Sub-division of Ro-Ro ships for enhanced safety in the damaged condition

CENTRUM TECHNTKI OKRFTOWEJ

ÔK XVIII - _{NR B066 - ISSN 0860-6366}

4

TECHJISChE UNIV R$ITEIT .aboratorftjm

Sthshydromechaj

Arcblef

Mekelweg 2. 2628 _{co Deift}

015-781838

SUBDIVISION OF RORO SHIPS

FOR. ENHANCED

SAFETY

IN THE DAMAGED

_CONDITION

Maciej PavWowski, Professor,

_{D. Sc. (Eng.)}

ZESZYTY

_PROBLEMOWE

Ship Design & Research Centre

Research & Development Department

Gdañsk

B-066

SUBDIVISION OF RO-RO SHIPS

FOR ENHANCED SAFETY

IN THE DAMAGED CONDITION

EDITO& _{Math Kubacka}

PUB LISHE&

EDITORIAL:.OFFICE:

Ship Design & Research Centre 80-958 Gdaiisk

uL Waly Pi stowkie i box 270, POLAID telefax: O-5831-16-83

telexf 512474-76

Division of Productivity, information

& Scientific-Technical Studies 80-958 Gdañsk

ul Waly PistOwki.i phone: O-58 374-275

CONTENTS

-Abstract

.. 7

Inttoductiön ₈

Current subdivision arrangement of ro-ro ships ₉ Provision of double hull and deep sinkage after_flooding 1

Provision of buoyant decks ₁₆

Numerital examples ₁₉

Conclusiòns ₂₃

Appendix ₂₄

Maciej Pawlowski

Professor, Ship Design and Research Centre, Gdaiísk

MACIEJ PAWLOWSKI is a Professor in the Faculty of Ocean Engineering & _Ship Technology at the Technical University _{of Gduisk where he graduated in 1970 and where he} continues to work He works also part time as consultant for the Ship Design and Research Centre in Gdaiísk. He lectures _{on various aspects of theoretical naval architecture including numerical} methods, ship hydrostatics, fluid mechanics and applied ship hydrodynamics _{He spent a year at} Glasgow University, and three years in two periods at Newcastle University as a visiting Senior Research Fellow.

As a researcher he specialises in ship static, with particular emphasis on the probabilistic assessment of ship safety in the damaged condition. Connection with this since 1972 he has been active in the SLF Sub-Comn:ijttee_{of 1MO and contributed significantly}

to probabilistic subdivision regulations for dry cargo ships.

Progress papers were presented at:

the i 2th International Conference & Exhibition on Marine Transport using Roll-on/Roll- off Methods, R0R094, Göteborg, 26-28 April 1994, vol.2.;

Polish Maritime Research, No 1, September 1994, voLl, p.7-12: also in Proc., 5th

mt.

_{Conf on Stability of Ships}

_{and Ocean Vehicies-STAB'94,}

Florida institute of Technology, November _{1994, Melbourné, Fi., USA, vol.6 (Discussions), ibid.;} The Naval Architect, April 1995, _{p. £198, and E201-203.}

The paper shows that ro-ro ships can be as safe in the damaged condition _as other ship types without restnctmg their design

_{features, i e, with no transverse}

and/or, horizontal subdivision within the _{cargo spacé liable todainage, if theré the} provisions'for reserve büoyáñcy above the vehicle deck - the 'first deck abòve the deepest waterline. For this purpose, these ships should embody a double hull over the éñtire length Of the thgo part of the ship ,

terminated at the 'se'cáñd dékabòè

the' waterline :and,

_{- in addition, -double decks at least the fi±st deck aboyé the}

waterline, preferably inclined upwards in the longitudinal direction. The 'double

hull and double decks should be sufficiently

_{densely subdivided by watertight}

bulkheads into watertight compartments, the former preferably cross-connected and of ' a breadth less than «B/S. Cargo

_{spaces below the double decks should be}

provided with efficient air escapes for removing air cushions from the undersides of

the decks. A deck (or decks) if

_{any, below the first deck above the waterline,}

together with this deck should be designed as opened to the passage of flooding. water, incorporating efficient down-flooding _{arrangements.}

INTRODUCHON

Ro-ro ships are considered by the maritime profession and travelling public as the most unsafe ships in operation, and this is not surprismg when one considers their very low indices of subdivision, usually far below the required valu This

comes fact that these ships were often poorly designed :with little

_{or no;}

concern for damaged stabthty The large open vehicle decks of ro-ro vessels makè them particularly sensitive to the presence of water on such decks which may flood them due to collision damage or other accidental operational. reasons like flrè

''

fighting, intake of water due to the bow door being left open (as in the case of the Herald of Free Enterprise), or leakage of water through the aft door deprived of weathertightness, as was most ce1y the case of the Jan Heweliusz, a Polish ferry which capsized in January 1993 during extremely heavy weather, causing the deáth

of 55 passengers and crew members, with only nine persons rescued.

These two disasters clearly illustrate the potentially devastating influence ¿f' -.

an open, deck on the damaged stability of a ro-ro :vessel. In the absence of

transverse subdivision, even a very small amount of water on such a deck can lead to rapid heeling and l6ss of stability, usually associated with a large loss f life.

Here arises the question.as to whether we are faced then with the necessity of abandoning such an operationally efficient concept of sea transport in the pursuit of higher safety standards. Fortunately, there are alternative design configurations

which may provide the necessary improvements in, safety standards without

incurring the obvious operational penalties that subdivision of the open deck would impose, but there have been few studies in this area to pròvide any firm guidance.

This paper aims to show how signif cant improvements could be made to the

survivability of existing and future - ro-ro's, withoüt impairing their present

successful operationàl features. There are feasible solutions to the associated design problems, the principles of which may be applied to car and cargo ro-ro ferries and vessels of every shape, size and description. These solutions are considerably more tangible than warning lights or video cameras focused on bow and stem doors in a bid to ensure that they are firmly closed! They are entirely based on new design configurations, providing ro-ro ships with a high level of passive (built-in) safety, easily meeting the new requirements concerning ship survivability, based on the

probabilistic concept.

I CURRENT SUBDIVISION

_{ARRANGEMENT OF RO-RO SnIPS}

.For some forty years there have been cargo ships and passenger feñies

having no transverse watertight _{bulldieads within cargo spac, iñtended primanly} for the câmage of roll-onlroll-off cargo -They havi usually the following watertight compartments double bottom, forepeak, afterpeak, engine room and wing-tanks .The fore'and aft collision bul1theads,irig tanks md other trarisieiie bulltheads are

terminated as aruleat th

_{bulkhead deck the first deck abò the deepest load}

line, called also vehicle (car) deck. -. S..:

- Until 1 February 1992 there were no subdivision requirements for cargo ro-ro

ships. That is why tanks on such ships were applied with ballasting in view and

fréquently due to

_{psychological reasons rather}

_{than due to subdivision}

considerations. They could save the ship only in cases of shallow damage in _{one of}

those tanks.

- There are known car-passenger ferries (of ro-ro type), that are subject to

sùbdivision and damage stability

_{requirements contained in the 1974 Solas}

Convention. Space below the bullthead

_{deck où such ferries is usually densely}

subdivided by transverse bulkheads, _{extending from side to side. In such a case,} wing tanks are not appliéd and many of the compartments below the bulkhead deck are neither used for the carriage of cargo nor for other purposes. On the remaining ro-ro passenger ships, compartments of breadth B/5 are applied below the bulkhead

deck, which are relatively short and cross-connected to avoid asymmetrical

flooding. This type of subdivision_{arrangement is shown in Fig. 1.}

The above solutions do not provide sufficient safety for passènger ro-ro ships

in case of collision. On the

_{contrary, : these solutions appear to be extremely}

dangerous as they do not secure a ferry against rapid capsize in the Oase of sea water accidentally entering the bulkhead _{deck. A good evidence for this was the}

tragic capsizing of the European

_{Gateway in 1982 and the Herald}

_{of Free}

Enterprise in 1987, to mention only two recent well known disasters.

OECK4. I DECK 3 DECK 2

\/

DECK i B/S _B/5

Fig. 1. A typical but extremely dangerous subdivision on some large ro-ro, ships

-The two ships had the same type of subdivision, derived from the _SOLAS

Coii'iention, where the thip due to low freeboard, is densely subdivided

_with

transverse bulkheads below the bulkhead deck in order to get one compartment standard and with n reserve of buoyancy above it... _{s the compartments are then} very short, probability of flooding more than one compartment is therefore high, résultiñg in verf low probabilities of surviving for such ships and thus objectively

onfrfning theirbad performance rn case of collision

Jnaddition,» the .dense

iibdivision öaiises the machinery spacè to be divided

into smaller watertight compartments and this in turn opens up an area for human error. A good example of this illusory subdivision was demonstrated by the sinking of the European Gateway [1].The ship received a small damage below the bulkhead deck: but between the .bulkhèads of the machinery part of the ship Instead of surviving this _potentially safe standard case of damage, she sank very quickly (within some twenty minutes) as all watertight doors within that part of the ship were left open, leading to the flooding of four compartments instead of one. The crew undertook desperate action to close the doors but tragically failed to do so.

The new probabilistic rules [2] 'which éntered into force in February 1992, require the same level of safety for all dry cargo ships irrespective of their type.

Thus new ro-ro ships will hâve to be equally safe (have the

_{same indices of}

subdivisions) as the remaining dry cargo ships. The indices of subdivision for existing ro-ro ships are very low, if not marginal, frequently not exceeding a value of 0.1 whilst for other dry cargo ships this index value is

above 0.5. There is no possibility whatsoever of increasing the indices of

subdivision so markedly within the currently applied concept of

ro-ro ship subdivision, except

through a considerable increase in freeboard or

.

by the

application of removable transverse bulkheads. in holds intended for ro-ro cargo. Such solutidns are clearly contradictory to the. basic operational features of.ro-ro ships and should bé applied only in the last resort.

...

.

..

.. ...

2. PROVISION OF DOUBLE IIULL AND DEEP SINKAGE AFTER FLOODING

:

6,.feasible and efficient remedy for the poor safety of ro-ro ships is

application ôf the idea of deep sinkage after flo5ding, presénted in detail in [3], and briefly summarised here. It stems simply from the fact that the damaged stability of a ro-ro ship with its bulkhead deck immersed, which is a typical case, mcreases the deeper the ship sinks. _{This startling observatiäñ is not difficult to explain. An} increase in damaged draught for any constant damaged displacement allows the

centre of buoyancy to move closer to the centre of gravity thereby improving

stability. Moreover, experiments have shoi that in ships with the much deeper

draught associated with the final stage of flooding, any roll motion in waves almost

completely disappears so that only heave motion remains. It is therefore

very unlikely that such a vessel would be capsized by wave action when it is floating deeply immersed in a ñear upright position.

In the light of the remarks above an increase in the number df bulkheads below the vehicle deck is found to reduce damaged stability dramatically. This situation is opposite to that for conventional ships and is confirmed by mòdel tests

[4]. It is evident from the foregoing that the primary safety feature for a ro-ro vèssel should be a mandatory double skin extending fröm the inner bottom to the second deck above the waterline (the upper deck). The wing compartments so formed

should be transversely subdivided throughout and incorporate modest flare,

if possible.

Apart from this the number of transverse bulkhèads should be limited to the forward and aft peak bulkheads and those required to adequately _{subdivide the}

non-vehicùlar spaces such as the machinery spaces. The - strength of these

bullcheads should, of course, be adequate for. the pressure loads imposed by the deep draught in a damaged condition. No further transverse bulkheads should be provided, as their function is replaced by the wing compartments.

.this type of subdivisin arrangement is shown in

_{Fig.2. Thereadth of the}

wihg tanks preferably equals B/b, half

as large as in the previous case. As such

ro-ro vessels are capable, as a rule, of surviving a major flooding, at least in

a partial loading condition, there is no need to increase the height of the double bottom. On the contrary, from the standpoint of damage stability, the minimum height is preferable.

DECK 1'. X.

/:;

'Vf

Y

\

/

t!':

DECK i (

\

'-.---.

Fig2. A typical subdivision arrangement for ro-ro ships based on the deep-sinkage-after- flooding concept

To limit the effects of flooding, the wing compartments should be relatively

short,

_{identically subdivided bn - bdth sides and cross-cànnected to prevent}

asymmetric flooding, which is always detrimental to a ship in a damaged condition. In the case of passenger _{ro-ro vessels, the current SOLAS regulations require that} lower wing compartments should have a breadth of not less than B15 and no wing tanks above the bulkhead deck, as shown in Fig. 1.

If one assumes that major flooding of inboard _{spaces represents the loss of a}

ro-ro ship then it would be necessary

_{to require, for ship safety, the wing}

compartments below the car deck to be as wide as possible to minimise the risk of such a possibility However, that is not the case and, therefore, there is no need to

impose such broad wing compartments in this position.. To withstand

major

flooding, it is most important for a ro-ro ship to ensure positive stabthty at the final

stage of th&event when the bullthead deck its mnìthersed.. It has beèn shown that thi

is quit& practicable and reqùires ònly that

_{narros :wing öomartments be fitted}

below and above the vehicle deck, as shown in Fig.2, to ensure both stability and

sufficient reserve of buoyancy. Such is the purpose of providing these wing

compartthents. V

Merit of a Double Skin

Wing compartments on a ro-ro ship can fulfil many other important functions

They greatly enhance the ability of the ship's sides

to absorb the energy of

a collision, thereby decreasing the extent of damage, while also increasing the

resistance to breaching during minor collisions.

They provide a positive contribution to the vessel's overall strength.

They provide essential trimming ballast capacity in the lower hull.

Thcy contribute directly to improved damaged stability. lThcy smooth sides make cargo handling easier in the holds.

E Thcy effectively protect the ship agairist the effects of leakage due to cracks or

.sthall bréaches of the shell..:.

Intermediate Stages Of Flooding

Thus far stability during the intermediate stages of flooding _{has not attracted the}

attention it deserves. Work done to date supports the intuitive notion that the

intermediate conditions are not usually

.

a problem if the final condition is

acceptable, provided the angle of heel is not so large as to cause cargo shift and the water can freely spread over the entire compartment. The deck _{edge then remains} above the water all the time during transient flooding [5].

The same applies also for

ro-ro vessels with double skin arrangement

provided that the decks are made opened _{to the flooded water which is crucial for}

the safety of these ships. . i

Thus if there are efficient down- or cross- flooding arrangements, it is entirely sufiicient as far as damaged stability is concerned to check only the maximum angle of equilibrium during flooding, and focus attention _{on the safety of the ship in the}

final stage

of flooding.

Hence, the above theoretical development has

a considerable impact on the simplification in damage stability assessments.

Owing to physical reasons, stability during the intermediate stages of

flooding should be analysed for the freely floating ship longitudinally balanced at

each angle of heel, using the added

_{mass methocL There are usùaliy marked}

differences between the GZ-curves calculated for the free trim condition and for fixed trim, particularly if the deck edge becomes immersed _{and the ship has large} longitudinal asymmetry. However, in the case of horizontal subdivision without efficient downfloading arrangements, it should be assumed that after the immersion of the edge of the watertight deck, the level of water above such a deck coincides with the level of water outside. This

_{covers the ease öf amál1 hoI&bèlow and}

a very large one above the horizontal subdivision,

_{a typical damage when the}

striking ship has a bulbous bow associated with a large flare - see the case of the European Gateway [1].

The current regulations [2] overlook entirely this problem. This is one reason why naval architects consider horizontal subdivision, particularly on ro-ro ships, as beneficial to their safety. Unfortunately, this is not the case and it is now high time to tell this loudly and clearly in an attempt to divert the way things are developing.

Perforated Vehicle Decks

An important point on all ro-ro véssels concèrns the watertight integrity

_of

the main and other vehicle deck, i.e., the présence of horizontal _{subdivision. From} the previous discussion, it should bè èléar that any deck, including the vehicle

_declç

which may suffer flooding from whatever source,:should be non-watertight.

Furthermore, such decks should be designed to allow both water and air to pass

freelythroughthem.

::

How this shoildbe cc

_{hractice is an interesting}

_{challenge for}

the designer. The drainage systems must be capable of allowing vely large quantities of water to drain directly into the lower cargo spaces without access to machinery or other critical _{spaces, V which must be effectively sealed from the}

cargo spaces at all times. This has the

_{effect of maximising the damaged}

metacentric height by both eliminating isolated free water surfaces and lowering

the centre of gravity.

Watertight vehicle deck _{or tWeeñdeòks cannot be recommended for the}

following reasoñs;

E Decks below the vehicle deck are not usually designed to withstand the

pressure _{forces that would be imposed by serious flooding either above or}

below them.

E When flooding occurs above such a deck, a large free water surface is formed which immediately reduces the vessel's metacentric height, usually causing a

large angle of heel or capsizing. V

E These decks can trap large quantities of air beneath them _{during sinkage,} maintaining an additional free surface effect, which would be eliminated tf the compartment were free to fill completely. In addition, _{these air ;..cushions}

-contribute to

the creation of

an additional heeling moment öf V significant

value as they are formed usually

_{at the outmost areas beneath the decks}

close to the side

V opposite to damage. As

a result, these air cushions are

extremely dangerous and lead to the capsizing of the ship, othérwisé safe, before reaching the finalstage of flooding.. _.. r V V V

;.

V

.

EWáéitih

ramps and decks are more expensive than their

_{non-watertight}

counterparts. V

V - V

V

V V

In view of these points, there seems no good reason to retain the concepts of either horizontal or vertical watertight subdivision applied to internal vehicle spaces. In particular, retaining the vehicle deck as a bulkhead deck is particularly dangerous and should be abandoned _{as a design objective.} V

There are two further reasons why the bulkhead deck within the cargo

space should be made transparent to the flooded water. Such a deck virtually eliminates the accumulation of the flooded

_{water above this deck due to the}

action of waves which is foúnd to be

_dangerou

_{and it leads}

_eventuali

to

capsize [6,7]. Due to a very similar reason, the watertight deck is also detrimental to stability during the _{intermediate stages of flooding which is rarály}

analysed

dunng Uesignzng and _{overlooked by the current regulations}

- -,.

--

_{The idea of deep}

_{smkage was implemented}

at _{the Gdansk Shipyard,}

-Poland by deigniriï

_{pasengertfreight ro-ro vessel of 12 000 DWT and with}

:the 6sráli length

_{of I 83m, based òn the}

_{double hull arrangement, as shown}

in :Fig2.- The bulkhead

_{deck was designed,}

however, as watertight thus only

partly filfihIing the _{necessary requirements for a really safe ro-ro vcsscl. To make}

this deck open to the passage of water appeared to be too challenging for the

3. PROVISION OF BUOYANT DECKS

It is difficult to achieve deep sinkage after flooding on real ro-ro ships clue t the large longitudinal unbalance between the aft part containing the machinery

room and the forepeak.As flésül

_{the:ship assumes after floódingan extremely}

l-large trim by :the bow which is not as beneficial to damaged ship safety as deej

sinkage on an even keel

It is worth cànsidenng, therefore, fithng

- the ship additionally' with à buoyànt deck

_{or deckaïleaitthe bulkhead deckfriièrselr}

and longitudinally subdivided by watertight bulkheads _{- see Fig.3. As previously,} cargo spaces should be provided with efficient air-escapes (vents) placed at the sides, close to the top of cargo spaces, to eliminate detrimental air cushions which may occur during flooding. The brèadth of the double sides. is definitely less than

B/5; they should be subdivided into wing tanks by

_{transverse bulkheads and}

preferably be cross-connected. The height of the double decks is preferably not greater than the depth of deck girders for relevant single decks. The double_bottom should be preferably of the minimum height required by _{classification rules.}

The bulkhead deck and a deck below, if any, should be designed as

prmeable (transparent) for the flooded water to ensure free flooding, i.e., uniform

spread of water over the whole compartment during intermediate _{stages of flooding.} With the provision of buoyant decks, sinkage after flooding .is obviously reduced

and, in the extreme, can be as small as to-keep the bulkhead deck emerged.

DECK 4

DECK 3

DECK2

_J/ \

-<-:

\ /

DECK i

Fig.3. Subdivision of a ro-ro ship based on the extnded double shell concept

-Ro-ro ships; in general, have deep deck girders because of the large

unsupported deck spans. In view of the problem of cargo handling, stowage is usually restricted to spaces below the flanges of these girders. There is opportunity, therefore, to seal the space upwards from the flanges_{o the deck girders to the deck} plating to form a chamber that can provide additional buoyancy and depending on

its

_{1ocatior, height and extent, be of some advantage in}

_{terms of damage}

survivability.

:The problem of locating this buoyant deck is a fairly involved exeicise owever, it can be shown that for such

_{a buoyant deck with adij1àèèmeñfófo}

the stability..coefficient will be increased, if the buoyant deck is located at a height

H-satisfying the relation

-.Hdk >Tdani +

¿j

where:

T , - draught in the damaged condition without the buoyant deck;

&j, ii - change in the moments of inertia of the undamaged waterplane arid the free surface of the water due to change in displacement of ¿\ Vu caused by fitting the buoyant deck.

- Because ¿j _{o if the vehicle deck remains submerged and ¿J /LV is positive} then it is practically impossible to satisf' the above inequality unless there is _{a large} reduction in the free surface moment of inertia due to partial emergence of the buoyant deck. Unless this inequality can be satisfi ed, a buoyant vehicle deck will

have a nearly neutral effect

_{on initial}

_{stability in the flooded condition and}

consequently on the ship safety. Even though effective increase in freeboard, due to

the provision of the buoyant deck, _{increases stability at large angles of heel, it is} rather unlikely that this will be of much practical benefit in ship survival except in situations when the angles of flooding _{are very small.,}

However, it is not difficult to design for significant _{reductions in the free} sui-face moment of inertia. This is because in thè májority Of damagè cases there will be a trim by the bow due to the comparatively large mathinery spacé. In an appropriate combinations of buoyant vehicle deck and wing spaces, a situation may be reached that for a largenumber of damage cases the next higher deckcomes iiftà

contact with the flooded water.

If this higher deck is also made buoyant in the forward part of the thip,

a significant gain in the index A value may be obtained and an advantage from utilisation of spaces that are usirnily non-productive anyway from the cargo carriage point of view may also be reached Another possibility is to use a buoyant vehicle deck which is slightly inclined upwards in the longitudinal direction _{so that after} damage the entire deck continues to remain above water in spite of bow trim:- -.

Moreover, active consideration might

_{be givcn to designing the forward}

upper part of a ro-ro cargo ship as a rectangular box, like in an aircraft canier {8}, to improve matters forther in _{cases of deep sinkage after flooding.}

The effect of a buoyant bulkhead deck is relatively modest in the casei where the deck is chosen with no concern regarding the reduction of free surface. It can be of the order of a 5% _{increase m index A values [9] The improvement, obviously,} .may .be considerably greater, if multiple buoyant decks aré iìséd, as may b&feasible in some ro-ro vessels, or when the vehicle deck is mclmed and remains above water in the majority of-damage scenarios. :1

Benefits of Novel Subdivision

The benefits of a subdivision arrangement based on the extended double shell concept are twofold:

-From the design and operation standpoints:

E It is possible to obtain high indices of subdivision for ro-ro ships required by the

new subdivision regulations, without impairing their successful

_operational

features, based on non-subdivided horizontal cargo spaces; From the technical standpoint:

EThe cargo space is not reduced. The double decks _{make use of the space on the} underside of single decks, contained between the huge deck girders, useless for

cargo anyway. Confinement of this space by relatively thin watertight

shell

plating, replacing the thick flanges of deck girders, converts this inefficient space into a double buoyant deck .of considerable volume, reducing bow trim after

flooding, - - - -

-E The weight of the ship is only marginally increased thus neárly the same

dead-- weight is maintained;

E Overall ship and deck strength is improved;

E Smooth sides make cargo handling and insulation.works _easier.

Overall, it can be expected ..that building time ïnd.Jhu the

_{cost ¿f ship}

production may be reduced.

4. NUMERICAL EXA1'vIPLES

To see how this conct

_{brks, a rö-ro ship designed at the Gdask}

Shipyard

was examined, its main, particulars _{were as follows:}

Subdivision/överall length Length between perpendiculars Breádth, moulded

Depth, to main/upper dçck Depth, to weather deck Draught, design/scantling Supply/water ballast tanks

Dead-weight at scantling draught Breadth of wing t.nks

KG for full load condition at draught 7.40 m

KG for partial load cOndition _{at draught 6.11}

Permeability i

Required subdivision index_{R value}

l77,50/183.00m

l:171.30m

28.70m'

8.90/Ï 5.23 m 21.20/23.10 m 6.80/7.40 m 1880/9500 m3 12400 t 2.80m 13.65 m m 13.67m 0.80 0.545

EXAMPLE 1: The ship with a subdivision arrangement as in Fig.2, with no cross-flooding, deck No 3 (upper deck) watertight (which is _{not realistic in this case) For} such a ship the attained _{subdivision index value is}

much below the required one and

equals A = 0.5 1.3

EXAMPLE 2: The ship as above but with cross floOding. The index is then: A' = 0.58 L As can be seen, cross-flooding caused a significant increase in the

index _{value here It should be assumed as a rule that cross-flooding is always}

beneficial for ship safety, and therefore, it should be applied whenever possible. EXAMPLE 3: The ship as in Example 2 but with Deók 3 treated as non-watertight which is in compliance with the actual design. The attained index value is now much lower and equals _{A=0.512, which should obviously}

be expected. It is then quite sensible to make the upper deck watertight, if possible: Moreover,'as the ship has typically _{a large bow trim after flooding and thus small angles of flooding,} active consideration might be given to a deck or decks made. buoyant at the forward

end, to increase the height of openings above the

_{damage waterline, thereby}

improving stability.

EXAMPLE 4: The ship _{as in Example 3 but with Deck 2 as a pontoon, creating} a buoyant double deck of 1600mm

_{depth as shoi in Fig.3.The}

attained index value is now A= 0.519, which is only marginally higher than in the previous _case This is bccause the, buoyant

_{deck as it is ,due}

_{to bow trini ,in the majority of}

damagc scenarios, still remains under water _{over the majority of its length, thus} insignificantly contributing to the reductión of the free _{surface cilòct.}

- This example provides a good lesson:

_{not every buoyant deck can be}

expected to contribute significantly to ship safety. To do so, the whole subdivision arrangement must be carefully chosen so that the buoyant deck could remain above water m prevailing cases of flooding

However, it is not drfficult to do so Keeping the

remaining subdivision unchanged, there are two immediate possibilities: _{a slight increase of the heightòf} Deck 2 maintaining the underside structure of the deck...with the original depth which is equivalent to an increase of the. pontoon depth by the same value; and/or a slight inclination upwards in the longitudinal direction of the topside of the _deck.. The application of medium-speed engines for ship propulsion provides another possibility if such engines are located iii the wing compartments, then the lower cargo hold can be significantly extended afi thus largely reducing bow trim after

flooding. .

EXAMPLE 5: The ship

as in Example 4 but vith the ship's depth to

. Deck 2 increased by 0.2 m from 8.9 to 9. 1 m. The depth of the pontoon is simutanpeously increased from i 600 to i 800 mm keeping the underside structure of the deck at the previous height. The attained index is

now A

0.556, which is higher than the

required value R=O.545. It is worth noting the incredible increase of the index due to the increase of the depth to Deck 2 by only O.2m .This example shows how sensitive ship safety is to some parameters of subdivision _{arrangement containing :a} buoyant deck and that is why it is so easy to be disappointed with it, if it is not properly chosen. Most important of all is to keep, as far as practicable, the buoyant deck dry (to remain above water) ini the majority of damage _cases.

EXAMPLE 6: The ship as in Example. 5 but with Deck 2 inclined upwards in the longitudinal direction by Im in the foremost end of this deck, as shown in Fig.4.

The attained index value is now A = 0.621 and it is thus drastically higher than in the previous case. Such a result. should obviously be expected in the light of the previous remarks. From the examination ofsome of the most representative cases

of flooding for the previous case study, it followed that the depth of the flooded water at the forward end of Deck 2 did not exceed a value of 1m. This is why the free-surface effect could be reduced _{now in the case of the 1m sheer of Deck 2 tó} nearly nothing in most cases of damage, thus markedly increasing the index valúe.

The rise of Deck 2 by 1 metre at its foremost end is not much. Examining Fig.4., one can hardly believe that this deck is inclined at all. All other decks above Deck 2, must have obviously, the same sheer,, to keep them parallel to one another.

In all the examples, Deck 2 was treated as opened for the passage of water and air, to eliminate the many adverse effects, discussed above and not accounted for in the current regulations. Owing to that reason, horizontal subdivision due to Deck 2 was simply ignored, and this was for the benefit of the ship.

L

Fig.4. An cxarnple of a large ro-ro ship subdivision based on the extended double-shellconcept. Note the i m

upward incliñe at the forward end of the main deck.

EXAMPLE 7: The ship as in Fig.5 with narrow double sides of B/1O at the lower

hold and with _{an increased width of the side compartments of B/5 between the main}

and upper decks. Such an arrangement was eventually adopted by the Gdañsk

Shipyard on the FINNHA_NSA _{- the first of four luxurious ro-ro vessels, sister ships}

ordered by Finncarrier. The _{attained index value is now A = 0.668, as obtained by} the Shipyard according

_{to the regulations for passenger ships, contained in}

resolution A.265 (Vm). This value

_{of the index, hòwever,}

_{cannot be directly}

compared with the indices given in the previous examples, as they were calculated according to the regulations for dry

_{cargo ships and the two methods are not}

identical. Nevertheless, the value is high - greater then the required value R0,578

and the Shipyard and Shipoer

_{are very proud of it [10-13]..}

The design, however, should not be recommended for the following reasons: The side compartments at Deck 2, _{intended for the carriage of passenger cars,} are sub-divided by a number of transverse bulkheads

_{fitted with watertight}

doors,, automatically operated. The entrance and way out from these

_{spaces is}

through side gates, closed also by large watertight doors. Apart from being very

costly, _{unreliable and ineffective in terms of stowage, such}

an arrangement is illusive regarding watertight integrity of these _{spaces, bearing in mind the large} distortions the ship can sustain at the moment of collision;

fZ Ventilation ducts _{run vertically along the outer side, starting 0.800 m below}

Deck 2, leaving room for progressive flooding of the lower

_{hold in case of}

damage in way of Deck 2 or above;

ÍDeck 2 is not made _{as open for the passage of water and air so the stability in}

case oU water entering the hull is much _{poor than that which was calculated;}

iInsuIation of the underside structure of Deck 2 required - a large labour

Consumption;

Despite the requirement, _{an increased height of the double bottom should not}

app'y in this case as the design is capable of withstanding

_{major flooding.}

Consequently the dead-weight of the ship is reduced by 1700 tons. Moreover, despit _{the apparently high value of the index, the ship is far from what can be} realistically achieved, whose safety

_{s based on wishful thinkirg rather than òn}

rational principies. Such

_{iitisthereforëjjdt recommended.}

DEO(4

-VATERT (CHI j , 7: OUR DECK 2 DECK 3 DECK t

Fig.5 A subdivision arrangement found on B5O1f Type cambi ro-ro built in Stocznia Gdaríska

General arrangement of the above ship and its _{brief technical description is} given on the following two pages, taken from a Commercial leaflet issued by the

Shipyard.

'il

CONCLUSIONS

'l'he probabilistic subdivision

_{regulations for diy cargo ships [2] provide}

à framework for the rational assessment of competing ro-ro ships design from the damagcsurvivability point ofview It is clear from the results reported above that it is pssible to achieve a satisfactory subdivision rndex value _{for such ships without} upper deck Their mtended function

:is1adl,

_{narrow wing cômpai-tthents exteñdinjfroth the bottom to the upper}

declçctoss-connected, and

_{a buoyant deck or decks, opened for the}

_passage of water and air below the upper deck, leaving thi deck area clear for through

transport. L .

:

The judicious distribution of reserve buoyancy in the longitudinal, transverse and vertical directions is important in the design of these ships and since there are

many ways of doing this satisfactorily, there i _{obvious scope for optimisation in} the arrangement of such vessels. The performance of these ships in the damaged

condition is very sensitive to

_{some particulars of the sübdivision arrangement}

containing a buoyant deck, depending

_{onpresence of water on the deck in}

a floóded condition.

lt is important to note that the

_{current survivability regulations merely set}

standards, though imperfectly, and

_{are not prescriptive as regards an actual}

arrangement. The designer, therefore, retains the opportunity to meet the range of design objetives. Subdivision arrangement based on double hull and double deck seems to be particularly efficient and _{beneficial for these ships.}

I/ti I_I_________... -t

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.

4

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Commercial Division _{phone+39 22 34, 39 22 94}

ul. Doki i

fax-i-48 58 31 99 25

80-958 GDAÑSK POLAND

tlx 512028 sg pl

APPENDL

cov'Bg

CO BI RO

-RO

B5Ö1u/j TYPE

TCCZN1A GDAÑSKA

SA.

Commercial Division _{phone+39 22 34, 39 22 94}

ut. _{Doki 1}

_{fax48 58}

_{31 99 25}

80-958 GDAÑSK POLAND

_{tlx 512028 sg pl}

MAIN PARTICULARS

TYPE OF VESSEL

Innovative highly automated multi-purpose double skinned, ice strengthened Baltic combi ro-ro carrier

designed for carriage of passengers and cargoes like:

paper, timber products, roll trailers, road trailers,

transfiats, containers, cars, lorries, chilled fruit in the

lowest hold; 93lEU can be carried on the fourth deck; the vessel is designed for future installation of about

510 m of railway tracks on the second deck; twin

propeller vessel with twin skeg transom stern, raked stem, bulbous bow, two bow and two stern thrusters,

four cargo decks, all cargo decks free of any pillars, five

tier superstructure, two high lift Jastram type rudders;

fitted with aritiheeling and stabilizing system. CLASS OF VESSEL

Det Norske Ventas class notation

1A1 CAR FERRYAEO, Ice-lA, corr, TMON

Conventions.and rules met by the design:

SOLAS-74/89, 1MO Resolution A265 (VIlI) concerning damage stability, TON-69, COLREG-72, MARPOL-73/78, LL-66, lLO-92, rules of Kiel, Suez and Panama Canal Authorities, ITU, IEC and Finnish Board of

Navigation Rules, dangerous cargoes according to

IMDG code can be carried on the fourth deck and in the

open part of the third deck (Class 1,2,3,4,5,6,7,8,9), while closed decks No. 1,2 and 3 are restricted to few

classes of dangerous goods.

-

CARGOAôCESSEQUlPMENT-Movable ramps

-Two stem hydraulically operated and battened combined ramps:

. .. - . -

-one on the second deck: Length - 12.5 m drive width

'r21.65m,hight..5.30m, '.

-- one on the third deck: length -- 13.45+3.0 m, drive

width-9.Om. - . .

Fixed internal ramps

-- one centrally positionned internal fixed ramp between

the secon and the first decks (drive width - 4.40 m

with cover panels, drive height - 4.8 m).

-- one starboard internal fixed ramp between the second

- and the third cargo deck with drive width - 4.3 m,

- one portside internal fixed ramp between the third and the fourth decks with drive width - 4.2 m and height

-4.8m.

ENGINE ROOM.

Main engine

Reduction gears

Manoeuvring gear

Bow thrusters two of 900 kW each

Stern thrusters two of 450 kW each (in skegs) Generating sets

- two shaft generators of 1,750 kVA each, - one diesel generator df 1,570 kVA, -. - one diesel generator of 1,175 kVA,

- one emergency diesel generator of .450 kVA, all

-generators: 3x380 V, 50Hz. -.

Boilers . .

-- one vertical water--tube oil--fired auxiliary boiler of 4,000 kg/h steam capacity at 0.8 MPa

- four exháust-gas boiler of 1,000 kg/h steam capacity

at 0.8 MPa.

ACCOMODATION . -.

All accomodation is designed to a very high standard as

on cruise passenger -vessels, with single cabins for

officers and crew, 24 luxurious three berth and 10 four

berth cabins for passengers. -.

LIFE SAVING APPLIANCES -

-- two GRP lifeboats for 48 persons each, - two fast 20 kts rescue boats, _-:

-- four 16 person inflatable life rafts - one inflatable raft for 6 persons.

}

Length, o.a. - - 183.00 m

Length, b.p. -. _{:»-17130 -m}

Breath, moulded _{- -m}

::Depthto bulkhead deck 15.23 _-rn Depth to weather deck _{23.1/21.2 m} Scantling draught

-Scantling deadweight 10.700 t

Design draught -.

-6.80 m

Design deadweight 8.500 t

Car lanes (width 2.85 m) 3.200 m

Trial speed 21.3 kn

Crew berths 23

Passengers berths 112

Tank capacities:

- heavy fuel oil _{1,450 m3}

- diesel oil 350

- lubricating oil 60 m3

- fresh water 250 m3

- water ballast 10,000 m3

- antiheeling, stabilizing tanks 1.050 m3

Type Zgoda-Sulzer BZAL4OS 4

MCR 5,760 kW at 510 rpm each

SFOC 179 g/kWh +5%

HFO viscosity 600 cSt at 500C Propeller two CP type

REFERENCES

..i. Spouge, J.R. : The technical investigation

of the sinking of the

ro-ro ferry

European Gateway, Trans. RINA, vol. 128, 1 986,

_{pp 49-72; also in Naval}

.

Architect, March 1986, ibid. - . . .

.:

2. Resolution MS C i 9(5 8) _{on the adaptation ofamendmèñt tó the i 974 SOLAS} Convention regarding _{ubdivision and damàge stability of dry}

-cargo-ships):-London, 1990, l3pp:

:

Pawlowski, M.,Winlde, I.E.: Capsize resistance through flooding

_{- a new}

approach to ro-ro safety, Proc., 9th_{Int.Conf on through Transprt using} Roll-oniRoll-off Methods, Ro-Ro 88', Gothenburg, June 1988, BML, pp. 250-261. Grochowalski, S., Pawlowski, M.: .The satety of ro-ro vessels in the light of_the probabthstic concept for standardizing unsinkabthty, Tnt Shipbild Progress, vol.28, No.3 19, March 1981, pp.63-72.

Pawlowski, M.: Bezpieczeñstwo niezatapia1nociowe statków (Safety of ships in thedamaged condition), Journal of Tech. Univ. of Gdañsk

_{"BudoiictWo..}

Okrtowe", No.42/392, Gdañsk 1985, 132 pp.

Turan, O., Vassalos, D.: Dynamic stability assessment of damaged passenger ships, RJNA Spring Meeting,. 1993.

Vassalos, D.: Damage survivability of passenger ships in a seaway, Proc., Tnt. Workshop on the problems of physical and _{mathematieal stability modelling,} Kaliningrad 1993, vol.1, paper No.10, l6pp.

Wahl, J.E.: New catamaran

_{ro-ro design for Norwegian coastal service}

-a bre-akthrough in hull design, Ro-Ro'88 Proc., 9th Tnt. Conf. on Through Transport using Roll-on/Roll-off Methods, Gothenburg, 7-9 June 1988, BML, 1988, pp.101-119.

Sen. P., Pawlowski. M., Wimalsiri, W.K.:

_{Ro-Ro cargo ship design for}

enhanced survivability in the damaged condition, _{Proc.,9th mL Sythp. on Ship} Hydromechanics, Gdañsk, 17-19 September 1991, vol.11, _{5 pp.}

Mustainäki, E.: FG-Shipping's _{new Baltic combi-roro's - large 3200 lane-meter} ships with two-level stem access and passenger âccommodation, Proc.,12th lut.

Conf. & Exh. on Marine Transport using

_{Roll-on/Roll-off Methods,}

R0R094, Göteborg, April 1994, vol.2, session10, 11 str. I

Boyce, J.: Finnhansa-a Luxurious ro-ro vessel, .Cruisé & Fery Info, No. 11/94,

pp. .18-21.

Polish built Fi.nnhansa leads _{a new class of Baltic safe/passenger ferry, The} Naval Architect, January 1995, pp. E 15-24.

Wilson, T.: Freight ro-ro's are adapted to meet route demands, Motor Ship, January 1995, _{pp. 12-17.}

In the series of ZESZYTY PROBLEMOWE

_{the following papers have been}

published sofar:

B-001 L Malak: Prognozowanie obci±eñ statku _{na fall. Xl 1978.}

B-002 L Konieczny: Wtrzymaoó ogólna kadluba

_{z uivzdrieniern sprzenia}

skrcania i zginania poprzecznego. XI I 978.

B-003 k Baraniak, Domariski, U. Sznajder Wpl,w struktury _{geometrycznej} _:.

powierzchni blach okrtowych na wlasnoci ochronne powok malarskich.

111979.

B-004 Z.Bilicki: _{Metoda okrelania wspóczynników wnikania ciepa podczas}

wrzeniafreonu w przeplywie. III 1979;

B-005 Z. Winiewski: System hybrydowy APII-600 i

jego zastosowanie w

mechanice konstrukcji okrtu. V 1979.

B-006 A: Galewskj, L. Konieczny: Computer calculations of ship hull longitudinal

strenght with the- interaction between torsion and horizontal _{bending. VI}

1979.

B-007 W Ojak: Problemy drgañ wymuszonych _{rubk okrtowa na wspólczesnych} statkach. Vibration problems _{on modem ships due to propeller excitations.}

IX 1979.

B-008 A. Nowaljriskj, T. Rajewska: Wykadzina _{bezspoinowa typu "kt na pokady}

stalowe statków. IX 1979.

B-009 W. Ojak: Reduktor drgañ pochodzacych _{od ruby okrtowej. XII 1979.}

B-010 _{J. Gatz: Systematyczna seria modell kontenerowców i semikontenerowców.}

Badania oporu i napdu. XII 1979.

B-011 K Kalinowskj: Zastosowanje ukadów pompowego i termostatycznego do

zasilania chodnic powietrza _{w ladowniach statków rybackich. III 1980.}

B-012 S. Szpak-Szpakowski, W. Witkiewicz, A. Zitek: Nowe materiay

kompo-zytowe o osnowie polimerowej i mo±liwoci ich wykorzystanla w

okrtowr,jctwje.V 1980

B-013 W. Ojak: Propozycje oceny nara±eñ na drgania spowodowane cinieniami

hydrodynamicznymj od ruby. Proposed estimation of the excitation severity caused by propeller pressure amplitudes. VIII 1980.

B-014 Praca zbiorowa: Dobór stafi _{kadlubowych na elementy konstrukcyjne}

statków zagro±one pkniciami lamelamymi. _{XI 1980.}

B-015 _{N. Bieniek: Problemy budowy modell matematycznych w projektowaniu}

syatemów wyposazenia okrtowego. XII 1980.

B-016 K Cichowski, K. _{Somla: .Badania eksperymentalne}

_wiaciwoci

dynam icznych konstrukcji okrtowych _{metodami cyfrowym i. Experimental}

investigations of the dynamic properties _{of ship structures with digital}

methods. 111981.

B-017 W. Ojak: Projektowanie i _{kontrola statku pod kq.tem drgañ. III 1981.}

B-016 M. Banacki, A. Bujnicki: Badania modelowe ksztal'táw do moduiowego

LI

B-019 J. Kozlowski: Zastosowanie wzbudnika drgari do .dynamicznych : badati

- statków. IX 1981.

B-020 J. Kalicitiski: Ukiad napdowy statku jako nieliniowy objekt regulacji

automatycznej. Xli 1981. . .

-B-021 G C Volcy Wzajemne oddziaiywanie ukadu napdowego i kadkiba óraz ich - swobodne iwymuszone drgania. III 1982.

B-022 _{J. Piotrowski, W. Winiewski: Przektadnie pianetame bezjarzniowe typu}

-

--WPSVl1982--:

B-023 A. Domatiski, J. Blm, A. Glazur, M. Urbaríczyk: Korozja w wodzie morskiej

kadlubowych poa,.czeñ spawanych ze szczegóinym uwzgdnieniem stati

przeznaczonych do ekspioatacji w niskich temperaturach. Vili 1982.

B-024 A. Giryn, K.. SomIa Hydroakustyczne rozpoznawanie biologicznych ceiów

podwodnych Xii 1982

B-025 Q. Skjbskj:

Ocena wjacjwocj

dynamicznych paszczowo-rurowych

wymienników ciepla z przegrodami segmentowymi na podstawie ¡ch

odpowiedzi skókowych. Iii 1983.

B-026 J. Dudziak: Prawdopodobierístwo przewrócenia si statku pod dzialaniem

bocznej fall i wiatru. iV 1983.

B-027 L. Malak: Charakterystyka warunków falowania rnorskiego oraz

prognozowanie odzewu kadluba na to faiowanie. XII 1983.

B-028 O. Skibski: Systemy diagnostyki pracy okrtowych siiników wysokopr±nych.

XII 1983.

B-029 J. Dudziak: Prognozowanie cinie,i dynamicznych na powierzchni kadluba

statku plyna..cego na fall reguiarnej. IV 1984.

B-030 A. Galewski: Wstçpna probabilistyczna metodyka analizy wytrzymalociowej

statków otwartych. Viii 1984.

B-031 _{J. Kaliciriski, E. Peika: F'4umeryczne prognozowanie waciwoci}

manewro-wych statku we wczesnych fazach projektowanla. Xii 1984.

B-032 M. Kubacka: Próbá opracowania normatywnego wzorca jakoci wymagati

ergonomicznych w okrQtownictwie. 11985..

-B-033 T. Laskowski: Dynamiczne metody wyznaczania redniego wspólczynnika

przenikania ciepta przez okrtowe przegrody izolacyjne. IV 1955. ...

B-034 N. Bieniek: Modeiowanie uktadów elekttycznych rnetoda. grafów wi.zarí.

Vii 1985.

B-035 K Szponar: Porównanie metod projektowania i badania okrçtowych

pdników rubowych na przyktadzie projektu pdnika kontenerowca. IX

1985.

B-036 W.. Ojak: Teoretyczno-doáwiadczaine rozwiq.zania dotyczace rubowych

waiów okrtowych mocowanych eiastycznie. Vi 1986. B-037 W. Gasparski: O projektowaniu inaczej. IX 1986.

B-038 W. Ojak: Drgania i halasy w wodzie wytwarzane przez statki rybackie. Czçá i. X 1986.

B-039 W. Ojak: Drgania i haiasy w wodzie wytwarzane przez statki rybackie.

B-040 Ai. Maksjmad±i: Dialektyka norrnowania wytrzymaloci kadK.ibów

okrtowych. III 1988.

B-041 W. Trafaiski: Strukturà prôblernatykirÖzwojowej w mechanice konstrukcji

pod katem potreb przemyslu okrtoWego. VII 1988.

B-042 W. Trafalski: Praktyka projektowania, jej uwrunkowania i postulaty. VII 1988.

B-043 W. Trafaiski: Wspomaganie jako przedmiot w okrtownictwie. VII 1988. B-044 W. Trafalski: Projektowanie, wspomaganie, komputeryzacja. Studiúm

metodyczne. VII 1988.

B-045 W. Trafalski: Postpowanie weryfikacyjne w komputeryzacji projektowania

okrtowego. VII 1988.

B-046 M. Kubacka: Ergonomiczne aspekty projektowania statków rybackich.

III 1990.

B-047 J. KaIicirski: Numerical simulation f ship manoeuvring tests with wind,

wave and shallow water effect taken intO account. IX 1990.

B-048 M. Kubacka, J. Urban: Produktywnoá. Productivity. VII 1992.

B-049 Sachiro Nagashima, M. Kubacka: Produktywho = efektywno. X 1992.

B-050 M.Kubacka: Oceanotechnika. X 1992.

B-051 L. Murawski: Metodyka obliczeri drgañ osicwych walów korbowych

wolnoobrotowych silników okrtoWyth. XI 1992.

B-052 A. Baczyríski, L. Konieczny, A. Listkowski: Zastosowanie metody

poszukiwania minimum w hiperpaszczy±nie stycznej do hiperpowierzchni

ograniczerí (TSM) przy optymalizacji ram. XII 1992.

B-053 M. Kubacka: Logistyka w gospodarce morskiej. III 1993. B-054 M. Kubacka: Ergonomia w oceanotechnice. VI 1993.

B-055 J. Bim: Ochrona przed körozjq i porastaniem okrtowych instalacjì

chodzacej wody mors kiej. IX 1993.

B-056 T. Zdybek: Wykorzystanle wyników systematycznych badañ modelowych charakterystyk hydrodynamicznych podwodzi statków nówej generacji do

oceny wplywu dryfu na ich wIaáciwoci ±eglugowe. X 1993.

B-057 W. Bogotko: Wspóczesne zagadnienia - ochrony elektrochemicznej

podwodnej czci kadubów statków. X 1993.

B-058 L. Murawski: Wybrane problemy _wyznaczania

sprawnoci ukiadw

napdowych statków. Metodyka pomiarów i ich przetwarzania. XI 1993.

B-059 L. Murawski: Numeryczna symulacja stanów dynamicznych o±ysk giównych

wolnoobrotowych silnikóW okretowych. XII 1993.

B-060 A. Sowiak: Zastosowanie programu MAESTRO w analizie konstrukcji

masowca o noánoci 164 000 t. XII 1993.

B-061 J. Dudziak: Symulacja komputerowa kolysari boczñych statku na fali.

XII 1993.

B-062 M. Pawowski: -Energy loss in ship's collisions. IX 1994.

B-063 _{J. Jankowski: Experimental verification of mathematical models describing} the ship moving on the free surface. XII 1994..

B-064 L Murawski: Numeryczna symulacja stanów dynamicznych _{tiumików drgaii}

wzdlu±nych wolnoobrotowych silników okrtowych. XI 1994.

B-065 L. Murawski: Numeryczna symulacja stanów dynamicznych

toysk

oporowych wolnoobrotowych silników okrtowych. XII 1994.