Technical Field
[0001] The present invention relates to a cargo tank support structure, a floating structure
and a method of supporting a cargo tank, more specifically, a support structure bearing
vertical and horizontal loads applied by a cargo tank mounted on a floating structure,
a floating structure including the support structure, and a method of supporting a
cargo tank.
Background Art
[0002] Floating structures, such as carrier vessels or offshore floating equipment, for
transporting or storing liquid cargo, such as petroleum, LPG (liquefied petroleum
gas) or LNG (liquefied natural gas), of an independent tank type, namely having cargo
tanks for such liquid cargo, independent from the floating structure, are in wide
use (see patent documents 1 and 2, for example).
[0003] While traveling or moored, floating structures experience heave, or liner vertical
motion, sway, or linear lateral motion, surge, or linear longitudinal motion, pitch,
or rotation about the transverse axis, yaw, or rotation about the vertical axis, and
roll, or rotation about the longitudinal axis, caused by waves. Actually, they experience
complex motions resulting from combinations of these motions. It is therefore important
to stably support independent cargo tanks that can move relative to the floating structure.
[0004] GB 1 328 758 A, which is considered the closest prior art and which relates to a storage tank assembly
comprising a plurality of pairs of guide blocks disposed such that one block of each
pair is connected to either the bottom or the ceiling of a tank supported for movement
on a horizontal plane and the other block of each pair is connected to the respective
bottom or ceiling of a tank supporting structure at ambient temperature associated
therewith, the guide blocks in each pair being in side-to-side contact with each other
for relative sliding movement along a respective one of at least two vertical planes
passing through the vertical central axis of the tank and intersecting at said central
axis, each pair being spaced from adjacent pairs, said two vertical planes defining
four sections or quadrants, such that in one pair of mutually opposite sections or
quadrants are located only the guide blocks attached to the tank and in the other
pair of mutually opposite sections or quadrants are located only the blocks attached
to the tank supporting structure the arrangement being such that the tank is free
to expand or contract about said central axis whereas rotational and horizontal movement
of the tank is prevented.
[0005] FR 1 317 043 A relates to a tank for boats which is intended to carry low-temperature liquids, such
as liquefied methane, said tank being immobilized laterally with respect to the hull
structure of the boat, while being free to expand and shrink laterally, said lateral
immobilization of the tank being ensured by at least two substantially horizontal
keys that relate the tank bottom to the structure of said hull.
[0006] In bulk fluid carrier constructions according to document
US 3 064 612 A, the temperature of the cargo may vary from the ambient temperature of the carrier.
The carrier has a hull having plural aligned holds within, each said hold including
one tank which extends substantially fully abeam the carrier and is spaced on all
sides from said hold. Each said hold further includes means fixed to the floor of
the hold anchoring said tank including vertically aligned tank slide and foundation
assemblies in longitudinal and transverse coextension of the bottom of the tank, the
assemblies each being fixed respectively to tank and floor, raising the tank above
the floor. The tank further includes a plurality of pins extending through respective
foundation and slide members. Both said foundation and slide members having aligned
pin-engaging apertures, the apertures of the slides being of greater dimension than
the apertures of the corresponding foundations, whereby controlled expanding and contracting
movements of tank relative to foundation may occur upon cargo temperature variation.
[0007] Patent document 1 discloses, in Figs. 5 and 6, a cargo tank support structure comprising
bearing seats, anti-floatation chocks and anti-roll chocks, where the bearing seats
bear a vertical load applied by a cargo tank, the anti-roll chocks bear a horizontal
load applied by the cargo tank displaced sideway by roll of the ship, and anti-floatation
chocks restricts floatation of the cargo tank when the ship is flooded. In this support
structure, loads applied by the weight of the floating structure itself and various
motions of the floating structure caused by waves are borne primarily by the bearing
seats and the anti-roll chocks. As seen in patent document 1, the bearing seats are
provided at the floor of the hull, and the anti-roll chokes are provided at the ceiling
and the floor of the hull.
[0008] Patent document 2 discloses, in Fig. 6, a structure in which support members for
supporting an independent tank are provided at varying density considering the magnitude
of reaction force to be borne by respective support members.
[0009] The support structure disclosed in patent document 2 is created paying attention
to distribution of the vertical load applied by the cargo tank, and exhibits only
those support elements which correspond to the bearing seats in patent document 1.
Prior Art Document
Patent Document
Summary of the Invention
Problems to be solved by the Invention
[0011] The cargo tank support structure disclosed in patent document 1 comprises support
members (bearing seats) bearing the vertical load applied by the cargo tank, support
members (anti-roll chocks) bearing the horizontal load applied by the cargo tank,
and also support members bearing the horizontal load, provided at the ceiling of the
floating structure. Since the support members are provided at the floor and the ceiling,
construction of the cargo tank as well as construction of the floating structure takes
much time. Further, since the cargo tank experience reaction force at the locations
at which the cargo tank is supported by the support members, reinforcing members need
to be provided on the inner side of the cargo tank at those locations. Also for this
reason, a greater number of support members and/or a wider distribution of support
members results in a greater amount of time taken for cargo tank construction and
higher production costs.
[0012] For the cargo tank support structure disclosed in patent document 2, it is necessary
to calculate reaction force to be borne by respective support members and determine
in what shapes and at what locations to provide support members on the floating structure,
leading to much time taken for design work. In addition, only providing the support
members designed to bear the reaction force is not enough to bear a large horizontal
load applied when the floating structure experiences motions such as roll, sway and
yaw; the provision of support members bearing the horizontal load, such as the anti-roll
chocks disclosed in patent document 1, is required. The cargo tank support structure
disclosed in patent document 2 is therefore not free of the problem with the structure
disclosed in patent document 1.
[0013] The present invention has been made in view of the above problems. An object of the
present invention is to provide a cargo tank support structure, a floating structure
and a method of supporting a cargo tank, requiring a reduced number of support members
and a reduced number of locations at which to provide support members, and thus, enabling
a reduction in time taken for construction work and a reduction in construction costs.
Means for Solving the Problems
[0014] In order to achieve the above object, the present invention provides a floating structure
comprising a cargo tank and a cargo tank support structure for supporting the cargo
tank mounted in a hold in the floating structure, the cargo tank support structure
comprising: a plurality of first support portions provided at a bottom of the cargo
tank in a distributed manner, a second support portion provided at the bottom of the
cargo tank to continuously extend in a longitudinal direction of the floating structure,
and an engagement portion provided at a floor of the hold along the length of the
second support portion to engage with the second support portion, wherein when a load
is applied by the cargo tank, at least the first support portions bear a vertical
load and at least the second support portion and the corresponding engagement portion
bear a horizontal load in both width directions of the floating structure, and wherein
the horizontal load is split into a first horizontal load in a width direction of
the floating structure and a second horizontal load in the longitudinal direction
of the floating structure, the first horizontal load being borne by the second support
portion and the corresponding engagement portion, and the second horizontal load being
borne by the first support portions.
[0015] In the above-described cargo tank support structure and floating structure, the second
support portion may be provided along the longitudinal center line of the floating
structure. The hold may have a ceiling covering the cargo tank, the ceiling having
no support portion bearing the horizontal load applied by the cargo tank.
[0016] The second support portion may be adapted to bear the vertical load applied by the
cargo tank. The cargo tank support structure may further comprise first seats and
a second seat provided at the floor of the hold, the first seats being adapted to
support the first support portions in a manner allowing the first support portions
to slide thereon, and the second seat being adapted to support the second support
portion, wherein the engagement portion is provided at the second seat.
[0017] The horizontal load may be split into a first horizontal load in a width direction
of the floating structure and a second horizontal load in the longitudinal direction
of the floating structure, the first horizontal load being borne by the second support
portion and the corresponding engagement portion, and the second horizontal load being
borne by the first support portions.
[0018] The cargo tank support structure may further comprise engagement portions provided
at the floor of the hold along the width of the floating structure to engage with
corresponding ones of the first support portions so that the second horizontal load
is borne by the engagement portions and the corresponding first support portions.
[0019] The first and second support portions each may comprise a frame providing a downwardly-open
recess and a support block fixed in the recess to project from the frame downward.
[0020] The cargo tank support structure may further comprise a plurality of reinforcing
members provided at an inner side of the bottom of the cargo tank to extend in the
longitudinal direction of the floating structure, parallel to each other, wherein
the support block has a width smaller than a distance between the adjacent reinforcing
members.
[0021] The present invention also provides a method of supporting a cargo tank mounted in
a hold in a floating structure, wherein a vertical load and a horizontal load applied
by the cargo tank is borne by support portions all provided on the floor side of the
hold.
Advantageous Effects of the Invention
[0022] In the cargo tank support structure, the floating structure and the cargo tank supporting
method according to the present invention, support portions bearing the vertical and
horizontal loads applied by the cargo tank are all provided on the floor side of the
hold, where the horizontal load is borne by the second support portion provided to
continuously extend in the longitudinal direction of the floating structure. This
enables the vertical and horizontal loads applied by the cargo tank to be borne by
a reduced number of support portions at a reduced number of locations, and thus, enables
a reduction in time taken for construction work and a reduction in construction costs.
Further, omission of chocks at the ceiling means increased independence of the cargo
tank, which provides increased freedom of deck design and construction, leading to
a reduction in costs and wider application.
Brief Description of the Drawings
[0023]
Fig. 1 is a cross-sectional view showing a first embodiment of a cargo tank support
structure according to the present invention,
Fig. 2A is a partial enlarged view showing a first support portion of the support
structure shown in Fig. 1,
Fig. 2B is a partial enlarged view showing a second support portion of the support
structure shown in Fig. 1,
Fig. 3A is a diagram showing a bottom structure of a cargo tank, a constituent part
of the support structure shown in Fig. 1,
Fig. 3B is a diagram showing a floor structure of a hold, a constituent part of the
support structure shown in Fig. 1,
Fig. 4A is a diagram showing a bottom of a cargo tank for explaining how a horizontal
load is borne in a prior-art structure,
Fig. 4B is a diagram showing a top of a cargo tank for explaining how a horizontal
load is borne in the prior-art structure,
Fig. 5A is a diagram showing a second embodiment of the cargo tank support structure
according to the present invention,
Fig. 5B is a diagram showing a third embodiment of the cargo tank support structure
according to the present invention,
Fig. 5C is a diagram showing a fourth embodiment of the cargo tank support structure
according to the present invention,
Fig. 5D is a diagram showing a fifth embodiment of the cargo tank support structure
according to the present invention,
Fig. 6A is a diagram showing a sixth embodiment of the cargo tank support structure
according to the present invention,
Fig. 6B is a diagram showing a seventh embodiment of the cargo tank support structure
according to the present invention,
Fig. 7A is a diagram schematically showing the overall structure of a ship, an embodiment
of a floating structure according to the present invention, and
Fig. 7B is a diagram schematically showing the overall structure of off-shore floating
equipment, another embodiment of the floating structure according to the present invention.
Mode for Carrying out the Invention
[0024] With reference to Figs. 1 to 7, embodiments of the present invention will be described.
Fig. 1 is a cross-sectional view showing a first embodiment of a cargo tank support
structure according to the present invention, Figs. 2A a partial enlarged view showing
a first support portion of the support structure shown in Fig. 1, Fig. 2B a partial
enlarged view showing a second support portion thereof, Fig. 3A a diagram showing
a bottom structure of a cargo tank, and Fig. 3B a diagram showing a floor structure
of a hold, the bottom structure and the floor structure being constituent parts of
the support structure shown in Fig. 1.
[0025] For convenience in the description, the length, width and height of a floating structure
1 are chosen as X-axis, Y-axis and Z-axis, respectively, in Figs. 1 to 3.
[0026] As shown in Figs. 1 to 3, a first embodiment of a cargo tank support structure according
to the present invention, designed to support a cargo tank 2 mounted in a hold 11
in a floating structure 1, comprises a plurality of first support portions 3 provided
at the bottom 2a of the cargo tank 2 in a distributed manner, a second support portion
4 provided at the bottom 2a of the cargo tank 2 to continuously extend in the longitudinal
direction X of the floating structure 1, and an engagement portion 5 provided at the
floor 11a of the hold 11 along the length of the second support portion 4, thus in
the X-direction, to engage with the second support portion 4, where a vertical load
Fz applied by the cargo tank 2 is borne by at least the first support portions 3 and
a horizontal load applied by the cargo tank 2 (first horizontal load Fy, in particular)
is borne by at least the second support portion 4 and the engagement portion 5. The
horizontal load can be split into a first horizontal load Fy in the width direction
Y of the floating structure 1, and a second horizontal load Fx in the longitudinal
direction X of the floating structure 1.
[0027] The floating structure 1 is a LNG carrier of a self-supporting prismatic type, for
example. As seen in Fig. 1, the self-supporting prismatic LNG carrier (floating structure
1) has a double-hull 12 defining a hold 11 inside for carrying a cargo tank 2. Since
the cargo tank 2 is prismatic in shape, the hold 11 is also prismatic in shape.
[0028] The hold 11 is defined by a floor 11a and a ceiling 11b, the floor 11a facing the
bottom 2a of the cargo tank 2 and the ceiling 1b covering the top of the cargo tank
2. In the present embodiment, the ceiling 11b has no support portion bearing the horizontal
load applied by the cargo tank 2. Support portions are all provided at the bottom
2a, as will be described below.
[0029] The cargo tank 2 is designed to hold liquid cargo, such as petroleum, LPG or LNG
(liquefied natural gas). The present embodiment is based on the assumption that LNG
is held in the cargo tank. LNG is natural gas that has converted to liquid form by
cooling it to -162°C or below, and requires maintaining at low temperature. Thus,
the outer side of the cargo tank 2 is covered with a heat insulating material 21 shaped
in panels. This cargo tank 2 is an independent type, namely constructed independently
from the hull 12.
[0030] The cargo tank 2 is mounted in the hold 11, where in order to support its own weight
and reduce heat transfer from the hull 12, the cargo tank 2 has support members (first
support portions 3 and second support portion 4, for example) at the bottom 2a, which
allows the cargo tank to be mounted with the support members on the floor 11a of the
hold 11. The present invention is characterized by this cargo tank 2 support structure.
Although the cargo tank 2 has various reinforcing members on the inner side, Fig.
1 shows only those reinforcing members 22 provided to extend in the longitudinal direction
X of the hull 12, parallel to each other.
[0031] The first support portions 3 bear the weight of the cargo tank 2 itself, or vertical
load Fz applied by the cargo tank 2. As shown in Fig. 2A, the first support portions
3 each comprise a frame 31 providing a downwardly-open recess and a support block
32 fixed in the recess to project from the frame 31 downward. The support block 32
is fitted and fixed in the frame 31. The support block 32 is made from square timber,
for example, and fixed in the frame 31 by press-fitting. The support block 32 may,
of course, be fixed to the frame 31 with metal fastening pieces. A reinforcing material
31a is provided to surround the frame 31 in an appropriate geometry. The support block
32 may be a conventional support block. For example, it may be made from an elastic
material having low thermal conductivity, such as rubber or resin, or square timber
with a coat of such elastic material.
[0032] As seen in Fig. 2A, at the floor 11a of the hold 11, first seats 13 are provided
to face and support the first support portions 3, respectively, in a manner allowing
them to slide thereon. The first seat 13 is a solid or hollow or symbol "#"-shaped
metal portion with an approximately-flat top face. A reinforcing material 13a is provided
to surround the first seat 13 in an appropriate geometry. The cargo tank is mounted
with the support blocks 32 of the first support portions 3 slidably seated on the
top faces of the first seats 13. The first seats 13 may be made by machining the floor
11a of the hold 11 itself. When unnecessary, the first seats 13 may be omitted so
that the support blocks 32 are supported directly by the floor 11a.
[0033] As seen in Fig. 3A, the first support portions 3 are arranged on both sides of the
longitudinal center line L of the floating structure 1, in a manner distributed over
the bottom 2a of the cargo tank 2. In the shown embodiment, the first support portions
3 are arrayed in two rows and eight columns on the portside as well as on the starboard
side. As seen in Fig. 3B, the first seats 13 are arranged at the locations corresponding
to the first support portions 3.
[0034] The cargo tank support structure may be designed such that the second horizontal
load Fx is borne by the first support portions 3 while the first horizontal load Fy
is borne by the second support portion 4 and the engagement portion 5. Specifically,
as seen in Fig. 3B, the first seats 13 in the second column from the left each have
an engagement portion 15 similar in shape to the engagement portion 5, described later.
The engagement portions 15 are provided at the floor 11a of the hold 11, along the
width of the floating structure 1, thus in the Y-direction, to engage with the corresponding
first support portions 3 so that the second horizontal load Fx is borne by the engagement
portions 15 and the corresponding first support portions 3. The provision of the engagement
portions 15 makes it possible to bear the horizontal load applied in varying magnitude
and direction. The engagement portions 15 may be provided in a desired manner; an
increased number of the engagement portions 15 may be provided, and the engagement
portions 15 may be provided at different locations, as compared with the example shown
in the Figure. If the second horizontal load Fx is negligibly small in magnitude as
compared with the first horizontal load Fy, the engagement portions 15 may be omitted.
[0035] The second support portion 4 bears at least the horizontal load (first horizontal
load Fy) applied by the cargo tank 2. While traveling or moored, the floating structure
1 experiences various motions (heave, sway, surge, pitch, yaw, roll) caused by waves,
so that the cargo tank 2 applies first and second horizontal loads Fy, Fx, namely
loads in the width and longitudinal directions Y, X of the hull, respectively. The
second support portion 4 bears the first horizontal load Fy. Floating structures having
a long and thin hull 12, such as LNG carries, in particular, are likely to experience
a great load in the width direction Y; the first horizontal load Fy is likely to be
greater than the second horizontal load Fx.
[0036] As seen in Fig. 2B, the second support portion 4 comprises a frame 41 providing a
downwardly-open recess and a support block 42 fixed in the recess to project from
the frame 41 downward. The support block 42 is fitted and fixed in the frame 41. The
support block 42 is made from square timber, for example, and fixed in the frame 41
by press-fitting.
[0037] The support block 42 may, of course, be fixed to the frame 41 with metal fastening
pieces. A reinforcing material 41a is provided to surround the frame 41 in an appropriate
geometry. The support block 42 may be a conventional support block. For example, it
may be made from an elastic material having low thermal conductivity, such as rubber
or resign, or square timber with a coat of such elastic material.
[0038] As seen in Fig. 2B, at the floor 11a of the hold 11, a second seat 14 is provided
to face and support the second support portion 4. The second seat 14 is a solid or
hollow or symbol "#"-shaped metal portion with an approximately-flat top face. A reinforcement
material 14a is provided to surround the second seat 14 in an appropriate geometry.
[0039] The second seat 14 has the top face at the same level as the top faces of the first
seats 13, on which the support block 42 of the second support portion 4 is seated.
The second support portion 4 thus shares the vertical load Fz applied by the cargo
tank 2. By the second support portion 4 sharing the vertical load Fz, the load to
be borne by the first support portions 3 is reduced, which allows a reduction in number
of the first support portions 3 and/or a reduction in size of the first support portions
3.
[0040] As seen in Fig. 2B, the engagement portion 5 is provided at the second seat 14. The
engagement portion 5 is formed by attaching pieces of structural steel, such as steel
angle or plate, to either side of the second seat 14 in the longitudinal direction
X, by welding or other process. The engagement portion 5 may be formed by attaching
the pieces of structural steel to either the top or the sides of the second seat 14.
The engagement portion 5 provided this way can bear the first horizontal load Fy,
restricting the movement of the support block 42 on the second seat 14 in the width
direction Y
[0041] As seen in Fig. 3A, the second support portion 4 is provided to extend on the longitudinal
center line L of the floating structure 1 in the X-direction. As seen in Fig. 3B,
also the second seat 14 and the engagement portion 5 extend on the longitudinal center
line L of the floating structure 1 in the X-direction. The second support portion
4 and the engagement portion 5, both extending long in the longitudinal direction
X, provide a pressure-receiving area great enough to bear the first horizontal load
Fy.
[0042] Although in the shown embodiment, the engagement portion 5 extends in the X-direction
over the entire length of the second seat 14, the engagement portion 5 may have any
length enough to bear the expected magnitude of the first horizontal load Fy. The
engagement portion 5 may be made of separate longitudinal portions arranged in the
longitudinal direction X.
[0043] Figs. 4A and 4B are diagram showing a bottom and a top of a cargo tank, respectively,
for explaining how a horizontal load is borne in a prior-art support structure.
[0044] As seen in Figs. 4A and 4B, in the prior art, the cargo 20 tank support structure
typically comprises a plurality of tanks supports 30 provided at the bottom 20a of
the cargo tank 20 in a distributed manner, and a plurality of anti-roll chocks 40
provided at the top 20b of the cargo tank 20 on the longitudinal center line L of
the hull. The cargo tank 20 is mounted with the tank supports 30 on the hold floor
and with the anti-roll chocks 40 engaged with engagement portions provided at the
hold ceiling. Thus, the vertical load applied by the cargo tank 20 is borne by the
tank supports 30, and the horizontal load by the anti-roll chocks 40 and some of the
tank supports 30. The cargo tank 20 has a tank dome 20c at the top, which provides
access to the inside of the cargo tank for carrying in and out LNG and for tank maintenance.
[0045] The above-described prior-art support structure having the support members (tank
supports 30 and anti-roll chocks 40) at both the bottom 20a and the top 20b of the
cargo tank has a drawback such that construction of the floating structure as well
as construction of the cargo tank 20 takes much time. The present embodiment, by contrast,
has a portion functioning as anti-roll chocks at the bottom 2a of the cargo tank 2.
Specifically, the present embodiment is a method of supporting a cargo tank 2 mounted
in a hold 11 in a floating structure 1, wherein the horizontal load (first horizontal
load Fy and second horizontal load Fx) as well as the vertical load Fz applied by
the cargo tank 2 is borne by support portions all provided on the floor 11a side of
the hold 11. The present embodiment thus does not require that support portions bearing
the horizontal load (first horizontal load Fy and second horizontal load Fx) applied
by the cargo tank 2 be provided at the top of the cargo tank 2. The present embodiment
thus allows a reduction in number of locations at which to provide support members
and a reduction in size of support members, which leads to reduced time taken for
construction work.
[0046] As seen in Fig. 3A, the second support portion 4 extending linearly and continuously
in the longitudinal direction X leads to simple arrangement of heat insulating material
2 around it, as compared with the prior art in which the heat insulating material
needs to be arranged to surround each of the separate tank supports 30 provided in
a distributed manner in the area of the second support portion 4. This also leads
to reduced time taken for construction work.
[0047] Next, other embodiments of the cargo tank support structure according to the present
invention will be described. Figs. 5A to 5D show second to fifth embodiments of the
cargo tank support structure according to the present invention, respectively, and
Figs. 6A and 6B show sixth and seventh embodiments of the cargo tank support structure
according to the present invention, respectively. Those components which are similar
to components of the first embodiment are denoted by the same reference characters,
and the description thereof will be omitted.
[0048] In the second to fifth embodiments shown in Figs. 5A to 5D, the first support portions
3 and/or the second support portion 4 is provided in an altered arrangement. Figs.
5A to 5D each show the bottom 2a of the cargo tank 2 in a manner comparable to Fig.
3A.
[0049] In the second embodiment shown in Fig. 5A, the second support portion 4 is divided
into parts. Although in the shown example, the second support portion 4 is divided
into two parts, it may be divided into three or more parts.
[0050] Dividing the second support portion 4 into parts provides a passage between the adjacent
parts, through which a worker can come and go between the opposite sides of the second
support portion 4. This is convenient for maintenance work and others.
[0051] In the third embodiment shown in Fig. 5B, the second support portion 4 is provided
to extend in the longitudinal direction X, off the longitudinal center line L. Although
it is normally desirable to arrange the second support portion 4 on the longitudinal
center line L, the second support portion 4 may be arranged on any longitudinal line
other than the longitudinal center line as in the third embodiment, to suit the expected
horizontal load, which varies depending on ship type, cargo, shipping route and others.
[0052] In the fourth embodiment shown in Fig. 5C, the second support portion 4 includes
a part arranged on another longitudinal line than the longitudinal center line L.
[0053] Specifically, the second support portion 4 is divided into three parts, of which
the middle one 4 is arranged on a longitudinal line near a longitudinal edge of the
bottom 2a of the cargo tank 2 and the other two 4 are arranged on the longitudinal
center line L. The second support portion 4 may be provided in a distributed manner
as in the fourth embodiment to suit the expected horizontal load, which varies depending
on ship type, cargo, shipping route and others, within the constraints on arrangement
imposed by the hull.
[0054] In the fifth embodiment shown in Fig. 5D, the first support portions 3 are approximately
rectangular in shape.
[0055] Although in the shown example, the first support portion 3 has a greater size in
the width direction Y of the floating structure than in the longitudinal direction
X thereof, the first support portion 3 may have a greater size in the longitudinal
direction X than in the width direction Y.
[0056] This type of first support portion 3 is provided, as it were, by combining some conventional
first support portions 3 into one. Choosing the rectangular shape in place of the
square shape makes it possible to reduce the number of support portions 3 while providing
the pressure-receiving area enough to bear the vertical load Fz, leading to a reduction
in time taken for construction work.
[0057] In the sixth and seventh embodiments shown in Figs. 6A and 6B, the second support
portion 4 has an altered structure.
[0058] Figs. 6A and 6B each show the second portion 4 in a manner comparable to Fig. 2B.
[0059] In the sixth embodiment shown in Fig. 6A, the second seat 14 is omitted. The second
seat 14 can be omitted, for example when the first seats 13 are omitted or when the
second support 4 is not intended to bear the vertical load Fz. As seen in the Figure,
the engagement portion 5 is provided directly at the floor 11a of the hold 11. A reinforcing
material 5a may be provided on the outer side of the engagement portion 5. In the
shown example, the second support portion 4 is not intended to bear the vertical load
Fz (the vertical load Fz is borne only by the first support portions 3), and thus,
the block 42 is not in contact with the floor 11a of the hold 11. It may be altered
such that the block 42 is in contact with the floor 11a so that the second support
portion 4 shares the vertical load Fz.
[0060] In the seventh embodiment shown in Fig. 6B, the cargo tank 2 has a plurality of reinforcing
members 22 provided on the inner side of the bottom to extend in the longitudinal
direction X, parallel to each other, where the support block 42 has a width Yb smaller
than the distance Yg between the adjacent reinforcing members 22, 22. This can reduce
the area not covered with the heat insulating material 21, and thus, provide improved
cold storage performance. When the heat insulating material 21 is shaped in panels,
the second support portion 4 is easily provided between the panels. The second support
portion 4 of this type can therefore reduce the area not covered with the heat insulating
material 21, and at the same time facilitates application of the heat insulating material
21.
[0061] This feature is applicable to the first support portions 3. Last, embodiments of
a floating structure 1 according to the present invention will be described. Fig.
7A is a diagram schematically showing the overall structure of a ship, an embodiment
of a floating structure according to the present invention, and Fig. 7B shows off-shore
floating equipment, another embodiment of the floating structure.
[0062] The floating structures 1 shown in Figs. 7A and 7B each comprise a main body 1a floating
by being supported by a buoyant force, the main body 1a having a hold 11 with cargo
tanks 2 mounted in. Specifically, the floating structure 1 shown in Fig. 7A is a self-supporting
prismatic LNG carrier, and the main body 1a is a hull 12. The floating structure 1
is not restricted to the LNG carrier; it may be a petroleum tanker, an LPG carrier,
a chemical tanker or the like although it needs to be a vessel designed to carry self-supporting
prismatic cargo tanks 2.
[0063] The floating structure 1 shown in Fig. 7B is offshore-floating self-supporting prismatic
LNG equipment exemplified by an FPSO (floating production, storage and offloading
system). The FPSO is a floating structure 1 moored offshore by mooring cable 1b, having
LNG production equipment 1c on the deck, wherein the LNG produced is stored in cargo
tanks 2 within the FPSO until offloaded onto a carrier. The FPSO may be designed for
processing petroleum or LPG. If the production of such fuel is not intended, the floating
structure 1 may be an FSO (floating storage and offloading system) which is offshore
floating equipment not comprising production equipment 1c. The FSO is designed to
only store and offload fuel.
[0064] The floating structure 1 has cargo tanks 2 independent from the main body 1a, and
the cargo tanks 2 are supported with the support structure according to the present
invention, exemplified by the above-described first to seventh embodiments, and thus,
the support portions bearing the vertical load Fz and horizontal load (first horizontal
load Fy and second horizontal load Fx) applied by the cargo tank 2 are all provided
on the floor 11a side of the hold 11.
[0065] This makes it possible to reduce the number of support members and the number of
locations at which to provide support members, leading to reduced time taken for and
reduced costs of constructing the floating structure 1.
[0066] In the above description of the cargo tank 2 support structure, the floating structure
1 and the method of supporting the cargo tank 2, the "vertical load" is a load acting
vertically on the floating structure 1 buoyed by static water, and the "horizontal
load" is a load acting horizontally on the floating structure 1 buoyed by static water.
The frame of reference within which these loads are measured may be either a relative
coordinate system varying depending on oscillation of the floating structure 1 or
an absolute coordinate system fixed irrespective of oscillation of the floating structure
1.
[0067] The present invention is not restricted to the described embodiments, which can be
altered in various ways without departing from the scope of the present invention.
For example, the present invention is applicable to floating structures 1 having anti-floatation
chocks and floating structures 1 not having a ceiling 11b of a hold 11 covering a
cargo tank 2.
Explanation of Reference Signs
[0068]
- 1
- Floating structure
- 1a
- Main body
- 2
- Cargo tank
- 2a
- Bottom
- 3
- First support portion
- 4
- Second support portion
- 5
- Engagement portion
- 11
- Hold
- 11a
- Floor
- 11b
- Ceiling
- 13
- First seat
- 14
- Second seat
- 15
- Engagement portion
- 22
- Reinforcing member
- 31, 41
- Frame
- 32, 42
- Support block
1. A floating structure (1) comprising a cargo tank (2) and a cargo tank support structure
for supporting the cargo tank (2) mounted in a hold (11) in the floating structure
(1), the cargo tank support structure comprising:
a plurality of first support portions (3) provided at a bottom (2a) of the cargo tank
(2) in a distributed manner,
a second support portion (4) provided at the bottom (2a) of the cargo tank (2), and
an engagement portion (5) provided at a floor (11a) of the hold (11) along the length
of the second support portion (4) to engage with the second support portion (4), wherein
when a load is applied by the cargo tank (2), at least the first support portions
(3) bear a vertical load (Fz) and at least the second support portion (4) and the
corresponding engagement portion (5) bear a horizontal load (Fy) in both width directions
of the floating structure (1), and characterized in that the second support portion continuously extend in a longitudinal direction of the
floating structure (1) and that the horizontal load is split into a first horizontal
load (Fy) in a width direction of the floating structure (1) and a second horizontal
load (Fx) in the longitudinal direction of the floating structure (1), the first horizontal
load (Fy) being borne by the second support portion (4) and the corresponding engagement
portion (5), and the second horizontal load (Fx) being borne by the first support
portions (3).
2. The floating structure (1) according to claim 1, wherein the second support portion
(4) is provided along the longitudinal center line (L) of the floating structure (1).
3. The floating structure (1) according to claim 1, wherein the hold (11) has a ceiling
(11b) covering the cargo tank (2), the ceiling (11b) having no support portion bearing
the horizontal load applied by the cargo tank (2).
4. The floating structure (1) according to claim 1, wherein the second support portion
(4) is adapted to bear the vertical load (Fz) applied by the cargo tank (2).
5. The floating structure (1) according to claim 4, further comprising first seats (13)
and a second seat (14) provided at the floor (11a) of the hold (11), the first seats
(13) being adapted to support the first support portions (3) in a manner allowing
the first support portions (3) to slide thereon, and the second seat (14) being adapted
to support the second support portion (4), wherein the engagement portion (5) is provided
at the second seat (14).
6. The floating structure (1) according to claim 1, further comprising engagement portions
(15) provided at the floor (11a) of the hold (11) along the width of the floating
structure (1) to engage with corresponding ones of the first support portions (3)
so that the second horizontal load (Fx) is borne by the engagement portions (15) and
the corresponding first support portions (3).
7. The floating structure (1) according to claim 1, wherein the first and second support
portions (3, 4) each comprise a frame (31, 41) providing a downwardly-open recess
and a support block (32, 42) fixed in the recess to project from the frame (31, 41)
downward.
8. The floating structure (1) according to claim 7, further comprising a plurality of
reinforcing members (22) provided at an inner side of the bottom of the cargo tank
(2) to extend in the longitudinal direction of the floating structure (1), parallel
to each other, wherein the support block (32, 42) has a width (Yb) smaller than a
distance (Yg) between the adjacent reinforcing members (22).
9. The floating structure (1) according to any of claims 1 to 8, wherein the second support
portion (4) is divided into parts and the engagement portion (5) is made of separate
portions.
10. The floating structure (1) according to any of claims 1 to 9, comprising a main body
(1a) floating by being supported by a buoyant force, the main body (1a) having the
hold (11) with the cargo tank (2) mounted in, wherein
the cargo tank (2) is supported with the cargo tank support structure.
1. Schwimmstruktur (1), einen Ladetank (2) und eine Ladetankträgerstruktur umfassend,
um den in einer Halterung (11) in der Schwimmstruktur (1) angebrachten Ladetank (2)
abzustützen, wobei die Ladetankträgerstruktur umfasst:
mehrere erste Trägerabschnitte (3), die an einer Unterseite (2a) des Ladetanks (2)
auf eine verteilte Weise vorgesehen sind,
einen zweiten Trägerabschnitt (4), der an der Unterseite (2a) des Ladetanks (2) vorgesehen
ist, und
einen Eingriffsabschnitt (5), der an einem Boden (11a) der Halterung (11) entlang
der Länge des zweiten Trägerabschnitts (4) vorgesehen ist, um einen Eingriff mit dem
zweiten Trägerabschnitt (4) einzugehen,
wobei, wenn eine Last durch den Ladetank (2) angelegt wird, zumindest die ersten Trägerabschnitte
(3) eine vertikale Last (Fz) tragen, und zumindest der zweite Trägerabschnitt (4)
und der entsprechende Eingriffsabschnitt (5) eine horizontale Last (Fy) in beiden
Breitenrichtungen der Schwimmstruktur (1) tragen,
und dadurch gekennzeichnet, dass sich der zweite Trägerabschnitt durchgehend in einer Längsrichtung der Schwimmstruktur
(1) erstreckt, und dass die horizontale Last in eine erste horizontale Last (Fy) in
einer Breitenrichtung der Schwimmstruktur (1) und eine zweite horizontale Last (Fx)
in der Längenrichtung der Schwimmstruktur (1) unterteilt ist, wobei die erste horizontale
Last (Fy) durch den zweiten Trägerabschnitt (4) und den entsprechenden Eingriffsabschnitt
(5) aufgenommen wird, und die zweite horizontale Last (Fx) durch die ersten Trägerabschnitte
(3) aufgenommen wird.
2. Schwimmstruktur (1) nach Anspruch 1, wobei der zweite Trägerabschnitt (4) entlang
der Längsmittellinie (L) der Schwimmstruktur (1) vorgesehen ist.
3. Schwimmstruktur (1) nach Anspruch 1, wobei die Halterung (11) eine Decke (11b) hat,
die den Ladetank (2) abdeckt, wobei die Decke (11b) keinen Trägerabschnitt hat, der
die durch den Ladetank (2) angelegte horizontale Last trägt.
4. Schwimmstruktur (1) nach Anspruch 1, wobei der zweite Trägerabschnitt (4) dazu angepasst
ist, die durch den Ladetank (2) angelegte vertikale Last (Fz) zu tragen.
5. Schwimmstruktur (1) nach Anspruch 4, darüber hinaus erste Aufnahmen (13) und eine
zweite Aufnahme (14) umfassend, die am Boden (11a) der Halterung (11) vorgesehen sind,
wobei die ersten Aufnahmen (13) dazu angepasst sind, die ersten Trägerabschnitte (3)
auf eine Weise zu tragen, welche die ersten Trägerabschnitte (3) darauf gleiten lässt,
und die zweite Aufnahme (14) dazu angepasst ist, den zweiten Trägerabschnitt (4) zu
tragen, wobei der Eingriffsabschnitt (5) an der zweiten Aufnahme (14) vorgesehen ist.
6. Schwimmstruktur (1) nach Anspruch 1, darüber hinaus Eingriffsabschnitte (15) umfassend,
die am Boden (11a) der Halterung (11) entlang der Breite der Schwimmstruktur (1) vorgesehen
sind, um einen Eingriff mit entsprechenden der erste Trägerabschnitte (3) einzugehen,
so dass die zweite horizontale Last (Fx) durch die Eingriffsabschnitte (15) und die
entsprechenden ersten Trägerabschnitte (3) aufgenommen wird.
7. Schwimmstruktur (1) nach Anspruch 1, wobei die ersten und zweiten Trägerabschnitte
(3, 4) jeweils einen Rahmen (31, 41), der eine nach unten offene Ausnehmung bereitstellt,
und einen Tragblock (32, 42) umfassen, der in der Ausnehmung fixiert ist, um vom Rahmen
(31, 41) nach unten vorzustehen.
8. Schwimmstruktur (1) nach Anspruch 7, darüber hinaus mehrere Verstärkungselemente (22)
umfassend, die auf einer Innenseite der Unterseite des Ladetanks (2) vorgesehen sind,
um sich in der Längsrichtung der Schwimmstruktur (1) parallel zueinander zu erstrecken,
wobei der Tragblock (32, 42) eine Breite (Yb) hat, die kleiner ist als ein Abstand
(Yg) zwischen zueinander benachbarten Verstärkungselementen (22).
9. Schwimmstruktur (1) nach einem der Ansprüche 1 bis 8, wobei der zweite Trägerabschnitt
(4) in Teile aufgeteilt ist, und der Eingriffsabschnitt (5) aus separaten Abschnitten
besteht.
10. Schwimmstruktur (1) nach einem der Ansprüche 1 bis 9, einen Hauptkörper (1a) umfassend,
der schwimmt, indem er von einer Auftriebskraft getragen wird, wobei der Hauptkörper
(1a) die Halterung (11) mit dem Ladetank (2) eingebaut hat, wobei
der Ladetank (2) mit der Ladetankträgerstruktur getragen wird.
1. Structure flottante (1) comprenant une citerne de charge (2) et une structure de support
de citerne de charge destinée à supporter la citerne de charge (2) montée dans un
logement (11) dans la structure flottante (1), la structure de support de citerne
de charge comprenant :
une pluralité de premières portions de support (3) prévues au niveau d'un fond (2a)
de la citerne de charge (2) de manière distribuée,
une deuxième portion de support (4) prévue au niveau d'un fond (2a) de la citerne
de charge (2), et
une portion de mise en prise (5) prévue au niveau d'un plancher (11a) du logement
(11) le long de la longueur de la deuxième portion de support (4) pour se mettre en
prise avec la deuxième portion de support (4),
sachant que lorsqu'une charge est appliquée par la citerne de charge (2), au moins
les premières portions de support (3) portent un effort vertical (Fz) et au moins
la deuxième portion de support (4) et la portion de mise en prise (5) correspondante
portent un effort horizontal (Fy) dans les deux directions de largeur de la structure
flottante (1),
et caractérisée en ce que la deuxième portion de support s'étend continuellement dans une direction longitudinale
de la structure flottante (1) et en ce que l'effort horizontal est divisé en un premier effort horizontal (Fy) dans une direction
de largeur de la structure flottante (1) et un deuxième effort horizontal (Fx) dans
la direction longitudinale de la structure flottante (1), le premier effort horizontal
(Fy) étant absorbé par la deuxième portion de support (4) et la portion de mise en
prise (5) correspondante, et le deuxième effort horizontal (Fx) étant absorbé par
les premières portions de support (3).
2. La structure flottante (1) selon la revendication 1, sachant que la deuxième portion
de support (4) est prévue le long de la ligne centrale longitudinale (L) de la structure
flottante (1).
3. La structure flottante (1) selon la revendication 1, sachant que le logement (11)
présente un plafond (11b) recouvrant la citerne de charge (2), le plafond (11b) ne
présentant pas de portion de support portant l'effort horizontal appliqué par la citerne
de charge (2).
4. La structure flottante (1) selon la revendication 1, sachant que la deuxième portion
de support (4) est apte à porter l'effort vertical (Fz) appliqué par la citerne de
charge (2).
5. La structure flottante (1) selon la revendication 4, comprenant en outre des premiers
appuis (13) et un deuxième appui (14) prévus au niveau du plancher (11a) du logement
(11), les premiers appuis (13) étant aptes à supporter les premières portions de support
(3) de manière à permettre aux premières portions de support (3) de coulisser sur
ceux-ci, et le deuxième appui (14) étant apte à supporter la deuxième portion de support
(4), sachant que la portion de mise en prise (5) est prévue au niveau du deuxième
appui (14).
6. La structure flottante (1) selon la revendication 1, comprenant en outre des portions
de mise en prise (15) prévues au niveau du plancher (11a) du logement (11) le long
de la largeur de la structure flottante (1) pour se mettre en prise avec des portions
de support correspondantes parmi les premières portions de support (3) de sorte que
le deuxième effort horizontal (Fx) soit absorbé par les portions de mise en prise
(15) et les premières portions de support (3) correspondantes.
7. La structure flottante (1) selon la revendication 1, sachant que les premières et
la deuxième portions de support (3, 4) comprennent chacune un cadre (31, 41) fournissant
un évidement ouvert vers le bas et un bloc de support (32, 42) fixé dans l'évidement
pour dépasser du cadre (31, 41) vers le bas.
8. La structure flottante (1) selon la revendication 7, comprenant en outre une pluralité
d'éléments de renfort (22) prévus d'un côté intérieur du fond de la citerne de charge
(2) pour s'étendre dans la direction longitudinale de la structure flottante (1),
parallèlement les uns aux autres, sachant que le bloc de support (32, 42) a une largeur
(Yb) inférieure à une distance (Yg) entre des éléments de renfort (22) adjacents.
9. La structure flottante (1) selon l'une quelconque des revendications 1 à 8, sachant
que la deuxième portion de support (4) est divisée en parties et la portion de mise
en prise (5) est composée de portions séparées.
10. La structure flottante (1) selon l'une quelconque des revendications 1 à 9, comprenant
un corps principal (1a) flottant en étant supporté par une force de flottaison, le
corps principal (1a) présentant le logement (11) avec la citerne de charge (2) montée
dans celui-ci, sachant que
la citerne de charge (2) est supportée au moyen de la structure de support de citerne
de charge.