Structural Analysis of
Offshore Surface Units through
Full Length Finite Element Models
April 2010
Rule Note
NR 551 DT R00 E
Marine Division
92571 Neuilly sur Seine Cedex – France
Tel: + 33 (0)1 55 24 70 00 – Fax: + 33 (0)1 55 24 70 25
Marine website: http://www.veristar.com
Email: [email protected]
2010 Bureau Veritas - All rights reserved
MARINE DIVISION
GENERAL CONDITIONS
ARTICLE 1
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13.3. - The definitions herein take precedence over any definitions serving the same purpose which may
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BV Mod. Ad. ME 545 k - 17 December 2008
RULE NOTE NR 551
NR 551
Structural Analysis of Offshore Surface Units
through Full Length Finite Element Models
SECTION 1
April 2010
VERISTAR-HULL FLM
Section 1
VeriSTAR-Hull FLM
1
General
1.1
1.2
2
General requirements
Model construction
Model extension
Finite element models
Boundary conditions of the model
6
General
Loading conditions
Recommended procedure for the calculation of wave loads
Load cases
Stress calculation
4.1
2
3
Load model
3.1
3.2
3.3
3.4
4
Application
Definitions
Structural modelling
2.1
2.2
2.3
2.4
2.5
3
3
8
Stress components
Bureau Veritas
April 2010
NR 551, Sec 1
SECTION 1
VERISTAR-HULL FLM
Symbols
g
: Gravity acceleration, equal to 9,81 m/s2
• still water loads
∆
: Moulded displacement in seawater, in t
• wave loads
B
: Moulded breadth, in m
• dynamic loads
L
: Rule length, in m
• local loads
σMASTER : Master allowable stress, in N/mm², as defined in
Pt D, Ch 1, Sec 7, [5.6] of the Offshore Rules
λ
: Wave length, in m
T
: Wave period, in s
ω
: Wave circular frequency, in rad/s.
1
1.1
• hull girder loads
• loading condition
• load case.
1.2.2
General
Application
1.1.1 The requirements of the present Rule Note apply for
the analysis criteria, structural modelling, load modelling
and stress calculation of offshore surface units intended to
be granted the additional class notation VeriSTAR-Hull
FLM, as defined in the Offshore Rules, Pt A, Ch 1, Sec 2,
[6.2.14].
1.1.2 This Rule Note deals with that part of the structural
analysis which aims at calculating the stresses in the structure for yielding and buckling checks.
Ship Rules
When the “Ship Rules” are mentioned in the present Rule
Note, reference is made to NR467 Rules for the Classification of Steel Ships. The applicable requirements are those
for ships greater than 65 m in length. The party applying for
classification is to contact the Society for information about
any amendments of these Rules.
1.2.3
Offshore Rules
When the “Offshore Rules” are mentioned in the present
Rule Note, reference is made to NR445 Rules for the Classification of Offshore Units. The party applying for classification is to contact the Society for information about any
amendments of these Rules.
1.2.4
Design Criteria Statement
1.1.3 The yielding and buckling checks of the structure are to
be carried out according to the Offshore Rules, Pt D, Ch 1,
Sec 7, taking into account values of stresses calculated in
accordance with the present Rule Note.
Design Criteria Statement is a document issued by the Society and based on the information provided by the party
applying for classification, listing the services performed by
the unit and the design conditions and other assumptions
on the basis of which the class is assigned to the unit.
1.1.4 The additional class notation VeriSTAR-Hull FLM is
to be applied in addition to the additional service feature
VeriSTAR-Hull, as defined in the Offshore Rules, Pt A, Ch 1,
Sec 2, [7.6], involving a structural finite element calculation
based on at least three cargo holds model.
Further details about the Design Criteria Statement are
given in Pt A, Ch 1, Sec 1, [1.6] of the Offshore Rules.
1.1.5 Fatigue checks are not covered by the additional class
notation VeriSTAR-Hull FLM. Fatigue assessment is to be
carried out in accordance with the requirements of the Offshore Rules, Pt D, Ch 1, Sec 7, [7].
1.2
General
The definition of the following terms are indicated in Pt B,
Ch 5, Sec 1, [1] of the Ship Rules:
April 2010
2.1
Structural modelling
General requirements
2.1.1 The unit is to be modelled through a full length finite
element model, including aft and fore parts.
The structural model is to represent the primary supporting
members with the plating to which they are connected.
Definitions
1.2.1
2
Ordinary stiffeners are also to be taken into account in the
model in order to reproduce the stiffness and the inertia of
the actual hull girder structure.
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3
NR 551, Sec 1
2.1.2 The structural analysis on fine mesh models is to be
carried out by applying one of the following procedures:
• an analysis of the full length three dimensional model
based on a fine mesh model, as defined in [2.4.3]
• an analysis of the full length three dimensional model
based on a coarse mesh model, as defined in [2.4.2],
from which the nodal displacement and forces are used
as boundary conditions for analyses based on fine mesh
sub-models. The minimum extent of fine mesh submodels is to comply with the relevant requirements of
[2.4.3].
2.1.3 The following areas are to be investigated based on
fine mesh models, as defined in [2.4.3]:
• typical full cargo tank in midship area, including independent tanks when relevant
• aft and fore ends of the cargo area with extended overlapping structure
• typical topsides stools or supports, in midship area
• risers supporting structure ends, when relevant
2.2.2 Elements
Finite elements used in the structural model are to comply
with the requirements given in [2.4], for the relevant type of
finite element model.
2.3
2.3.1 General
The full length model is to be such as the following effects
are properly taken into account in the structural analysis:
•
effect of the vertical bending moment and shear force
•
coupling between torsion and horizontal bending
•
effects of sea pressures and pressures in internal capacities
•
global and local deformations of structural items
•
effects of local loads.
2.3.2 Hull structure
Finite element model of unit’s hull is to include the following primary supporting members:
•
outer shell, inner bottom, longitudinal and transverse
bulkhead plating
•
double-bottom longitudinal girders
•
horizontal stringers
•
deck longitudinal girders
•
transverse web frames
•
stringers of transverse bulkheads.
• turret supporting structure for weathervaning units
• typical supports and keys of independent tanks, when
relevant
• typical reinforced frames including stiffening rings of
independent tanks, when relevant.
Other areas may be required to be analysed through fine
mesh models, when deemed necessary by the Society,
depending on unit’s structural arrangement and loading
conditions, as well as on the results of the coarse mesh
analysis.
2.1.4 Areas, for which the equivalent stress σVM (as defined
in [4.1] and obtained through fine mesh analysis) is greater
than 0,95 σMASTER, are to be investigated through very fine
mesh analysis based on the requirements of [2.4.4], and the
criteria given in Pt D, Ch 1, Sec 7, [5.6.4] of the Offshore
Rules are to be checked.
The very fine mesh analysis, may be performed on separate
finite element sub-models, having boundary conditions
obtained from the fine mesh model. As an alternative, very
fine mesh zones incorporated in the fine mesh model may
be used.
The Society may require additional very fine mesh analyses
for areas where the assessment through fine mesh models is
not judged as satisfactory.
2.2
2.2.1
Model construction
Net scantlings
All the elements in [2.1.1] are to be modelled with their net
scantlings according to the Offshore Rules, Pt D, Ch 1,
Sec 3, [3].
4
Model extension
2.3.3 External turret
For surface units moored with external turret, the cantilever
structure is to be included in the finite element model.
2.3.4 Topside supports
Topsides supporting structure is to be modelled in order to
input mass and/or forces coming from topsides equipment.
2.3.5 Mass of topsides
The mass of topside equipment is to be taken into account
in the model, at the satisfaction of the Society, in order to
reproduce the correct lightweight distribution and inertial
loads on topside supports. The model of topside equipment
is not to restrain the relative displacement of topside supports.
2.3.6 Deckhouses and superstructures
Deckhouses and main superstructures connected to the
main deck are to be included in the structural model. Their
modelling is to corectly represent their weights and local
effects on hull girder stiffness and deck behaviour.
2.3.7 Riser supporting structure
When relevant, the riser supporting structure is to be modelled on the side shell, in order to evaluate the interaction
with hull girder strength of the unit.
Bureau Veritas
April 2010
NR 551, Sec 1
2.3.8
Units with independent tanks
For units with independent tanks, the structural model is to
include the primary supporting members of the hull (see
[2.3.2]) and the tank with its supporting members and key
system.
The cargo tank model is to include the following primary
members:
• shell plating
• bulkhead plating, including wash bulkheads if any
• top plating
• transverse web frames
• girders.
Supports and keys of independent tanks are to be modelled
using the following types of element:
or
• non-linear elements: contact elements.
Linear elements used for the modelling of supports and keys
not allowing tension loads are to be deleted when they are
in tension.
2.4.3
Fine mesh
The structural model is to be built on the basis of the following criteria:
• webs of primary members are to be modelled with at
least three elements on their height
• the plating between two primary supporting members is
to be modelled with at least two element stripes
Finite element models
General
Finite element models are generally to be based on linear
assumptions. The mesh is to be executed using membrane
or shell elements, with or without mid-side nodes.
Meshing is to be carried out following uniformity criteria
among the different elements.
In general, the quadrilateral elements are to be such that the
ratio between the longer side length and the shorter side
length does not exceed 4 and, in any case, is less than 2 for
most elements. Their angles are to be greater than 60° and
less than 120°. The triangular element angles are to be
greater than 30° and less than 120°.
Further modelling criteria depend on the accuracy level of
the mesh, as specified in [2.4.2] to [2.4.4].
• the ratio between the longer side and the shorter side of
the elements is to be less than 3 in the areas expected to
be highly stressed
• holes for the passage of ordinary stiffeners may be disregarded.
When fine mesh analysis is performed through sub-models,
as stated in [2.1.2], the minimum extent of the sub-model is
to be such that its boundaries correspond to locations
where the deformations of the global model are accurately
calculated, at the satisfaction of the Society. In general, it
corresponds either to the adjacent or to the second adjacent
primary supporting member.
In some specific cases, some of the above simplifications
may not be deemed acceptable by the Society in relation to
the type of structural model and the analysis performed.
Coarse mesh
The number of nodes and elements is to be such that the
stiffness and the inertia of the model represent properly
those of the actual hull girder structure, and the distribution
of loads among the various load carrying members is correctly taken into account.
To this end, the structural model is to be built on the basis of
the following criteria:
• ordinary stiffeners contributing to the hull girder longitudinal strength and which are not individually represented in the model are to be modelled by rod elements
and grouped at regular intervals
April 2010
• holes for the passage of ordinary stiffeners or small pipes
may be disregarded
The unit’s structure may be considered as finely meshed
when each longitudinal secondary stiffener is modelled; as
a consequence, the standard size of the finite elements used
is based on the spacing of ordinary stiffeners.
• linear elements: bar, flexible mounts, springs
2.4.2
• the plating between two primary supporting members
may be modelled with one element stripe
In some specific cases, some of the above simplifications
may not be deemed acceptable by the Society in relation to
the type of structural model and the analysis performed.
• horizontal stringers
2.4.1
• face plates may be modelled with bars having the same
cross-section
• manholes (and similar discontinuities) in the webs of
primary supporting members may be disregarded, but
the element thickness is to be reduced in proportion to
the hole height and the web height ratio.
• bottom plating
2.4
• webs of primary supporting members may be modelled
with only one element on their height
2.4.4
Very fine mesh
The extent of a very fine mesh zone is not to be less than the
relevant spacing of ordinary stiffeners in the considered
structural region, in all directions from the area under investigation. When separate sub-models are used, the extent is
to be such that the calculated stresses within the investigated area are not significantly affected by the imposed
boundary conditions and application of loads.
Additional requirements related to very fine mesh models
are given in Pt D, Ch 1, Sec 7, [5.4.5] of the Offshore Rules.
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5
NR 551, Sec 1
2.5
Boundary conditions of the model
3.1.5
2.5.1 In order to prevent rigid body motions of the overall
model, the constraints specified in Tab 1 are to be applied.
Table 1 : Boundary conditions to prevent
rigid body motion of the model
Boundary conditions
X
Y
Z
free
fixed
fixed
One node on the port side shell at
aft end of the unit (2)
fixed
free
fixed
One node on the starboard side shell
at aft end of the unit (2)
free
fixed
fixed
Boundary conditions
X
Y
Z
free
free
free
One node on the port side shell at
aft end of the unit (2)
free
free
free
One node on the starboard side shell
at aft end of the unit (2)
free
free
free
(1)
(2)
3
3.1
•
the wave pressure
•
the wave induced inertial loads.
The values of dominant load effects are to be taken as
required in [3.3.9].
A recommended procedure to compute the characteristics
of the design wave and wave induced loads is provided in
[3.3]. Other methods may be accepted by the Society, provided that relevant documentation is submitted to the Society for review.
ROTATION
around axes (1)
One node on the fore end of the unit
Wave loads include:
Wave loads are to be determined through direct hydrodynamic calculations. The various load components which
occur simultaneously may be combined by setting the characteristics of regular waves that maximise the dominant
load effects listed in [3.3.2].
DISPLACEMENTS
in directions (1)
One node on the fore end of the unit
Wave loads
3.1.6
Local loads induced by the topsides
Topside inertial loads are to be obtained by applying the
wave induced accelerations corresponding to each loading
case to topside structural model, having a mass as required
in [2.3.5].
X, Y and Z directions and axes are defined with respect
to the reference co-ordinate system in Pt D, Ch 1, Sec1,
[4.3] of the Offshore Rules.
The nodes on the port side shell and on the starboard
side shell are to be symmetrical with respect to the
unit’s longitudinal plane of symmetry.
Load model
3.1.7
Summary of the loading procedure
Applicable loading conditions given in [3.2] are to be analysed through:
•
the computation of the characteristics of the finite element model under still water loads (as required in
[3.2.3])
•
the selection of the load cases critical for the strength of
the structural members (see [3.4]).
General
3.1.1 Loading manual
A loading manual of the unit is to be submitted for approval.
The loading manual is to be in compliance with the requirements of Pt D, Ch 1, Sec 5, [2] of the Offshore Rules.
3.2
Loading conditions
3.2.1 As a minimum, the loading conditions defined in Tab 2
are to be considered. These loading conditions are to be
selected from the loading manual.
3.1.2 Loading conditions
The loading conditions for which the structural analysis is
carried out are to comply with the requirements of [3.2].
Table 2 : Loading conditions
Symbol
Loading condition
3.1.3 Lightweight
The lightweight of the unit is to be distributed over the
model length, in order to obtain the actual longitudinal distribution of the still water bending moment, as indicated by
the loading manual of the unit.
LC1
Loading condition giving maximum still water
hogging bending moment on-site
LC2
Loading condition giving maximum still water
sagging bending moment on-site
LC3
Minimum draught condition on-site (1)
3.1.4 Still water loads
Still water loads include:
LC4
Full load condition on-site (2)
LC5
Loading condition maximizing hull girder still
water shear force on-site
LC6
Typical towing/transit condition
• the still water sea pressure, based on the procedure
defined in Pt B, Ch 5, Sec 5 of the Ship Rules.
• the still water internal loads for cargo tanks and ballast
tanks, defined in Pt D, Ch 1, Sec 5 of the Offshore Rules
or in NR542 Rules for the Classification of Offshore
Floating Gas Units, Section 4, as relevant.
6
(1)
(2)
Bureau Veritas
This loading condition is to be considered only when it
is different from LC1
This loading condition is to be considered only when it
is different from LC2
April 2010
NR 551, Sec 1
3.2.2 In addition to the loading conditions specified in
[3.2.1], loading conditions which are assumed to represent
typical loading/offloading sequences are to be considered.
3.2.3 For each loading condition mentioned in [3.2.1] and
[3.2.2], the longitudinal distribution of the still water shear
force and bending moment is to be computed and checked
by reference to the loading manual. The convergence of the
displacement, trim and vertical bending moment is deemed
satisfactory within the following tolerances:
• 2% of the displacement
• 0,1 degree of the trim angle
• 10% of the still water bending moment.
3.2.4 Following the specificities of the design and/or operation of the considered unit, the Society may require the
investigation of additional loading conditions considered
relevant for structural check. In such a case, the additional
loading conditions are to be stated in the Design Criteria
Statement, as defined in [1.2.4].
3.3.4
Definition of design wave parameters
For each load case, the unit is considered to encounter a
regular wave, defined by its parameters:
• wave length λ (in m), wave period T (in seconds) or
wave circular frequency ω (in rad/s)
• heading angle α (see Fig 1), in degrees
• wave height H (double amplitude), in m
• wave phase (see Fig 1).
The wave length λ and the wave period T are linked by the
following relation:
λ = g T2 / 2 π
The wave period and the wave circular frequency ω are
linked by the following relation:
T=2π/ω
Figure 1 : Wave heading
Wave propagation
direction
α = 90˚
3.3
Recommended procedure for the
calculation of wave loads
ES
λ
3.3.1 Design wave approach
The determination of the design wave characteristics for
each load case includes the following steps:
• computation of the response operators (amplitude and
phase) of the dominant load effect
• selection of the wave length and heading according to
the guidelines in [3.3.5] and [3.3.6].
• determination of the wave phase such that the dominant
load effect reaches its maximum
• computation of the wave amplitude corresponding to
the design value of the dominant load effect.
3.3.2 Dominant load effects
Each critical load case maximises the value of one of the
following load effects having a dominant influence on the
strength of some parts of the structure:
• wave induced vertical bending moment
• wave induced vertical shear force
• accelerations in three directions
• relative wave elevation
• wave induced horizontal bending moment
• wave torque (for units with large deck openings).
The values of these effects are to be specified over the
length of the unit.
3.3.3 Response Amplitude Operators
The Response Amplitude Operators (RAO’s) and associated
phase characteristics are to be computed for the load effects
listed in [3.3.2]. The calculation of RAO’s is to be in compliance with the requirements of Pt D, Ch 1, Sec 4 of the Offshore Rules.
The amplitude and phase of other dominant load effects
may be computed at relevant wave period, using the RAO’s
listed above.
April 2010
CR
Y
T
ξc
α
α = 0˚
α = 180˚
CR
F
X
ES
T
Phase angle (degrees) = ξ c . 360
F : center of rotation
3.3.5
λ
Design wave length
Design wave length, period and frequency are generally to
correspond to the peak value of the investigated dominant
load effect’s RAO.
3.3.6
Design wave heading
RAO’s of the investigated dominant load effect are to be calculated for several wave headings, as required in Pt D,
Ch 1, Sec 4 of the Offshore Rules.
Design wave heading is to be in accordance with the operational conditions for the sea states contributing the most to
the long term value of the dominant load effect.
3.3.7
Design wave phase
The design wave phase angle is to be taken such that the
investigated dominant load effect reaches its maximum.
This value corresponds to the phase of dominant load
effect, given by the hydrodynamic analysis.
3.3.8
Admissible design waves
Design waves used for the finite element calculations are to
comply with the following requirements:
a) the wave height H is limited by the maximum wave
steepness according to the relation:
Bureau Veritas
H < 0,02 g T2
7
NR 551, Sec 1
b) the wave length λ is to comply with the relation:
λ>2B
3.4
c) the wave period T is to be less than 30 s.
3.3.9 Design value of dominant load effect
The values of dominant load effects are to be taken as follows:
a) for on-site loading conditions (as defined in [3.2]):
site long-term response corresponding to a probability
of 10−8,7
b) for towing/transit loading conditions (as defined in [3.2]):
long-term response corresponding to a probability of
10−5,
computed through direct hydrodynamic analysis complying
with the requirements of Pt D, Ch 1, Sec 4 of the Offshore
Rules.
3.3.10 Design wave definition
The amplitude of the design wave is obtained by dividing
the design value of the dominant load effect (as defined in
[3.3.9]) by the value of the RAO of this effect computed for
the relevant heading and wave length.
3.4.1 General
The load cases to be considered, as a minimum, through
the structural analysis are given in Tab 3. The definition of
the loading conditions corresponding to the load cases from
Tab 3 is given in [3.2].
3.4.2 Additional load cases for wave torque
For units with large deck openings, additional load cases
maximizing wave torque are to be added for each loading
condition. These cases are to be considered as follows:
•
design value of dominant load effect: maximum wave
torque as calculated by the hydrodynamic analysis
•
location: midship section, section at 0,25 L and section
at 0,75 L.
3.4.3 Other additional load cases
The Society may require the analysis of additional load
cases, taking into the specificities of design, operation or
towing/transit of the unit and including the eventuality of
downgraded situations.
The relevant wave length, heading and phase are to be
taken as required in [3.3.5] to [3.3.7].
4
The design wave is to be applied in a nonlinear sense with
at least Froude-Krylov nonlinearities included.
4.1
3.3.11 Finite element model loading
The loads are applied to the finite element model according
to the following indications:
a) Sea pressures applied on the hull are to be obtained
through direct calculation; these pressures are to combine hydrostatic pressures and wave pressures.
b) Wave pressures up to the incident wave profile (Froude
Krylov nonlinearities).
c) The fluid pressure in tanks is to be calculated taking into
account the relevant acceleration components for the
considered load case (see [3.4]).
d) For dry cargoes, the inertial forces are computed at the
centre of mass, taking into account the mass moment of
inertia.
e) Inertial loads for structure weight, topside equipments
and dry uniform cargo are computed using local accelerations calculated at their location.
Load cases
Stress calculation
Stress components
4.1.1 Stress components are generally identified with
respect to the element co-ordinate system, as shown, by
way of example, in Fig 2. The orientation of the element coordinate system may or may not coincide with that of the
reference co-ordinate system in Pt D, Ch 1, Sec 1, [4.3] of
the Offshore Rules.
The following stress components are to be calculated at the
centroid of each element:
•
the normal stresses σ1 and σ2 in the directions of element co-ordinate system axes
•
the shear stress τ12 with respect to the element co-ordinate system axes
•
the Von Mises equivalent stress, obtained from the following formula:
σVM =
σ1 + σ 2 – σ 1 σ 2 + 3τ 12
2
2
2
Figure 2 : Reference and element co-ordinate systems
Z
3.3.12 Equilibrium check
The finite element model is to be in equilibrium condition
with all the still water and wave loads applied. The equilibrium condition is to be obtained through the application of
an acceleration field coherent with the loads acting on the
structural model.
2
X
Element
An equilibrium condition is accepted by the Society if:
• the unbalanced forces in the three axes are not to
exceed 2% of the displacement
• the unbalanced moments are not to exceed 2% of ∆⋅B
around Y and Z axes and 0,2% of ∆⋅B around X axis.
1
Y
8
Bureau Veritas
X, Y, Z :
reference co-ordinate system
April 2010
NR 551, Sec 1
Table 3 : Definition of load cases
Load
case
Loading
condition
1
LC1
Maximum vertical wave bending moment
in hogging condition
MWV,H
Midship section
(1)
2
LC1
Maximum relative wave elevation in head
sea conditions
h1,M
Midship section
(1)
3
LC1
Maximum relative wave elevation in beam
sea conditions
h2,M
Midship section
(1) (4)
4
LC1
Maximum vertical acceleration
aZ, top
Center of gravity of the heaviest topside
module in the midship area
(1)
5
LC1
Maximum transverse acceleration
aY, top
Center of gravity of the heaviest topside
module in the midship area
(1)
6
LC1
Maximum longitudinal acceleration
aX, top
Center of gravity of the heaviest topside
module in the midship area
(1)
7
LC2
Maximum vertical wave bending moment
in sagging condition
MWV,S
Midship section
(1)
8
LC2
Maximum vertical acceleration
aZ
Center of gravity of typical cargo tank at
midship section
(1)
9
LC2
Maximum transverse acceleration
aY
Center of gravity of typical cargo tank at
midship section
(1) (5)
10
LC2
Maximum horizontal wave bending
moment
MHW
Midship section
(1) (5)
11
LC2
Maximum vertical acceleration
aZ, top
Center of gravity of the heaviest topside
module in the midship area
(1)
12
LC2
Maximum transverse acceleration
aY, top
Center of gravity of the heaviest topside
module in the midship area
(1)
13
LC2
Maximum longitudinal acceleration
aX, top
Center of gravity of the heaviest topside
module in the midship area
(1)
14
LC3
Maximum vertical wave bending moment
in hogging condition
MWV,H
Midship section
(1)
15
LC3
Maximum relative wave elevation in head
sea conditions
h1,M
Midship section
(1)
16
LC3
Maximum relative wave elevation in beam
sea conditions
h2,M
Midship section
(1)
17
LC4
Maximum vertical wave bending moment
in sagging condition
MWV,S
Midship section
(1)
18
LC4
Maximum vertical acceleration
aZ
Center of gravity of typical cargo tank at
midship section
(1)
19
LC4
Maximum transverse acceleration
aY
Center of gravity of typical cargo tank at
midship section
(1)
20
LC4
Maximum horizontal wave bending
moment
MHW
Midship section
(1)
21
LC5
Maximum vertical wave shear force
QWV
Location of maximum still water shear
force, according to the loading manual
(1)
22
LC6
Maximum vertical wave bending moment
in hogging condition
MWV,H
Midship section
(2) (3)
23
LC6
Maximum relative wave elevation in head
sea conditions
h1,M
Midship section
(2) (3)
24
LC6
Maximum vertical acceleration
aZ, top
Center of gravity of the heaviest topside
module in the midship area
(2) (3)
25
LC6
Maximum transverse acceleration
aY, top
Center of gravity of the heaviest topside
module in the midship area
(2) (3)
(1)
(2)
(3)
(4)
(5)
Design value of
dominant load effect
Symbol
Location
Remarks
The design value of dominant load effect is to be taken as defined in [3.3.9] for on-site conditions.
The design value of dominant load effect is to be taken as defined in [3.3.9] for towing/transit conditions.
This load case is requested only if the design value of the dominant load effect for towing/transit is above the one for on-site condition.
This load case is not requested when LC1 is different from LC3.
This load case is not requested when LC2 is different from LC4.
April 2010
Bureau Veritas
9
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April 2010