EP2572976B1

EP2572976B1 - Transporting barge, floating structure installation system, and floating structure installation method

Info

Publication number: EP2572976B1
Application number: EP11783589.2A
Authority: EP
Inventors: Takayuki Sawai; Hitoshi Kumamoto
Original assignee: Mitsubishi Shipbuilding Co Ltd
Current assignee: Mitsubishi Shipbuilding Co Ltd
Priority date: 2010-05-20
Filing date: 2011-05-18
Publication date: 2021-06-16
Anticipated expiration: 2031-05-18
Also published as: CN102869568A; KR101432416B1; EP2572976A1; EP2572976A4; CN102869568B; KR20120138819A; WO2011145655A1; JP5490230B2; JPWO2011145655A1

Description

Technical Field

The present invention is related to a transportation barge, an offshore structure installation system and a method of installing an offshore structure, and especially, to a transportation barge, an offshore structure installation system and a method of installing an offshore structure, which are suitable to install a structure such as a wind turbine offshore.

Background Art

Generally, when transporting and installing a structure such as a wind turbine offshore, parts of the structure, a basis structure to install the wind turbine offshore and so on are loaded on a transportation barge which is provided with a jack-up unit, and a deck crane, and the transportation barge moves to an installation area of sea through navigation or tow.
After the movement, in the condition which jack-up legs are lowered to a sea bottom to raise the hull of the barge above the sea surface, an installation work of hoisting each part from the transportation barge by using the deck crane is carried out.
Also, when a working barge is resident in the installation area of sea, the transportation barge is jacked up in the neighborhood of the working barge, and then the parts of the wind turbine loaded on the transportation barge are hoisted by a deck crane of the working barge and are used for installation.
Patent Literature 1 (Japanese Utility Model Publication JP H07-11033Y2 ) discloses a motion reducing unit for reducing pitching and rolling operations of the structure in a ship.
Patent Literatures 2, 3, 4, 5 and 6 are further prior art.

Citation List

[Patent Literature 1] JP H07-11033Y2
[Patent Literature 2] KR 2009 0094561 A
[Patent Literature 3] US 2 934 905 A
[Patent Literature 4] JP S60 9525 A
[Patent Literature 5] GB 2 165 188 A
[Patent Literature 6] US 4 174 188 A

Summary of the Invention

However, in a conventional technique, an operation is required in which the transportation barge is moved to an installation area of sea, and then is jacked up to unload the transportation freight to fix the transportation barge.
Also, the installation area of sea for the wind turbine is far from the shore and is deep in water depth in many cases, and the wind turbine itself tends to have a larger size. For these reasons, an installation time is elongated and an installation cost is increased.
The present invention is made in view of such circumstances, and has as an object, to provide a transportation barge, and an offshore structure installation system, in which the installation time and cost can be reduced and transportation freight can be unloaded without damaging the transportation freight.
The present invention is defined by a transportation barge as recited in claim 1, and a method of installing an offshore structure as recited in claim 8. Optional features are specified in the respective dependent claims.
In order to achieve the above object, the transportation barge in the first viewpoint of the present invention is used to install a structure offshore. The transportation barge is provided with a loading platform for loading the structure. The loading platform is allowed to move up and down in the barge.
Conventionally, because the heaving of a hull of the transportation barge occurs due to waves when unloading the transportation freight from the transportation barge, the transportation barge is jacked up to the sea bottom previously and the work is carried out in a stationary condition in which the transportation barge is fixed.
Therefore, the loading platform of the transportation barge is configured to be moved up-and-down and the loading platform is moved down when hoisting the transportation freight from the loading platform.
Therefore, the influence of the heaving of the transportation barge due to waves can be eased without jacking up the transportation barge to the sea bottom. In this way, a collision of the transportation freight and the loading platform can be prevented when the transportation freight is hoisted. Also, the time for the jacking-up and the use cost of the transportation barge provided with an expensive jack-up unit can be reduced.
The transportation barge in the first viewpoint of the present invention is provided with an actuator group which drives the loading platform to move up and down. The actuator group moves the loading platform down based on a first manual operation. It is easy to control the timing of moving the loading platform down because the loading platform is moved down based on the manual operation.
It is desirable that the actuator group moves the loading platform down at timing of an upper limit of the heaving of the transportation barge. By moving the transportation barge down at the timing of the upper limit of the heaving of the transportation barge, the movement down of the transportation barge and the movement down of the loading platform by the actuator group overlap to leave the loading platform from the hoisted transportation freight promptly. Thus, the collision of the transportation freight and the loading platform can be more surely prevented.
Moreover, in the first viewpoint of the present invention, the transportation barge is further provided with an actuator control unit which automatically controls the actuator group based on the pitching or rolling operation of the transportation barge so that the motion of the loading platform can be reduced.
The pitching or rolling motion in addition to the heaving due to waves can be reduced by providing the actuator control unit for the transportation barge, and an unloading work of the transportation freight can be easily carried out.
Moreover, in the first viewpoint of the present invention, it is desirable that the transportation barge is provided with motion reducing boards which reduces the pitching and rolling motions of the transportation barge.
By providing the motion reducing boards for the transportation barge to reduce the pitching or rolling operation of the transportation barge, it is possible to ease the influence of the pitching and rolling operations in addition to the heaving due to the waves, and the unloading work of the transportation freight can be carried out easily.
The offshore structure installation system in a second viewpoint of the present invention is provided with the above transportation barge and a crane ship. The transportation barge is provided with the actuator group which drives the loading platform to move up and down. The crane ship is provided with a deck crane, an actuator operation unit which generates a first operation signal through a first manual operation and a crane operation unit which generates a second operation signal through a second manual operation. The actuator group moves the loading platform down based on the first operation signal. The deck crane hoists the transportation freight loaded on the loading platform based on the second operation signal.
Because the system is provided with the crane operation unit which generates the operation signal for the actuator group to move down the loading platform of the transportation barge and the actuator operation unit which generates the operation signal for a deck crane of the crane ship to hoist the transportation freight, the timing of moving down the loading platform and the timing of hoisting the transportation freight can be correctly adjusted, and the unloading work of the transportation freight can be carried out without damaging the transportation freight.
In the offshore structure installation system in the second viewpoint of the present invention, the transportation barge is further provided with a heaving sensor which detects the heaving of the transportation barge to output a heaving detection signal. It is desirable that the crane ship is provided with a display unit which displays the heaving of the transportation barge based on the heaving detection signal.
The heaving of the transportation barge due to the waves is detected and displayed on the display unit of the crane ship. Therefore, it is easy that the deck crane hoists the transportation freight loaded on the loading platform at the timing of the upper limit of the heaving of the transportation barge, and the actuator group moves down the loading platform at the timing of the upper limit. Accordingly, by easing the influence of the heaving of the transportation barge due to the waves, and by hoisting the transportation freight and moving down the loading platform at the timing of the upper limit, the collision of the transportation freight and the loading platform when hoisting the transportation freight can be avoided and the transportation freight can be easily unloaded.
Moreover, it is desirable that the crane ship includes a hull provided with the deck crane and a jack-up unit to support the hull on the sea bottom.
By supporting the crane ship provided with the deck crane to hoist the transportation freight to the sea bottom by the jack-up unit, the motion of the crane ship due to the waves can be eliminated and the transportation freight can be easily unloaded.
A method of installing an offshore structure in the third viewpoint of the present invention is provided with hoisting the transportation freight loaded on the loading platform of the transportation barge offshore, and moving down the loading platform when hoisting the transportation freight.
Therefore, the influence of the heaving of the transportation barge due to the waves can be eased without jacking up the transportation barge to the sea bottom. Therefore, the collision of the transportation freight and the loading platform can be prevented when hoisting the transportation freight, and the time of jacking up the transportation barge and the use cost of the transportation barge provided with the expensive jack-up unit can be reduced.
The method of installing an offshore structure is further provided with the actuator operation unit outputting a first operation signal based on a first manual operation and the crane operation unit outputting a second operation signal based on a second manual operation. The actuator group of the transportation barge moves down the loading platform based on the first operation signal in the moving down the loading platform. The deck crane of the crane ship hoists the transportation freight based on the second operation signal in the hoisting of the transportation freight. The actuator operation unit and the crane operation unit are provided for one of the transportation barge and the crane ship.
Because the actuator operation unit and the crane operation unit are provided for one of the transportation barge and the crane ship, the timing of moving down the loading platform and the timing of hoisting the transportation freight can be correctly adjusted, and the unloading work of the transportation freight can be carried out without damaging the transportation freight.
When the actuator operation unit and the crane operation unit are provided for the crane ship, it is desirable that the method of installing an offshore structure in the third viewpoint is further provided with detecting the heaving of the transportation barge and displaying the heaving of the transportation barge on a display unit of the crane ship.
It is desirable that the hoisting of the transportation freight and the moving down of the loading platform are carried out at the timing of the upper limit of the heaving of the transportation barge.
It is desirable that that the crane ship supported on the sea bottom by jack-up legs hoists the transportation freight in the hoisting of the transportation freight.
According to the present invention, the transportation barge, the offshore structure installation system and the method of installing an offshore structure are provided to prevent the collision of the transportation barge and the transportation freight when hoisting the transportation freight from the transportation barge moving up and down due to the waves.

Brief Description of the Drawings

The above object, other objects, effects and features of the present invention would be made clear from the following description of embodiments in conjunction with the following drawings:

FIG. 1 is a diagram showing an offshore structure installation system according to a first embodiment of the present invention;
FIG. 2 is a conceptual diagram showing a control system of the offshore structure installation system according to the first embodiment;
FIG. 3A is a diagram showing a procedure of a method of installing an offshore structure according to the first embodiment;
FIG. 3B is a diagram showing a procedure of a method of installing an offshore structure according to the first embodiment;
FIG. 3C is a diagram showing a procedure of a method of installing an offshore structure according to the first embodiment;
FIG. 3D is a diagram showing a procedure of a method of installing an offshore structure according to the first embodiment;
FIG. 4 is a conceptual diagram showing a control system of the offshore structure installation system according to a second embodiment of the present invention;
FIG. 5 is a conceptual diagram showing the control system of the offshore structure installation system according to a third embodiment of the present invention;
FIG. 6 is a diagram showing a transportation barge according to a fourth embodiment of the present invention;
FIG. 7 is a diagram showing the transportation barge according to a fifth embodiment of the present invention;
FIG. 8 is a diagram showing the transportation barge according to a sixth embodiment of the present invention; and
FIG. 9 is a diagram showing the transportation barge according to a seventh embodiment of the present invention.

Description of Embodiments

A transportation barge, an offshore structure installation system and a method of installing an offshore structure according to embodiments of the present invention will be described below with reference to the attached drawings.

[First Embodiment]

A first embodiment of the present invention will be described with reference to FIG. 1. The offshore structure installation system 10 is provided with a transportation barge 20 and a crane ship 40. The transportation barge 20 is provided with a hull 21, a loading platform 22 and an actuator group 23. The crane ship 40 is provided with a hull 41, a jack-up unit 42, a deck crane 43, and a crane operator room 44. The deck crane 43 and the crane operator room 44 are provided on the hull 41. The jack-up unit 42 is provided with jack-up legs 42a. The deck crane 43 is provided with a hook 43a which hoists transportation freight. The transportation barge 20 and the crane ship 40 are possible to self-navigate or be towed.
FIG. 2 is a diagram schematically showing a mechanism which hoists the transportation freight loaded on the loading platform 22 of the transportation barge 20. The transportation barge 20 is provided with an actuator control unit 24 and an actuator operation unit 25. The actuator group 23 is provided with a plurality of actuators 23A to 23D. The actuators 23A to 23D are connected with the loading platform 22 and support the loading platform 22 in a position above the hull 21. The actuator group 23 can drive the loading platform 22 to move up and down. The actuator operation unit 25 outputs an operation signal through a manual operation. The actuator control unit 24 controls the actuators 23A to 23D based on the operation signal outputted from the actuator operation unit 25. The crane ship 40 is provided with a crane operation unit 45 in the crane operator room 44. The crane operation unit 45 outputs an operation signal through a manual operation. The deck crane 43 operates based on the operation signal outputted from the crane operation unit 45.
Hereinafter, in the present embodiment, a case that a structure installed offshore by the offshore structure installation system 10 is a wind turbine will be described. However, the structure installed offshore may be a petroleum platform, a bridge pier and so on.
Referring to FIG. 1, the crane ship 40 is used for a crane work for the installation of the wind turbine. If the crane ship 40 is arranged in a desired place on a sea area for wind turbine installation, the jack-up legs 42a of the jack-up unit 42 are downed to the sea bottom to lift the hull 41 above the sea surface. In this way, the crane ship 40 is supported on the sea bottom through the jack-up legs 42a. The transportation barge 20 is used for the transportation of parts and fundamental structures of the wind turbine. The transportation freight 60 such as the parts and fundamental structures of the wind turbine is loaded on the loading platform 22. The transportation barge 20 transports the transportation freight 60 from a harbor to the sea area for wind turbine installation, and lies around the crane ship 40, desirably in a place neighboring the crane ship 40.
After that, the transportation freight is unloaded by the crane. The crane work contains a hoisting work of hoisting the transportation freight 60 from the transportation barge 20. When carrying out the hoisting work, a hoisting worker 101 and an actuator operator 102 work on the transportation barge 20 and a crane operator 103 operates the deck crane 43 in the crane operator room 44.
In the hoisting work, a slinging worker hangs the transportation freight 60 from a wire 50 with the hook 43a. Here, the slinging worker hands the transportation freight 60 from the wire 50 such that the transportation freight 60 does not rise from the loading platform 22 when the transportation barge 20 comes to a lower limit of the heaving and that the wire 50 sags when the transportation barge 20 comes to the upper limit of the heaving. The slinging worker may be the hoisting worker 101 or the actuator operator 102.
FIG. 3A is a diagram showing the transportation freight 60 and the wire 50 when the transportation barge 20 came to the lower limit of the heaving. FIG. 3B is a diagram showing the transportation freight 60 and the wire 50 when the transportation barge 20 came to the upper limit of the heaving. Because the crane ship 40 is supported to the sea bottom through the jack-up legs 42a, the hook 43a does not move up and down due to waves. When the transportation barge 20 comes to the lower limit of the heaving, the wire 50 stretches such that the transportation freight 60 does not rise from the loading platform 22. When the transportation barge 20 comes to the upper limit of the heaving, the wire 50 sags.
The hoisting worker 101 gives a sign by using an instruction tool such as a flag, a whistle or a transceiver at the timing when the transportation barge 20 comes to the upper limit of the heaving. The crane operator 103 carries out the manual operation to the crane operation unit 45 according to the sign from the hoisting worker 101. The crane operation unit 45 outputs the operation signal based on the manual operation of the crane operator 103. The deck crane 43 hoists or lifts the transportation freight 60 based on the operation signal outputted from the crane operation unit 45. The actuator operator 102 carries out the manual operation to the actuator operation unit 25 according to the sign of the hoisting worker 101. The actuator operation unit 25 outputs the operation signal based on the manual operation of the actuator operator 102. The actuator control unit 24 controls the actuator group 23 such that the actuator group 23 lowers the loading platform 22 based on the operation signal outputted from the actuator operation unit 25.
Therefore, as shown in FIG. 3C, at the timing when the transportation barge 20 comes to the upper limit of the heaving, the transportation freight 60 is hoisted up, and the loading platform 22 is lowered or moved down. As a result, as shown in FIG. 3D, the heaving of the hull 21 due to the waves is eased and a sufficient distance is promptly kept between the transportation freight 60 and the loading platform 22. Thus, when the transportation freight 60 is hoisted, the collision of the transportation freight 60 and the loading platform 22 due to the heaving can be prevented. Moreover, it is possible to prevent that the transportation freight 60 and the loading platform 22 collide at the timing of the upper limit of the next heaving after the transportation freight 60 is hoisted.
According to the transportation barge 20, the offshore structure installation system 10 and a method of installing an offshore structure in the present embodiment, the collision of the transportation freight 60 and the transportation barge 20 can be prevented when the transportation freight 60 is hoisted from the transportation barge 20 which moves up and down due to the waves. The work steps can be reduced in the transportation barge 20, the offshore structure installation system 10 and the method of installing a offshore structure according to the present embodiment, compared with a case where the transportation freight 60 is lifted in the condition which the transportation barge 20 has been jacked up and a case where the transportation barge 20 is used for both of the transportation of the transportation freight 60 and the crane work. Because the work steps for raising and falling the jack-up legs of the jack-up unit can be reduced, the transportation barge 20, the offshore structure installation system 10, and the method of installing an offshore structure according to the present embodiment are favorable especially when the structure such as the wind turbine is installed in the sea area with deep water depth. Moreover, because the transportation barge 20 is not required to be provided with the expensive jack-up unit, the chartered vessel cost of the transportation barge 20 can be reduced.

[Second Embodiment]

The offshore structure installation system 10 and the method of installing an offshore structure according to a second embodiment of the present invention will be described with reference to FIG. 4. The offshore structure installation system 10 and the method of installing an offshore structure according to the present embodiment are different from those of the first embodiment in the following point, and are the same as those of in the other points.
The transportation barge 20 is provided with a pitching sensor 27 and a rolling sensor 28. Each of the pitching sensor 27 and the rolling sensor 28 is provided with an accelerometer or a draft gauge. The pitching sensor 27 detects a pitching operation of the hull 21 and outputs a pitching detection signal. The rolling sensor 28 detects a rolling operation of the hull 21 and outputs a rolling detection signal. The actuator control unit 24 automatically controls the actuator group 23 to reduce the motion of the loading platform 22 based on the pitching detection signal and the rolling detection signal. When receiving the operation signal outputted from the actuator operation unit 25, the actuator control unit 24 controls the actuator group 23 to stop the automatic control for reducing the motion of the loading platform 22, and to lower the loading platform 22. Or, the actuator control unit 24 may carry out both of the automatic control for reducing the motion of the loading platform 22 and the lowering control of the loading platform 22 in response to the operation signal outputted from the actuator operation unit 25.
According to the present embodiment, because the pitching operation and rolling operation of the loading platform 22 are reduced, it is possible to carry out the hoisting operation more easily.

[Third Embodiment]

The offshore structure installation system 10 and the method of installing an offshore structure according to a third embodiment of the present invention will be described with reference to FIG. 5. The offshore structure installation system 10 and the method of installing an offshore structure according to the present embodiment are different from those of the first embodiment in the following points, and are the same as those of the first embodiment in the other points.
The transportation barge 20 is provided with a heaving sensor 26 which outputs a heaving detection signal, when detecting the heaving of the transportation barge 20 (e.g. the hull 21). The heaving sensor 26 is provided with an accelerometer or a draft gauge. The crane ship 40 is provided with an actuator operation unit 46 and a display unit 47. The actuator operation unit 46 and the display unit 47 are provided in the crane operator room 44. The display unit 47 receives the heaving detection signal outputted from the heaving sensor 26 in wired or wireless communication, and displays the heaving of the transportation barge 20 (e.g. the hull 21) to the crane operator 103 based on the heaving detection signal. For example, the display unit 47 is an oscilloscope. The actuator operation unit 46 outputs the operation signal through the manual operation. The actuator control unit 24 receives the operation signal outputted from the actuator operation unit 46 in the wired or wireless communication.
The crane operator 103 determines the timing of the upper limit of the heaving of the transportation barge 20 based on the heaving of the transportation barge 20 displayed on the display unit 47, and carries out a manual operation to the crane operation unit 45 and the actuator operation unit 46 at the determined timing. The operation of crane operation unit 45 based on the manual operation of the crane operator 103 and the working of the deck crane 43 are same as described in the first embodiment. The actuator operation unit 46 outputs the operation signal based on the manual operation of the crane operator 103. The actuator control unit 24 controls the actuator group 23 to move down the loading platform 22 based on the output operation signal outputted from the actuator operation unit 46.
According to the present embodiment, because the hoisting operation of the transportation freight 60 and the lowering operation of the loading platform 22 are carried out with the manual operations in the same crane operator room 44, it is easy to adjust the timing of the lifting operation of the transportation freight 60 and the timing of the lowering operation of the loading platform 22.
It should be noted that another crane operation unit (not shown) different from the crane operation unit 45 may be provided near the actuator operation unit 25, and the hoisting operation of the transportation freight 60 and the lowering operation of the loading platform 22 may be carried out based on the manual operation of the actuator operator 102. Moreover, the actuator control unit 24 may execute the same control as the second embodiment.

[Fourth Embodiment]

The transportation barge 20 according to a fourth embodiment of the present invention will be described with reference to FIG. 6. The transportation barge 20 according to the present embodiment, another loading platform 22 and another actuator group 23 are added to the transportation barge 20 according to either of the first to third embodiments. The other loading platform 22 and the other actuator group 23 are configured and work in the same manner as the loading platform 22 and the actuator group 23. Other transportation freight 60 is loaded on the other loading platform 22.
According to the present embodiment, because the loading platform 22 is provided for each of transportation freights 60, the hoisting operation becomes easy.

[Fifth Embodiment]

The transportation barge 20 according to a fifth embodiment of the present invention will be described with reference to FIG. 7. The transportation barge 20 according to the present embodiment is provided with swinging motion reducing plates 29 to the transportation barge 20 according to either of the first to fourth embodiments. The swinging motion reducing plates 29 project from the hull 21 in front and back directions to reduce the pitching operation of the transportation barge 20 or project from the hull 21 to left and right directions to reduce the rolling operation of the transportation barge 20. According to the present embodiment, because the pitching operation or rolling operation of the transportation barge 20 is reduced, the hoisting work becomes easy. It should be noted that the swinging motion reducing plates 29 may be provided to reduce both the pitching operation and the rolling operation.

[Sixth Embodiment]

The transportation barge 20 according to a sixth embodiment of the present invention will be described with reference to FIG. 8. The transportation barge 20 according to the present embodiment has a ship shape different from that of the transportation barge 20 according to either of the first to fifth embodiments. The transportation barge 20 according to the present embodiment has a hull 21 of a SWATH (Small Waterplane Area Twin Hull) type. According to the present embodiment, because the amplitude of the heaving of the transportation barge 20 becomes small, the hoisting work becomes easy.

[Seventh Embodiment]

The transportation barge 20 according to a seventh embodiment of the present invention will be described with reference to FIG. 9. The transportation barge 20 according to the present embodiment has a ship shape different from that of the transportation barge 20 according to either of the first to fifth embodiments. The transportation barge 20 according to the present embodiment has a hull 21 of a semi-sub (Semi-Submersible) type. According to the present embodiment, because the amplitude of the heaving of the transportation barge 20 becomes small, the hoisting work becomes easy.
In the above, the transportation barge, the offshore structure installation system and the method of installing an offshore structure according to the embodiments of the present invention have been described. However, the present invention is only limited by the following claims.

Claims

A transportation barge (20) for installing a structure offshore, wherein the transportation barge is provided with a hull (21) and a loading platform (22) which is supported in a position above the hull (21) and on which the structure can be loaded in said transportation barge, wherein the loading platform is movable up and down, wherein
said transportation barge comprises
an actuator group (23) which is configured to drive said loading platform to move up and down with respect to the hull (21),

a pitching sensor (27) configured to detect a pitching motion of the hull (21) and output a pitching detection signal, and

a rolling sensor (28) configured to detect a rolling motion of the hull (21) and output a rolling detection signal,
said actuator group is configured to move down said loading platform (22) with respect to the hull (21) based on a first manual operation when the structure is hoisted, and
the transportation barge further comprises an actuator control unit (24) configured to automatically control said actuator group based on the pitching detection signal and/or the rolling detection signal such that the pitching motion and/or the rolling motion of said loading platform (22) is reduced.
The transportation barge according to claim 1, wherein said actuator group is further configured to move down said loading platform at a timing of an upper limit of a heaving of said transportation barge.
The transportation barge according to claim 1 or 2, further comprising swinging motion reducing plates (29) provided to reduce a pitching motion or a rolling motion of said transportation barge.
An offshore structure installation system comprising:
a transportation barge according to any one of the preceding claims; and

a crane ship,

wherein said crane ship comprises:
a deck crane;

an actuator operation unit (25) configured to generate a first operation signal through the first manual operation; and

a crane operation unit configured to generate a second operation signal through a second manual operation,

wherein said deck crane hoists the structure loaded on said loading platform based on the second operation signal.
The offshore structure installation system according to claim 4,
wherein said transportation barge comprises a heaving sensor configured to detect a heaving of said transportation barge to output a heaving detection signal, and
wherein said crane ship comprises a display unit configured to display the heaving of said transportation barge based on the heaving detection signal.
The offshore structure installation system according to claim 4,
wherein said deck crane is configured to hoist the transportation freight loaded on said loading platform at timing of an upper limit of the heaving of said transportation barge, and
wherein said actuator group is configured to move down said loading platform at the timing of the upper limit.
The offshore structure installation system according to any of claims 4 to 6, wherein said crane ship comprises:
a hull on which said deck crane is provided; and

a jack-up unit which supports said hull on a sea bottom.
A method of installing an offshore structure, comprising:
hoisting a transportation freight (60) loaded on a loading platform (22) of a transportation barge (20) offshore; and

moving down said loading platform when hoisting the transportation freight,

outputting a first operation signal from an actuator operation unit (25, 46) based on a first manual operation; and

outputting a second operation signal from a crane operation unit (45) based on a second manual operation,

wherein said moving down comprises moving down said loading platform by an actuator group (23) of said transportation barge based on the first operation signal,

wherein said hoisting comprises hoisting the transportation freight by a deck crane (43) of a crane ship (40) based on the second operation signal, and

wherein said actuator operation unit and said crane operation unit are provided for one of said transportation barge and said crane ship,

wherein said method further comprises

using a pitching sensor (27) of the transportation barge to detect a pitching motion of the hull (21) and output a pitching detection signal,

using a rolling sensor (28) of the transportation barge to detect a rolling motion of the hull (21) of the transportation barge and output a rolling detection signal, and

using an actuator control unit (24) of the transportation barge to automatically control said actuator group (23) based on the pitching detection signal and/or the rolling detection signal such that the pitching motion and/or the rolling motion of said loading platform (22) is reduced.
The method according to claim 8, wherein said actuator operation unit and said crane operation unit are provided for said crane ship, and
wherein said method further comprises:
detecting a heaving of said transportation barge; and

displaying the heaving of said transportation barge on a display unit (47) of said crane ship.
The method according to any of claims 8 and 9, wherein said hoisting and said moving down are carried out at a timing of an upper limit of the heaving of said transportation barge.
The method according to claim 8, wherein said hoisting comprises hoisting the transportation freight by a crane ship supported on a sea bottom through jack-up legs (42a).