An analysis of the application of aluminium alloys in ships structures. Suggestions about the riveting between steel and aluminium alloy ships structures

REPORT No. 20 S

January 1955 s

STUDIECENTRUM T.N.Ö. VOOR SCHEEPSBOUW EN NAVIGATIE

AFDELÍNG SCHEEPSBOUW/ - NIEUWE 'LAAN 76 - DÈLFT

(NETHERLANDS RESEARCH CENTRE T.NO. FÓR. SHIPBUILDING AND NAVIGATION) ('SHIPBUILDING DEPARTMENT - NIEUW'E LAAN 76 - DELFT)

*

An analysis öf the application

of aluminium alloys in ships' 'structures.

Suggestions about thç riveting between ste el

and aluminium alloy ships' structures.

by

PROF. IR. H. E. JAEGER.

Summary

A subdivision into groups, based upon the most noteworthy properties of aluminium alloys as used on board ship, is mâde. Fóllowing this subdivision, a description is given of the principles underlying the attempt to define the scantlings Qf aluminium-alloy superstructures and deckliouses. The.influence. of such tructures on the longitudinal strength of the ship: is stúdied.

A list of requirements for the scantlrngs of light-metal superstructures and deckhouses is given with a new proposal embracing the criticisms of the existing rules and regulations. An extensive bibliography follows.

§ 1. I,itroductión

This study must be viewed firstly as following that published as report No 3 of the Netherlands'

Research Centre T.N.O. for Shipbuilding and

Navigation, entitled: "Practical Possibilities of

Constructional Applications of Aluminium Alloys to Ship Construction" [1].

In the second place it seeks to serve as a step

towards the establishment of international regu lations for the standardization of the composition and the dimensions of light-metal alloys used in shipbuilding. This work has been entrusted to the

working group (W.G. 1) of the ISO/IC 8.

A combination of these two purposes is simple to achieve, as we have only to reconsider the two last paragraphs, 13 and 14, of the report mentioned,

and to rewrite them, whilst noting the differetit

regulations laid down by various organisations and subjecting them to technical criticism.

A few words about the desirability of using light-metal alloys are appropriate here. The application of aluminium-alloys to ships' structures depends on a complex of economic and technical consider-ations. A review of those parts of the ship which might be constructed in such alloys is only possible by an evaluation of these considerations.

The following subdivision is an attempt to give

an evaluation of the different considerations and is set out in such a way that a discussion of each separate type of construction mentioned is not

necessary. As a criterion of each group, the two

most characteristic properties of the aluminium-alloys are taken, viz, their great resistance to cor-rosion and their low specific weight. A subdivision into three groups is considered necessary, one group embracing those structures for which both

charac-teristic properties are important.

After the subdivisiàn into groups it will be

necessary to reconsider those groups which may be amenable to strength calculations: Several parts of the ships' structure require regulations for scant-lings, and a critical survey of what has been done

is given.

The method of determining these scantlings may be either comparative with the former steel

con-struction or the determination of the light-alloy

construction by means of a direct strength

calcu-lation, where only the mechanical properties of aluminium and its alloys replace those of steel

[10], [11].

A further point is the question of which criteria should be used as the basis for comparative calcu' lations. These may be given as:

a. The basis of equal strength as compared with

steel construction. This means that the factor of safety to the breaking point of the material, in

both cases (steel and aluminium-alloys), is at least

equal.

The basis of equal stiffness. In this case the deflection of both steel and aluminium-alloy struc-tures is the same.

A compromise between both preceding bases is, that the difference in deflection of the structural part in question is 50 % of that between the con-struction calculated on equal strength and the one calculated on equal stiffness.

In the following pages these three bases will be indicated as: basis of equal strength, basis of equal stiffness and basis of 50 % deflection.

2. Subdivision in groups of ships' structures,

which may be constructed in

aluminium-alloy with reference to the general advantages of such structures

Group I: Ships' structures made in light-metal alloys, where the advantages arise from the fact

that the specific weight of. these alloys is much lower than that of steel.

As already mentioned in [1], the decrease in weight of structures made in aluminium-alloy

instead of in steel can be used to:

Increase the carrying capacity (see A and G). Either to improve stability or, when: stability remains the same, to decrease the beam (see B, C, D and H)..

Decrease the resistance of the ship (see A and.G).

Decrease the dimensions of the ship with the same carrying capacity so that .the same speed can be attained with less power (see A and G).

Increase the radius of action with equivalent speed and bunker capacity (see A).

Reduce the draft, especially that of small ships, which assists navigation in shallow water

(see A sub 2).

Increase the depth of hull while maintaining displacement, so that with the same or a slightly

greater carrying capacity, a better cubic can be

obtained. As the centre of gravity i1l also rise, a decrease of beam will not be possible.

Muckle gives much consideration to this type of weight-saving by the use of light-metal alloys in an article in "The Shipbuilder" [.2]. From this the figures 1 and 2 are taken, giving direct information about sOme advantages obtained by weight-saving. Basing himself exclusively on this saving, Muckle

comes to certain conclusions about the possible reduction of the breadth, displacement, fuel-cost and capital-investment.

Indirect advantages of the saving in weight are better stress-distribution (see C) and greater ease in handling (see D).

The question of corrosion-tests will be treated by a special panel of ISO/TC 8/WG i and will be

treated in the Netherlands by

Corrosion-Com-mittee V.

Linings of fish-holds [14], [15], [16]

Covering of insulation in refrigerated ships

for the transport of fish, meat, vegetables. and fruit [17]

Covering of insulation in refrigerated spaces of passenger- and cargoships

Covering of oil-tanks

Covering of wine- and chemical-store tanks. Interior of galley's

Interior of kitchens

Interior of sanitary installations Port-holes and windows [18] Ships' furniture

Ships' decoration Electrical installation.

Group III: Ships' structures made in light-metal-alloys, where both the advantage of light-weight

and high resistance against corrosion are of

im-portance.

Under G those parts are listed, where construc-tion in aluminium-alloy has a direct influence on

the carrying capacity and the propulsion. Under

H those parts are listed which have a particularly good effect on the stability of the ship.

Ventilation-ducts

Pipe-lines

Parts of machinery

Floats, buoys and skimming-boards for

fishing-vessels.

Lifeboats [12] Lifefloats

Funnels [1], [19], [20].

§ 3. Ships completely constructed in

aluminium-allo y

These structures are given in group l.A. The

possibility or the desirability of constructing a ship

totally in light-metal must be judged from an

economic point of view in the first place. A calcu-lation of earning power will show that the

possi-bilities are, in general, limited to small and fast

ships, like those mentioned in this group. General rules are very difficult to give and each case has to be calculated individually. The small size of

these ships makes the question easy from the tech-nical aspect, though comparisons with steel ships are not advocated. Indeed the conditions of loading are quite different, due to the large weight-savings. As the hull-weight is determined by the load, these ships must be calculated directly as structures in light-metal.

A. Complete structure in aluminium-alloy for: Very fast ships such as:

Naval craft Police-boats [3] Patrol-boats Yachts [4]

Small passenger-vessels for inland navigition Whale-catchers.

Ships navigating in shallow water:

Barges [5], [8] and [9]

Coastal lifeboats.

B. Masts and derricks [10], [11] Davits [12] Deck-auxiliaries Deck-ventilators Rails. C. Superstructures Deckhouses

D. Hatches and hatchways

Hatchbeams and fore- and afters [6], [7, [8] and [9]

Removable masts Removable derricks

Ladders, stairways, gangways [13] Deck-awnings.

Group II: Ships' structures made in

light-metal-alloys, where the advantages arise from the fact that the resistance to corrosion is considerably higher than that of steel.

The use of aluÍninium-alloys shows many ad-vantages for parts of the ship where longevity and low cost of maintenance are essential (see E and F), or where expensive materials can be replaced by these alloys (see F).

As already pointed out in [1] there are three

types of corrosion:

General corrosion, which causes the surface of the material to be entirely removed by chemical solution of the oxide-skin.

Local corrosion, pit corrosion or pitting. This

is always electrolytic, a result of local galvanic elements. The latter come into being through dif-ferences of potential between the components of the alloy, sea-water generally acting as the électro-lyte. The corrosion penetrates deeply over a small surface, causing the peculiar forming of pits; hence the name.

Intercrystalline corrosion, which takes place

by the corrosion of the metal along the "grain"-boundaries. As the grains of aluminium may be considerably larger than those of iron and steel, intergranular corrosion is much more likely to occur. The Al-Mg-alloys with a large amount of Mg are typical of this.. Metallurgically there is a remedy, but the practice is now to restrict the Mg-percentage to 4.7 %.

il

i

w w w > O

< to

18

1.6

w-I__

I_

I

-ddißr

:10

o/68

h, HEIGHT 40 OF WEIGHT.GAIN ABOVE C.G. IN M.

--5 6

78

IO Il ia 13 14 15 Jó h IN M.

Fig. 1. Decrease of the height of ¡he centre of gravity o a ship in conjunction with the gain in weight (g) through the substitution of steel by aluminium-alloy at a height (h) above the C.G., (V) being the total displacement.

o

¿

s

+

POSSIBLE REDUCTION IN BREADTH OF SHIP IN M.

Fig. 2. Influence of ¡be gaul in weight (g) through substitution of steel by aluminuom-alloy, on the ship's breadth, assunsing

constant-stability value.

As the modulus of elasticity of

aluminium-alloys (Young's modulus) is quite different from

that of steel,

the buckling phenomena are not

comparable. Therefore,

not oniy the

bending-stresses, but also the buckling-stresses must be con-sidered separately. It is advantageous to use

longi-tudinal framing and the sheathing of the decks

with wood must be taken into consideration (see also § 8). Due to the lower resistance to buckling, the frame-spacing of aluminium-alloy constructed ships must be smaller [21].

Nevertheless, if comparative calculations are still made, Corlelt's and Muckie's methods and diagrams can be used [22] and [21]. These diagrams are also published in [1] as figures ;

io, 13, 14, 1, 16,

17 and 18.

The high price of the aluminium-alloys makes it desirablé to save weight by the use of welding. Modern welding-techniques make it possible to compete with riveting, which is still the normal

method of connecting light-metal plates and sec-tions of small thicknesses [23].

§ 4. Ships' fittings completely constructed in

aluminium-alloys

These structures belong to groups I.B. and I.D. The use of light-metal is governed by the wish to improve the ships' stability. The question of greater ease in handling is also a factor. This applies

es-pecially to parts which determine the scantlings of lifting gear. The cost of these parts is largely

influenced by easier fabrication in comparison with steel or other heavier metals.

As far as masts and derricks are concerned, calcu-lations against buckling or bending and buckling combined, make direct strength calculations for the

aluminium-alloy structure necessary [10], [11].

On the other hand, the stiffness of davits [12] and

stairways [13] must be the same as that of the

comparable steel structures and thus comparative calculations must be used. The same applies to ven-tilator-ducts, deck-rails, hatchbeams, etc. [6], [7]. A calculation based on equal bending stress

(equal strength) gives the requirement: Ja/ya = 1.65 la/ya. This factor of 1.65 is determined by applying the same safety factor against breaking

for the aluminium-alloy with 4 % Mg, using its

lowest breaking-point (26 kg/cm2) in comparison

to that of ordinary ships' steel, using its mean

breaking-point (42 kg/cm2). As E8/E5. = 3, where E8 = Young's modulus for steel and Ea = Young's

modulus of aluminium, the deflection becomes of the equivalent steel structure. Thus if fa is the

deflection of steel and fa that of the

aluminium-alloy

= 1.82 fa

For hatch-beams and fore- and afters in partic-ular, the necessary modulus must be found in the thickness of the web, otherwise wrinkling of the web may occur. Therefore the thickness of these webs, constructed in aluminium-alloys must be de-rived by the formula:

t, 1.44 t8 where

ta thickness of aluminium-alloy plate t.8 = thickness of steel plate.

For the determination of this formula and the calculation of hatch-beams with equal stiffness

(same deflection as steel beams) see § 8.

It is interesting to make hatch-beams for ships navigating in inland waterways in such a manner that they can float. This is easily possible by design-ing structures, which have the necessary

displace-ment [8], [9].

§ 5. Superstructures and deckhouses constructed

in aluminium-alloys. General observations. It is considered necessary to give first of all some definitions and axioms:

A long superstructure or a long deckhouse has

a length that is greater than 15 % of the ships'

length L. Therefore

I 15% L

A short superstructure or a short deckhouse is so dimensioned that

1< is

A superstructure is a structure that stretches from port to starboard, so that the sides continue the side-plating of the hull.

A deckhouse is a structure placed more or less

symmetrically on the hull, the sides not being in

the same plane as the ships' sides.

A superstructure may be constructed in such a

way, that the top-deck of the superstructure

be-comes the strength-deck of the ship. This will never be so in the case of the top of a deckhouse.

Long superstructures and long deckhouses may both contribute to the longitudinal strength of the

ship.

It is possible that long superstructures and long deckhouses will not contribute to the longitudinal strength of the ship. They are then constructed as "light" structures.

Short superstructures and deckhouses never

con-tribute to the longitudinal strength of the ship.

They are always constructed als "light" structures. The above mentioned structures belong to group I.C. They are by far the most important as regards the strength-calculations and the rules and regu-lations for aluminium-alloy scantlings. Therefore these structures are considered in extenso:

a) Those forming part of the strength-deck' of

Those contributing to the longitudinal strength of the ship. < 7)

Lightly constructed superstructures and

deck-houses. (SS 8. and § 9)

The decision whether the use of aluminiumalloy is economic was treated by Muckle, in his general review of the application of aluminium-alloys to shipbuilding [24], as long'ago as 1943, and to ships' superstructures at a later date [25]. He only

con-sidered the influence of the saving of weight in connection with the cargo carrying capacity and

the saving in power and fuel-costs if the deadweight remained the same. In [2] Muckle based himself on the same cônsiderations, therefore knowingly omit-ting all effects on the strength of the ship. Even so, he took into accOunt the possible reduction in beam due to the lower centre of gravity of the ship. These questions are taken up in the following paragraphs. Not explicitely mentioned in these paragraphs, are the considerations regarding:

The difference in the coefficients of expan-sion between aluminium-alloys and steel, treated by Mucizie in [24] and by Corleti in [26].

The danger of fire and the necessary fire-protection in ships with aluminium-alloy super-structures, a question treated by Venus, Coriett

[27] and Audigé [28].

The difficulties of 'obtaining adequate con-nections between the structural parts of

aluminium-alloy or of aluminium-aluminium-alloy and steel. This question

posed in [1] is treated by a separate panel of

ISC/TC 8/WG -. (See §12, 13 and 14)

The high price of aluminium-alloys.

§ 6. The alumtniwin-alloy top-decks of super'

structures forming part of the strength-deck of the ship

This question may be treated best by making the bold statement, that it has been proved that such a conception is not economically justified. I shall

come back to that point in the next paragraph

where the superstructures and long deckhouses

con-tributing to the longitudinal strength of the ship

are described.

The proof of this statement lies in the fact, that Muckle 'in [24] bases himself on calculations for top-decks of deckhouses, wherein the stresses never

or just reach the limit f the allowablestresses. Now

the basis for this calculation is a very rough ap-proximation, and in the discussion of [30], Teif er reproaches Muckle for not taking into consideration the much better modern views of Lyndbn Crawford [31] and H. Bleich [32]'.

But these modern, theories give a view of the

interaction of the superstructure and the hull, which indicates, that as, the bending theory as admitted by Mont go'merie and Muckle is not applicable, the

result is, that the stresses in light-metal

super-structures will be even smaller than those calculated

by Muckle [24]. Therefore' it is safe to assume,

that where increasing the thickness of the super-structure-deckplating has no sense if the

superstruc-ture or deckhouse is only "contributing" to the ships' longitudinal strength (see § 7), it 'certainly has no sense in the supposition that this deckplting should act as strength-deckplating. In that case the economic disadvantages would be still greater.

My observations in the discussion of [30] are therefore still valid. In reality the question is to

find the minimum thickness of the aluminium-alloy topplating on the supposition that the deck-house or superstructure is contributing to the longi-tudinal strength of the ship.

§ 7. Calculation of the thickness of deckplating.

Superstructures or deckhouses contributing to the longitudinal strength of the ship For practical purposes it is possible to base these

calculations on the papers of Montgomerie [29]

and Mucizle [24], [25]. Now the starting point for Mont gomerie was, that the section-modulus of 'the

ship with superstructure should be equal to the

section-modulus of the ship without superstructure.

Both authors indicate furthermofe that they are

consi4ering "light" deckhouses not contributing to the ships' strength.

Nevertheless Muckle in [25] pointed out, thit

Mont gomerie's 'method supposed a "certain" con-tribution to the strength of the ship. The supposition of Mont gomerie that a superstructure-deck takes

up a "certain amount of stress" in relation 'to its distance from the neutral axis, is very disputable, as this deck in his study has no material connection with the hull.

Now even starting from this very unfavourable basis, deckhouses have been constructed to Lloyd's regulations (based upon this study of Mont gomerie)

and were satisfactory. Muckle [25] pointed out,

that when this superstructure or deckhouse-top was constructed 'in aluminium-alloy, the situation be-came even more satisfactory.

The cross-sectional area of the superstructurc

deck "a" is given bij Montgomerie as:

T

a =

_{jiAo(yo±h)+Io}

....

(1)

where A0 = cross-sectional area of orIginal struc-ture

1 = moment of inertia of original struc-turc

Yo = distance

from neutral axis of the

original structure to the

strength-deck

h = height of superstructure deck above

main strength-deck

a cross-sectional area of the

superstruc-ture-deck

Muckle proves, that it is possible to derive (by a

similar process of reasoning as that adopted by

Mont gomerie) a formula for the minimum

cross-sectional area of a deck constructed of aluminium-alloy. This formula is:

'

A0{-(y0

_{+ b) _yo}}

2 (2)

Jo

A0(y0+h) +10

where apart from the symbols already mentioned: = stress in the steel structure

= stress in the alloy structure

-E8 = Young's modulus for steel

Ea = Young's modulus for aluminium-alloy Examining this equation (2) it will be seen that under certain circumstances a negative value of "a" may be obtained. This, of course, is not admissible and thus:

(Yo + h)> Yo

Now for Lloyd's quality of aluminium-alloy

= 1.70 (I have calculated 1.65) and - = 3.

7a _Ea

Therefore it will be seen that unless h/y0 is equal to or greater than 0,76, the area will be negative. This means that the stress in a superstructure deck, as calculated by Mont gomerie's method, can never rise to the value o, no matter what its cross-sectional area is. It therefore would appear that certainly in a

first tier of superstructures and probably ina second

tier also, the cross-sectional area of the

superstruc-ture-deck is of no importance from the point of

view of longitudinal strength.

Muckle proves [30], that for ships up to 600' in

length, this is true and that in the worst case, the stress in an aluminium house with the same

plate-thickness as steel, is only 74 % of the allowable

stress, while in a steel house the maximum stress rises to 100 % of the allowable stress. In no case does the absolute stress in the aluminium-alloy deck-house reach 55 % of the value of the stress in the steel deckhouse and in larger ships this percentage always remains under 50 %

Now, if all this is true for "light" deckhouses as conceived by Mont gomerie, it certainly will be true

in reality and even more so in the light of the

modern theories of Lyndon Crawford [31] and

Bleich [32].

Muckle has pointed out [24], [25], that this low stress in the aluminium-alloy superstructure-deck, being much lower than the one in a steel

superstruc-ture-deck, must put more load onto the original

strength-deck. This extra load may become so great,

that the buckling limit of the strength-deck may

be passed and he therefore gives a formula, which

'0

indicates what value

must have, so that the

Jo

buckling limit of the steel deck is just reached. If

we call = W, we find:

-y

-

₃

Io + A0 (yo + h)2 + W.h

He then observes, that it is possible to augment the thickness of the steel plates of the strength-deck and thus decrease the thickness of the aluminium-alloy superstructure-deck, as this is economically advisable. The increase in the cross-sectional area

of the steel deck may be:

E0

A0(W.y0-10)a

{W.h+Ao(Yo+h)2+Io} a-, =

Io + A.y2 + a..b2

(4)

In giving different values to "a", "a2" may be determined. Finally the aluminium-alloy

super-structure-deck must be safe from buckling, which may be controlled by Muckle's formula:

¡E, o

tO=tSA/_._

(5)

where: ta = thickness of deckplating in Al-alloy t0 = thickness of steel deckplating

This control is practically never necessary if the aluminium-alloy deck is covered with wooden deck-planking. As will be pointed out further-on, the

buckling strength of the

aluminium-alloy plates is very much increased in this case. Following Muckle's formulae from 1943, described above, one automatically comes to the conclusions:

That with Mont gornerie's theory developed in [29], the determination of the thickness of the aluminium-alloy deckplates will be on the safe side having regard to modern theories about the inter-action between the hull and long superstructures.

That even with the superstructure deckplates

contributing to the longitudinal strength of the

ship, the stresses remain so low, that a reduction of the thickness thus derived may be considered if the steel strength deck is re-inforced at the same time.

That such a procedure will always be followed for economic reasons.

That in that case the steel strength deck will become nearly as thick as the original case where the

presence of a superstructure was not taken into

account.

That indeed, that difference is so small and

the tendency to make the superstructure deck as

thin as possible so great, that it is better to consider

the superstructure in all cases as a "light"

deck-house.

This conclusion is somewhat astonishing, but this is the one, which Montgomerie [29] and Muckle [25] came to and which Muckle took up again in

his publication in 1952 before the Institution of

Naval Architects [30].

Therefore I consider that Tel f er's criticism,

though theoretically soúnd, is unjust and that my

own criticism must be revised in this sense, that it

is perhaps interesting to know how a superstructure

deck contributing to the longitudinal strength of

the ship should be designed, bût that economically speaking, it is better to make a superstructure deck

not contributing to the ships' strength and treat

that problem as Muckle did in [30].

§ 8. The dimensions. of "light" superstructures constructed in aluminium-alloys

The preceding paragraphs have settled thç

ques-tion of the design of superstructures and hâve restricted, thé problem to: How to calculate the

'dimensions of light, long deèkhouses?

.Corlett; [22] has indicated, that the. buckling

stress in an aluminium-álloy deckhouse will be

smaller than in a steel deckhouse' in proportion to

=

At the same time the limit of buckling

Ea

will be also be about that of steel X . So,

con-sidering that the buckling of the plates will be

fundamental for this structure, it would be logical

to take equal plate-thicknesses for the steel añd the

aluminium-alloy deckplates.

The stiffness of the whole'ship, however, would be somewhat smaller and therefore, in this case the stresses would become aJittle higher than

Ea

= 0.33.

Coriett calculated that 'the ratio of stress would be 0.35 to 0.37. Therefore hê proposed

ta = 1:10 t8

The limit of buckling however is proportional

to the square of the thickness. Therefore, ta oily

has to be = 6 % higher, so ta = 1.06 t8 iS

sufficient.

In steel construction a surplus of thickness for corrosion has been taken into account. This is not

necessary with aluminium-alloys. Therefore ta t8

might be adopted, basing our calculation on the

buckling limit. (See hereunder).

1Qe have already seen that Wa . 1.65 W8 if W

indicates

.- = section

modulus. If we consider

local strength, we obtain the following ratios: For equal strength t8 = 1.28 t8.

For equal stiffness t8 = 1.44 t8.

(I83Is,S0tal'3t)

For 50 % moré deflection than steel ta 1.26 t8.

(1. = 2 18, so la = t8)

"The reduction for the fact that an extra

al-lowance for corrosion is not necessary with alumi-nium-alloys, is determined as 'follows:

Light superstructure-deck in steel as, prescribed by Lloyd's (Mont gomerie-basis) for a ship of

L = 180 m is 7.6 mm. The corrosion-allowance herein is estimated to be '1 mm. Plate-thickness withOut corrosion-allowance = 6.6 mm. Therefore

the aluminium-alloy plate-thickness is: For equal strength

1.28 X 6.6 = 8.45mm = 1.11 X 7.6 mm.

For equal stiffness

1.44 X 6.6 = 9.5 mm = 1.24 X 7.6 mm.

For 50 % more deflection

1.26 'X 6.6 = 8.3 mm = 1.09 X 7.6 mm. From the' point of view of local strength the 10 % extra plate-thickness for the aluminium-alloy as proposed by COrI ett seems justified, but the example is given for a big ship, where the combi-nation of local strength and longitudinal strength

means that the load on the aluminium-alloy deck remains appreciably lower than with that combi-nation iû a steel deck. 'With a longitudinal stress of

about' that in a steel deck and Wa '1.65 W8,

we find that the load in the aluminium-alloy deck

in the longitudinal direction will be about

Ï.82 better. For small ships the corrosion-al-lowance is relatively much higher. Therefore it seéms justified to take 't8 = t8, even if the calcu-lation is based on local strength.

For deciding the deckpläte thickness of an alumi-nium-alloy superstructúre-deck, Muckie [30] 'has foll9wed the procedure already discribed in § 7.

Taking into account the smaller stiffness of-the

whole ship, when an aluminium-alloy superstructure is fitted instead of a steel one, he finds that the ratio of buckling-limit to buckling-stress is smaller for the aluminium-alloy than for steel. As' the buckling

limit is' proportional to the square of the

plate-thickness he arrives at the formûla already men-tioned in § 7:

Ea O',

Muckle then calculates 'for different ships'

lengths the necessary plate-thickness for the light-métal superstructure-deck, but it is curious to note thai the 'values given in his table V of [30] do not córrespond with formula (5), which' gives smaller

thicknesses.

-As he does not, take into account the corrosion-allowance, which gives relatively greater plate-'thickneses for small ships, the ratio for sthall

ships becomes greater. than for large ones and the result is, that for small ships, the plate-thickness

of the aluminium-alloy deckplates is too large for two reasons:

The corrosion-allowance for steel need not be added to the plate-thickness for

aluminium-alloys.

The ratio is too large for small ships (see fig. 1 in [30]. Here W1 is the sectional modulus

for a ship with superstructure and W, the

sectional-modulus for a ship without

super-structure.

When correcting the ratio's for as Muckle gives them for corrosion-allowance, then nearly all come to the formula

ta = 1.04 t8.

Muckle then gives some consideration to "elastic buckling". From his experiments and calculations the conclusion may be derived, that the buckling stresses are so small, that with his real ratio's t = = 1.14 t8 and ta = 1.27 t, there will never be any difficulty at all. Taking the plate-thickness of the

aluminium-alloy deck as small at Ea 1.04 to, it is

safe to suppose that even then the buckling limit will not be reached.

Both Corlett [22] and MuckJe [21] take into

account the wood deck-sheathing and its influence on the buckling of the deckplates. As already given

in [1] we find for plates of Y2" thickness and

planked with 2" teak the following ratio's: Unsheathed light metal . . . . 1

Unsheathed steel approx. . . 3 _J

Sheathed light metal approx. 9.1

Sheated steel approx. 10.4 _J

It will be clear therefore, that there is no reason to fear any difficulty in strength for sheathed light-metal decks compared with steel ones, if the un-sheathed decks give the measure of ratio-thickness between aluminium-alloy and steel.

Recapitulating the comparative dimensions to

steel as set up by Corleit and Muckle for light,

long deckhouses, we find these dimensions given in Table I. In the same table the proposed amendments on these figures are given.

The final proposal to ISO/TC 8/WG 1 is not

to take a certain percentage on the thickness of

the steel-deckplating, but to make all unsheathed aluminium-alloy decks OJ mm thicker than steel decks. This proposal is based on the following

reasons:

1) Thin plates receive a relatively greater

ad-ditional thickness than heavy ones. Therefore local strength, which is of more importance with smaller ships, is better allowed for in these ships.

ratio 0.33 ratio 0.87

Based on local streng/h: Equal strength

stiffness

0 % more deflection strength corrected for

cor-rosion allowance

stiffness corrected for

cor-rosion allowance

TABLE I

Requirements for aluminium-alloy

deckhouse-Platin g

Thicknesses are given as the ratio t8/t5, where = thickness of aluminium-alloy plating

Beams and s/i/fences

Section, Eq,l strength = We = 1.61 \01s Cslcu- ,. stiffness

-

la = 3 Is

latad on 10 % deflection

-

¡a = 2 Is

Eqeal buckling

-

_{¡a = LI Is}

I) _{The lower numbers ore for L = ISO m, the higher ones for L = 60}

es. 2) _{This is true for both types of ships (I tier and 2 tiar, of beams).}

The addition of 0.5 mm thickness, corre-sponds in ships varying from 60

m to 180 m in

length to an additional percentage in longitudinal

strength of 8 % to 6 %. These values are bigger than the 4 % allowed in the criticism of Muckle's

values.

As already mentioned the combination of

local strength and longitudinal strength of the ship gives an advantage to the aluminium-alloy struc-ture. Therefore the additional longitudinal strength percentage of 8 % to 6 %, is certainly covered by the 11 % local-strength addition as corrected for

corrosion-allowance.

For sheathed decks, the proposal is to take for aluminium-alloy decks the same thickness as for

steel decks. As MuckJe has taken _{no account of} wood sheathing, it is safe to assume that the 4 _% greater thickness as asked for by his method will be largely counterbalanced by the better strength-ratio (0.87 against 0.33) of the sheated decks in alumi-nium-alloy.

Concerning the sides of the deckhouses M lick! e

[25] proposes t = 1.15 t8 and GoncEE [22] ta to.

Both authors are illogical, but it may be that Conlef t takes into account the less important local loads and therefore drops his additional 10 %.

Va = 1.61 Ws; with un-sheathed deck, and heavy beams Va = 2 Vs. = ,, steel plating Item Corlett ta/is = Muckle io/is =

Based oie buckling limit:

Unsheathed deckplating 1.10 1.06 to 1.25')

Taking The longitudinal bending into ' The corrosion allowance account I. Both factors

1.06

Working with Muckle's J 1 Tier 1.07 to 1.241) formula I 2 Tiers. _{1.14 to 1.271)}

Taking into account "elastic buckling'

Sheathed deckplating

corrected for

cor-rosion allowance 1.00 1.00 1.12 to 1.21) 1.04 As criticized ia/is = 1.00 1.00 1.042) l.04) 1.00 1.00 1.00 1.28 1.44 1.26 1.24

Logically one can say, that the load on the

vertic-al vertic-aluminium-vertic-alloy house side, will be about 50 %

of that in the case: of a steel house side. As the

limits of buckling of the aluminium-alloy plating and steel plating are in the proportion of Ea : Ea =

= 1: 3, we may corsider that la = 0.5 X 3 18

=

= 1.5 L and therefore ta = 1.14 t8. This ratio cor-rected for corrosion-allowance on steel only, gives as a result:

ta 1.0 t8.

The proposal is to do the -same as in the case of

the deckplating and for the same reasons adopt an additional thickness of plating in aluminium-alloy of 0.5 mm.

The deckbeams must be considered- separately: Muc/de [25] gives for beams of:

a. Equalstrength Wa 1.65 (1.70) W8

- b. Equal stiffness 1 3 18

-c. 50_%more deflection f

-

2 L

Corlett [22] bases his tables on deflections of the beam of 1/500 with 2 feet cargo height and a

cargo density of 50 cubft/ton. Based on steel

scantlings as prescribed by Lloyd's, Corlett finds:

TABLE II

means (W

=)

= sectional modulus of

plate + profile of the aluminium-alloy strUcture.

W5_pof means (W = ) = sectional modulus

of profile of the steel structure.

We -see that Corlett allows deflections in the light-alloy beams more than twice as great as in

the steel- ones. = constant 1.7.

Bureau Ventas prescribes only that - = 1.5.

This gives still greater deflections of the beams as

compared with those of Cori ett, as

-'a

1.35.

It is difficult to make a choice from these three

propositions. The fact must be considered, that

with more than one tier of light-metal superstruc-ture decks, one of these decks is submittted to, what

Muckie [30] calls, the "eñd-effect" of the

deck-house and which -phenomenon is very clearly

described by Van der Neut [33]. The beams not

only must be strong enough, but also form a certain solid ground fOr the big "end-effect" forces of the

deckhouse above.

-A superposition- of the deflections of several

decks, where more tiers of decks are present, may

result in inadmissible deflections of the highest

deckhouse. Therefthe the stiffness should not be töo small and at least Wag8

= 165

1V,88 should be

obtained. .

For heavy bulb-sections the progress of I and W is equal. For wood deck-sheathing the deflection is

diminished. If there is no planking there should

be a tendency in big ships having deck-beams in

thé

f rm of bulb-sections to obtain minithum

deflections -and in this case lVat0, = 2 IVSO8 should

be proposed.

Muckle [30] studies the stiffeners of- the -sides

and around the openings for windows in

deck-houses. Now, de to the end-effect the forces taken by the front bulkheads and for a distance of about the breadth of the deckhouse along the longitudinal wall, will be between 70 % to 90 % of the total

vertical forces- working on the deckhouse-sides. In these parts the stiffeners have an important duty -to fulfil. If -there are "openings" in -the side, the normally calculated stiffeners should have an

in-crease in cross-sectional area of about 2.0-% to 30 %

according - to Muc/zie. Neither Coriett nor Bureau Ventas give indications on this subject.

Conlett gives for the normal stif-fener the

for-mula Wa = 1.-65 W8. The table given in [22] for the dimensions of these stiffeners has everywhere W8 > 1.65 W8 and la varying from 1.75 to 2.1 1. Muc/zle [30] indicates that stiffeners must be

dimensioned on the total stiffness of plate + section, which is interpreted by Robinson [34], as Ia = 2 1.

This should of course be l = 3 L for the section

only. Muckle's requiremçnts seem too heavy in this case, the more so as the -weight of the aluminium-alloy deckhoúse is much less than that of the steel deckhouse. Furthermore there is no reason, why we should hold to the requirement of equal stiffness as a little greater. deflection of the side will do no harm. Based on the buckling limit with a weight

load of 50 % of the steel house, one finds Ia = 0.5

X 3 Is 1.5 Is. Therefore it is proposed to accept here also the formula W = 1.65 W8 (see Corlett's

proposal). -

-The bulkheads inside the deckhouses and their stiffeners must remain relatively heavy. The fittings

of the house which are

not influenced by the

material in which the house is constructed, will remain of the same weight and that load will be

taken, for the most part, by the interior bulkheads. The corrosion-factor also plays a lesser part in considerations concerning the dimensions of these

-Il

Free length of beam: 1: 10' 20'

W'88,/ 1.80 1.94

1.70 1.70

1V0,.O1/ T"prof L63 1.90

inside structures. Therefore instead of the proposal

= t8 + 0.5 mm as for the unsheathed

deck-plating and the outer walls, the proposal here

should be

ta = t8 + 1mm.

For the stiffeners of these inner bulkheads the

same considerations as

for the other stiffeners

remain valid and therefore Wa = 1.65 W8.

For pillars, which are subjected only to

column-buckling it is clear that la = 318. Robinson [34]

gives a general survey of the comparative

dimen-NOTES: All scantlings for aluminium-alloys are based on the

relevant dimensions of steel. Thus I and i and W8 are the thickness, the moment of inertia and the sectional modulus for a steel structure.

COMMENTS ON THE TABLE ARE:

The higher figures for the shorter deckhouses.

(S) is for short deckhouses less than 0.20 L. (L) is for long deckhouse, greater than 0.20 L.

a) _{The lower W5 is permitted with a % Mg-alloy in light-hardened}

condition or Al - Mg - Si heat treated sections.

TABLE III

Requirements fore aluminium-alloy deckhouses

sions of light, long deckhouses in his paper read at Naples. He therein also compares the regulations laid down by the different classification societies. The table VIII of his paper is completed here with the proposals as put forward to ISO/TC 8/WG 1

and the result is given in toto as table 1H of this

study.

This proposal is simple and easy to handle. It is on the safe side as the breaking point of the

alumi-nium-alloy is the minimum one prescribed by

Lloyds, whereas for steel the meanbreaking point is taken.

3.0 I here applied to columns undergoing compression stresses stresses such as pillars etc.

For structural units under local loading and where equal

de-flections are required.

O) _{If the deck plating is connected to wood sheathing at centre of}

every beamspace, the thickness may be the same as for steel. 2W8 here applied to unsheathed decks of large ships, where the

deck-beams are bulb-sections.

3.0 1, here applied to columns undergoing compression stresses (Pillars).

Item Corlert Muckle

Norske Ventas 2) Bureau Ventas Registro Italiano In ac-cordance with Lloyd's practsce Proposal to ISO/TC 8 W.G. i Deckhouse-sides Plating 1.10 t8 1.15 t5

_j

' 1.20 t4 (S) 1.35 18 (L) 1.20 t8 J 1.45 t8

i

1.25 . 1.15 t8 t8 + 0.5 mm Stiffeners 1.70 W3 11.30 W8 (S) . 1.50 W8 (L) ¡1.30 W83) 11.20 W5 2.25 W8 1.70 W8 1.65 Ws Deckhouse-fronts 1.20 18 1.50 18 1.20 t8 18 + 0.5 mm Plating 1.10 Stiffeners . 2.0 W. { 1:30 W8 (S) isø W8 (L) 2.25 w8 2.00 W. 1.65 W3 Dec /zplating Sheathed 18 1.12-1.25 t8 1.20/3 (L) 1.20 t8 1.10 t8 O) t8 Unsheathed .. . . 1.10 t8 1.12-1.25 8 1 1.20 t4 (S) 1,35 t8 (L) 1.35 18 1.15 t8 t8 -+- 0.5 mm 1) Inner-bulkheads Lined Unlined t8+0.SmlTi_{t8 + 1.0mm} Stiffeners 2.0 18 2.0 I 2.0 18 1.65 W,5 Deckbeams . . . . 1.70 Ws ¡1.30 W8 (S) . 1.50 W8 (L) 1.50 W3 2.25 W8 1.70 W. 1.65 à 2 W. 7)

Beams and girders 2.0 '8 2.0 18 3.013 3.0134)

3.0I)

2.0 s

i

1 1.65 W,8_{3.0 188)}

Short superstructures and short deckhouses

As the

corrosion-allowance for thin plates is

relatively more important than for heavy plates,

the application of the above-mentioned rules for long deckhouses, to short superstructures and deck-houses will give the latter a greater factor of safety. As, on the other hand, the local loadings of these deckhouses are of the same order as those for long deckhouses, it is considered prudent, not to suggest a decrease in the thickness of the plating of these short superstructures and deckhouses, relative to the

long ones.

Therefore t = t, + 0.5 mm.

For the stiffeners W = 1.65 W8 is proposed.

The question of when a deckhouse is short or

long depends on the prescriptions of the classifi-cation societies. Norske Verjus considers a

deck-house short when I < 0.2 L, Lloyds when i <

0.15 L and Lyndon Crawford when I < 0.35 L

[31].

Corrosion-resisting coverings and linings of insulated cargo-spaces, tanks, kitchens, etc. and the fabrication of ships' fittings exposed

to corrosion

These types of application are indicated in the groups II. E and II. F. As the corrosion-resisting

qualities of the aluminium-alloys are the reason

why this material is chosen, there will be no need

to discuss the desirability of using it. Under this heading also falls the use of aluminium-foils for

insulating purposes.

The advantages of aluminium-alloys in this field

are more e'specially:

Gain in hold capacity and weight. Longevity of the coverings. Easy repair.

Gain in fire-protection as regards cork. Hygienic.

Resistance against corrosion by oil or wine. The thickness of the plating varies in this case

from 2 to 4.5 mm, depending on the supports

available. Ceilings

are constructed in plates of

1.5 mm to 2 mm. The bottomplating nearly always

has an increased thickness of 1.5 mm above the

wall-plating. The bottoms of cargo-spaces are still

Suggestions about the riveting between steel and aluminium alloy ship's structures.

§ 12. Introduction of this special subject

The only possible means of connect ng steel to aluminium-alloy structures are riveting and bolting.

In view of the difficulties arising from riveting

thick plates together, it might, first of all, be

sug-gested, that the idea of bolting together ships'

structures should not be disregarded without careful

study of the subject. Indeed fitted-bolts may be

cadmium plated or protected against corrosion in

often made in wood, as the wear and tear is great. For refrigerated cargo-ships see [17], for fishing

vessels [14], [15] and [16]. Good guidance for

the upkeep of these installations is to be found in [14] and [35]. The connection of these thin sheets by means of "cadmized" screws etc. is outside the scope of this study. Information about port-holes and windows is given in [18]. An increase of the

corrosion-resistance is

often brought about by

anodizing or other chemical treatment. Bimetallic contacts must be prevented at all costs.

§ Il.

Special ships' fittings, which must be light

and resistant against corrosion

These fittings are listed in the groups III. G and III. H. The use of aluminium-alloys may be stimu-lated by the ease of handling during the fitting of these parts. This especially is the case with

venti-lator-ducts, pipe-lines etc. The transport of very

corrosive fluids is best done by light-metal pipes. The dimensions are determined by normal

strength-calculations. Welding of pipes instead of flanging them and bolting them afterwards is in-creasingly used.

The use of light-metal lifeboats on board large passenger-ships saves an enormous amount of

top-weight, and the boats' davits may also be

con-structed in aluminium-alloy. Light-metal ships'

funnels have the same advantages Resistance against

corrosion at high temperatures is a question that

still needs some experimental research. Up to the present the full corrosion-allowance on the steel

has been kept for the light-metal funnels. The

upkeep of these big light-alloy funnels is described

in [19] and [20].

The scantlings of lifeboats and funnels may be determined by direct strength calculation. Though welding gives a saving in the quantity of material used, thin plates are more easily riveted and thus the above mentioned gain is small. Here the normal practice is to make the rivet spacing one diameter less than in the corresponding steel-riveted connec-tionS [36].

The choice of the aluminium-alloys used on

board is given in [1] and forms a part of the study of a special panel of ISO/TC 8/WG 1.

such a way, that they can take the place of rivets, even for great plate thicknesses.

But the object of this study is, to give informa-tion about the riveting of connecinforma-tions between steel and aluminium-alloys. Points of interest are:

Choice of rivet (see § 13).

Precautions against corrosion (see § 13 en 14). Execution of riveted construction (see § 14).

TABLE IV

General Survey of the possibilities, advantages and disadvantages of the use of hot- or cold riveted connections betiveen steel and

aluminium -alloy ships' structures

Riveting

Rivets

Rivet material

compared to plate material corrosion

Effect of

shrinkage of

rivet

Effect of tempe- rature of rivet on

.

material and packing

Max.

.

of rivet

.

Effect of rivet head

. . Pitch of rivets Corrosion of joint Hot riveted Steel rivets

If not alumited chance of much galvanic cor- rosion

Good shrinkage strong clamping of plates. Rivet little elongation and niuch heat con- duction. Tight joints, Temperature too high for plates, too iow for rivets,

Destruction of packing by heat. No alumiting possible. temp.: ± 6000 C. still too low Above 6 mm

Snaphead on the steel plate-side. With galvanised washer on Al-plate side

Normal

As packing is destroy- ed corrosion nearly in- evitable. Heat durable packing.

Al-alloy rivets

Rivet metal as far as possible the same as plate material to avoid galvanic corrosion

Good shrinkage. Good to doubtful clamping of plates. Rivet large elongation and much heat conduction. Tight joints, but doubtful with heavy plates. Dif- ficult to get the right temperature.

Destruction of packing by heat. Alumiting of steel plate nearly impos- sible. temp.: ± 5000 C. Above 8 mm

Snaphead on the Al-plate side. With galvanised washer on

Al..

plate side

About i d. smaller than with steel rivets, More rows of rivets

As packing is destroy- ed corrosion nearly in- evitable, Heat durable packing, not flexible enough.

Cold riveted

Steel rivets

If steel surface> than Al-surface: Snaphead on the side of steel plate if corrosion on that side. Corrosion smaller than with Al-rivets, Small corrosion on Al- plates.

No shrinkage; strong rivet with small 0 Certain strength in direction of rivet-axis, good if corrosion starts between plates.

Alumiting, cadmium plating and galvanizing possible

8 mm _{excep- tionally 10 mm}

Snapheaci on steel plate side

Normal. More rows than in steel construction due to small diameters Glue packing and paste without packing is pos- sible. Packing must be flexible and not hygro- scopie. Chemical and electrical isolating.

Al-alloy rivets

1f Al-surface > steel surface: Snaphead on the side of Al-plate if corrosion on that side. Bigger corrosion than with steel rivets. Big corrosion of rivet duc to steel plate. No shrinkage. Weak rivet with big 0 Doubtful strength and too much elongation in axial-direction. If cor- rosion starts no rigi- clity.

Alumiting, cadmium plating and galvanizing is possible

16 mm excep- _{tionally 22 mm} Snaphead on Al-plate side

About i d. smaller than with steel rivets, More rows of rivets Glue packing and paste without packing is pos- sible. Packing must be flexible and not hygro- scopie.

Chemical and

§ 13. Choice of the riveted-connection

(see Bibliography [37]-[44])

We have the following choices for riveting the

connections of steel to aluminium-alloy ships'

structures.

Use of hot-riveted steel rivets. Use of hot-riveted AL-rivets. Use of cold-riveted steel rivets. Use of cold-riveted A1.-rivets.

Table IV gives a general view of the possibilities; advantages and disadvantages of the use of these different methods; also the corrosion aspect.

§ 14. Execution of the steel-riveted joint

The use of steel rivets for this kind of connection is to be generally recommended (see Table IV). As

far as possible these steel rivets should be cold

riveted. If hot-riveting is unavoidable, the riveting

temperature must be kept as low as possible for

executing the riveting. In all cases these temper-atures should not be more than 6000 C.

If such high temperatures are necessary, galva-nised washers should be used.

H. E. Jaeger: 'Practical possibilities of constructional

appli-cations of aluminium-alloys to ship construction". Report

No 3 of the Netherlands' Research Centre T.N.0. for

Shipbuilding and Navigation, March 1951. See also Schip

en Werf", 27th April and 11th May 1951.

W. Muckje: 'The influence of weight-saving on dimensions

and form". The Shipbuilder, July 1952.

A. Pyszka: "Vedetten aus Leichtmetall", Zeitschrift der

Alu-minium Zentrale 1953, pag. 37.

'Aluminium Yacht of welded construction", Weld- and Metal-fabricatión, August 1953.

E. Helsengreen: 'Eine Vergleichsrechnung Stahl-Aluminium für

ein schnelles Revierschiff", Schiff und Hafen, July 1954. 'Leichtmetallmerkel", Hansa 1951, pag. 324.

H. G. Auerswaldand A. Scyrnans/ci: 'Schiebebalken aus Leicht-metall", Schiff und Hafen, September 1953.

W. Surmaier: Möglichkeiten des Leichtmetalleinsatzes im

Bin-nenschiffbau", Zeitschrift für Binnenschiffahrt, February

1953.

K. Suppus: "Die Entwicklung der Leichtmetall

Lukenabdeckun-gen", Zeitschrift für Binnenschiffahrt, February 1953.

Tb. Domes: "Spezielle rechnerische Grundlagen für die

Leicht-metallanwendung im Schiffbau", Jahrbuch der Schiffbau-technischen Gesellschaft 1952.

K. Su/ter: "Erfahrungen im Berechnen von

LeichtmetaÍlkon-struktionen", Wirtschaft und Technik im Transport,

July-November 1951.

"Rettungsbote",Hansa 1951, pag. 1672.

W. Fiedler: ,,Leichtmetallkonstruktionen für den Schiffbau",

Hansa 1950, pag. 1484.

F. Kraus and A. Müller-Busse: "Der Leichtmetallfischraum der

Arktis", Hansa 1951, pag. 61 2

Bibliography

Cold-riveted

rivets may with

advantage be

alumited, galvanised or cadmium plated. The rivet hole must be filled up with paste or paint. Rivet-holes must be made with the utmost care and the rivet-fitting must be as perfect as possible.

All packings must be flexible. Thereforé paste without fibre may be recommended as far as pos-sible. The more so, as every fibrous canvas is apt to be hygroscopic, so helping to introdiice corrosion. All paste should clear the joint for 2 or 3/mm.

The snaphead should be at the steel-plate sid'e of the joint. This side should be the most corrosive sided The joint, must be well above places where seawater may accumulate. The distance from the

bottom of the joint to a wood deck should be at

least 50 mm.

For hot-riveted joints the breadth of the overlap may be made somewhat larger than necessary from the strength point of view. In all cases > 75 mm.

Caulking of these "mixed" structures is not pos-sible. For obtaining watertightness, good "plane"

surfaces of both the steel and aluminium-alloy

plate. are necessary. After riveting, varnishing of

the joint with lacquers etc. may help to achieve

watertightness.

W. Fiedler: "Leichtmetallfischräume", Hansa 1951, pag. 1673.

"Der Arktis nach zweijähriger Betriebszeit", Hansa 1952,

pag. 428.

P. VidaI: "L'allègement de l'isolation è bord des navires

frigori-fiques", Bulletin Technique du Bureau Ventas, January 1951.

"Schiffsfenster" DIN. 81601, April 1953.

A. Cherrier: "Les cheminées de navires en alliage léger", Revue

de l'Aluminium, January 1952.

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Trans. N.E.C., 5 March 1948.

E. C. B. Corle/E: "Aluminium as a shipbuilding material",

Trans. N.E.C., 22 February 1952.

F. S. M. Brierly and J. E. Tom!inson: "Some recent develop-ments in the welding of aluminium-alloys and their future applications in the shipbuilding industry", British Welding Journal, 1954.

W. Muckle: "Some considerations on the application of light

alloys to -ship-construction", Trans. N.E.C., 20 December

1943.

'W. Muckle: "Application of light-alloys to superstructures of

ships". Trans. N.E.C., 26 April 1946.

E. C. B. Corle/E: "Thermal expansion effects in composite ships",

1.N.A. 1950.

J. Venus and E. C. B. Corle/E: "Fire protection in passenger ships", I.N.A. 1953.

A.Audigé: "Etudes récentes sur la protection cntre l'incendie la prévention dans la construction", A.T.M.A. 1954.'

J. Montgomerie: "The scantlings of light superstructures",

I.N-.A. 1915.

W.Muc'kle: "The scantlings of long deckhouses constructed of aluminium alloy", I.N.A. 1952.

Lyndon Crawford: "Theory of long ships' superstructures", 38. S.N.A.M.E. 1950.

H. B1eic: "A study on the strùctural acioh of superstructures on ships Ship Structure Committee No SSC 48 Washing ton,, January 1953.

A. - van der Nevé: "Beschouwingen over vormgeving van gelaste scheepsconstructies", Lassymposium der N.V.L., Utrecht, 26 October 1951.

L. M. C. Robinson: "Aluminium in ships' structures; .a review

of current practice". Trans. of the International Maritime

Congress, Naples, 30 September 1954.

-R. Klingholz: "Neuartiges Montagevexfahren an Bord von Schif-fen", Hansa 1952, page 1590.

J. E. Temple: "Handbook of structural designs in aluminium-alloys", Editiòñ: James Booth & Co.

37.- Aluminium Zentrale Düsseldorf, Aluminium Mérkblatt V 5.

J Reiprich: "Werkstoff- und Betriebstechnische Grundlagen für die Aluminiuthverwendung aúf Schiffen", Alumiñium im Schiffbau 19,53, Aluminium Zentrale, Düsseldorf. 39. "L'ùltilisation de l'Aluminium et de ses alliages en -construction.

navale". L'aluminium français, February 1954.

40 C V Boy/cia and M L Sellers Practical problems relative to the use of aluminium-alloys in ship construction'. S.N.A.M.E., New York 1953.

"Aluminium for marine uses", Ships' structures of the British Auninium Co. Ltd. 1953g

A.D.A. Information Bulletin No. 20, December 1952. W. Sandow: "La protection contre la corrosion des constructions

en métal léger", Aluminium Suisse; page 198, November 1954.

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