetic system'

The above mentioned remarks express the views-of the Organizers:.

Many contributions of intereitto the reader eon be found

in

this volume,Others,'not reoordeo'here will remain only.in

me-mory of the

Partipipants. But it is

believed that all of them

will be

reflected

somehow in

future

works on stability of ships .

and

oceap

vehicles. This is the only way to valueproperly the

'WELCOME

by: Prof. L.

Kobylitiski

aistinguished Guests,

Ladies and.Gentelmen,

On the opening

of the Third

International Conference. on;Stabi..

lity of Ships and

Ocean Vehicles on behalf. of the Programme

Committee and

Organizing Committee

,I would like to

welcome all

of You in

Gdalisk, in the Ship

Research Institute of

Gdalisk Teoh.

nical University.

In particular I

would like to

welcome cordially

Minister of Shipping

captain Ryszard Pospieszytiski

Rektor of' the

University Professor

Eugeniusz:Dembicki

and the Director

of the AdsOoiafion

of the Polish

Shipyards,

Mr Marian Kotlewski

who represent the

Institutions under

auspices of Which this

Conference is being held.

would also, like

to welcome

prominent representatives

of Naval

and Merchant

Hprine.Academiei,

ShipbuildiffgResearch and

Design

Organizations, Ship

Research Institute

of Gdalisk and

Szczecin,'

Polish Register

of Shipping,

Shipping Companies

'and

ing Press.

This a rare occasion

to assembly from

all over the world so

many

prominent soppntiste

who are working on

stability probleMe

from

the theoretical as

well practical point

of view.

We feel hodbured

that this

meeting id being held in

Gdalisk, in

the Ship Research Institute, which has its own small

contribu-tion to solving

stability problems,

'T can assure You

that

during this week

our staff

will make

ut-most effort to ensure

the Conference to

be moat-effective

and

we will do our

best that You feel

as coMfortable as at your

Introductory address at the OPENING SESSION OF STAB '86

12EL Prof. Ch. Mao

University of Strathclyde Dept. of Ship and Marine Technology

Professor KobyliAski, Minister

PospieszyAski, Rector Dembioki,

Director BurzyAski, Gentelmen: I think I speak for all the

de-legates from outside Poland when I say how delighted we are to be in Gdalisk and how much we appreciate the work done to organise this important event. I know what this has meant in terms of preparation, for my own association with

the

First International Conference on the Stability of Ships and Ocean Vehicles in Glasgow in 1975, and my involvement with Professor Motors( on the second one in Tokyo

in

1982. Our Polish collea-gues have devoted considerable time and effort to ensuring that the conference will be a success in technical terms and also memorable for those making their first visit to this wonderful country. I am sure all of us are hoping to see something of

,GdaAsk and get

to know a little of its history, culture

end

commercial activities and plow to

meet its people.

The conference, however is about "Stability". As everyone here will know, it was a subject of major interest in the late

nine-teenth century and then there was very little apparent progress for some seventy years.

Many people were, in

fact surprised that a conference devoted solely to the Stability of Ships

_and

_{Ocean Vehicles could} at-tract as many as twenty-four papers

in

_{1975! Yet the 1982}

con

-ference attracted even wider interest and support. STAB '86 has maintained the impetus and enjoyed an even greater

respon-se, with papers on topics ranging from "theoretical ;studies" to "experiments with models", and "practical criteria" to "sta-bility and design", not to mention the attention paid _{to new}

types _{of vehicle such as the semisubmersible. In fact,}

_the

subject is a popular one, as is evident from the number of

8

have come to this conference from all over the world, some of

whom have already established their reputation in other fields

such as theoretical hydrodynamics and ship motions.

There are plenty of convincing reasons for doing research on stability - so many in fact, that the dedicated researcher may feel its justification is self-evident. Capsizing, after all, must be prevented; the safety of those who work with the sea must be guaranted; investments must be protected; knowledge is

of value in itself; and so on. But can all these factors pro--ride the basis of a "carte -blanche" for continued and

increa-sed stability research?

Bearing in mind the fact that acceptable stability is only one

of around

fifteen key

parameters

in the

process whereby an

ini-tial concept is converted into a ship working to specification in the seaways, perhaps we should pause and ask ourselves

whether all the effort now being devoted to stability can real-ly be /notified.

Does capsizing take place

often

enough to Justify the amount

of time

and effort now being expended on its causes

and buret

Are we indulging in a luxury,

researching an

area

that we know is extremely

complicated and

offers few prospects of cost

re-duf4ion?

Let us examine some recent statistics. In

1975, the year of the

First Conference, the number of ships completed

worldwide was

2730. The annual fdLgure had dropped to 2312 by

the time of the

Second

Conference.

Information is

pot yet available for 1986, but the total

num-ber

of ohipe completed in 1985 had again

dropped, to

1962.

Significant sums of money have been spent on ship stability studies.in several

countries, particularly Dermeny,

Ca4da

and

the UK.

In the UK at least, -primegtions are being

raised about

the value of stability research, and attempts are

being

made to

quantify the cost against actual

loss of. life.

In Canada a Ro-yal Commiasien was

set up to

investigate

the

marine disaster associated

with

the capsize of the semisubmersible

"Ocean

Ran-ger" off the eastern coast of Canada in February 1982, with the loss of

eighty-four

crew members.

One outcome of this last

study is a set of

134

recommendations on

ways of

preventing another

such

tragedy, but the number of these recommendations requiring increased knowledge is actually quite small!

These developments could discourage efforts to improve the

sta-bility of ships and ocean vehicles and conferences and seminars

of interested parties to discuss problems and issues. In the light of this, how can we define a justifiable role for STAH86? Certain points do spring to mind at once. In the first place, it provides an opportunity for theoretical experts and practi-tioners to meet together. In the second place ,it

is

of benefit to participants from the host country, because it is such an opportunity to establish new contacts.

Thirdly,

it allows u0 to update ourselves on progress since 1982, and to compile a comprehensive set Of

paper* on

recent work in the area,

in no

more than two volumes. Other sithilar

reasons

can be added to

this list, but I do not think they are

Sufficient, Cicr

fully

satisfying;

No one needs remainding that the shipping industry is In the

midst of one of the longest economic recessions over known,and

shipyards

are being forced to lay off staff-and even

Olosd

through lack of demand,

'This 'Oat,

of

affairs is not helped by

the fact that

OneA4Viihe.biggest

users of ships, the oil in.

dustry, has itsolUtompororily

slowed down because of

a sharp

drop in the priCil'of oil:. In the fact of these difficulties it is essential that we should be positive and resourceful.

How-ever, a closer analysis of

the statistics -I gave earlier does

yield some enoouraging trends. For example, in the fishing vessel category - where stability

is highly

relevant - the

num.-bar of trawlers constructed did decrease from 717 in 1975 to

390 442

1902 but

this number has remained

steady since then,and

there appears

to

be an upward swing in the

demand

for

passen-ger ferries. However, for the industry as a whole to continue

to play a

key role into the twenty-first century, it is essen-tial for its products to achieve a high degree of

con-- 10

-tribution to this would be improving the performance of ships and ocean vehicles but this has to be done without impairing the stability characteristics of the vessels. Here is an op-portunity for stability research, but the emphasis must be on the application of the findings for the benefit of the

practitioners. The progress of our work can no longer be mea-sured by the solving of increasingly complex theoretical for-mulations. Instead it should be 'judged by the extent to which

' the users, whether designers or operators, can readily employ

the sound knowledge and relevant information that we have ac-quired over the years. Furthermore, we need to lay down a time Scale for establishing the applicability of research advances. May I suggest, therefore, that STAB

'86 should be

remembered as the international conference at which the emphasis of stability

tudies was placed firmly on improving the praotical

applica-tion of researoh findings, along with the warmth of the

THE CONFERENCE FINAL PROGRAMME

Monday - 22 September,

1986

Programme Committee Meeting Reception at the City Town Hall

RIX=4= -

Tuesday - 23 September,

1986

Opening Session

Welcome and introductory address by

representatives

of Polish Maritime Administration, Shipping Industry as well as Science and Eduoation

Introductory address by Prof. Ch. Kuo Session 1 - General

Chairman: Prof. 0. Krappinger W.A. Cleary, R.M. Letourneau

Design - Regulations yok..

XX /3.8/

H. Hermann, D. Wagner

Stability Crieteria for

Present

Day Ships Design 'vol. I /3.1/.

Session 2 - Theoretical Studies Chairman: Prof. T. Ozalp

E. Deakins, N.R. Cheesley, G.R. Crocker', C.T.Stookel

Capsize Prediction pping

a Test-Track

_Concept

' v91 II

00. 1 i'4.21/

A. Cardo, A. Francescutto, R. Nabergoj,'G. Trinoas Assymetric Nonlinear Rolling: Influence on

-

12

-F. Caldeira - Saraiva

The Boundedness of Rolling Motion of a Ship by Lyapunov's Method vol. I /1.11/

S.R. Philips

Applying Lyapunov Methods to

Investigate Roll

Stability

vol. I /1.10/

presented by K. Brook

SessionTheoretical

Studies

Chairmant Prof. R. Bhattacharyya

7, J. Wiiniewski

Floatien instead

of Statical Stability Proposal for Chang*. in Basic Definitions

vol. II /1.17/

S. H. B8tcher

Ship Motion Simulation

in Seaway Using Detailed

Hydrodynamic Feriae Coefficients

vol. II /1.13/.

P. K*Oger

Ship Motion Calculation it

Seaway by Moans of a

Combination of Strip Theory with Simulation IIAIdd. 1 /1.24/

Numerical Calculation of

Forces and Moments due

to Fluid Motions in

Tanks and Damagod

Compartments

vol. 1 /1.12/

H. S8ding, B. Telugu°

Computing Capsizing Frequencies

Seawayvol. II add.

of Ships in

_{1 /1.23/}

Session 4

Theoretical Studies

Chairman: Prof. M.N.

Rakhmanin

J.B. Roberts, R.G.

Standing

A Probabilistic Model of Ship Roll Motions for Stability Assessmest vol. II /1.15/

presented by K. Brook

W. J3locki

Probability of Non-Capsizing of a Ship as

e

Mea-sure of her Safety vol. IX /1.18/

13

J.T. Dillingham,

_{J.M. Falzarano}

Three Dimensional

_Numerical

Simulation of

_Green

Water on Deck

_{vol. I /1.9/}

C. Shin, M.

_Ohkusu

The Effects

_{of Deck}

_{Wetting on}

the Stability

_of

Ships in Beam

_Seas

_{vol. II /1.19/}

- Wednesday

_{- 24 September,}

1986

- Session

5

-Theoretical Studies

Chairman: Prof. S. Motors M. Hamamoto

Transverse Stability of _{Ships in}

Quatering

Sea

vol. I /1.2/

I.K. Boroday, _V.A.

Morensohildt

Stability _{and Parametric}

Roll of Ships in Waves

vol. I /1.4/ presented by

Prof.N.Rakhmsnin

V.

Shestopal, Yu. _Pashcbenko Approximate _Design Procedure of _Nonlinear Rolling in Rough Seas vol. I /1.5/ presented by Prof.A.Kholodilin ,19. Tn. _{Remez, I.} Kogan

Inclinations of a Ship _{due to Arising}

Seas vol. I /1.6/ presented by Prof.N.Rakbmanin A.N. _Kholodilin, V.K. Trounin, _B.N.

Oushakov

Some Aspects _{of Seakeeping}

for Small _Ships

vol. II /116/

Yu. Bilyansky, _{L. Dykhta,}

V. Kozlyakov

On the

_{Floating Dock}

a Dynamical

_Behaviour

under

Wind Squall

_in

_{Seaway'vol. I}

/1.7/

presented by

_{Prof.N.Rakhmanin}

R.E. Bishop, W.G. Price, P. Temerel

The Influence

_{of Load}

Condition in the Capsizing

of.Ships

_{vol. II}

add.

_{1 /1.22/}

--

14

-A. Campanile,

A. Cassella

BSRA

Trawler Series

Stability in

Longitudinal

Waves

vol. I

/4.3/

- Session 6 -

Stability

Criteria

Chairman: Prof.

M.Set. Denis

F. Plaza, A.A. Petrov

Further IMO

Activities in

the

Development of

Inter-national

Requirements

for the Stability of

Ships

vol. II

/3.5/

H. Bird,

A. Morrell

The Safeship

Project - a

Basis

for'Better

Design

and Stability Regulations'

-vol. II

/3.6/

N.A. Brook

A Comparison

of Vessel.

Safety

Assessment

Based on

Statical

Stability

Criteria and an

Simulated

Roll

Response Characteristics

in Extreme Sea States vol. II add. 1 /3.10/

H. Sadakane

A Criterion for Ship Capsize in

Beam Seas

vol.

I /3.1/

28' Ch. Kuo, D. Vassolos,

J.G. Alexander,

D. Barrie

The Application

of Ship

Stability

Criteria Based

on

Buergy Balance

vol. I

/1.3/

29. T.

Nedrelid,

E.

JullumstrO

The

Norwegian.Researeh

Project

Stability and

Safety for Vessels in

_{vol. I} /3.4/

Rough Weather

PANEL DISCUSSION I

-OUTLINE of RESEARCH PROGRAMME AIMED at STABILITY CRITERIA

Chairman: Dr A. Morrell + Prof. O.

Krappinger,

- 15

-- Thursday -- 25 September, 1986

Session - Stabilit and Desi Stabilit of S ecial Ship Types

Chairman: Prof. A. Kholodilin B.A. Dahle, D. Myrhaug

Probability of Capsizing in Steep Waves from the

Side in Deep Water

vol..I /4.1/

H. B. Guldhammer

Analysis of a Self Righting Test of a Rescue Boat vol. I /4.2/

M. Frtgokowiak, M. Pawlowski

The Safety of Small Open Deck Fishing Boats vol. II

/3.9/

L. Dykhta, B. Klimenko, Yu. Remez

. Determination of Heeling Moment due to Bulk Cargo

Movement under Harmonic Compartmeni:,s Oscillations vol. I

/4.4/

presented by Prof.N.Rakhmanin

34,

B. Kogan

Computer Aided Stability Calculations vol. I

/4.5/

presented by Prof.N.Rakhmenin - Session 8 - Stability of Semisubmersibles

Chairman: Dr B. Dahle

35;

B.O. Haciski, N.T. Tsai

' Stability Assessment of VISCG Barque Eagle

vol. I /4.6/

presented by W.A. Cleary

36,

R. Latorre, A. Slide, p. Magnier

' Utilization of Photogrammetry in Obtaining Hull

Offsets for Intact Stability Calculations

vol. II /4.0/

16

37, N. Takarada, T. Nakajima, R. Inoue

A Phenomenon of Large Steady Tilt of a Semi-Sub-mersible Platform in Combined Environmental

Load-ings vol. I /6.1/

38.

S. Takezawa, T. Hirayama

On the Dangerous Complex Environmental Conditions to the Safety of a Moored Semi-Submersible

vol. 1

/6.3/

39,

K. Ikegami, Y. Watanabe, M. Matsuura

Study on Dynamic Response of Semisubmersible form under Fluctuating Wind

vol. II

/6,6/

40.

H.H. Chen Y.S. Shin, J.L. Wilson

Towards Rational Stability. Criteria for Semisubmer-sibles - a Pilot Study

vol. II /6.5/

e"i°n9-Stabilita1

Stability °fS"ia1:.

Ship Types

Chairman: Dr J. Dudziak M. Jagielka

Stability Parameters of Ships Investigated by means of Discriminant Analysis

vol. II /3,7/

Y. Masuyama

Stability of Hydrofoil Sailing Boat in Calm Water and Regular Wave Condition

.

vol. I /4.7/

B.C. Nehrling, N.T. Tsai

Stability and Extraction of Grounded Icebreakers

vol. 11 /4.9/

P. Bogdanov, R.Z. Kishev

Dynamical Stability of Support Ship..Diving Bell Complex Vol. II /4.10/

M.R. Renilson

The Seabreake A Device for Assisting in

Preven-tion of Broaching -

too

- 17

-PANEL DISCUSSION II - RELATIONSHIP BETWEEN

STA-BILITY REQUIREMENTS and DESIGN

Chairman: W.A. Cleary + Dr J. Dudziak, B. Vermeer

Session 10 - Experiments with Models Chairman: Prof. W. Abioht P. Blume

The Safety

against Capsizing in Relation to

_Seaway

Properties in Model Tests

vol. I /2.1/

N. Umeda, Y. Yamakoshi

Experimental Study on Pure Loss of Stability _in

Regular and Irregular Following Seas

vol. I /2.2/

449. M. Kan T. Saruta, _Okuyama

Modl iXperiments on

Capsizing of a

Large Stern

Trawler. vol. I /2.4/

J.R. Spouge, N. Ireland, J.P. Collins

LOrge Amplitude Rolling Experiment Techniques vol. II /2.7/

50, H. Ad.. Bruce, M.S. Pantazopoulos

Experimental Investigation of a Vessel Response

in

Waves

with

_{Water Trapped on Deck}

Vol.

XI /2.8/

st.

P. Saderberg, S. GroohOwalskl, _{I. Bask}

'

capsizing Model Testi with

Stern Trawler

vol. XX add. 1 /2'.9/'

Session 11 - Stability in _Operation

Chairman;

Prof. A. Cardo 52. A. Sohafernaker, D. _Peace

An Overwiev of the Influence

_of

_{Stability Criteria}

on TLP Design _{vol. II add.}

1

/6.7/

F.L. Feeder

Improvement of Grain _{Loading Capacity for Dry}

18

-S. Kastner

Operational Stability of Ships and Safe Transport of Cargo vol. I /5.1/

E.A. Dahle, T. Nedrelid

Operational

Manuals for Improved Safety in a

Sea-way

vol. I /5.2/

M. Gerigk

The Human Factor Effect on

the Safety of Ship

Sta-bility at Sea

vol. II /5.3/

J. Stasiak

Lashing of Ship Cargo as an

Essential Factor

De-termining Stability Safety and

Economics of

Ves-sels

vol. II /5.4/.

_

Session 12

Other Problems

Chairman: Mr A. Vermeer

8. N. Hogben, j4A.B.Wi1ls

Environmental Data for High Risk Areas Relating to

'Ship Stability

vol. 1 /7.2/

_{presented by Dr A. Morrell}

590 D. Myrhaug,

S,P, Kjeldsen

On the Occurence of Steep

Asymmetric Wave in Deep

Water

vol. I /7,1/

60. B.A. Dahle, G. Moja

Improved Safety by Application

of

Subdivision of

Means of Flotation for

small Vessels

"

vol. II /7.5/

M. Sigurdsen, S. Russia

Subdivision Standard for Dry

Cargo Ships Based on

the Probabilistic Concept of Survival

vol. II add. 1 /7.7/

Y. Terao, K. Ninohara

On a Micro Computer Based Passive Controled

roll Tank System jSystem Simulation

and roa

B000

Measurements/ vol. II

/7.4/

sions.

THE CLOSING SPEACH

DLL Prof. L. KobyliAski

Ladies and Gentelmen,

The Conference STAB

'06

_{is approaching}

the end. .

Perhaps it is ttOt the _{place to sum_}

up

_{the results}

and-achie-venents of the

_{Conferences. This}

almost certainly will come

la-ter,as.partioipana will

_{have enough}

_time

to4qnietly assess all

the papers presentedand

thoughts expressiduring

_{the discus.,}

.

Therefore I restrict myself to formal

results only. To the

Con-. ference' 72

papers were submitted

and.lnajority.ef.them were pre..

sented'by.the.Outhersor _{by partioipants.acting on}

their

behelf.

99

_{pertieipents, were 'Present during-the}

Conference from

Papers

_{Were_divided}

_{under 7}

headings:. Theoretioel Studies

Stability Criteria,

1

Stability _{and Design,}

Stability of

_{Special Ship}

_TYpes'

Stability of Semi-submersibles, Experiments with

_Models,.,

'.- Stability In Operation

_and

Other problems /mainly _{damage stability!.}

Valuable

_{contributions}

_{were,nade during}

the panel-discussions

and in order

_{they were not}

_forgotten

we kindly request _{all 604.;} -tributors to submit those contributions _{by December,}

1St this

.

Year-Other

_{contributors are also invited}

to send their

_{comments by}

this deadline. All this contributions will be

printed in the .

Addendum 2 to vol. IT and

442tributed amongst the participants. All four parts of the

proceedings will be then _{submitted to}

_the

Subcommittee on Stability,

Load Lines and Fishing _Vessels

Sa-fety of IMO _{for information.}

All participants _{and in particVlar} members of the Programme

not be held.

-

20

-observations in writting regarding

possible organization of the next conference. Comments will be passed

to the members of Programme Committee.

Yesterday there was a meeting of

the members of the Programme

Committee. This meeting

proposed that,

in

the future conference

-be maintained aa the

'open

'conference and

that no

separate

or-ganization

or

permanent

secretariat is necessary. Simply, the

host organization of the next,

conference will'create the

secre-tariat',end

will undertake the

task

of preparatory

work for

the

next\conference. New Programme

Committee will be composed and this Committee will help the organizers

to formulate

the

pro-gramme of the conference.

7 already spoke about the next conference.

Yesterday, during

he dinner I announced that prof.

Cassella from the University

If:

Naples kindly offered the next; fourth

conference to be held n Naples. But I would like to ask

you if this propodal may be

ccepted by the Conference. So may I ask if

anybody has other

)roposal? If no,

then by

applause we may unanimously

accept

Aie proposal and I will send a letter

on behalf of the

Confe-rence

informing Prof. Cassella about your

decission.

must draw.your attention to, the certain

coincidence. Today

the

World Maritime Day declared

by.IMO under the. heading

-- International Cooperation for

Safety at Sea

and

Pollution

Prevention. So we have another reason

to celebrate - succesful closing of the Conference and the World Maritime

Day.

take that this is of a good omen

for our future work.

Finally I would

like to express

deep gratitude to

_the

members of

the Programme Committee for

their effort

towards the success of

ae Conference,all Chairmen for their help

to

ooflduct the

ses-ions, for the authors for their achievements

and to all

parti-cipants for

their coming

gnd for

their patience

foz4 all our

-aults. I wish all of You happy return

journey home. I wish to

.hank whole

heartedly to all members of the

Organizing Committee

composed of the staff of our Institute for

their tremendous

ef-fort before

and during the Conference.

I want to

thank also

to

all those members of staff'of the

Institute and others 'who

wor-ked behind the Conference

but without

-

21

Panel Discussion I

" Outline of Research Programme

22

-Open discussions: The -Open Discussions on Wednesday afternoon Sept., 24, was chaired by:

Dv A. Morrell British Maritime Technology Ltd assisted by: Prof. O. Krappinger Hamburgische

Schiffbau-Versuchsanstalt GmbH

Prof. S. Motors

Foundation for Shipbuilding Advancement, Tokyo

Mt T. Nedrelid

MARINTEK A/S

Trondheim, Norway

ontribution

for Panel Discussion I:

0RESEARGIAND DEVELOPMENT NEEDS FOR STABILITY

CRITERIA" A. Morrell

.NTRODUCTION

In his introductory address Professor Kuo raised the question as to whether the number of actual capsizings

justify the

re-search. Should, for example, a cost benefit analysis be carried out based on the number of lives and vessels lost, to justify

the research?

In My view this is not the best way to proceed, but it

has

to

be recognised that research is expensive

and

safety related research must be

Coat

affective in terms of the benefit it

pro-Vida. What Professor 4110

also

'said was that the sensible role

Or

Stab

'86 was to

provide a key strategy for taking stability criteria into the 21st century. One such role could be in the application of

findings of research for the

benefit of practi-tioners. Another important aspect ts to put a

time...Pcs1e ou.r

the application of

findings.

A possible

framework for stability research

A number of papers have been written on the philosophical

as-pects of

intact stability criteria

and Possible solutions for

the means of achieving the end

result. However,

the desired

result has so far proved unobtainable and this needs to be exa-mined in the experience of the last 10 years of stability

re-search.

In the author's opinion, several factors have emerged that-have meant that apart from the IMO Weather Criterion, no _new stabi-.1ity.oriterion has received international support sinoe the

in-troduction of the IMO criterion A167 introduced in

_1968.

Seve-ral factors have conspired to make progress in this

area

par-ticulary

slow, and

some of the reasons why new

stability

cri-teria have proved elusive

are

as follows:

1/ The absence of an adequate theoretical model to model

cap-size. It should be appreciated by now that if

existing

theo-retical.modele are used it is not possible to *predict"

cap-size or even estimate the probability of _{capsize, beoause} the problem is too poorly defined.

2/ The extremely complex natureof the problem

_{and the}

_number

of different modes of capsize, i.e. pure loss of stability and broaching etc. has tended to direct

effort

_into

long-term research programmes.

3/

The difficulty of defining the _{problem to be solved, i.e.}

_what is, the real problem

_and

_{how can it}

_be-.solvedw

4/ The absence of _{any clear objective as to}

_{what end rbsult is}

required,

i.e. !tat.

_{level and}

_{for What}

_application.

Although the

_{problem of}

_{intact stability is worthy}

of research

on several.frOnts, it has lacked realism and has

left

_the

_case

for

°capsize"

_{research overstated. For example,}

if

no adequate

theory exists to predict _{capsize, why no simplify the}

problem

to large amplitude roll motion whithin the limitations of

_f60i

theory?

2 .

The most important aspect must be the overall objective; whet-her to improve the state of knowledge in several areas of

in-terest or to strive for obtainable results

whithin a

reasonable

timescale.

Research for Stability Criteria

There are several ways that research into stability criteria ha i been conducted in recent years which are worthy of conside-ration and each have their own contribution to make to this complex subject.

The three main approaches may be described

as pregmatio,ad-hoc,

-Isinly theoretical and model experiments. Pragmatic

Stability research in this category includes studies related to

the problem area of roll stability and includes topics such as he Rahola-type of stability criteria where every effort is ma-e to producma-e practical and usablma-e criteria. Although the re-sults of this approach to stability has provided the most widely

sed methods to date, they usually have severe limitations

such

smallness of sample of casualty data used or in the absence external

forces etc.

Ad-hoc

In this category stability criteria research is often centred on investigations of a particularly casualty such as the loss

a fishing vessel or loss of an Oil rig from which general in-dications are sought on how stability criteria might be modified

or

improved.

Mainly theoretical

The last two International

Conferences on

stability have seen a greet number of papers in this category; they are usually ba-sed on complex

mathematic

theories to describe roll

motion ad

capsize but rarely conclude with a practical stability criteria that could be used by regulatory bodies.

- 25

Model Experiments:

Model tests have been used _{extensively world wide to}

help bring an understanding of the physics of the

capsizing mechanism. The most notable examples in this area are the identification of pure loss of stability and of

parametric resonance by Professor

Paulling for example and _{extensive physical modelling}

of the

complex and non-linear problem of broaching by Profs. _Motors and Fujin°.

Although much research has combined

_theory

_{with experimental}

measurement, the purely _{experimental approaoh is}

limited by the type of ship model and

_{the range of experiment.}

In view of this - situation, stability assessment could be considered as

_an

as-pect.of Beekeeping performanoe in whioh _{motion and acceleration'}

limits could be set _{for safe operation in}

a seaway.

In this context it _{is the seakeeping qualities of a ship}

that

are

Of vital

_concern

in assessing adequate levels of intact stability.

The question

remains - what is sufficient stability?,

Framework for

Stabilit

Criteria

_Research: The objectives _{for stability}

research should clearly be defindd at the outset

_and

consideration given _{to the}

_{particular area of}

application and the

_{duration of the}

_{research. These}

aspects are

as outlined below:

1. State objective: a/ design

criteria

b/ _{regulatory criteria:}

i/ modification _{of Res. A167}

ii/ new

_criteria

iii/ guidelines

0/

_{short-term /5 years/}

- 26

2. Realistic assessment:

Any new stability criteria should be based on a

realistic assessment of what can be achieved and whether it will be accepted nationally or internationally.

a/ limited objective:

i/ beam sea criteria

ill following sea criteria

bir international/national acceptability

0/

credibility:

i/ based on physics end theory

ill validated

by simulation/full

scale trials

iii/ appropriate for different ship types. Stability Criteria

Stability oriteria in the future oould be based on

the following oonsiderationst

i/ design wave

ii/ operational

limits of

roll

motion

Ai/ probability

that maximum

roll will

not exceed say

40° in -4

lo

in short-term sea state

iv/ roll angle in a specified wave Steepness has probability

-4

of occurence of 10 t9 ip-6, Design Criteria:

a/ bulk mineral cargoes .

.b/ lashings

for r9 ro ships

c/ angle of heel

in turn/crowding of passengers

- 27

Finally, in my opinion, intact stability research

t^r. the

fu-ture

should have limited objectives and more

importantly it is

essential for a

consolidation of the research on stability that

has taken place since

the first

international conference on

stability

in 1975.

This consolidation should provide

the

desi-gner and "practitioner" with .practical means of assessing

sta-bility in the

short-term and for the development of improved

Contribution

for Panel Discussion I:

"RESEARCH AND DEVELOPMENT FOR STABILITY CRITE.:i

RIA - STABILITY RESEARCH DISCUSSION ON

STABI-LITY CRITERIA"

kx_ To Nedrelid

MARINTEK A/S

Trondheim, Norway

STABILITY CRITERIA

SAFETY OF A VESSEL Theoretical stability Intact vessel Real life 0% - 28 -Calm water Waves Calm water Motions in waves 50% Operational aspects Wrong stability Wrong manoeuvring Water ingress Shipping of cargo 100% Traditional static criteria gives 100% safety Traditional static criteria gives. 95-99% safety Traditional static criteria still gives 100% safety

Traditional static criteria does not give adequate safety

29

Ships very seldom capsize as an intact vessel. Even in waves it

is difficult to capsize an intact vessel. Only in certain breaking waves or in some following wave situations is an intact

vessel likely to capsize.

The intact vessel situation, and how it responds to waves is therefore very theoretical when talking about safety.

The inquiry records from casualties always refer to non-intact

vessels. The capsize is caused due to mal-operation, damage,

cargo shipping, etc. These events are influenced by the waves and the motions of the vessel.

Future criteria should reflect this, and future research should

be considered around ship motions and how abrupt events occur. In

this way we define critical physical situations - vessel

description, vessel condition, waves - motions, operational

failure.

The results of findings from casualty investigations and research

should then be included in a total stability criteria concept.

A warning should be given to the people involved in stability

research.

don't be too academic or theoretical when defining or simplifying the actual situation that is being considered.

don't believe that it is possible to simplify the knowledge into static thinking or simple formulae.

traditional

stability

criteria and new findings

design and approval phase general risk -analysis of types of vessels and operations using modern techniques and advanced motion calculations

'

authorities responsibility

Further stability criteria concept should involve a total capsizing

safety,. and be built up of:

operational procedures and manual taking care of operational stability, keeping a weather-tight vessel, emergency procedures,

Contribution to the Group Discussion:

",RESEARCH PROGRAMME AIMED AT STABILITY CRITERIA"

bz

O. Krappinger

Ins titut fer Schiffbau der Universitet Hamburg

At the first and

second International Conference on Stability

.f' Ships and Ocean Vehicles

a wealth of valuable papers was presented, The same holds true for this, the third Conference. ' In spite of this fact not much progress has been achieved

re-garding an agreement on how to prescribe safety against

capsi-zing or how to make stability rules.

What are the reasons for this frustrating situation? It

appe-ars to me that

there are two main reasons which

prevent

pro-greos:

The first is to ask for too much: Scientific concepts. which are basically sound but

which cannot be realized,

at the time

'being are of little use to improve the present situation. Of

course we should go on to develop these concepts, but these efforts are an

investment into the future.

They

cannot

help

to solve the problems of today.

The second reason which prevents

progress is to pretend

that

the problem can be solved

by

methods which are

too prnilitive

and physically unsound.

What we need is an approach which is somewhere in betweeen the

two

extremes lust mentioned.

I do not think

it

wise at the time

being

to aim at a general solution of the problem of

safety against

capsizing which holds for all kinds of ships. In order to make progress

we

should try

31

Therefore in the following _{I shell restrict myself to ships}

the typeof whioh has been defined yesterday by Mr Hormann

and Mr Wagner, namely container vessels or Ro-Ro-vessels _etc. In order to develop

stability criteria for this group of

ships it seems

proper to start with the physics

oe

capsizing. I shell not go much into details _here.

In principle either experiments _{or theoretical models can be}

used. If sufficiently

developed mathematical models would be available, the outcome would be the _{same from both methods*}

We would find _{for a given ship}

with a certain draft in

_gi

von seaway that the safety varies with _{KG or with GM. It is} possible to determine _{limiting value}

GML with which _the

ship is just safe.

This can be done for different ships, each on different drafts.

For each oase we would find a value

_for

the limiting _{GML /Fig. 1./.}

But this is not yet the solution _{of our problem}

for two res.,

sons:

I cannot. think

_{of stability}

_{regulations prescribing}

model

testa be equivalent

theoretioal simulations. _Per regula-tions the outcome of such researoh _{has to be}

stipulated in

a simple and greet/cable _manner.

All physical investigations do not give any

_information

which level of

_safety

_{should be required.}

Testing ships

/physioally or by eimulition/

in the most severe which

_are

still realistic /although not _{very likely to occur/}

would lead to

requirements which _are

_{not reasonably}

acceptable.

\

In order to _{get a practically}

applicable representation _{of the}

results of _{experimental or}

theoretical investigations we may

try to find

_{a function of ship characteristic}

such that

it

assumes the same _value

for any ship when it has the limiting

Such a function

_{may be considered}

as a stability

crite-rium. While there is no straight

forward method to find such a function the _usefulness

of heuristically

_found

_fusictions

- 32

-For different ships the

values of GML vary in a wide range

/Fig. 2./. If we try e.g. the GZ

- values which correspond

to the GML - values the variation

would be muoh smaller, but

it would still be too big. If we use

the product

CGZ

max lee

defined in the paper presented

yesterday by Mk Hormann and

Mk Wagner/ corresponding to the GML

-values we find that it

is very much the same for all the different ships

in spite

of the

wide

scatter of their particular

GML . Therefore this

product can

be used as criterion. What we need next is a calibration of

this criterion so that

it provides a proper standard of

safety. It is not yet pos-sible to base such a calibration on

the probability that a

ship'will not capsize during its lifetime.

But we can find an /implicitly/ accepted standard

of safety by

determining

the values of the criterion for existing ships

which are cow-%

sidered just

sufficiently safe.

Finally I

would like to

summarize the

steps which

I ;think are

ne-cessary

in order to

end up with a

oriterion which can be

pra-ctically used for stability

regulations for a particular group of ships:

Systematic investigation of the physics

of capsizing

/

model tests or theoretical methods validated

by tests/.

2.

Representation

of the results

of the

syetematic

investiga-tion

in a form

suiied for

tability

regulOions.

The

sui-tability of

ouch

forme /or

criteria/ has to

be

proved by demonstrating that it reflect, the boundary

between safe

and unsafe

/as determined

by the systematic

investigation/

for all ships

of the

peneicler04

group.

.

Calibration of

the criterion:

An indication

ol the

presen-tly accepted

safety level can

be derived

by determining

the values

which the

oriTerion aseumee'for emiating

abips

are

considered juet

sufficiently

oaf?.

safe

KGs

GMs

just

safe

< KGL

> GML

Fig. 1

capsize

<

_KGc

>

_GMc

Fig. 2

(f = frequency)

GM Z1-flax

31+

-Comments to the "FLOATATION INSTEAD OF STATICAL STABILITY, PROPOSAL OF CHANGES IN BASIC DEFINITION"

by J. WiAniewski - presented on discussion session by the Author

J. Wiliniewski

Ship Research Institute Technical University of Gdadsk

Mk Chairman, Gentelmen,

You know the main, idea of my proposal from the title of my

pa-per. I would like to give you now short comments, explaining

this idea and its

supporting arguments.

Let us start from the definition of floatation. I hope every-body will agree that this is the ability of ship to float

in

he position of

stable equilibrium under .the

aotion of graVi..

4 and buoyancy forces. If somebody cannot aooept this

deftpition

please correct me.

Now as a consequence

let us deduce the conditions of float... tion which must be

fulfilled within

the framework of this

ac-cepted definition, We may use for

this purpose the commonly .

_ocepted law of mechanics that associates the minimum

poten-tial energy of an object with the

state of

stable equilibrium.

I have just done this in my

paper, simplyfying the deduction.

I have considered separately the changes of position coordiim

mates of the ship in water, treating them as displacements

with one degree of freedom, There are two reasons

for

doing

this: firstly, to be in accordance with classical

simplifi-oations, common in naval architecture, and secondly, because the general solution in vector notation is

not easy. I have

never found it published anywhere.

-

35

-them are connected with one notion. _{The ship in}

order to be floating at rest must have both

forces equal and colinear,

and the area of

_{equilibrium waterplane}

and the smallest

meta-centric hight must

_{be positive:::}

Then we have

_{conditions of}

_{floatation and}

the set of

parame-ters connected

_{with them. In}

_{my. paper /including}

the appendix/

examples are given of the range of practical _problems

which

are to be solved

_when

examining ship floatation. _{Floatation is} to be understood

in aocordance

_{with the}

proposed definition. This range of problems _{is large. It}

includes practically _the

'whole of

_{ship hydrostatics.}

-And now to the

_{subject of}

_{stability. Its}

definition

may be

quoted from

contemporary approaches in mechanics _{as: the}

abi-lity to retain

an

_{acceptable magnitude and}

character of res-ponse under existations of

_{predetermined}

magnitude and

charac-ter. This _definition

involves both the statical _{and dynamical} stability of the ship. But _{there are}

practically _{no other stem,}

tical ezitations on a ship, _{other than change}

in magnitude

and position

_{of her gravity force}

/changed with

_{zero velooi..}

ty/. And _{these problems}

are involved in _{our definition}

of

no..

station. Hence the title of _{my paper.}

Somebody _{may ask me what}

all this is for?

My _{response would be}

Firstly _{to be in accordance with}

general mechanics, _{one must}

be precise when talking

about equilibrium _{of a system}

of

for-ces.

Secondly

to clean the platform of

understanding in stahility

research.

Thirdly

- to

rationalise the Use of computers. _Inlay

paper

together with problems

concerning floatation I he*. _briefly described the state of the

_art

_{of their}

solution. These solu-tions are included in _contemporary

software. In my opinion

some changes

_{are possible}

and

_advisable. And forthly - the personal

reason - I see as a teacher _some elegance in this proposal, _{and I like}

its results. That is all I would like to _present.

-

36

-Panel Discussion

II

-

Relationship between

Stability,

-

37

-Open discussions: In the -Open Discussions period on Thursday

afternoon Sept., 25,

chaired by Mr Cleary

assisted Vy Dr Dudziak and Mr Vermeer, the

subject was DESIGN AND REGULATIONS

Mr A. Cleary

U.S. Coast Guard

Washington

USA

Dr J. Dudziak

CTO-OHO

Gdalisk, Poland

Mt H. Vermeer

Directorate General of Shipping

and Maritime

Affairs

Netherlands

Mr Cleary presented thoughts on the practical _{reasons for}

sta-bility research

and

the regulatory review cyole.

He

also presented a

_{figure compering the amounted of total}

sa-fety in design. of very Urge ships versus very small ships in a full ocean storm. it _{Was. suggested that tete' safety is} com-posed of design safety, operator safety and always there is

so-me safety

left to Ohaebe. Absolute safety is never Possible in

advance. In *ho smeller ship. *104 is more affected by large

seaways

in

major

_{storms, it was remognized that a larger} per-centage of safety must

ba left

_{to the 'operator or required of} the operator.

He felt the most difficult

area in

_{application of regulatory}

standards occurs

wheq

it is realized

_{that there is not euffia.}

cient information

to

_{decide immediately whOther'}

an existing

standard is

adequate

or

_{not. The many maritime nations of the}

world ought to be

_{active in research because the existing}

- 38

-applicability.

Dr Dudziak emphasized that the form of each stability crite-ria is not necessarily the most important problem before us. Rather, attention should be paid to which items of stability evaluation should be included in the evaluation.

He recommended

that the criterion can

be effective if

it suc-ceeded in preventing a sudden capsize. He also mentioned weight

growth

and gyradius changes which should be kept below a 10%

,change. Finally he recommended stability evaluations of ships using cross curves on waves and in various seaways.

Dr Vermeer completed the comments from the panel by

ealphasi-zing that stability criteria ought to be coupled With

consi-deration of the Type of Ship Hull; that operational limits may

be necessary for new ship types such as offshore Crane vessels and submersible Wessels; and finally that on.-board Computers for maintaining current stability information should be exami-ned and utilised

using new

high speed electronic memory capa-bilities.

The voluntary speakers at this session

were Mr Zychski

of

the

Gdynia Shipyard, Professor Kholodilin of

Leningrad Shipbuild-ing Institute, Professor S. Kastner

of

Bremen University. Dr Dahle of Pet Norske

Veritas and Professor Kobylidski.

Mr Zychski spoke particularly

of the need for

subdivision flo-oding protections in dry cargo ships. He pointed out the error committed by deaigners who calculate damage stability only to the margin line because international rules do not necessari-ly require the designer to view all the aspects of design we-akness. This error he referred to as "margin line sickness". professor

Kholodilin

spoke of the need to

utilize

the probabi." lity approach to stability accidents and the need to solve the

dynamics of seaway motion in an accurate representation of te

-

39

-Professor Kastner _recalled

Professor

_{Krappinger's comment that}

stability criteria _{should be}

simple in

application. _{He noted} that

_{ship Masters}

are eager to

_obtain

information _{from ship}

researchers, _{that Masters}

can effectively

increase the safety level, if

they know that to do.

_{He also}

mentioned

_{as an item}

of

_{concern the}

relatively

_{new development}

of cargo related

0e-sualties,

_{whether from inadequate}

lashings or

stowage, _{or frog}

extreme ship

_motions.

Dr Dahle

_supported

Dr Dudziak's

_comments

on proper

_design

es-pecially with regard to _large

_{ships and}

that a

_{sudden capsize}

is not

acceptable and

_should

cause

administrations to develop

more conservative

criteria. He noted that

speed is an ignored but important

factor in _{most stability}

criteria.

_{Finally be}

spoken of the use of

warnings, to MASTERS _{as often}

not general-.

ly applicable

_{to all}

situations.

Professor

_Kobylideki

reminded the

delegates that there is _much

more to the

_{selection of}

design

_{standards than}

a hydrodynamic

examination. Criteria _{must include}

the broader

problems suoh as Environment,

Construction _{features and skills,}

and

Opera-tion. He recalled _{that 70% of all}

oasuelties _{have an}

element

of human

_{error as}

part of _the

cause or as the _{reason why}

a

email _eenident

became a

_major

Contribution

for Panel

Discussion

II:

"RELATIONSHIP BETWEEN STABILITY

REQUIREMENTS

AND DESIGN"

kx_ S. Kastner

Bremen

Polytechnic

I am

going to

deal with,

in my

view, three basic problems.

First on

deriving

practical

stability

criteria now:

Defining and

calibrating a

measure from

comparison

with a set

of experiments, as

Prof.

Krappinger

pointed out

yesterday, is

certainly

the most

practical way.

It is

important to

agree

in-ternationally on

some

formulation

of that

measure

to allow

for

sound criteria and

regulations on stability.

More than 20 years ago, we

pursued basically the same appro-ach in Wendel's group in Hamburg.

We had evaluated free water

model tests

and

capsizing runs

and compared

the results

with

Ample wave

crest and

through

calculations as

a

practical

pre-Aura.

Then, A

moment

balancing method for

regulations Wan developed, which included the wave

crest

reduction.

,A main difference

of the new criteriou devised by Dr Blume

ba-sed on HSVA tests is to relate

experiments on capsizing regular seas with the still water

righting arm solely, and to

derive a

formula

his C-factor

- to

make things

even easier to

apply.

Any of those measures

are just comparative simplified measures,

based

on the

need to

cover a very complex and complicated

be..

haviour of the ship in a most simple way.

We may call criteria of

Olt, kind

to be a suitable replace-ment for

the real

thing, quite ficticious

inT;a way,

This leads we to my

second

point, whigth'has been clearly

ref-lected in Mr Nedrelid's

remarks in the

Panel

discussion,

Ship masters tend to apply

regulatory stability criteria

-some measure and guidance how to operate a ship. However, any

criterion of the above kind does not show the specific events covered. Thus, there is a need to develop information to the master on his ship behaviour in severe environment.

What happens, if a ship in the future capsizes after

fulfil-ling the newest develop international criterion, due to

impro-per oimpro-peration? There is always some probability for capsizing left, and it is up to the operator of the ship to operate sa-fely. Naval architecture is now at a stage, where we know e-nough on motion behaviour, and we must convey our knowledge

In

an efficient and simplified way.

Finally, do

not

let us forget on the dangers from the feed-back of the cargo, as cargo oonstitutes the moat part of the

tzi-31 ship mews. This relates with questions of lashing and securing of cargo in order to prevent shifting.. Shifting of

cargo has been the cause of many recent capsizes and ship

142

ontribution for Panel Discussion II:

"RELATIONSHIP

BETWEEN STABILITY REQUIREMENTS

AND DESIGN"

bz.

J. Stesiek

Ship Research Institute Technical University of

Gdatisk

'Whenever we talk 'about _{stability criteria we are nearly} al-ways thinking about the ship safety against dapsizing.

However these two problems are not identity as have been re-marked today both by Prof. Kastner and Mt Nadrelid. For this reason the stability criteria themselves,

_even

_{if the best,} are never univooally of the solution of the safety

_{problem be..}

r1OUSO:

they do not oomply with structure _{and operation of the} man-ship-environment system,

they are solutions of long-term _{prediction character}

prescinding from the constantly changing

conditions of the ship's exploitation,

they do not take into consideration _'such: phenome-na as flooding and shift of cargo for example,

they do not take into consideration

_{the economioal}

as-pects of shipping,

they ignore the subjeotive rale of a man as the opera-tor of the system.

my opinion the real problem of safety _{against capsizing' is} ! system-subject, a cybernetic one and such also should be its

3222112221.

A good measure of the safety is.a space of condition in which this safety have been kept /see Fig.1/.

-A magnitude of space conditions of potential ship's safety /P.S./ is specified by the inherent

ahip's

_{stability only,} whereas the real safety /R.S./ conditions resulted from inhe-rent stability as well as from the operational decisions of