2964.1.Gastech 2006-Cambos

BUREAU VERITAS ENVOLVEMENT IN NEW DESIGN OF LARGE LNG CARRIER
EXAMPLE OF A 165000M 3 LNG C PROJECT
Bureau Veritas / Marine Division, 92077 – Paris La Défense Cedex, France
Philippe CAMBOS
Technical Management
Head of Oil & Gas Section
Mirela ZALAR
Research Department
Head of Sloshing Assessment Section
Sime MALENICA
Research Department
Hydrodynamic Engineer
Rina TANI-MORATALLA
Technical Management
Head of hydrodynamic
Gwendal BACHELOT
Technical Management
Hull surveyor
ABSTRACT
Bureau Veritas has developed a unique technical expertise in the LNG industries.
In the LNG industry, Bureau Veritas has classified more than 60 LNG carriers and has provided a wide
range of services (from design review to project certification) on over 10 LNG receiving terminals
around the world. More than 20 LNGC are now under building with Bureau Veritas class.
Methodologies have been developed to assist shipyards in the design phase of new projects .
The paper will show how the latest research and development improvements are taken into account
for the assessment of new designs of LNG Carriers . The methodologies are illustrated through the
example of a 165000m 3 recently ordered with BV class.
The following different topics will be addressed in this paper:
Ø
Ø
Ø
Ø
Ø
Ø
Hydrodynamic analysis ,
Structural analysis of ship hull by three cargo tank model and full ship analysis,
Spectral Fatigue analysis,
Buckling analysis,
Liquid motion analysis,
Bow impact analysis,
1. INTRODUCTION
In the LNG industry, Bureau Veritas has classified more than 60 LNG carriers and has provided a wide
range of services (from design review to project certification) on over 10 LNG receiving terminals
around the world. More than 20 LNGC are now under building with Bureau Veritas class.
Methodologies have been developed to assist shipyards in the design phase of a new project. This
paper, based on an actual case list the tasks carried out by Bureau Veritas to help the ship design.
The purpose of the present paper is to show how computerised calculations are applied to the design
of a modern LNG carrier of large size. The subject is treated through the example of a 165000m 3
membrane type LNG carrier recently classified by Bureau Veritas.
The following different topics will be addressed in this paper:
Ø
Ø
Ø
Ø
Ø
Ø
Hydrodynamic analysis ,
Structural analysis of ship hull by three cargo tank model and full ship analysis ,
Spectral Fatigue analysis,
Buckling analysis,
Liquid motion analysis,
Bow impact analysis.
2. HYDRODYNAMIC ANALYSIS
Hydrodynamic analyses in Bureau Veritas are performed using advanced in-house program
HYDROSTAR. HYDROSTAR is powerful 3D diffraction/radiation potential theory 3-D panel software
for wave-body interactions taking into account wind & current loads, multy-body interaction, effects of
forward speed and internal liquid motions. Evaluation of 1st and 2nd order wave loads, motions,
accelerations, relative motions, wave elevation is dedicated to all types of marine structures.
HYDROSTAR is constantly improved by integrating the most recent theories and powerful algorithms,
fully validated through the comparisons with semi-analytical studies, computation results from
recognized numerical tools and experiments.
Seakeeping analyses for 165 000 m3 LNGC project were carried out for two loading conditions, Ballast
and Full Load. Examples from hydrodynamic computation are presented in Figure 1 , demonstrating
3D panel model, vessel motion on the waves and wave load distribution on underwater hull.
Figure 1 - Hydrodynamic models, motion on the waves and wave loads
North Atlantic wave data, according to IACS URS 34 [1 ] is used for this analysis as shown figure 2.
The spreading function given in the same recommendation was used.
Figure 2 - North Atlantic: Areas 8, 9, 15 and 16
The results of the hydrodynamic analysis are input data for the following analysis:
•
•
•
Spectral fatigue analysis,
Sloshing analysis,
Bow impact analysis.
3. STRUCTURAL ANALYSIS
The ship has received the notation VeriSTAR hull, the structural analysis is carried out within the
scope of classification.
The ship is completely modelled as shown on the figure 4 & 5.
Figure 3 - Complete Ship Model
Figure 4 - Half-view of the complete ship model
The structural analysis is carried out in two parts :
•
•
3.1.
Partial models extended over three cargo tanks loaded by rule waves,
Complete ship model loaded through hydrodynamic analysis.
3 cargo tanks models
The calculation has been performed with VeriSTAR Hull software developed by Bureau Veritas. This
software is a powerful integrated finite element software carrying out structural assessment with
respect of Bureau Veritas rules [2].
Each typical cargo tank model is calculated separately. An example of a three cargo tank model is
shown on the figure 6.
Figure 5 – Model for Center Cargo tank (Coarse Mesh Half Model)
Figure 6 – Model for Cargo Tank No 1 (Coarse Mesh Half Model)
Figure 7 – Model for Cargo Tank No 4 (Coarse Mesh Full Model)
Beyond the 3D coarse mesh, several refined analysis of selected structural members have to be
performed on the basis of 3D fine mesh models, namely:
•
•
•
•
•
•
Cargo tank transverse web frame, as shown figure 9,
Tank longitudinal girders in way of the cofferdam bulkhead, as s hown figure 10,
Cofferdam between tank 1 & 2, as shown figure 11,
End of trunk deck, as shown figure 12,
Connection of Trunk Deck structure with Deck House, as shown on figure 13,
Connection of Pump Room on Trunk Deck, shown on figure 13.
Figure 8 – Fine Mesh Model for Transverse web
Figure 9 – Web Frame Section for Cargo Hold
and No1
Figure 1 0 – Cofferdam between Tanks No1
Figure 11 – Forward End of Trunk Deck
Deck House
Figure 12 – connection of Trunk Deck with
Figure 13 – Connection of Pump Room on Trunk Deck
Calculations have been carried out for the most severe conditions, as given in the loading manual,
with view of maximizing the stress in the primary supporting structure of the ship. Beyond the current
homogeneous and alternate loading conditions, alternate loading conditions have been taken into
account.
For each internal loading condition, appropriate external loading corresponding to head sea, beam sea
or quartering sea have been taken into account. These conditions have been summarised in the table
1 hereafter. They combine the various dynamic effects of the environment on the hull structure, i.e.
external sea conditions (hull girder wave loads and wave pressures ) and internal dynamic cargo
pressures in accordance with Bureau Veritas rules.
The specific densities considered are 0.5 for LNG and 1.025 for sea water.
N°
Description
Draught
SWBM
A1
LC1
Homogeneous loading conditions
T
MSW,S
LC2
Ballast conditions
TB
MSW,H
X
LC3
Alternate loading conditions
0.9 T
0.9 MSW,H
X
LC4
Alternate loading conditions
0.75 T
0.9 MSW,S
Ship
Inclined
upright
ship
A2
B
X
X
C
Harbour
D
X
X
X
X
X
X
X
Table 1 - Load cases applied to 3 cargo tanks model
The results are analysed according to the following rules criteria:
•
•
Combined stress,
Buckling criteria.
Several reinforcements have been recommended based on this analysis as for example:
•
•
•
•
3.2.
Floors at side in typical cargo tank and fore cargo tank,
Cofferdam bulkhead for buckling,
Cofferdam between tanks 1 & 2,
Additional brackets at connection of tank 4 and accommodations.
Complete ship model
In addition to the previous analysis, the full ship was analysed using VeriSTAR CSM (Complete Ship
Model) The methodology used by this software was described in a separate paper [3 ].
This software is used as a complement of the VeriSTAR 3 cargo tanks, which is based on the
assumption that the warping of the structure is negligible. This assumption is generally reasonable for
membrane type LNG carriers. This calculation is generally necessary for ships with large opening on
decks as for example, container vessels or Moss type LNG carriers.
However the calculation, requested by the ship owner was carried out in order to identify any
additional hot spot area on the vessel.
The boundary conditions on the model are limited to one point, in order to avoid rigid body motion. It is
verified that the reaction at this node is negligible.
The model is to be balanced under the internal loads, including self weight and accelerations, and the
external sea pressures on the hull.
The software is based on the method of equivalent wave: an hydrodynamic software is used to define
the ship motions due to a regular wave, and the pressures due to the wave and the accelerations are
applied to the structural model. The wave is chosen to apply on the structural model, the effects of the
sea states as: hull girder bending moment, maximum acceleration, relative wave elevation as given by
Bureau Veritas rules.
This balancing method has been developed in VeriSTAR CSM, with many automatic routines which
make the calculation user friendly, despite the complexity of the method.
7 load cases were chosen as shown in the table 2.
Wave
Target Effect
Targeted
Rule Value
Case
LC
1
Full load
Head Sea
2
Full load
Quartering
Sea
Heading 120°
3
Ballast
Head Sea
4
Alternate
Beam Sea
Wave Induced Vertical acceleration
5
Alternate
Beam Sea
Wave Induced Horizontal acceleration
6
Alternate
Head Sea
Relative Motion at Midship
Maximum
Angle of Rolling
7
Alternate
Beam Sea
Relative Motion at Sides
Difference of
height at sides
Wave Induced Vertical Bending Moment
in Hogging condition
Wave Induced Horizontal Bending
Moment
in Hogging condition
Wave Induced Vertical Bending Moment
in Sagging condition
Maximum
Bending Moment
Maximum
Bending Moment
Maximum
Bending Moment
Maximum
Torsion Moment
Maximum
Torsion Moment
Table 2 - Load cases for complete ship model
The figures 14 and 15 show results of the complete ship model with VeriSTAR CSM for two load
cases.
Figure 14 - Hydrodynamic analysis in head sea condition
Figure 15 - Equivalent stress for Full model
Figure 16 - Equivalent stress for Cargo area
This analysis has conformed that there was no additional hot spot are a or needed reinforcement after
the 3 cargo tank model calculations.
This analysis is also used to verify that the stress level in the structure supporting the membrane is in
accordance with the membrane designer requirements.
4. SPECTRAL FATIGUE ANALYSIS
Since the use of computers for design leading to structural ship size increase, scantling reductions and
of high strength steels to reduce hull weight, the fatigue cracki ng becomes a major failure mode for
LNG carriers .
A failure in the double hull may have significant consequences:
•
•
Water may leak from the ballast to the insulation leading to serious damage,
The rewelding of the double hull is difficult due to the presence of the insulation (risk of fire)
This question was addressed by the publication in 1987 of a guidance note "Cyclic Fatigue of Nodes
and Welded Joints of Offshore units" followed the following year 1988 by another guidance note
"Cyclic Fatigue of Welded Joints on Steel Ships". Then an updated guidance note introducing the
probabilistic approach was edited in 1988 "Fatigue Strength of Welded Ship Structures" and
compulsory rules were introduced in 2000 classification rules [2].
During the same time, the enormous progresses in IT allowed the development of tools to compute the
ship behaviour on regular and irregular waves, the resulting static and cyclic loads, and finite elements
modelling to compute the stresses at the designer desired detailed level.
3
The in-house developed software and gained experience, in particular for 120.000 m LNG carriers,
but also for in -service tankers and FPSO, and the numerous participations to European and
international R&D projects place Bureau Veritas as one of the major actors in ship and offshore fatigue
method development.
Bureau Veritas has developed a class notation “VeriSTAR Hull DFL 40 years” which may be granted to
LNG carriers which have been subject to a fatigue analysis. It is the case of the 165000m3 LNG
carrier taken as example of this section.
4.1 Rule requirement
The verification of fatigue strength of the structure of seagoing ships has been developed and based
on a deterministic methodology. In the early 1980s, this methodology was introduced with the purpose
to assure that the seagoing ships could respect a fatigue life of 20 years, in North Atlantic sea
conditions, with a cumulative damage ratio of 1, taking into account the SN curve at minus two
standard deviations.
At that time, a guidance notes for fatigue assessment have been developed by BUREAU VERITAS.
Fatigue assessment became mandatory, for ships more than 170 m in length, in 2000.
In the case of membrane type LNG carriers, fatigue calculations are manda tory for structural details as
Ø Connection of longitudinals with transverse web frames ,
Ø Hopper knuckles ,
Ø Stringer connection ,
Ø Tank dome (particularly for some containment systems which request large dome openings).
The rules developed by BUREAU VERITAS [4] comply with IACS recommendation No56 [5], the IIW
documents, and the results of the JIP fatigue [6].
Different methodologies may be applied to take into account the wave load in the fatigue analysis:
•
Deterministic calculation
The stress ranges are calculated based on loads at a probability level of 10- 5. The loads take into
account the hull girder ending moment and shear forces, the wave pressure on the shell and the
internal tank pressure due to the accelerations, which are taken from rule formula.
The distribution of long term stress range assuming a Weibull distribution, and rule formula are used to
define the shape parameter.
The deterministic methodology has been calibrated using the spectral methodology, described
hereafter, as well as return of experience.
•
Spectral calculation
The spectral fatigue analysis includes the following steps:
Ø
An hydrodynamic cal culation in the frequency domain, using 3D diffraction radiation, by which the
vessel motions, accelerations and wave pressures on the hull are obtain.
Ø
A structural analysis, also in the frequency domain, using a 3D FE model. BV generally make full
ship model.
Ø
From RAO’s of stress range, in the short term stress distribution is obtained by the technique of
Spectral analysis. The figure 3 shows an example of RAO of stress.
Ø
Calculation of the long term stress distribution by summation over the wave scatter diagram, of
the short term distribution. Generally North Atlantic sea conditions from IACS are used.
Ø
Calculation of the fatigue damage ratio by the Miner sum.
BV uses HydroSTAR software and VeriSTAR hull, full ship. A interface between the two software have
been developed .
In the case of the 165000m3, the Spectral fatigue calculation was applied.
The following load cases were taken into account:
• 25 frequencies,
• 2 drafts (ballast and full load)
• 7 headings ( 0°, 30°, 60°, 90°,120°,150°,180°)
For the 165000m3, taking into account the 2 load cases for intermittent wetting, the total number of
load cases is 702.
Structural models
The figure 17 , 18 and 19 show some fine mesh models for the fatigue analysis of the knuckles, the
foot of cofferdam bulkhead and the tank dome.
Figure 17 - Liquid Dome Opening
Figure 18 – Fine mesh for fatigue of knuckles 1 & 2
Figure 19 - Foots of cofferdam bulkhead
This analysis has led to significant structural detail improvements, in knuckles, cofferdam bulkheads,
dome, bottom longitudinal stiffeners, ends of trunk deck…
The reinforcements were performed by local increased thickness and scantlings, addition of inserts,
grinding, improve of bracket shapes…
5. BUCKLING ANALYSIS
Two parts of the structure were analysed through linear buckling analysis, in order to assess the
strength of these connections.
These two parts are:
•
•
Knuckle in trunk deck at side,
Bilge.
Concerning the trunk deck, the loads are hull girder stress, when for bilge, there in addition to hull
girder the lateral sea pressure was taken into account.
Boundary conditions were applied at the border of the model to allow longitudinal displacements.
Simple supports were prescribed in way of transverse frames.
The analysis has shown a safety coefficient of the structure. In particular it was shown, in both cases,
that the most critical area was not the bent plate, but the flat plate stiffened by longitudinal stiffene rs,
adjacent to the bent plate.
Consequently, there was no modification of the structure.
The figures 20 & 21 show the models and the results of the analysis.
Figure 20 – Buckling analysis of Knuckle in trunk deck at side
Figure 20 – Buckling analysis of bilge
6. LIQUID MOTION ANALYSIS
Bureau Veritas is extensively involved in studies dedicated to the new -generation large LNG vessels,
relying on the comparative approach supported by the competence gained through the almost 40
years of experience in LNG Carriers. One of the key issues for the design of the large size LNG
carriers is the effect of the LNG flows in the large tanks, on the following members:
•
•
•
Containment system (membrane),
Hull supporting the membrane,
Pump support tower.
Common operation of membrane type LNG Carriers is carried out with the cargo tank fully laden or
with minimum cargo contents during the return ballast voyage. A large number of sloshing studies
carried out since early 70's resulted with the conclusion that severe sloshing effects can be mitigated
by accommodation of large chamfers in the upper part of the tanks, enabling the extension of upper
filling limit to 80% and then even to 70% of filling height for conventional LNG Carriers.
Up to now, the conventional membrane type LNG vessels were approved for conventional filling levels
3
3
(below 10% and above 70%) for ship with a capacity less than 155 000 m . As the subject 165 000 m
vessel is beyond standard capacity and therefore beyond conventional limitations, particular attention
was given to the investigation of sloshing flows occurring at various fillings and their effects on
different structural members.
To assess the strength of the different structural parts of LNG vessels, a comprehensive methodology
has been developed in Bureau Veritas which may be summarised on the Figure 2 1.
Figure 21 – Overall Methodology for Sloshing Assessment in Bureau Veritas
Overall sloshing assessment methodology incorporated in basic principles of Bureau Veritas
procedure for qualification of containment system resistance and verification of double-hull scantlings
against sloshing loads, employs a complex set of information, tools and methods, such as:
•
•
•
•
•
Seakeeping analysis (basin model test and hydrodynamic computation),
Sloshing analysis (small-scale experiments and CFD computation),
Structural examination (material and mechanical tests of structural properties in static,
dynamic and cryogenic conditions),
Fluid-structure interaction (hydro-elastic FEM analysis),
Experience feed -back (analysis of sloshing-induced damages and full -scale measurement).
Bureau Veritas sloshing assessment methodology has been subject of a paper presented in
GASTECH 2005 conference [7]. It should be underlined that the current state of the art in sloshing
assessment is essentially a comparative one, due to the limited knowledge of real physical models.
As regard to particular BV sloshing assessment procedure, response-based sea-states are introduc ed
in order to avoid penalisation of ship scantlings due to the non -realistic operation conditions. Limitation
of excessive motions has been performed through the comparison of absolute ship response on the
extreme sea-states to the selected operability parameters (as roll angle and accelerations) according
to BV Rules recommendation.
Ship absolute response to the environmental conditions has been determined by means of spectral
analysis, combining ship RAOs (from hydrodynamic computation) and selected sea -states (from
operational conditions).
According to the results of hydrodynamic computation and subsequent spectral analysis, set of
representative cases was selected and dominant motions and liquid flows identified.
Representative tank for the sloshing study has been selected according to the criteria of the largest
capacity being the most agitated on-board the vessel. For the subject 165,000 m3 LNG Carrier,
selected tank is Tank N°2, due to it's furthest disposition measured from the ship centre of gravity.
Liquid motion analyses have been carried out for several different filling levels of Tank No2:
•
•
Low filling level:
High filling levels:
R = 10%L
R = 70%H, 80%H & 95%H
Using the most severe states identified in study of Tank No2, additional examination of sloshing loads
has been performed on Tank No1, to verify influence of its particular geometry on generated LNG
flows.
Various scenarios related to the type and natures of liquid flow have been set for each filling level,
governed by the contemplati on of the following conditions:
→ Resonance condition, since sloshing is a typical resonance phenomenon occurring when the
ship motion contains energy in the vicinity of the highest tank natural period,
→ Maximum motion condition, following the consideration of vessel design requirement to
sustain extreme environmental loads.
→ Intermediate condition, for screening of fluid flow variation in function of wave headings and
periods.
Numerical analyses have been performed using HydroSTAR (for sea-keeping part) and CFD software
FLOW3D (for liquid motion part). As for it concerns CFD applicability for LNG sloshing problem, it
should be noted that pressure calculated in each mesh cell does not consider impact pressure. Impact
pressure is strongly related to both, liquid and gas compressibility and hydro-elasticity effects that are
not taken into account in actual CFD model. Thus, we prefer evaluating kinetic energy of the liquid and
“quantify” impact only by the impact velocity, impact angle and geometry of the jet before the impact.
Nevertheless, pressures or forces of quasi-static nature are also calculated and provided for
verification of double-hull back-up structure.
For each studied filling level, a period scanning analysis has been carried out to determine the
numerical resonance period, which is needed to accurately simulate resonant liquid flows. Moreover, a
Full Zone Approach (FZA) is performed to analyse spatial and temporal distribution of sloshing loads in
predefined hot-spot zones inside the cargo tanks.
Ta nks have been meshed using Volume of Fluid technique (VOF), and models of Tank No2 and Tank
No1 are presented on Figure 22 and 2 3, respectively.
Figure 22 – Tank No2 VOF model
Figure 23 – Tank No1 VOF model
3
Throughout all sloshing numerical analysis carried out for 165 000 m project, different types of fluid
flows have been observed for different filling levels.
In the case of very moderate excitation, free surface remains flat moving in a succession of staticequilibrium states. Contrary, when th e excitation velocity increases, two quite different kinds of fluid
flows will appear according to the filling rate and tank proportions.
For the shallow filling depth, hydraulic bores and travelling waves appear moving back and forth
between tank walls. At high fillings, standing waves appear moving upwards and downwards with one
or two nodes depending on excitation period.
Some examples of captured instants from sloshing simulation for different tank geometry and different
fillings are displayed on Figures 24 to 26 below.
Figure 24 – Tank No2
70%H filling level
Figure 25 – Tank No2
10%L filling level
Figure 26 – Tank No1
70%H filling level
Maximum quasi-static pressures and impact velocities were obtained for 10%L filling level. But
significant impact values have also been witnessed for high filling levels.
Finally, liquid motion analysis of carried out for 165 000 m 3 project has led to the following :
•
•
•
•
•
Confirmed feasibility of 165 000 m3 LNGC design with 4 -tanks arrangement from liquid motion
point of view,
Confirmed model tests results,
Many reinforcements in the double hull, particularly the ordinary stiffeners in the midship
section,
Local reinforcements of the containment system,
Strength assessment of the pump mast, by verification of the pump mast designer.
Figure 27 shows the area of the midship section candidates for reinforcements against sloshing loads.
Figure 27 – Area of the midship section candidates for reinforcements against sloshing loads
6. BOW IMPACT ANALYSIS
The purpose of this analysis is to assess the strength of the bow against slamming impact and to
specify structural reinforcements if necessary.
The strength of the bow was assessed against rules criteria prior to this analysis.
The zones of interest which were identi fied as critical and representative for the ship fore part are
shown in Figure 28.
Figure 28 - Representative zones in which the slamming loads are evaluated.
The overall computational scheme for local slamming calculations is shown in Figure 2 9. This
methodology was subject of a article [8].
This methodology includes :
•
•
•
•
Sea keeping calculations in frequency domain using the 3D panel code HYDROSTAR in order
to determine the global ship motions and relative ship motions at the bow.
Time domain simulations (frequency domain reconstruction for this case) in order to determine
the impact occurrences and impact conditions (relative geometry and velocity).
Slamming calculations for specified ship sections in order to calculate the time history of the
pressure distribution.
Structural assessment of bow structure against impact pressure.
Figure 29 - Computational scheme.
The slamming code is based on 2D generalized Wagner approach. The boundary value
problem at each time step is solved using the singularity distribution method.
Once the RAO’s are calculated, spectral analysis on relative motions and velocities is performed in
order to identify the most critical conditions from the slamming point of view. In Figure 30, the
maximum relative motions and velocities are given for different loading conditions and for the sea
states defined by the North Atlantic wave envelope as previously discussed.
Figure 30 - Maximum responses in terms of relative motions and velocities at the bow, for
different loading conditions.
Once the critical conditions identified, the time domain simulations can be performed and the exact
impact conditions identified. This procedure is briefly illustrated in Figure 31 . The history of the relative
motion and velocity is calculated at the same time. In that way we are able to identify the instant when
the relative motion exceed the draught and subsequently the instant when the section hits the water
i.e. impact occurrence. For that particular time instant we know also the relative velocity which is used
as input to the slamming code.
Figure 31 - Determination of the impact conditions.
The above described procedure is valid for any particular point on the ship hull. Here below we first
apply it to the bow stem.
The state of the art in slamming calculations do not allow for 3D calculations, so that the usual
procedure employs the so called strip approach which is believed to be conservative since the 3D
effects tend to reduce the slamming loads
The figure 32 shows typical pressures results.
Figure 32 - Maximum pressure at different points
The calculation is carried out in North Atlantic sea conditions with reduced speed for maximum Hs and
for reduced Hs for maximum speed.
The structural assessment was carried out taking into account the obtained pressures, using rule
formula for scantlings of stiffeners and plating. The analysis led to some local reinforcements of plating
and stiffeners in the upper part of the bow.
7. CONCLUSION
During the last years Bureau Veritas has developed several methodologies and tools to assess the
ship hull against differentloads. These tools take into account the l atest developments made by
shipping and offshore industries, by the mean of research groups, JIPs…
The paper shows how this means may be used by shipyards, shipowners or charters to improve the
new designs of LNG carriers, on a rationally basis.
8. REFERENCES
[1]
IACS, Recommendation 34: “Standard Waves Data for Direct Wave Load Analysis”, IACS Blue
book.
[2]
BUREAU VERITAS , Rules for steel ships, 2006 .
[3]
M. FRANCO, F. BIGOT, VeriSTAR Hull, un systéme integer de suivi de l’état structurel des
navires, ATMA, Number 101, 2002.
[4]
BUREAU VERITAS , Spectrale Fatigue Analysis Methodology for Ships and Offshore Units,
2006.
[5]
IACS, Recommendation No56, “Fatigue assessment of ship structure”, IACS Blue book.
[6]
BUREAU VERITAS, DNV , Fatigue Design Recommendations for FPSOs, revision 2, 2003.
[7]
M. ZALAR, P. CAMBOS, P. BESSE, B. Le GALLO, Z. MRAVAK, Partial filling of membrane
tank LNG carriers, GASTECH, Bilbao, 2005.
[8]
J.F. SEGRETAIN, “Structural damages due to slamming”, Boxship, London, Oct. 2003.