Floating ocean platform and assembly thereof

Abstract

The invention relates to a kit comprising a floating ocean platform and an assembly tool for assembling the floating ocean platform, a floating ocean platform includes a central post, a plurality of peripheral posts circumferentially surrounding the central post, a radially extending overhang bracket connecting the peripheral posts with the central post, and a tendon spanning between each pair of adjacent peripheral posts, where the peripheral posts include tendon receptors having tool interfaces, shim chambers, and tendon channels, and where the shim chambers are disposed between the central post and the peripheral posts, and where the shim chambers are disposed between the central post and the peripheral posts, and the shim chambers are disposed between the central post and the peripheral posts. An assembly tool includes a tool connector, a tendon tensioner, and a tension shim installer, where the tendon tensioner includes a tendon puller.

Description

Background Art

[0001] The present invention relates to a floating offshore platform comprising a central column, a plurality of peripheral columns circumferentially surrounding the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons spanning between each pair of adjacent peripheral columns. This type of floating offshore platform can be used to form the base of a floating wind turbine for offshore power generation. Summary of the Invention

[0002] Components of a floating offshore platform can be manufactured at various locations and transported to the assembly site at the marshaling port. The tendons are installed and pre-tensioned in the final stage, where they must absorb the difference between their nominal length and their actual required length between the outer columns. Therefore, tendon installation and pre-tensioning are complex operations, necessitated by a large-scale, fast-paced approach to meet the growing demand for floating wind turbines. Therefore, the central column, outer columns, outriggers, and tendons are manufactured to close tolerances to achieve reasonable assembly times for the floating offshore platform.

[0003] It is an object of the present invention to provide a floating offshore platform and method of assembly thereof that allows for fast-paced assembly on a large scale, preferably without pushing the manufacturing tolerances of the components to unreasonably small variances.

[0004] According to a first aspect, the present invention provides a kit comprising a floating offshore platform and an assembly tool for assembling the floating offshore platform,

[0005] wherein the floating offshore platform comprises a central column, a plurality of peripheral columns circumferentially surrounding the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons spanning between each pair of adjacent peripheral columns, wherein the peripheral columns comprise circumferential walls and tendon receivers located on the circumferential walls for receiving tendon ends, and wherein the tendons comprise elongated tubes and tensioning heads at the ends of the elongated tubes,

[0006] wherein the tendon receiver comprises a receiver frame and a tool interface on the receiver frame, wherein the receiver frame defines a shim chamber and a tendon channel and comprises a tensioning surface facing the shim chamber,

[0007] wherein the tensioning head is enclosed in a gasket chamber and an elongated tube extends through the tendon passage,

[0008] The floating offshore platform includes a tensioning gasket for inserting between a tensioning head and a tensioning surface in a gasket chamber.

[0009] wherein the assembly tool comprises a tool frame, a tool connector on the tool frame, a tendon tensioner and a tensioning gasket installer, the tool connector being used to engage a tool docking portion to connect the tool frame to a receiver frame, wherein the tendon tensioner comprises a tendon puller for engaging the tendon, the tendon puller being movable relative to the tool frame in the elongated direction of the elongated tube over a pre-tensioning stroke, and wherein the tensioning gasket installer comprises a tensioning gasket holder for the tensioning gasket, wherein the tensioning gasket holder is movable relative to the tool frame transversely to the elongated direction of the elongated tube over an installation stroke to install the tensioning gasket in a gap formed or expanded between the tensioning head and the tensioning surface.

[0010] The kit according to the present invention comprises an assembly tool comprising a tool connector that engages with a tool interface of a tendon receiver; a tendon tensioner for pre-tensioning the tendon; and a tensioning shim installer for subsequently inserting a tensioning shim between the tensioning head and the tensioning surface to maintain the pre-tension. The positions of the tool interface, tool connector, tendon tensioner, and tensioning shim installer are well defined by a common tool frame, and thus their positions relative to the tendon receiver and tendon ends are well defined. This allows for large-scale, fast-paced assembly of such floating offshore platforms. Furthermore, the assembly tool can be used at a consolidation site or marshaling port, or even while the floating offshore platform is already afloat in the water. The assembly tool can be remotely controlled, which is safe and particularly useful when used underwater.

[0011] In one embodiment, the tendon includes a tool-engaging head located on an elongated tube and spaced apart from a tensioning head, wherein the tendon puller includes an abutment body for abutment of the tool-engaging head. Engagement of the tendon for tendon pretensioning occurs spaced apart from the tensioning head and thus does not interfere with the tensioning head and tensioning surface, which require a tensioning shim to be installed therebetween. The portion of the tendon between the tool-engaging head and the tensioning head can be maintained free of bending moments while applying high pretensioning loads.

[0012] In an embodiment, the tool interface and the tool connector include a tool slot and an insertion wall for insertion into the tool slot in an insertion direction transverse to the elongated direction of the elongated tube. In practice, the peripheral posts are upright and the tendons extend in a horizontal direction, and the cooperating tool slot and insertion wall allow the assembly tool to be lowered onto the tendon receiver to engage the tool connector with the tool interface.

[0013] In an embodiment, the tendon tensioner comprises a first actuator between the tendon puller and the tool frame, the first actuator being for moving the tendon puller over a pre-tensioning stroke.

[0014] In an embodiment, the tension shim installer comprises a second actuator located between the tension shim holder and the tool frame, the second actuator being used to move the tension shim holder over the installation stroke.

[0015] Preferably, the kit comprises a remote control for the first actuator and / or the second actuator, whereby the assembly tool can be controlled from a safe distance when used underwater, and in particular in the absence of a human diver.

[0016] In an embodiment, the receiver frame comprises two opposing tensioning walls spaced apart from each other, the two opposing tensioning walls defining the tendon channel and forming the tensioning surface.

[0017] In an embodiment, the shim chamber and the tendon channel are open at one side to receive the tendon in a receiving direction of the tendon receiver.

[0018] In an embodiment, the receiving direction of the tendon receiver points downwards to receive the end of the tendon from above, whereby the tendon end can be lifted into the tendon receiver.

[0019] In an embodiment, the tensioning gasket comprises a tensioning gasket plate having an elongated tensioning gasket slot opening at an edge of the tensioning gasket plate to define a receiving direction into the tensioning gasket, wherein the elongated tube extends through the tensioning gasket slot of the inserted tensioning gasket.

[0020] In an embodiment, the tension shim slot extends through the center of the tension shim plate.

[0021] In an embodiment, a floating offshore platform includes a tolerance shim located between the tensioning head and the tensioning surface within a shim chamber and arranged in series with an inserted tensioning shim in the elongated direction of the elongated tube. The tolerance shim can be used to minimize any play between the tensioning head and the tendon receiver at each end of the tendon when the tendon is not yet pre-tensioned. In this manner, pre-tensioning can be performed with high precision by the assembly tool. The tolerance shim allows components of the floating offshore platform to be manufactured within reasonable tolerances typically applied in shipyards or offshore fabrication yards, while achieving the desired pre-tension in the tendon.

[0022] In an embodiment of the present invention, the tolerance shim includes a tolerance shim plate having an elongated tolerance shim slot opening at an edge of the tolerance shim plate to define a receiving direction into the tolerance shim, wherein the elongated tube extends through the tolerance shim slot.

[0023] In an embodiment of the present invention, the tolerance shim slot extends through the center of the tolerance shim plate.

[0024] In an embodiment, the tensioning shim includes a tensioning shim plate having an elongated tensioning shim slot, the elongated tensioning shim slot opening at an edge of the tensioning shim plate to define a receiving direction into the tensioning shim, wherein the elongated tube extends through the tensioning shim slot of the inserted tensioning shim, and wherein the floating offshore platform includes a tolerance shim located between the tensioning head and the tensioning surface in the shim chamber and in series with the tensioning shim in the elongated direction of the elongated tube, wherein the tolerance shim includes a tolerance shim plate having an elongated tolerance shim slot opening at an edge of the tolerance shim plate to define a receiving direction into the tolerance shim, wherein the elongated tube extends through the tolerance shim slot, and the inserted tensioning shim and the tolerance shim together completely surround the elongated tube behind the tensioning head. The cooperating tensioning shim and tolerance shim keep the tendon end capped in the tendon receiver. The tensioning shims and tolerance shims may be of the same shape and thickness to reduce the amount of different parts that must be available on site.

[0025] In an embodiment of the invention, the receiving direction into the tensioning shim is opposite and aligned with the receiving direction into the tolerance shim.

[0026] In an embodiment, the inserted tensioning shims and tolerance shims are mounted to the receiver frame, whereby the tensioning head itself remains able to absorb any bending of the elongate tube relative to the tendon receiver.

[0027] According to a second aspect, the present invention provides a method for assembling a floating offshore platform,

[0028] wherein the floating offshore platform comprises a central column, a plurality of peripheral columns circumferentially surrounding the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons spanning between each pair of adjacent peripheral columns, wherein the peripheral columns comprise circumferential walls and tendon receivers located on the circumferential walls for receiving tendon ends, and wherein the tendons comprise elongated tubes and tensioning heads at the ends of the elongated tubes,

[0029] wherein the tendon receiver comprises a receiver frame defining a shim chamber and a tendon channel and comprising a tensioning surface facing the shim chamber,

[0030] wherein the tensioning head is enclosed in a gasket chamber and an elongated tube extends through the tendon passage,

[0031] The floating offshore platform includes a tensioning gasket and a tolerance gasket in a gasket chamber, wherein the tolerance gasket is connected in series between the tensioning head and the tensioning surface.

[0032] wherein the tensioning shim comprises a tensioning shim plate having an elongated tensioning shim slot, the tensioning shim slot opening at an edge of the tensioning shim plate to define a receiving direction into the tensioning shim, and wherein the tolerance shim comprises a tolerance shim plate having an elongated tolerance shim slot, the tolerance shim slot opening at one edge of the tolerance shim plate to define a receiving direction into the tolerance shim,

[0033] wherein the elongated tube extends through the tendon passage, the tolerance shim slot, and the tensioning shim slot, and wherein the shim chamber and the tendon passage are open at one side to receive the tendon in a receiving direction of the tendon receiver,

[0034] wherein the method comprises the steps of inserting a tolerance shim into a shim chamber, wherein a receiving direction of the tolerance shim is in the same direction as a receiving direction of the tendon receiver; and lowering an end of the tendon into the tendon receiver, wherein the tensioning head is received in the shim chamber and the elongated tube is received in the tolerance shim slot and in the tendon channel.

[0035] the step of pre-tensioning the elongated tube in its elongated direction relative to the tendon receiver, wherein a gap is formed or enlarged between the tensioning head and the tensioning surface, and

[0036] The step of inserting a tensioning shim into the gap, wherein the elongated tube is received in the tensioning shim slot and the tolerance shim and tensioning shim together completely surround the elongated tube behind the tensioning head.

[0037] The tolerance shims installed in the first step serve to minimize any play between the tensioning heads and tendon receivers at each end of the tendon, while the tendon has not yet been pre-tensioned. From this point of view, pre-tensioning can be performed with high precision in a further step. The tolerance shims allow components of floating offshore platforms to be manufactured within the reasonable tolerances typically applied in shipyards or offshore fabrication yards, while achieving the prescribed pre-tensioning force in the tendon. As before, the cooperating tensioning and tolerance shims keep the tendon ends trapped in the tendon receivers.

[0038] In an embodiment, the method further comprises the step of mounting a tensioning shim and a tolerance shim to the receiver frame.

[0039] In an embodiment, the receiving direction into the tensioning shim is opposite and aligned with the receiving direction into the tolerance shim.

[0040] In an embodiment, tolerance shims are inserted into the tendon receivers at both ends of the tendon, wherein the tolerance shims at both ends have a cumulative thickness in the elongated direction of the elongated tube corresponding to the clearance between the tensioning head and its nearest tensioning surface in the elongated direction of the tendon tube.

[0041] In an embodiment, the method is performed by an assembly tool, wherein the tendon receiver includes a tool dock on a receiver frame, and wherein the assembly tool includes a tool frame, a tool connector on the tool frame, a tendon tensioner and a tensioning gasket installer, the tool connector being for engaging the tool dock to connect the tool frame to the receiver frame, wherein the tendon tensioner includes a tendon puller, the tendon puller being for engaging the tendon when the tensioning head is enclosed in the gasket chamber, and the tendon puller being movable in the elongated direction of the elongated tube relative to the tool frame in a pre-tensioning stroke, and wherein the tensioning gasket installer includes a tensioning gasket retainer for the tensioning gasket, wherein the tensioning gasket retainer is movable transversely to the elongated direction of the elongated tube relative to the tool frame in an installation stroke, wherein the method includes the steps of engaging the tool dock with the tool connector, pre-tensioning the elongated tube relative to the tendon receiver to form or expand a gap by means of the tendon tensioner, and installing the tensioning gasket in the gap by means of the tensioning gasket installer.

[0042] Each aspect and feature described and illustrated in this specification may be applied independently wherever possible. These individual aspects, in particular the aspects and features described in the accompanying dependent claims, may be the subject of divisional patent applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention will be explained based on exemplary embodiments shown in the accompanying drawings, in which:

[0044] Figure 1 It is an isometric view of a floating ocean platform supporting wind turbines;

[0045] Figure 2 for Figure 1 An isometric view of only relevant parts of a floating offshore platform;

[0046] Figure 3A-3C yes Figure 2 an isometric view, a top view, and an exploded view of one of the peripheral columns of a floating offshore platform;

[0047] Figure 4A and Figure 4B For use in Figure 3A-3C Isometric and top views of an assembly tool according to the present invention for assembling a floating offshore platform at a peripheral column; and

[0048] Figure 5-Figure 7 It is the use of Figure 4A and Figure 4B Isometric view of the subsequent steps of assembly of the assembly tool. DETAILED DESCRIPTION

[0049] Figure 1A floating offshore platform 1 is shown, which in this example supports a wind turbine 300 to form a floating wind turbine 5. Wind turbine 300 has a vertical tower 301, a nacelle 302, and a rotor 303. Rotor 303 has a hub 304 connected to a generator within nacelle 302. Wind turbine 300 and, in this example, three blades 305 radiating from hub 304. Wind turbine 300 is capable of generating over 1 MW of electricity, currently reaching approximately 10 MW to 15 MW. For wind turbines over 10 MW, the base diameter of tower 301 can be between 5 and 10 meters. The three blades 305 can each be over 100 meters long. An example is the 12 MW Haliade X turbine from General Electric. Other turbine designs, such as vertical-axis wind turbines, can also be supported by floating offshore platform 1.

[0050] Figure 2 The floating offshore platform 1 is shown without the wind turbine 300 and without gangways, railings and mounting facilities in order to illustrate some steps of manufacturing its structural parts.

[0051] like Figure 2 As shown, the floating offshore platform 1 includes a central column 10 made of steel. The central column 10 has a vertical cylindrical upper circumferential wall section 11, which is closed by a top wall 17 and, in this embodiment, merges downwardly via a flared wall section or conically widening intermediate circumferential wall portion 12 into a vertical cylindrical lower circumferential wall section 13. The cylindrical lower circumferential wall section 13 is closed at the bottom by a bottom wall 14 to define an interior chamber 16. The central column 10 has a diameter at the upper circumferential wall section 11 that is approximately equal to the bottom diameter of the tower 301, and increases in diameter toward the bottom or keel of the central column 10 via the conically widening intermediate circumferential wall portion 12. The central column 10 may be provided with a foot (not shown) below the bottom wall section 13, the foot having a larger diameter to provide additional volume. When the legs are filled with air, they help support the weight of the wind turbine 300. When the legs are filled with water, they help provide stability to the floating wind turbine 5. Alternatively, the central column 10 has a vertical cylindrical wall having a constant diameter throughout its height, wherein the constant diameter is preferably approximately equal to the base diameter of the tower 301.

[0052] In this example, the floating offshore platform 1 includes three vertical cylindrical stabilizing or peripheral columns 30 made of steel. The peripheral columns 30 are radially arranged every 120 degrees around the central column 10. Each peripheral column 30 includes a vertical cylindrical circumferential wall 31 having a central axis A, which is closed at the upper side by a top wall 32 to form an internal chamber 34. The peripheral columns 30 include a watertight flat member just below the mean waterline inside the internal chamber 34, and because of the watertight flat member, the internal chamber 34 is open to the sea. The peripheral columns 30 include a skirt 33 around the bottom edge of the circumferential wall 31 and a plurality of radially extending reinforcement plates 35 between the circumferential wall 31 and the skirt 33. The skirt 33 extends transversely to the central axis A of the circumferential wall 31.

[0053] Floating offshore platform 1 includes three outriggers 50 extending radially between central column 10 and peripheral columns 30. Outriggers 50 are made of steel and comprise upper and lower tubular members 51, 52, which in this example extend parallel to one another and are interconnected by diagonal braces 53. Alternatively, at least one of upper and lower tubular members 51, 52 may be diagonally aligned with the other. Alternatively, upper and lower tubular members 51, 52 may be stand-alone components not interconnected by braces. Upper and lower tubular members 51, 52 are connected to central column 10 and to peripheral columns 50 by flange connections, welding, or any other rigid connection.

[0054] The floating offshore platform 1 includes three pre-tensioned elongated upper structural members or tendons 60 of equal length interconnected to the upper ends of the perimeter columns 30, and three pre-tensioned elongated lower structural members or tendons 65 of equal length interconnected to the lower ends of the perimeter columns 30 at the skirts 33. The tendons 60, 65 are embodied as steel tubes, and their opposite ends are connected to the perimeter columns 30 in the same manner as described in detail below for the lower tendons 65 and perimeter columns 30, as shown on the right side of the drawing.

[0055] The central column 10 has a base diameter of up to 20 meters. The central column 10 and the peripheral columns 30 typically have a total height of 20-30 meters, in this example about 24 meters. The diameter of the peripheral columns 30 is between 6-12 meters. The tendons 60, 65 each have a length of 60-90 meters.

[0056] As in Figure 3CAs best shown in FIG, for a lower tendon 65, each tendon 60, 65 is received in a tendon receiver 40 on the peripheral column 30 to which it is connected in the same manner according to the present invention. The connection for the lower tendon 65 is disclosed below, with the emphasis on the connection of the upper tendon 65 to the peripheral column 30 in the same or similar manner according to the present invention. The tendon receiver 40 comprises a receiver frame 41 comprising two parallel side walls 42 formed from sheet steel welded on one side to the peripheral wall 31, and a bottom wall 44, optionally formed transversely to the side walls 42 by sheet steel welded to both the side walls 42 and the peripheral wall 31. For the lower tendon 65, the bottom wall 44 is formed by a portion of the existing skirt 33. The tendon receiver 40 comprises two tensioning walls 43 formed from sheet steel extending in the same plane and parallel to the central axis A. The tensioning wall 43 is welded to the side walls 42 and the bottom wall 44 and defines a tendon channel 46 that extends parallel to the central axis A of the circumferential wall 31 and is open at its upper side. The tensioning wall 43, the side walls 42, the circumferential wall 31, and optionally the bottom wall 44 together define a shim chamber 45, wherein the tensioning wall 43 forms a tensioning surface facing the shim chamber 45. On the opposite side, the tensioning wall 43, the side walls 42, and optionally the bottom wall 44 delimit a tendon tensioner chamber 50, wherein the bottom wall 44 may include a bottom opening 47 between and spaced apart from the tensioning wall 43 and the side walls 42. The tendon receiver 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.

[0057] Tendon receiver 40 includes a tool interface 71 on the outside of side wall 42. Tool interface 71 includes a first interface wall 72 on each side, which may be formed from the same plate as the adjacent tensioning wall 43. Tool interface 71 includes a shorter second interface wall 73 on each side, extending parallel to and spaced apart from first interface wall 72 to define a tool slot 75 therebetween, extending parallel to central axis A of circumferential wall 31, and a catch wall 74 at an angle to second interface wall 73 to converge into tool slot 75. First interface wall 72, second interface wall 73, and catch wall 74 are formed from sheet steel and welded to the respective side wall 42.

[0058] The lower tendon 65 is made of steel and includes an elongated tube 66 having a central axis B, which is hollow and cylindrical in cross-section. The elongated tube 66 has an outer diameter of 300-600 mm and a nominal wall thickness of 15-35 mm, which increases locally to 30-60 mm at the joint. The lower tendon 65 includes a tensioning head 67 at each end of the elongated tube 66, the tensioning head 67 having a circular cross-section protruding radially from the elongated tube 66, and a tool engagement head 68 having a circular cross-section at the end of the elongated tube 66 and spaced apart from the tensioning head 67. The tensioning head 67 of the lower tendon 65 is received in the shim chamber 45, the tool engagement head 68 is received in the tendon tensioner chamber 50, and a head shaft section 69 of the elongated tube 66 extending therebetween is received in the tendon passage 46.

[0059] The floating offshore platform 1 includes a tolerance shim 80 defined within the shim chamber 45. The tolerance shim 80 is made of steel plate and includes: two parallel side edges 81 extending parallel to the side walls 42 and fitting between the side walls so as to abut the two tensioning walls 43; a bottom edge 82 abutting the bottom wall 44; a top edge 85; and an elongated slot 84 centrally opened upward in the top edge 85 to receive the head shaft section 69 between the tensioning head 67 and the tool engagement head 68 into the tolerance shim 80 in a receiving direction.

[0060] Floating offshore platform 1 includes a tensioning shim 90 defined between tolerance shim 80 and tensioning head 67 within shim chamber 45. Tensioning shim 90 is fabricated from sheet steel and includes two parallel side edges 91 extending parallel to and fitting between side walls 42, a top edge 92, a bottom edge 93 abutting bottom wall 44, and an elongated slot 94 centrally located and downwardly open in bottom wall 93 to receive head shaft segment 69 within tensioning shim 90 in a receiving orientation. Both tolerance shim 80 and tensioning shim 90 are U-shaped and have identical outer dimensions, abutting each other over their entire areas along their respective side edges 81, 91. The tolerance shim 80 and tensioning shim 90 have elongated slots 84 and 94 pointing upward and downward in opposite directions aligned with and parallel to central axis A of circumferential wall 31, such that together they completely surround head shaft segment 69.

[0061] like Figure 4A and Figure 4BAs best shown in FIG, the tensioning spacer 90 is installed by an assembly tool 100. The assembly tool 100 includes a tool frame 101 having two parallel side walls 103, a rear wall 106 having a downwardly opening central opening 107 between the side walls 103, a tool connector 110 having two insert walls 111 projecting inwardly from the side walls 103 in the same vertical plane, and a bridge 112 having a central slot 113 connecting the insert walls 111 to each other at their top sides. The side walls 103, rear wall 106, insert walls 111, and bridge 112 are made of steel plates welded to each other. Insert wall 111 fits within tool slot 75 of tendon receiver 40 , whereby assembly tool 100 may be coupled to tendon receiver 40 by vertical translation in direction G parallel to central axis A of circumferential wall 31 or transverse to central axis B of lower tendon 65 .

[0062] The assembly tool 100 includes a tendon tensioner 120 located within the tool frame 101. The tendon tensioner 120 includes a tendon puller 121 formed from a steel plate and having a downwardly opening central opening 122 and a steel support body 123 extending along the central opening 122. The tendon tensioner 120 includes two first linear guides 125 for guiding the tendon puller 121 to reciprocate in a linear sliding direction E transverse to the central axis A of the circumferential wall 31 or parallel to the central axis B of the lower tendon 65 during a pre-tensioning stroke. This reciprocating sliding is powered by two pairs of first hydraulic cylinders 127 between the tool frame 101 and the tendon puller 121.

[0063] Assembly tool 100 includes a tensioning shim installer 130 positioned forward of insertion wall 111. The tensioning shim installer 130 includes a tensioning shim holder 131 for receiving and holding the tensioning shim 90; and two second linear guides 135 for guiding the reciprocating sliding movement of the tensioning shim holder 131 in a linear sliding direction F parallel to the central axis A of the circumferential wall 31 or transverse to the central axis B of the lower tendon 65 during the installation stroke. This reciprocating movement is powered by a pair of second hydraulic cylinders, not shown. The first hydraulic cylinder 127 of the tendon tensioner 120 and the second hydraulic cylinder of the tensioning shim installer 130 are connected to a remote or 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, particularly when used underwater.

[0064] The floating marine platform 1 is modular in structure, with the central column 10, peripheral columns 30, outriggers 50, and tendons 60, 65 manufactured to reasonable tolerances typically used in a shipyard or offshore fabrication yard. The tendons 60, 65 are installed after the outriggers 50 have been connected to the central column 10 and peripheral columns 30, so they must absorb the difference between their nominal length and the actual required length, which can be 500 mm or less. The ability to absorb these differences allows reasonable manufacturing tolerances for other components. The tendons 60, 65 can also be reinstalled on-site and underwater during the service life of the moored floating marine platform 1, for example to extend its service life or in the unlikely event that a tendon 60, 65 is lost or damaged. The lower tendon 65 can be located approximately 10-15 meters underwater.

[0065] The method for assembling the floating offshore platform 1, in particular the method for installing the lower tendon 65 thereof by means of the assembly tool 100, is followed by Figure 3C and Figure 5-Figure 7 . The installation of the upper tendons 65 is performed in the same or similar manner using the assembly tool 100 according to the present invention. Any small manufacturing tolerances in the central column 30, the peripheral columns 30, and the outriggers 50 have an impact on the assembly of the tendons 60, 65, which are installed as the last step in the entire manufacturing process of the floating marine platform 1.

[0066] like Figure 3C As shown, a longitudinal play or "as-build" distance is determined between the tensioning walls 43 and the tensioning head 67, and at least at one illustrated end of the lower tendon 65, a tolerance shim 80 is installed in the shim chamber 45 in a direction C parallel to the central axis A of the circumferential wall 31 and secured against the two tensioning 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 narrow tolerances. Subsequently, the lower tendon 65 is lifted by the brace, brought between the peripheral 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 remains perpendicular to the central axis A, whereby the head shaft section 69 is received in the elongated slot 84 of the tolerance shim 80 and the tensioning head 67 abuts the tolerance shim 80.

[0067] like Figure 5As shown, the assembly tool 100 is brought to a first position in which the first hydraulic cylinder 127 of the tendon tensioner 120 is retracted, thereby bringing the tendon puller 121 in the direction E to the receiving position, and the second hydraulic cylinder of the tensioning pad installer 130 is extended, thereby bringing the tensioning pad holder 131 to the upper standby position in which the tensioning pad 90 is positioned in the tensioning pad holder 131. In this first position, the entire assembly tool 100 is raised and lowered onto the tendon receiver 40 in the direction G parallel to the center axis A of the circumferential wall 31, wherein the insertion wall 110 of the tool connector 110 enters the tool slot 75 of the tool interface 75 and finally lands on the bottom wall 44, as shown in FIG. Figure 5 As shown, the tool frame 101 is thereby connected to the receiver frame 41 .

[0068] Then, if Figure 6 As shown, the assembly tool 100 is brought to a second position in which the first hydraulic cylinder 127 of the tendon tensioner 120 is hydraulically extended in a pre-tensioning stroke, thereby engaging the tendon puller 121 with the tool engagement head 68 in direction E and subsequently assuming a final pre-tensioning position. In this pre-tensioning stroke, the lower tendon 65 is pre-tensioned along its center axis B, and a gap is formed between the tensioning head 67 and the tolerance washer 80. The tendon tensioner 120 performs an online tensioning of the lower tendon 65, since a displacement of the tool engagement head 68 causes a similar displacement of the tensioning head 67 in the direction of the center axis B of the lower tendon 65, and the tensioning force is transmitted in this direction to the tool interface 71.

[0069] Then, if Figure 7 As shown, the assembly tool 130 is brought to the third position, in which the second hydraulic cylinder of the tensioning shim installer 130 is hydraulically retracted and thereby the tensioning shim holder 131 is lowered in direction F and the tensioning shim 90 fills the gap between the tensioning head 67 and the tolerance shim 80.

[0070] Finally, assembly tool 100 is brought to a fourth position, in which first hydraulic cylinder 127 of tendon tensioner 120 is hydraulically retracted to bring tensioning head 67 into final engagement with inserted tensioning shim retainer 131. Tolerance shims 80 and tensioning shims 90 are attached to tensioning wall 43 to lock lower tendon 65 within tendon receiver 40. After performing the assembly method, lower tendon 65, and ultimately all tendons 60, 65, are pre-tensioned by inducing a pre-tensioning stroke of between 0.04% and 0.07% of the length of tendon 60, 65, preferably between 0.05% of the length of tendon 60, 65. In this way, permanent deformation of tendons 60, 65 will remain very small, as they operate within their elastic range. Consequently, tendons 60, 65 will remain tensioned throughout the service life of floating offshore platform 1. Due to the pre-tensioning, the tendons 60, 65 remain taut at all times, except during the largest waves of the strongest storms, whereby they may occasionally become slack for short periods of time, such as a few seconds of wave period at most.

[0071] In an embodiment, the outriggers 50 (particularly the tubular members 51, 52 thereof) are offset in their elongated direction toward the central column 10, preferably, the tubular members 51, 52 extending in a common horizontal plane have the same offset, thereby providing stiffness to the tubular members 51, 52 in the horizontal plane and thus reducing moments in the tubular members 51, 52. The offsets in the upper and lower tubular members 51, 52 may be different from each other to further improve the stiffness of the outrigger 50.

[0072] The method for mounting the tendons 60, 65 ensures that at least at one end of each tendon 60, 65, there is a set of a tolerance shim 80 and an oppositely directed tensioning shim 90 in the tendon receiver 40, with the tolerance shim 80 and the oppositely directed tensioning shim 90 being present between the tensioning head 67 and the tensioning wall 43, which together completely surround the slender tube 66 within its opposite and facing slender slots 84, 94 to bridge the distance between the tensioning wall 43 and the tensioning head 67.

[0073] The installation of the tendons 60, 65 can be safely performed at the integration site for a newly built floating offshore platform 1, at a marshaling port, and during the service life of a moored floating offshore platform 1, for example in the event of a collision with a ship or any other unexpected failure of the tendons 60, 65. In the latter case, the tendons 60, 65 can be replaced without divers and in mild sea conditions with wave heights of less than 2 meters and low currents by lowering a remotely controlled assembly tool 100 having tensioning pads 90 in its tensioning pad holders 131.

[0074] It should be understood that the above description is included to illustrate the operation of the preferred embodiment and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to those skilled in the art, which variations will still be encompassed by the scope of the present invention.

Claims

1. A kit comprising a floating offshore platform and an assembly tool for assembling the floating offshore platform, in, The floating offshore platform comprises a central column, a plurality of peripheral columns circumferentially surrounding the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons spanning between each pair of adjacent peripheral columns, wherein the peripheral columns comprise circumferential walls and tendon receivers on the circumferential walls for receiving tendon ends, and wherein the tendons comprise elongated tubes and tensioning heads at ends of the elongated tubes. wherein the tendon receiver comprises a receiver frame and a tool interface on the receiver frame, wherein the receiver frame defines a shim chamber and a tendon channel and comprises a tensioning surface facing the shim chamber, wherein the tensioning head is enclosed in the gasket chamber and the elongated tube extends through the tendon passage, wherein the floating offshore platform comprises a tensioning gasket for being inserted between the tensioning head and the tensioning surface in the gasket chamber, wherein the assembly tool comprises a tool frame, a tool connector on the tool frame, a tendon tensioner and a tensioning gasket installer, the tool connector being used to engage the tool docking portion to connect the tool frame to the receiver frame, wherein the tendon tensioner comprises a tendon puller for engaging the tendon, the tendon puller being movable relative to the tool frame in the elongated direction of the elongated tube during a pre-tensioning stroke, and wherein the tensioning gasket installer comprises a tensioning gasket holder for the tensioning gasket, wherein the tensioning gasket holder is movable relative to the tool frame in the elongated direction transverse to the elongated tube during an installation stroke to install the tensioning gasket in a gap formed or expanded between the tensioning head and the tensioning surface.

2. The kit according to claim 1, wherein The tendon includes a tool engaging head on the elongated tube spaced apart from the tensioning head, and wherein the tendon puller includes an abutment body for abutment of the tool engaging head.

3. A kit according to any one of the preceding claims, wherein The tool interface and the tool connector include a tool slot and an insertion wall for insertion into the tool slot in an insertion direction transverse to the elongated direction of the elongated tube.

4. A kit according to any one of the preceding claims, wherein The tendon tensioner includes a first actuator between the tendon puller and the tool frame for moving the tendon puller in the pre-tensioning stroke.

5. The kit according to claim 4, wherein The kit includes a remote control for the first actuator.

6. A kit according to any one of the preceding claims, wherein The tension shim installer includes a second actuator located between the tension shim holder and the tool frame, the second actuator being used to move the tension shim holder during the installation stroke.

7. The kit according to claim 6, wherein: The kit includes a remote control for the second actuator.

8. A kit according to any one of the preceding claims, wherein The receiver frame includes two opposing tensioning walls spaced apart from one another, the two opposing tensioning walls defining the tendon channel and forming the tensioning surface.

9. A kit according to any one of the preceding claims, wherein: The shim chamber and the tendon passage are open at one side to receive the tendon in a receiving direction of the tendon receiver.

10. The kit of claim 9, wherein: The receiving direction of the tendon receiver is directed downward to receive the end of the tendon from above.

11. A kit according to any one of the preceding claims, wherein The tensioning gasket comprises a tensioning gasket plate having an elongated tensioning gasket slot which opens at an edge of the tensioning gasket plate to define a receiving direction into the tensioning gasket, wherein the elongated tube extends through the tensioning gasket slot of the inserted tensioning gasket.

12. The kit of claim 11, wherein: The tension shim slot extends through the center of the tension shim plate.

13. A kit according to any one of the preceding claims, wherein The floating offshore platform includes a tolerance shim located in the shim chamber between the tensioning head and the tensioning surface and in series with the tensioning shim inserted in the elongated direction of the elongated tube.

14. The kit of claim 13, wherein: The tolerance shim includes a tolerance shim plate having an elongated tolerance shim slot that opens at an edge of the tolerance shim plate to define a receiving direction into the tolerance shim, wherein the elongated tube extends through the tolerance shim slot.

15. The kit of claim 14, wherein: The tolerance shim slot extends through the center of the tolerance shim plate.

16. A kit according to any one of the preceding claims, wherein The tensioning gasket includes a tensioning gasket plate having an elongated tensioning gasket slot, the tensioning gasket slot opening at an edge of the tensioning gasket plate to define a receiving direction into the tensioning gasket, wherein the elongated tube extends through the tensioning gasket slot of the inserted tensioning gasket, and wherein the floating marine platform includes a tolerance gasket, the tolerance gasket being located between the tensioning head and the tensioning surface in the gasket chamber and in series with the tensioning gasket in the elongated direction of the elongated tube, wherein the tolerance gasket includes a tolerance gasket plate having an elongated tolerance gasket slot, the tolerance gasket slot opening at an edge of the tolerance gasket plate to define a receiving direction into the tolerance gasket, wherein the elongated tube extends through the tolerance gasket slot, and the inserted tensioning gasket and the tolerance gasket together completely surround the elongated tube behind the tensioning head.

17. The assembly of claim 16, wherein: The receiving direction into the tensioning shim is opposite and aligned with the receiving direction into the tolerance shim.

18. The kit of claim 17, wherein: The inserted tensioning shims and the tolerance shims are mounted to the receiver frame.

19. A method for assembling a floating offshore platform, in, The floating offshore platform comprises a central column, a plurality of peripheral columns circumferentially surrounding the central column, radially extending outriggers connecting the peripheral columns to the central column, and tendons spanning between each pair of adjacent peripheral columns, wherein the peripheral columns comprise circumferential walls and tendon receivers on the circumferential walls for receiving tendon ends, and wherein the tendons comprise elongated tubes and tensioning heads at ends of the elongated tubes. wherein the tendon receiver comprises a receiver frame defining a shim chamber and a tendon channel and comprising a tensioning surface facing the shim chamber, wherein the tensioning head is enclosed in the gasket chamber and the elongated tube extends through the tendon passage, wherein the floating offshore platform comprises a tensioning shim and a tolerance shim in the shim chamber, the tolerance shim and the tolerance shim being connected in series between the tensioning head and the tensioning surface, wherein the tensioning shim comprises a tensioning shim plate having an elongated tensioning shim slot, the tensioning shim slot opening at an edge of the tensioning shim plate to define a receiving direction into the tensioning shim, and wherein the tolerance shim comprises a tolerance shim plate having an elongated tolerance shim slot, the tolerance shim slot opening at one edge of the tolerance shim plate to define a receiving direction into the tolerance shim, wherein the elongated tube extends through the tendon passage, the tolerance shim slot, and the tensioning shim slot, and wherein the shim chamber and the tendon passage are open at one side to receive the tendon in a receiving direction of the tendon receiver, wherein the method comprises the steps of inserting a tolerance shim into the shim chamber, wherein a receiving direction of the tolerance shim is in the same direction as a receiving direction of the tendon receiver; and lowering an end of the tendon into the tendon receiver, wherein the tensioning head is received in the shim chamber and the elongated tube is received in the tolerance shim slot and in the tendon channel, the step of pre-tensioning the elongated tube in its elongated direction relative to the tendon receiver, wherein a gap is formed or enlarged between the tensioning head and the tensioning surface, and The step of inserting a tensioning shim into the gap, wherein the elongated tube is received in the tensioning shim slot and the tolerance shim and tensioning shim together completely surround the elongated tube behind the tensioning head.

20. The method of claim 19, further comprising the step of mounting the tensioning shim and the tolerance shim to the receiver frame.

21. The method according to claim 19 or 20, wherein The receiving direction into the tensioning shim is opposite and aligned with the receiving direction into the tolerance shim.

22. The method according to any one of claims 19 to 21, wherein Tolerance shims are inserted into the tendon receiver at both ends of the tendon, wherein the tolerance shims at both ends have a cumulative thickness in the elongated direction of the elongated tube, and the cumulative thickness corresponds to the clearance between the tensioning head and its nearest tensioning surface in the elongated direction of the tendon tube.

23. The method according to any one of claims 19 to 22, performed by means of an assembly tool, wherein The tendon receiver includes a tool interface on the receiver frame, and wherein the assembly tool includes a tool frame, a tool connector on the tool frame, a tendon tensioner, and a tensioning shim installer, the tool connector being adapted to engage the tool interface to connect the tool frame to the receiver frame, wherein the tendon tensioner includes a tendon puller adapted to engage the tendon when the tensioning head is enclosed in the shim chamber, and wherein the tendon puller is adapted to pull the tendon in the elongated direction of the elongated tube during a pre-tensioning stroke. The tool frame is movable relative to the tool frame, and wherein the tensioning gasket installer includes a tensioning gasket holder for the tensioning gasket, wherein the tensioning gasket holder is movable relative to the tool frame in the elongated direction transverse to the elongated tube during an installation stroke, wherein the method includes the steps of: engaging the tool interface with the tool connector, pre-tensioning the elongated tube relative to the tendon receiver by means of the tendon tensioner to form or expand the gap, and installing the tensioning gasket in the gap by means of the tensioning gasket installer.

Images