(SANITIZED)UNCLASSIFIED SOVIET PAPER ON TRENDS IN SCIENTIFIC RESEARCHES IN THE FIELD OF THE STRENGTH AND STRUCTURE OF MERCHANT SHIPS IN THE USSR(SANITIZED)

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A015200110001-0
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 6
• Document Creation Date: December 22, 2016
• Document Release Date: January 6, 2012
• Sequence Number: 1
• Publication Date: January 30, 1962
• Content Type: REPORT

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THE PRINCIPAL TRENDS IN SCIENTIFIC RESEARCHES IN THE FIELD OF THE
STRENGTH AND STRUCTURE OF MERCHANT SHIPS IN THE USSR
During the last few )ears tht principal
scientific research work in the USSR on the
ship strength and structure was directed to-
wards the solution of the following two inter-
connected problems:
a) The improvement of the existing Rules
of the Register of Shipping of the USSR for
classification and construction of seagoing steel
vessels.
b) A further development of the calculation
method in determining the scantlings of the
structure of merchant ships.
The object of the first problem is:
To supplement the Rules in force with new
data regulating more precisely the relationship
between loading and scantlings of the hull
structure, ensuring a more rational use of hull
steel.
In 1956 the Register of Shipping of the USSR
reissued rules for the classification and the
construction of seagoing steel ships which were
supplemented in 1958 and 1959 with the two
chapters prescribing: the first - supplementary
requirements about scantlings of structures of
ore carriers and the second - provisions to take
into account peculiarities of a general arrange-
ment and shape of the hull. At present a new
edition of these Rules is in preparation for pub-
lication. The results of the latest scientific re-
searches during the mentioned period will be ta-
ken into account as well as the experience
gained in regard to the construction and navi-
gation of ships built in conformity with the
Rules.
In the new edition of the Rules an estimate
of the scantlings of all principal structures of
the hull is envisaged depending on the value of
the loading that is assumed can be encountered
by ships during the navigation, thus taking into
consideration individual peculiarities of ships.
Essential amendments and additions based on
the results of appropriate theoretical and expe-
rimental research works are being introduced.
These amendments and additions will give the
possibility to take into account such essential
factors, which have not had enough considera-
tion in the Rules at present in force, viz.:
1. Slamming.
2. The use of low alloy (high tensile) steel,
aluminium alloys and other materials, taking
into account their mechanical properties.
3. The use of corrugated bulkheads in hull
construction.
4. Designing of multi-tier superstructures of
complicated configuration.
5. Ice strengthenings of the hull structures
in merchant ships and tlz structures of ice-
breakers.
The new rules will contain essential data
about constructive details of different hull mem-
bers, chiefly intermittent ones, which can be a
source of stress concentration, and also specific
provisions as called forth by the widespread use
of various types of welding in hull construc-
tion now exclusively used in the USSR instead
of riveting.
It should be noted that in the USSR, and
apparently abroad as well, the question of us-
ing riveted seams in welded hulls as barriers
against the spreading of cracks still remains
unsettled.
The opponents of such crack arresters consi-
der that the use of steel, which in itself is ca-
pable to resist against the spreading of brittle
fractures, excludes the necessity of using riveted
seams.
In spite of the amendments introduced into
the Rules of the Register of Shipping of the
USSR, these rules, owing to their inherent de-
ficiency, are not able to fully meet the require-
ments of rational designing of hulls of various
types of merchant vessels.
The principal deficiency of the Rules is that
they are essentially empirical and, while dealing
with strength and the safety of the ships, do not
give enough consideration to possibilities of re-
ducing the weight of the hull, admitting in some
cases an excessive margin of strength.
The above mentioned shows the necessity of
further amendments of the Rules in force and
simultaneously calls for the development of the
calculation method in designing hulls of mer-
chant vessels.
This method should be understood as a ge-
neral process of determining scantlings of the
main hull structure, ensuring general and local
strength on the basis of the ship strength theory
in conformity with the standards of loading and
permissible stresses prescribed by the Register.
Wear, the margin for the corrosion of the mate-
rial used and other prescribed norms and regu-
lations should also be taken into account.
The scantlings of the hull girders and structu-
res should be submitted to approval in an ap-
propriate form in accordance with the special
practice of hull designing.
"The Standards of Strength for Seagoing
Steel Vessels" and a "Manual for the Calcula-
tion of the Strength of Seagoing Steel Vessels"
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were published in the USSR in 1958. They are
based on experience collected by that time in
designing, construction and navigation of ships
as well as on theoretical and experimental re-
searches.
According to the general regulation, in the
first chapter of the "Standards of Sir(-ngth for
Seagoing Steel Vessels" theses standards arc
valid for vessels of 60 Ill. or more in length
and shall be also used for the checking of (lie
structure strength of vessels of 110 fit in length
and over, designed in accordance with the Rules
for the classification and construction of seago-
ing steel vessels.
These "Standards" include special instruc-
tions for the calculations of the general strength
of the hull allowing for the dynamic component
of the bending moment. For this purpose corres-
ponding rated formulae and diagrams are gi-
ven. For the estimation of the Margin of
strength in the most unfavourable sea condi-
tions, the strength calculation, based on limit-
ing moments shall be carried out. The terns
"limiting moment" denotes that under its action
the stresses in one of the extreme laminas of the
weakest sections in the middle part of the ship
attain the yield point of the material
cepted.
The "Standards" also include instructions
for the setting of rated loadings and norm, of
permissible stresses as well as a selection of the
design of ship sections and the definition of
structural members to be included into the sec-
tion modulus of the ship, an estimation of the
width of the conjunctive plating to be taken into
c,ccount in the local strength of ship's members,
a reduction of the plates' sectional area if they
can be buckled under the action of compressive
forces, as well as other provision "Standards
of Strength" published in 1958 enabled us to put
into practical use the calculation method for the
designing of ship structures. The theoretical and
experimental study carried out since that time in
the field of external forces acting on a ship's
hull in rough seas, more precise methods of cal-
culation, the analysis of navigational and ser-
% data as well as the experience gained in
;tPPlying the "Standards of Strength" in the last
three years had made necessary their amend-
ments and additions.
The "Standards of Strength" have recently
been revised and a new edition is in prepara-
tion. To this end the scientific research has
been carried out along the following lines:
I. A more precise estimation of the general
bending forces acting on ships.
II. A study of internal stresses arising in the
tr ucture of hulls and working out of more pre-
cise methods of their calculation.
III. A revision of the coefficients of the mar-
gin of strength.
IV. The working out of other guiding instrtrc-
lion, for the calculation of structures of mer-
H'-1nl vc,sels.
A MORE PRECISF ESTIMATION OFF THE GENERAL BENDING FORCES
ACTING ON SHIPS
A more precise estimation of the general
bending forces acting oil ships is primarily cr,n
nected with a manifold study of external load-
ing acting on the ship's hull in rough this
is studied both theoretical l} and experiflit ntally
The said field of knowledge presents special dif-
ficulties for investigation.
A number of views exists, and each has ,t
o%11 followers. During the past few years at-
tempts were made to apply the theory of sta
tionary accidental processes and statistical dv
namics to the problem of external forces, acting
on the ship in irregular waves at sea.
Some works on the said suhjc~ct suggest the
evaluation of strength based on the examina-
tion of the probable collapse of a structure tinder
the action of loading instead of on the basis of
permissible stresses. A number of Soviet aut-
hors who do not share the expediency of using
the apparatus of accidental function- for prac-
tical methods of calculation, devote their inves-
tigations to the matter of using statistical nteth-
ods for establishing relationships between the
height and the length of the rated waves as well
the establishment of necessary margins of
't rength.
Summarizing the researches carried out in
the USSR and abroad it became possible to
4
c,'ahlish the length to height ratios of the wa-
hich should fW-T11 the basis of calculations
"t ?hc longitudinal strength of ships.
Its studying external forces much attention
ha, been given to slamming.
I'he problem of ensuring a greater strength
of the hull against slamming is very important,
espec?i.1k nowadays, because of the growing
tendency of increasing speed of merchant ships
in high seas. 'I'bis can be seen. in the first ins-
tance, from the increasing number of experi-
Mental and theoretical researches devoted to
Ihis problem during the past few years, both
in the USSR and ahri,ad, and secondly, from
the fact that foreign classification societies (for
instance the British Lloy,l's Register of Shipp-
ing) found it necessary to add to the Rules a
clause stipulating a special increase in thick-
ness of the strength deck . c.ckoning with the
effect of ,lamming.
(Itc' measurements of 't~,-,rs in hull mem-
d>,'r al the instants of sl:nur:Cnig in heavy seas
ho? that the frequency if flexural vibrations
of the hull due to slamming are close to the
Itip natural frequency of the first mode stres-
ses in the main structures of the hull due to this
vibration and are added to the stresses caused
by the general bend of the hull ir.~lf when the
,tui, -;fit- in a rough sea
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As a result of theoretical and experimental
researches the general effect of slamming in
heavy seas was studied, and a practical method
was proposed for the computation of the design
values of external forces when checking the
general and the local strengths of ships' hulls
in a rough sea.
Simultaneously mth thcwrelical i ivestiga
tions model tests in model basins as ~k ~ 11 as spc?
cial trials of ships are conducted in order to as
certain the behaviour of sbips' structures in hea
%y seas. The model proposed b\ E. l.ea is (with
a cut into which resilient materials are put in)
as well as other models (patented in the USSR)
have been tested. In particular, a model con-
sisting of a large number of compartments fas-
tened to a resilient beam modelling the rigidity
i,f the hull has also been tested. These resea-
ches as well as tests of ships at sea proved
the incompetence of the hypothesis that the pres-
sure at each point of the submerged surface of
the vessel would be equal to the pressure in the
corresponding point in the mass of water under
the wave surface. The effect of the hull on the
structure of waves was found very essential,
,specially in regard to ships having a compa-
atively big breadth.
Extensive strength tests were carried out on
diesel -electric dry-cargo ship of 5000 tons car-
r\ rrrg capacity in the Atlantic Ocean in the win-
ter and spring of 1961. Numerous measurements
wire taken of stresses due to the general lon-
gitudinal bending and to the vibration follow-
ing slamming. The impacts of hydrodynamic
pressures against the bowpart of the ship were
also recorded. These tests will be resumed and
continued this autumn.
A STUDY OF INTERNAL STRESSES ARISING IN THE STRUCTURE OF HULLS AND WORKING OUT OF MORE
PRECISE METHODS OF THEIR CALCULATIONS
1. Hull damages made the shipbuilders in
many countries reckon with the effect of stress
concentration and pay special attention to the
correct designing of hull members at sections
where sharp changes of their area take place.
In this connection in the USSR the work
on the theory of strains of intermittent mem-
hcrs of hull was developed. rind it ,nahled ship-
huilders to determine by this a!cu!ation method
the coefficient of concentration at points of
sharp changes of section areas at the ends of
superstructures, large openings, etc.
2. In the USSR in connection with the con-
stantly increasing construction of merchant
ships with superstructures of complicated con-
figuration and a variable rigidity along their
length and with various openings and recesses.
Soviet ship designers show a keen interest in
the problem of strength calculations and the
framing of such superstructures. A number of
theoretical works on the subject was published,
in which this problem was approached by means
of applying the theory of intermittent members
and the theory of elasticity.
Special attention is now being paid to the
investigations of the stress distribution at the
ends of superstructures and at the openings for
doors and windows.
3. Much attention is given in the USSR to
the question of carrying capacity of hull struc-
ture, which is connected with a study of plastic
strains of material. This is naturally being stu-
died as a whole, both theoretically and experi-
mentally. Together with the development of the
mathematical theory of elasticity, works on
applied technical theory of plasticity are also
carried on.
In order to estimate the carrying capacity
of statically indeterminable structures, various
methods have been worked out and further re-
search work in this field is being conducted on
different methods of calculation of combined ef-
fect of normal stresses, shearing forces, stret-
!iing, etc. In so far as the use of new building
materials, such as aluminium alloys and such
grades of steel which have no distinctly expres-
~ed yield point, it is necessary to reckon with the
t i feect of self strengthening, a number of authors
propose different methods enabling ship desig-
ners to formulate and solve differential equa-
tions defining the interdependence between
-tresses and strains in an elastic-plastic re-
gion. Besides the estimation of the carrying ca-
,aacity of the structural members under the
stress action, there appears a necessity of re-
gulating general deflections of structures. These
circumstances require the working out of prac-
tical formulae which would enable the designers
to define the residual deflection of structures.
The scientific research in the above mention-
ed field made a noteworthy progress and found
a practical application in the designing of ice-
breakers and the strengthening of ships' hulls
for the navigation in ice conditions.
4. The question of the definition of the vir-
tual width of the conjunctive plating of struc-
ture members subjected to compressive forces,
bending and other kinds of loadings continue to
draw the attention of scientific workers. Such
factors as the degree of excessive active com-
pressive forces in rigid members as compared
with Euler stresses in plating, the initial plate
deflection, if any, and its form, the transverse
loading, the stretching effect of the framing,
etc., are also considered in these researches.
5. In connection with the tendency to enlarge
cargo hatchways, the stability under compress-
ive forces of deck structures is being investiga-
ted in relation to this particular case.
6. To ensure the wide uses in hulls of corru-
gated bulkheads of a channel and wavy type,
a complex theoretical and experimental research
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was made-with a view of establishing a practi-
cal method of calculation of strength and sta-
bility of corrugated bulkheads under various
loading that may be encountered in the actual
service of the ship. The said research permitted
in the end to arrive at satisfactory solutions of
all the vital questions.
7. Considerable attention is paid to the vibra-
tion of the hull and its structures.
A steady tendency to increase speed with a
corresponding increase of the power of ship's
main engines urgently required the working out
of methods aiming at the elimination, as far as
possible, of the vibrations of the hull and of
ship's installations. The main trend in the scien-
tific research in our country in this connection
is given below:
Firstly, it is the study of the cause and na-
ture of the existing forces and secondly - the
study of the dynamic characteristics of the ship's
hull and structures, as well as the use of vibra-
tion dampers of different types.
Investigations of vibration by means of cal-
culations of separate ship structural members
with due regard to dynamics ppnstitute an
important part of the conduettd r1/earches.
The importance of this part q( the problem
is well known and primarily consists in the fact
that an increased local vibration can cause the
apprearance of a considerable number of fatigue
cracks, i. e. a failure of strength of such impor-
tant members of the hull as the shell and deck
plating.
A study of local strength of structures which
are subject to forces exciting vibration is being
realized with due regard to variQUS kinds of
unlineal factors (chain stresses, clearances in
structures and others), a work coaporned with
the physical nature and quantitative values of
sources of damping as well as Investigations
of vibrations of hull girders for modes above the
two node mode are being carried out.
It should be noted that along with the theo-
retical investigations of the ship's vibrations,
serious attention is given to experiments. Tests,
as a rule, are made in conjunction with some
new theoretical contributions, and they are ge-
nerally mutually complementary.
In compliance with tl;g foreign practice of
fixing the permissible stresses for longitudinal
hull members subjected to the longitudinal bend,
the 1958 edition of "Standards" prescribed dif-
ferent permissible stresses in the hulls of ships
up to 100 m. in length. from 100 to 200 in. in
length and, finally, 200 and more meters in
length. Higher rated stresses were allocated
to ships of a greater length. For all that the
length of a calculated trochoidal wave was con-
sidered to be equal to the ship's length; and the
height of the wave to be equal to 3u + 2 for
ships up to 120 m in length and o for ships
120 m and more in length (with I. standing for
the sbip's length).
The data collected by different investigators
show that the relative height of the wave de-
creases with the increase of its length; this cir-
cumstance predetermined the necessity of cor-
recting the rated wave length to a height rela-
tionship that had previously been assumed to be
directly proportional for ships above and below
120 m in length. On the grounds of supplemen-
tary analysis it is considered at present to, be
expedient to accept uniform standards for per-
missible stresses of a general strength irres-
pective of the ships' length. In connection with
this, corresponding alterations in the estimation
of the wave characteristics have been intro-
duced.
In addition, researches are continued for the
amendments of standards of permissible stres-
ses for hull members taking part in the longi-
tudinal and the local strengths of the ship.
THE WORKING OUT OF OTHER GUIDING INSTRUCTIONS FOR THE CALCULATION OF STRUCTURES OF
MERCHANT VESSELS
Along with theoretical and experimental
researches in the line of the ship's hull strength
studies are also made of different instructions
and of the guiding technical data on ship true
ture, which are from time to time amended and
supplemented. Having regard to the fact that
the strength and the reliability of structure, are,
to a considerable degree, dependent on the chi
racter of the interconnections of different tru,
tural members, the instructions contrihutu!I; t~!
a rational designing of welded hulls an.i wcorn,
mendations for the designing of diff# r, n' hull
structures are now worked out.
The reliable service of welded hulls h,
ensured only by using material possess!!rl;
Lain desired qualities, such as weldabilit\. Irla,-
ticity and strength, resistance to brittle fractu-
res under actual service conditions as well as
the keeping of these properties after the ter-
mination of different operations connected with
the technological process of construction. In or-
der to establish the quantitative values of these
propertie, and the methods of their assessment,
the requirements to shipbuilding materials are
constant!v corrected to keep pace with the pro-
gress in the improvements of material. These re
quirements are based on the results of research
work, and experience gained in using weldable
mater al' in shipbuilding, as well as on the
stud, w " shipbuilding materials (light al
lov, I! ;,,i-!1 ?111,4r)
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The results of theoretical and experimental
research in the field of ship strength in the
1'SSR found thleir reflection in the three volu-
mes of the reference handbook on ship strength,
published in 1958---1960. The results of some re-
searehcs are published in the transactions of the
Scientific Technical Society of Shipbuilding In-
dustry, in the reports of specialized institutes
and scientific papers of shipbuildin colleges.
Research in the field of strengt~ and struc-
ture -t ships are based On achievements in the
theorn of strength and in the applied theories
of ela,ticity and plasticity in the I'SSR, taking
into account the development of these sciences
ahroad.
During the past few years along with the
achievements of sciences and t(c hniyuc in all
branches of knowledge, the shipbuilding scien-
ces have also made great stride ahead.
)ne of the problems of the Congress, as seen
br the Soviet delegation, is the coordination of
efforts in improving hull structures of merchant
vessels. We have learned from the special lite-
rature already published, that strength tests of
vessels when at sea are being carried out in a
number of foreign countries. In these tests, a,
far as it is known, synchronous measure-
ments of parameters of rolling and stresses of
ship structures and parameter, of external con-
ditions which cause the rolling of the ship. Such
tests provide vast statistical data, which are
very useful for the amendments of the method
of ship strength calculations.
Similar tests are being carrier) out in the
USSR, and the results achieved are already be-
ing put into practical use for the henefit of all
maritime countries.
If the experimental data available in many
countries were to be pooled together. it would
be possible to attain better result in solving
problems connected with the t eternal forces
acting upon hulls under actual service condi-
tions.
The above does not, however, give an exhau-
stive answer to all questions which would have
been jointly solved according to a research pro-
gram specially drawn up for this purpose and
agreed upon by all concerned. We are, however,
sure that the work to be done by the Interna-
tional Congress on the subject of ship structures
and ship strength problems would be of great
use for the progress of shipbuilding in all co-
untries.
We hope that the participation of the So-
viet delegation in the proceedings of the Con-
gress may be taken as the first step on the way
of a creative cooperation directed towards the
solution of technical problems confronting ship-
builders in the whole world.
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