Floating offshore platform and its assembly

Abstract

This relates to a set including a floating offshore platform and assembly tools for assembling the floating offshore platform. The floating offshore platform comprises a central column, a number of peripheral columns extending circumferentially around the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons stretched between each pair of adjacent peripheral columns. The peripheral columns are equipped with a tendon receiving section with a tool dock, shim chamber, and tendon passage. The assembly tool comprises a tool connector, a tendon tensioning device, and a tension shim installer. The tendon tensioning device is equipped with a tendon tensile device.

Description

Background Art

[0001] The present invention relates to a floating ocean platform comprising a central column, a plurality of peripheral columns extending circumferentially around the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons stretched between each pair of adjacent peripheral columns. This type of floating ocean platform can be used as a foundation for a floating wind turbine for offshore power generation.

Summary of the Invention

[0002] Each component of the floating ocean platform is manufactured at different locations and may be transported to an integrated base at a port. The tendons are installed at the final stage and prestressed. At this stage, the tendons need to absorb the difference between the nominal length and the actual required length between the peripheral columns. Therefore, the installation and prestressing of the tendons are complex operations, and a large-scale and rapid pace is required to meet the increasing demand for floating wind turbines. For this reason, the central column, peripheral columns, outriggers, and tendons are manufactured with strict tolerances to achieve a reasonable assembly time for the floating ocean platform.

[0003] [[ID=十六]]

[0004] According to a first aspect, the present invention provides a set including a floating ocean platform and an assembly tool for assembling the floating ocean platform. The floating ocean platform comprises a central column, a plurality of peripheral columns extending circumferentially around the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons stretched between each pair of adjacent peripheral columns. The peripheral columns comprise a peripheral wall and tendon receiving portions on the peripheral wall for receiving tendon ends. The tendons comprise an elongated tube and tension heads provided at the ends of the elongated tube. ​The tendon receiving portion comprises a receiving portion frame and a tool dock on the receiving portion frame, the receiving portion frame connecting the shim chamber and the tendon passage and having a tension surface facing the shim chamber. The tension head is enclosed within the shim chamber, and a slender tube extends through the tendon passage. The floating offshore platform includes tension shims inserted into shim chambers between the tension head and the tension surface. Here, the assembly tool comprises a tool frame, a tool connector on the tool frame for engaging with a tool dock and connecting the tool frame to a receiving frame, a tendon tensioning device, and a tension shim installer, wherein the tendon tensioning device comprises a tendon tensile device for engaging with a tendon, the tendon tensile device is movable relative to the tool frame in the elongated direction of the elongated tube over a pre-tensioning stroke, and the tension shim installer comprises a tension shim holder for a tension shim, the tension shim holder is movable relative to the tool frame in a direction perpendicular to the elongated direction of the elongated tube over an installation stroke, and the tension shim is installed in a gap formed or expanded between the tensioning head and the tensioning surface.

[0005] The present invention provides an assembly tool comprising a tool connector that engages with a tool dock of a tendon receptacle, a tendon tensioning device that applies pretension to the tendon, and a tension shim installer for inserting a tension shim between the tension head and the tension surface to maintain pretension. The positions of the tool dock, tool connector, tendon tensioning device, and tension shim installer are clearly defined by a common tool frame, and therefore their positions relative to the tendon receptacle and tendon end are also clearly defined. This allows for rapid large-scale assembly of such floating offshore platforms. Furthermore, the assembly tool is applicable at integration sites, port of operation, or even when the floating offshore platform is already floating in the water. The assembly tool is remotely operable, safe, and particularly useful when used underwater.

[0006] In one embodiment, the tendon comprises a tool engagement head positioned at a distance from the tension head on an elongated tube, and the tendon tensile device comprises a contact body for contacting the tool engagement head. Since the engagement for pre-tensioning the tendon is performed at a distance from the tension head, it does not interfere with the tension head and the tension surface between them where tension shims need to be installed. The portion of the tendon between the tool engagement head and the tension head can remain free from bending moments even when a high pre-tensioning load is applied.

[0007] In one embodiment, the tool dock and tool connector comprises a tool slot and an insertion wall for inserting the elongated tube into the tool slot in an insertion direction perpendicular to the longitudinal direction. In practice, since the peripheral column is upright and the tendon extends horizontally, the cooperation of the tool slot and the insertion wall allows the assembly tool to be lowered onto the tendon receiving portion and the tool connector to engage with the tool dock.

[0008] In one embodiment, the tendon tensioning device includes a first actuator between the tendon tensioning device and the tool frame for moving the tendon tensioning device over a pre-tensioning stroke.

[0009] In one embodiment, the tension shim installer includes a second actuator between the tension shim holder and the tool frame for moving the tension shim holder over the mounting stroke.

[0010] Preferably, the set includes remote controllers for the first and second actuators, thereby allowing the assembly tool to be controlled from a safe distance, especially when the assembly tool is used underwater, without the need for human divers.

[0011] In one embodiment, the receiving frame comprises two spaced-apart opposing tension walls that define the tendon passage and form a tension surface.

[0012] In one embodiment, the shim chamber and tendon passage are open on one side to receive the tendon in the receiving direction of the tendon receptacle.

[0013] In one embodiment, by orienting the tendon receiving portion downwards and receiving the end of the tendon from above, the end of the tendon can be wrapped up inside the tendon receiving portion.

[0014] In one embodiment, the tension shim comprises a tension shim plate having an elongated tension shim slot that opens at the edge of the tension shim plate and defines the direction of reception to the tension shim, and an elongated tube extends through the tension shim slot of the inserted tension shim.

[0015] In one embodiment, the tension shim slot extends through the center of the tension shim plate.

[0016] In one embodiment, the floating offshore platform is equipped with tolerance shims in series with tension shims inserted between the tension head and tension surface in the shim chamber, along the longitudinal direction of the elongated tube. These tolerance shims can be used to minimize play between the tendon receptors at both ends of the tendon and the tendon itself, before the tendon has been pre-tensioned. From this state, pre-tensioning can be applied with high precision by an assembly tool. These tolerance shims allow the components of the floating offshore platform to be manufactured within reasonable tolerances commonly applied in shipyards and offshore manufacturing plants, while simultaneously achieving the specified tendon pre-tensioning.

[0017] In this embodiment, the tolerance shim comprises a tolerance shim plate having an elongated tolerance shim slot that opens at the edge of the tolerance shim plate and defines the direction of reception to the tolerance shim, and the elongated tube extends through the tolerance shim slot.

[0018] In one embodiment, the tolerance shim slot extends through the center of the tolerance shim plate.

[0019] In one embodiment, the tension shim comprises a tension shim plate with an elongated tension shim slot that opens at the edge of the tension shim plate and defines the direction of reception to the tension shim, and the elongated tube extends through the tension shim slot of the inserted tension shim, and the floating offshore platform comprises a tolerance shim in series with the tension shim in the longitudinal direction of the elongated tube between the tension head and the tension surface in the shim chamber, and the tolerance shim comprises a tolerance shim plate with an elongated tolerance shim slot that opens at the edge of the tolerance shim plate and defines the direction of reception to the tolerance shim, and the elongated tube extends through the tolerance shim slot, and the inserted tension shim and tolerance shim completely enclose the elongated tube behind the tension head. The interlocking tension shim and tolerance shim hold the tendon end within the tendon receiving portion. The tension shim and tolerance shim can be the same shape and thickness to reduce the number of parts that must be provided on site.

[0020] In one embodiment, the direction of reception to the tension shim is opposite to and aligned with the direction of reception to the tolerance shim.

[0021] In one embodiment, the inserted tension shim and tolerance shim are attached to the receiving frame, so that the tension head itself can absorb any bending of the elongated tube relative to the tendon receiving portion.

[0022] According to a second aspect, the present invention provides a method for assembling a floating offshore platform. The platform comprises a central column, a number of peripheral columns extending circumferentially around the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons stretched between each pair of adjacent peripheral columns. Each peripheral column comprises a circumferential wall and tendon receiving portions on the circumferential wall for receiving tendon ends. Each tendon comprises an elongated tube and tension heads provided at the ends of the elongated tubes. The tendon receiving portion comprises a receiving portion frame that surrounds the shim chamber and the tendon passage, and has a tension surface facing the shim chamber. The tension head is enclosed within the shim chamber, and a slender tube extends through the tendon passage. The floating - type ocean platform has a tension shim and a tolerance shim provided in series in a shim chamber between a tension head and a tension surface. The tension shim includes a tension shim plate having an elongated tension shim slot that opens at the edge of the tension shim plate to define the receiving direction into the tension shim. The tolerance shim includes a tolerance shim plate having an elongated tolerance shim slot that opens at the edge of the tolerance shim plate to define the receiving direction into the tolerance shim. The elongated tube extends through a tendon passage, a tolerance shim slot, and a tension shim slot. The shim chamber and the tendon passage are open on one side to receive a tendon in the receiving direction of the tendon receiving portion. The method includes inserting a tolerance shim into the shim chamber, orienting the receiving direction of the tolerance shim to be the same as the receiving direction of the tendon receiving portion, and lowering an end of the tendon into the tendon receiving portion. The tension head is received in the shim chamber, and the elongated tube is received in the tolerance shim slot and the tendon passage. Pre - tensioning an extension tube in the extension direction with respect to the tendon receiving portion, wherein a gap is formed or enlarged between the tension head and the tension surface. Inserting a tension shim into the gap, wherein the elongated tube is received in the tension shim slot, and the tolerance shim and the tension shim together completely surround the elongated tube behind the tension head.

[0023] The tolerance shim installed in the first step can be used to minimize the play between the tension head and the tendon receiving portions at both ends of the tendon when the tendon has not yet been pre - tensioned. From this state, high - precision pre - tensioning can be performed in the next step. With the tolerance shim, the components of the floating - type ocean platform can be manufactured within reasonable tolerances commonly applied in shipyards and offshore manufacturing plants, and at the same time, the pre - tension of the tendon can be obtained as specified. As described above, the cooperating tension shim and tolerance shim fix the end of the tendon within the tendon receiving portion.

[0024] In one embodiment, the method further includes attaching the tension shim and the tolerance shim to a receiving frame.

[0025] In one embodiment, the receiving direction into the tension shim is opposite to and aligned with the receiving direction into the tolerance shim.

[0026] In one embodiment, the tolerance shims are inserted into the tendon receiving portions at both ends of the tendon, and the tolerance shims at both ends have a longitudinal cumulative thickness corresponding to the play between the tension head in the longitudinal direction of the tendon tube and their nearest tension surfaces.

[0027] In one embodiment, this method is carried out using an assembly tool, the tendon receiving portion has a tool dock on the receiving frame, the assembly tool includes a tool frame, a tool connector on the tool frame for engaging the tool dock to connect the tool frame to the receiving frame, a tendon tensioning device, and a tension shim installer. The tendon tensioning device includes a tendon tensioning device for engaging the tendon when the tension head is accommodated in the shim chamber. The tension head is movable relative to the tool frame in the elongated direction of the elongated tube over a pre-tensioning stroke. The tension shim installer includes a tension shim holder for the tension shim, and the tension shim holder is movable relative to the tool frame in a direction transverse to the elongated direction of the elongated tube over an installation stroke. This method includes the step of engaging the tool dock to the tool connector using the tendon tensioning device. Pre-tension the elongated tube relative to the tendon receiving portion to form or expand a gap, and install the tension shim into the gap by the tension shim installer.

[0028] The various aspects and features described and shown herein can be applied individually as much as possible. These individual aspects, particularly the aspects and features described in the appended dependent claims, can be the subject of a divisional patent application.

Brief Description of the Drawings

[0029] The present invention will be described based on exemplary embodiments shown in the accompanying drawings. [Figure 1] FIG. 1 is an isometric view of a floating ocean platform supporting a wind turbine. [Figure 2] Figure 2 is an isometric view showing only the relevant parts of the floating offshore platform. [Figure 3A] Figure 3A shows isometric, top, and exploded views of one of the surrounding columns of the floating offshore platform shown in Figure 2. [Figure 3B] Figure 3B shows isometric, top, and exploded views of one of the surrounding columns of the floating offshore platform shown in Figure 2. [Figure 3C] Figure 3C shows isometric, top, and exploded views of one of the surrounding columns of the floating offshore platform shown in Figure 2. [Figure 4] Figure 4 shows isometric and top views of the assembly tool according to the present invention for assembling a floating offshore platform on the surrounding columns shown in Figures 3A to 3C. [Figure 5] Figure 5 is an isometric view showing the subsequent steps of assembly using the assembly tools shown in Figures 4A and 4B. [Figure 6] Figure 6 is an isometric view showing the subsequent steps of assembly using the assembly tools shown in Figures 4A and 4B. [Figure 7] Figure 7 is an isometric view showing the subsequent steps of assembly using the assembly tools shown in Figures 4A and 4B. [Modes for carrying out the invention]

[0030] Figure 1 shows a floating offshore platform 1 in which a wind turbine 300 is supported to form a floating wind turbine 5 in this example. The wind turbine 300 has a vertical tower 301, a nacelle 302, and a rotor 303. The rotor 303 has a hub 304 connected to a generator in the nacelle 302. The wind turbine 300 and in this example have three blades 305 that radiate from the hub 304. The wind turbine 300 can produce more than 1 MW of power, and currently reaches about 10-15 MW. The bottom diameter of the tower 301 may be 5-10 meters for wind turbines exceeding 10 MW. The three blades 305 may each be more than 100 meters long. An example is General Electric's 12 MW Haliade X turbine. Other turbine designs, such as vertical-axis wind turbines, can also be supported by the floating offshore platform 1.

[0031] Figure 2 shows the floating offshore platform 1 with the wind turbine 300, walkways, handrails, and attached equipment removed to illustrate part of the manufacturing process of the structural components.

[0032] As shown in Figure 2, the floating offshore platform 1 comprises a steel central column 10. The central column 10 has a vertical cylindrical upper perimeter wall 11 closed by an upper wall 17, which in this embodiment is connected downwards via a flared wall or a conically expanding intermediate perimeter wall 12 to form a vertical cylindrical lower perimeter wall 13, the lower part of which is closed by a bottom wall 14 to define an interior chamber 16. The diameter of the upper perimeter wall 11 of the central column 10 is approximately equal to the diameter of the base of the tower 301, and the diameter increases toward the base or keel of the central column 10 via the conically expanding intermediate perimeter wall 12. The central column 10 may be provided with a larger diameter foundation (not shown) below the bottom wall 13, thereby increasing its volume. If the foundation is filled with air, it helps to support the weight of the wind turbine 300. If the foundation is filled with water, the stability of the floating wind turbine 5 is improved. Alternatively, the central column 10 has a vertical cylindrical wall with a constant diameter along its entire height, which is preferably approximately equal to the diameter of the base of the tower 301.

[0033] In this example, the floating offshore platform 1 comprises three vertical cylindrical stabilizing columns or peripheral columns 30 made of steel. The peripheral columns 30 are arranged radially around the central column 10 at 120-degree intervals. Each peripheral column 30 has a vertical cylindrical peripheral wall 31 with a central axis A, and the upper side of the peripheral wall 31 is closed by an upper wall 32, forming an interior chamber 34. Inside the interior chamber 34, the peripheral column 30 has a watertight flat section just below the mean draft, and the interior chamber 34 is open to the sea from this watertight flat section. The peripheral columns 30 have a skirt 33 around the lower edge of the peripheral wall 31, and a plurality of radially extending reinforcing plates 35 are provided between the peripheral wall 31 and the skirt 33. The skirt 33 extends laterally with respect to the central axis A of the peripheral wall 31.

[0034] The floating offshore platform 1 includes three outriggers 50 that extend radially between a central column 10 and surrounding columns 30. The outriggers 50 are made of steel and consist of an upper tubular member 51 and a lower tubular member 52, in this example extending parallel to each other and interconnected by diagonal braces 53. Alternatively, at least one of the upper tubular member 51 and the lower tubular member 52 may be oblique to the other. Alternatively, the upper tubular member 51 and the lower tubular member 52 are separate members not interconnected by braces. The upper tubular member 51 and the lower tubular member 52 are connected to the central column 10 and surrounding columns 50 by flange joints, welding, or other rigid joints.

[0035] The floating offshore platform 1 comprises three pre-tensioned elongated superstructure members or tendons 60 of the same length that connect the upper ends of the perimeter columns 30 to each other, and three pre-tensioned elongated substructure members or tendons 65 of the same length that connect the lower ends of the perimeter columns 30 to each other at the skirt 33. The tendons 60, 65 are embodied as steel pipes, and all of their opposite ends are connected to the perimeter columns 30 in the same manner as the lower tendons 65 and the perimeter columns 30 as will be described in detail below, as shown on the right side of the drawing.

[0036] The base diameter of the central column 10 is a maximum of 20 meters. The total height of the central column 10 and the surrounding columns 30 is typically 20 to 30 meters, and in this example, it is approximately 24 meters. The diameter of the surrounding columns 30 is 6 to 12 meters. The lengths of the tendons 60 and 65 are 60 to 90 meters, respectively.

[0037] As best illustrated in Figure 3C for the lower tendon 65, each tendon 60, 65 is housed in the same manner in the tendon receiving section 40 on the connecting peripheral column 30 according to the present invention. The connection for the lower tendon 65 will be described below, but it should be emphasized that the upper tendon 65 is also connected to the peripheral column 30 in the same or similar manner according to the present invention. The tendon receiving section 40 comprises a receiving section frame 41 having two parallel side walls 42 formed of steel plates welded to the peripheral wall 31 on one side, and an optional bottom wall 44 formed of steel plates welded to the side walls 42 and the peripheral wall 31, optionally crossing the side walls 42. In the case of the lower tendon 65, the bottom wall 44 is formed by a portion of the skirt 33. The tendon receiving section 40 comprises two tension walls 43 formed of steel plates extending parallel to the central axis A in the same plane. The tension wall 43 is welded to the side wall 42 and the bottom wall 44, extending parallel to the central axis A of the circumferential wall 31 and defining a tendon passage 46 that is open on the upper side. The tension wall 43, the side wall 42, the circumferential wall 31, and optionally the bottom wall 44 together define a shim chamber 45, where the tension wall 43 forms a tension surface facing the shim chamber 45. On the opposite side, the tension wall 43, the side wall 42, and optionally the bottom wall 44 define a tendon tensioning device chamber 50, where the bottom wall 44 may have a bottom opening 47 spaced between the tension wall 43 and the side wall 42. The tendon receiving section 40 is open from above to receive the lower tendon 65 in a downward receiving direction D parallel to the central axis A of the circumferential wall 31.

[0038] The tendon receiving section 40 is provided with a tool dock 71 on the outside of the side wall 42. The tool dock 71 has a first dock wall 72 on each side, which may be formed from the same plate as the adjacent tension wall 43. On each side of the tool dock 71 is a short second dock wall 73 extending parallel to and spaced apart from the first dock wall 72, defining a tool slot 75 between them that extends parallel to the central axis A of the circumferential wall 31, and a catch wall 74 that converges into the tool slot 75 at an angle to the second dock wall 73. The first dock wall 72, the second dock wall 73 and the catch wall 74 are made of steel plate and are welded to their respective side walls 42.

[0039] The lower tendon 65 is made of steel and consists of an elongated tube 66 with a hollow cylindrical cross-section having a central axis B. The outer diameter of the elongated tube 66 is 300 to 600 millimeters, and the nominal wall thickness is 15 to 35 millimeters, with locally increasing thickness of 30 to 60 millimeters at the connection points. The lower tendon 65 includes tension heads 67 provided at both ends of the elongated tube 66, which has a circular cross-section and projects radially from the elongated tube 66, and tool engagement heads 68 provided at both ends of the elongated tube 66, which have a circular cross-section and are spaced apart from the tension heads 67. The tension heads 67 of the lower tendon 65 are housed in a shim chamber 45, the tool engagement heads 68 are housed in a tendon tensioning device chamber 50, and the head shaft portion 69 of the elongated tube 66 extending between them is housed in a tendon passage 46.

[0040] The floating offshore platform 1 includes a tolerance shim 80 housed in a shim chamber 45. The tolerance shim 80 is made of a steel plate and includes two parallel side edges 81 that extend parallel to the side wall 42 and fit between them to abut against two tension walls 43, a bottom edge 82 that abuts against the bottom wall 44, an upper edge 85, and an elongated slot 84 that opens upward in the center of the upper edge 85 to receive the head shaft portion 69 between the tension head 67 and the tool engagement head 68 within the tolerance shim 80.

[0041] The floating offshore platform 1 includes a tension shim 90 sandwiched between a tolerance shim 80 and a tension head 67 in a shim chamber 45. The tension shim 90 is made of steel plate and includes two parallel side edges 91 extending parallel to the side wall 42 and fitting between them, an upper edge 92, a bottom edge 93 that abuts against the bottom wall 44, and an elongated slot 94 that opens downward in the center of the bottom wall 93 and receives the head shaft portion 69 into the tension shim 90 from the receiving direction. Both the tolerance shim 80 and the tension shim 90 are U-shaped and have the same external dimensions, and they abut each other along their respective side edges 81, 91. The tolerance shim 80 and the tension shim 90 are located in elongated slots 84 and 94, which are aligned in a straight line with the central axis A of the peripheral wall 31 and oriented parallel to each other in opposite directions, upward and downward, so that together they completely enclose the head shaft section 69.

[0042] The tension shim 90 is attached by the assembly tool 100, as best shown in Figures 4A and 4B. The assembly tool 100 comprises two parallel side walls 103, a rear wall 106 with a downwardly opening central opening 107 located between the side walls 103, a tool connector 110 having two insertion walls 111 in the same vertical plane projecting inward from the side walls 103, and a bridge 112 having a central slot 113 and connecting the insertion walls 111 to each other on the upper side. The side walls 103, rear wall 106, insertion walls 111, and bridge 112 are made of steel plates welded to each other. The insertion walls 111 fit inside the tool slot 75 of the tendon receptacle 40, thereby allowing the assembly tool 100 to connect to the tendon receptacle 40 by vertical movement in a direction G parallel to the central axis A of the circumferential wall 31 or in a direction G perpendicular to the central axis B of the lower tendon 65.

[0043] The assembly tool 100 includes a tendon tensioning device 120 within the tool frame 101. The tendon tensioning device 120 comprises a tendon tensioning device 121 formed from a steel plate and having a downwardly opening central opening 122, and a steel contact body 123 along the central opening 122. The tendon tensioning device 120 includes two first linear guides 125, which are driven by two pairs of first hydraulic cylinders 127 between the tool frame 101 and the tendon tensioning device 121, and guide the reciprocating sliding motion of the tendon tensioning device 121 in a linear sliding direction E that crosses the central axis A of the circumferential wall 31 or is parallel to the central axis B of the lower tendon 65 over the pre-tensioning stroke.

[0044] The assembly tool 100 includes a tension shim mounting device 130 in front of the insertion wall 111. The tension shim mounting device 130 includes a tension shim holder 131 for receiving and holding a tension shim 90, and two second linear guides 135 for guiding the tension shim holder 131 to reciprocate and slide over an installation stroke in a linear sliding direction F parallel to the central axis A of the circumferential wall 31, or in a linear sliding direction F perpendicular to the central axis B of the lower tendon 65. This installation stroke is driven by a pair of second hydraulic cylinders (not shown). The first hydraulic cylinder 127 of the tendon tensioning device 120 and the second hydraulic cylinder of the tension shim mounting device 130 are remotely operated or connected to a remotely controlled hydraulic power pack. The entire assembly tool 100 can be suspended by a lifting cable. Thus, the assembly tool 100 can be controlled from a safe distance, especially when the assembly tool 100 is used underwater.

[0045] The floating offshore platform 1 is a modular structure, and the central column 10, peripheral columns 30, outriggers 50, and tendons 60, 65 are manufactured within reasonable tolerances commonly applied in shipyards or offshore manufacturing plants. Since tendons 60, 65 are installed after the outriggers 50 are connected to the central column 10 and peripheral columns 30, they need to accommodate the difference between the nominal length and the actual required length. This difference may be 500 millimeters or less. Because these differences can be accommodated, the allowable manufacturing tolerances of the other components remain reasonable. The tendons 60, 65 can also be reinstalled in the water at site during the service life of the moored floating offshore platform 1, for example, to extend the service life, or if tendons 60, 65 are lost or damaged. The lower tendon 65 is considered to be located approximately 10-15 meters below the water surface.

[0046] The assembly method of the floating ocean platform 1, particularly the method of installing the lower tendon 65 using the assembly tool 100, is shown in Figures 3C and 5-7. The installation of the upper tendon 65 is also carried out in a similar manner or similar way using the assembly tool 100 according to the present invention. Slight manufacturing tolerances in the central column 30, peripheral columns 30, and outriggers 50 will affect the installation of the tendons 60, 65, which are installed as the final stage of the overall manufacturing process of the floating ocean platform 1.

[0047] As shown in Figure 3C, the longitudinal play between the tension wall 43 and the tension head 67, i.e., the "after assembly" distance, is determined, and a tolerance shim 80 is installed in the shim chamber 45 at least at one illustrated end of the lower tendon 65, in a direction C parallel to the central axis A of the circumferential wall 31, and fixed to the two tension walls 43. The tolerance shim 80 at the illustrated end of the lower tendon 65 has a thickness, or the tolerance shims 80 at both ends have a cumulative thickness corresponding to the longitudinal play determined under the narrow tolerance. Subsequently, the lower tendon 65 is lifted by a spreader bar and carried between the perimeter columns 30, and lowered in a vertical direction D parallel to the central axis A of the circumferential wall 31, while the central axis B of the lower tendon 65 is maintained perpendicular thereto, thereby the head shaft section 69 is received in the elongated slot 84 of the tolerance shim 80 and the tension head 67 contacts the tolerance shim 80.

[0048] As shown in Figure 5, the assembly tool 100 is configured such that the first hydraulic cylinder 127 of the tensioning device 120 is retracted, the tendon tensioning device 121 is positioned in the receiving position in direction E, the second hydraulic cylinder of the tensioning shim installer 130 is extended, the tensioning shim holder 131 is positioned in the upper standby position, and the tensioning shim 90 is placed inside the tensioning shim holder 131. In this first position, the entire assembly tool 100 is raised and lowered on the tension device receiving section 40 in a direction G parallel to the central axis A of the peripheral wall 31, the insertion wall 110 of the tool connector 110 enters the tool slot 75 of the tool dock 75 and finally lands on the bottom wall 44 as shown in Figure 5, the tool frame 101 is retracted, the first hydraulic cylinder 127 of the tension device 120 is positioned, the tension shim pulling device 121 is positioned in the receiving position in direction E, the second hydraulic cylinder of the tension shim installer 130 is extended, the tension shim holder 131 is positioned in the upper standby position, and the tension shim 90 is placed inside the tension shim holder 131. In this first position, the entire assembly tool 100 is raised and lowered on the tension device receiving section 40 in a direction G parallel to the central axis A of the peripheral wall 31, the insertion wall 110 of the tool connector 110 enters the tool slot 75 of the tool dock 75, and finally lands on the bottom wall 44 as shown in Figure 5, the tool frame 101 is retracted, the second hydraulic cylinder 127 of the tension device 120 is retracted, and the tension shim 90 is connected to the receiving section frame 41.

[0049] Next, as shown in Figure 6, the assembly tool 100 is moved to a second position, in which the first hydraulic cylinder 127 of the tensioning device 120 is hydraulically extended over a pre-tension stroke, thereby moving the tendon tensioning device 121 in direction E to engage with the tool engagement head 68, and then moving to the final pre-tension position. Over this pre-tension stroke, the lower tendon 65 is pre-tensioned along its central axis B, creating a gap between the tensioning head 67 and the tolerance shim 80. The tendon tensioning device 120 performs linear tension adjustment of the lower tendon 65, as the displacement of the tool engagement head 68 induces the same displacement of the tensioning head 67 in the direction of the central axis B of the lower tendon 65, and the tension adjustment force is transmitted to the tool dock 71 in this direction.

[0050] Next, as shown in Figure 7, the assembly tool 130 is moved to a third position, in which the second hydraulic cylinder of the tension shim installer 130 is hydraulically retracted, the tension shim holder 131 descends in the F direction, and the tension shim 90 fills the gap between the tension head 67 and the tolerance shim 80.

[0051] Finally, the assembly tool 100 is moved to the fourth position, and the first hydraulic cylinder 127 of the tensioning device 120 is hydraulically retracted to finally engage the tension head 67 with the inserted tension shim holder 131. The tolerance shim 80 and tension shim 90 are connected to the tension wall 43, securing the lower tendon 65 within the tendon receptacle 40. After performing the assembly method, pretension is applied to the lower tendon 65, and eventually to all tendons 60, 65, by imparting a pretension stroke between 0.04% and 0.07% of the length of the tendons 60, 65, preferably 0.05% of the length of the tendons 60, 65. In this way, the permanent deformation of the tendons 60, 65 is very small. The tension is small because it operates within the elastic range. Thus, the tendons 60, 65 maintain a taut state throughout the service life of the floating ocean platform 1. This pretension ensures that the tendons 60, 65 always maintain a taut state, except during the strongest storms and maximum waves. During this time, tendons 60 and 65 may occasionally relax for short periods, such as a few seconds at the maximum of the wave period.

[0052] In one embodiment, the outrigger 50, particularly its tubular members 51 and 52, are biased toward the central column 10 in their extension direction, preferably the tubular members 51 and 52 extending in a common horizontal plane have the same bias, providing rigidity to the tubular members 51 and 52 in the horizontal plane, thereby reducing the moment force on the tubular members 51 and 52. The biases of the upper tubular member 51 and the lower tubular member 52 may be different from each other in order to further improve the rigidity of the outrigger 50.

[0053] The method for installing the tendons 60, 65 ensures that at least one end of each tendon 60, 65, within the tendon receiving portion 40, there is a set of tolerance shims 80 and one opposite tension shim 90 located between the tension head 67 and the tension wall 43, and that an elongated tube 66 is completely enclosed within the opposite, facing elongated slots 84, 94 to fill the distance between the tension wall 43 and the tension head 67.

[0054] The installation of tendons 60 and 65 can be safely carried out at the integration site or marshalling yard of the newly constructed floating ocean platform 1, as well as during the service life of the moored floating ocean platform 1, for example, in the event of a collision with a vessel or other unexpected failure of tendons 60 and 65. In the latter case, tendons 60 and 65 can be replaced without divers, in calm sea conditions with wave heights of less than 2 meters and weak currents, by lowering a tension shim 90 into a tension shim holder 131 using a remotely operated assembly tool 100.

[0055] It should be understood that the above description is intended to illustrate the operation of preferred embodiments and does not limit the scope of the invention. From the above discussion, many modifications that fall within the scope of the invention will be apparent to those skilled in the art.

Claims

1. A set comprising a floating offshore platform and assembly tools for assembling the floating offshore platform, The floating ocean platform comprises a central column, a plurality of peripheral columns circumferentially around the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons spanning between each adjacent pair of peripheral columns, wherein the peripheral columns comprise a circumferential wall and tendon receiving portions on the circumferential wall for receiving tendon ends, and the tendons comprise an elongated tube and a tension head at the end of the elongated tube. The tendon receiving portion comprises a receiving portion frame and a tool dock on the receiving portion frame, the receiving portion frame defining a shim chamber and a tendon passage, and having a tension surface facing the shim chamber. The tension head is surrounded by the shim chamber, and the elongated tube extends through the tendon passage. The floating offshore platform comprises a tension shim for insertion into the shim chamber between the tension head and the tension surface, The assembly tool comprises a tool frame, a tool connector on the tool frame for engaging the tool dock and connecting the tool frame to the receiving frame, a tendon tensioning device, and a tension shim installer, wherein the tendon tensioning device comprises a tendon tensioning device for engaging the tendon, which is movable relative to the tool frame in the longitudinal direction of the elongated tube over a pre-tensioning stroke, and the tension shim installer comprises a tension shim holder for the tension shim, which is movable relative to the tool frame across the longitudinal direction of the elongated tube over an installation stroke for setting the tension shim in a gap formed or enlarged between the tension head and the tension surface.

2. The set according to claim 1, wherein the tendon comprises a tool engagement head on the elongated tube spaced apart from the tension head, and the tendon tensioning device comprises a contact body for contact with the tool engagement head.

3. The set according to claim 1, wherein the tool dock and the tool connector each comprise a tool slot and an insertion wall for inserting the elongated tube into the tool slot in the insertion direction traversing the longitudinal direction of the tube.

4. The set according to claim 1, wherein the tendon tensioning device comprises a first actuator between the tendon tensioning device and the tool frame for moving the tendon tensioning device over the pre-tension stroke.

5. The set according to claim 4, wherein the set comprises a remote controller for the first actuator.

6. The set according to claim 1, wherein the tension shim installer comprises a second actuator between the tension shim holder and the tool frame for moving the tension shim holder over the installation stroke.

7. The set according to claim 6, wherein the set comprises a remote controller for the second actuator.

8. The set according to claim 1, wherein the receiving frame comprises two spaced-apart opposing tension walls that form the boundary of the tendon passage and the tension surface.

9. The set according to claim 1, wherein the shim chamber and the tendon passage are open on one side to receive the tendon in the receiving direction of the tendon receiving portion.

10. The set according to claim 9, wherein the receiving direction of the tendon receiving portion is oriented downward to receive the end of the tendon from above.

11. The set according to claim 1, wherein the tension shim comprises a tension shim plate, the tension shim plate having an elongated tension shim slot that is open at the edge of the tension shim plate to define a direction for receiving into the tension shim, and the elongated tube extends through the tension shim slot of the inserted tension shim.

12. The set according to claim 11, wherein the tension shim slot extends through the center of the tension shim plate.

13. The floating offshore platform is the set according to claim 1, further comprising a tolerance shim continuous with the tension shim inserted in the longitudinal direction of the elongated tube within the shim chamber between the tension head and the tension surface.

14. The set according to claim 13, wherein the tolerance shim comprises a tolerance shim plate, the tolerance shim plate has an elongated tolerance shim slot that is open at the edge of the tolerance shim plate to define a direction for receiving into the tolerance shim, and the elongated tube extends through the tolerance shim slot.

15. The set according to claim 14, wherein the tolerance shim slot extends through the center of the tolerance shim plate.

16. The set according to claim 1, wherein the tension shim comprises a tension shim plate, the tension shim plate having an elongated tension shim slot that opens at the edge of the tension shim plate to define a direction for receiving into the tension shim, the elongated tube extending through the tension shim slot of the inserted tension shim, and the floating offshore platform comprises a tolerance shim continuous with the tension shim in the shim chamber between the tension head and the tension surface, the tolerance shim comprising a tolerance shim plate, the tolerance shim plate having an elongated tolerance shim slot that opens at the edge of the tolerance shim plate to define a direction for receiving into the tolerance shim, the elongated tube extending through the tolerance shim slot, and the inserted tension shim and the tolerance shim together completely surround the elongated tube behind the tension head.

17. The set according to claim 16, wherein the receiving direction into the tension shim is opposite to and aligned with the receiving direction into the tolerance shim.

18. The set according to claim 17, wherein the inserted tension shim and tolerance shim are placed on the receiving frame.

19. A method for assembling a floating offshore platform, The floating ocean platform comprises a central column, a plurality of peripheral columns circumferentially around the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons spanning between each adjacent pair of peripheral columns, wherein the peripheral columns comprise a circumferential wall and tendon receiving portions on the circumferential wall for receiving tendon ends, and the tendons comprise an elongated tube and a tension head at the end of the elongated tube. The aforementioned tendon receiving portion forms the boundary between the shim chamber and the tendon passage and comprises a receiving portion frame having a tension surface facing the shim chamber. The tension head is surrounded by the shim chamber, and the elongated tube extends through the tendon passage. The floating offshore platform is provided with a continuous tension shim and tolerance shim in the shim chamber between the tension head and the tension surface. The tension shim comprises a tension shim plate, the tension shim plate having an elongated tension shim slot that opens at one edge of the tension shim plate to define a direction for receiving the tension shim into the tension shim, and the tolerance shim comprises a tolerance shim plate, the tolerance shim plate having an elongated tolerance shim slot that opens at one edge of the tolerance shim plate to define a direction for receiving the tolerance shim into the tolerance shim, The elongated tube extends through the tendon passage, the tolerance shim slot, and the tension shim slot, and the shim chamber and the tendon passage are open on one side to receive the tendon in the receiving direction of the tendon receiving portion. The method includes the steps of inserting the tolerance shim into the shim chamber, such that the receiving direction of the tolerance shim is in the same direction as the receiving direction of the tendon receiving portion, and lowering the end of the tendon into the tendon receiving portion, wherein the tension head is received in the shim chamber, and the elongated tube is received in the tolerance shim slot and the tendon passage. A step of pre-tensioning the elongated tube in its longitudinal direction relative to the tendon receiving portion, wherein a gap is formed or stretched between the tensioning head and the tensioning surface, A method comprising the step of inserting a tension shim into the gap, wherein the elongated tube is received in the tension shim slot, and the tolerance shim and the tension shim together completely surround the elongated tube behind the tension head.

20. The method according to claim 19, further comprising the step of placing the tension shim and the tolerance shim on the receiving frame.

21. The method according to claim 19, wherein the receiving direction into the tension shim is opposite to and aligned with the receiving direction into the tolerance shim.

22. The method according to claim 19, wherein tolerance shims are inserted into the tendon receiving portion at both ends of the tendon, and the tolerance shims at both ends have a cumulative thickness in the longitudinal direction of the elongated tube corresponding to the play between the tension heads and their nearest tension surfaces in the longitudinal direction of the tendon.

23. The assembly is performed using an assembly tool, the tendon receiving section comprising a tool dock on the receiving section frame, the assembly tool comprising a tool frame, a tool connector on the tool frame for engaging the tool dock and connecting the tool frame to the receiving section frame, a tendon tensioning device, and a tension shim installer, the tendon tensioning device being a tendon tensioning device for engaging the tendon when the tension head is surrounded by the shim chamber, and being movable relative to the tool frame in the longitudinal direction of the elongated tube over a pre-tensioning stroke. The method according to claim 19, comprising a tendon tensioning device, the tension shim installer comprising a tension shim holder for the tension shim, the tension shim holder being movable relative to the tool frame over an installation stroke across the longitudinal direction of the elongated tube, the method comprising the step of engaging the tool dock with the tool connector by the tendon tensioning device pre-tensioning the elongated tube with respect to the tendon receptacle to form or stretch the gap, and by the tension shim installer installing a tension shim in the gap.

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