US20210122446A1

US20210122446A1 - Anti-motion Structure of Column Floater

Info

Publication number: US20210122446A1
Application number: US17/139,501
Authority: US
Inventors: Zhirong Wu
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-08-06
Filing date: 2020-12-31
Publication date: 2021-04-29
Also published as: CN110803263A; AU2019317324A1; CN110972470B; AU2019317324B2; WO2020029704A1; GB2590840A; GB2590840B; CN110972470A; NO20201399A1; GB202102172D0

Abstract

An anti-motion structure of a column floater, being an annular structure surrounding the outer periphery of the bottom of a buoy of the column floater, and an annular radial gap between the two is, or optionally is not, set up. The anti-motion structure is connected to a horizontal roof plate, a horizontal floor plate, an outer annular vertical plate, and an inner annular vertical plate to form an annular box body; and the box body is divided into a plurality of watertight compartments; the horizontal roof plate and/or the horizontal floor plate corresponding to each watertight compartment are provided with damping holes capable of being opened or closed.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of International Application PCT/CN2019/093408 filed Jun. 27, 2019, which claims benefit of priority of Chinese application CN201810882470.3 filed on Aug. 6, 2018, both of which are incorporated herein by reference.

FIELD OF INVENTION

The present invention relates to the technical field of offshore engineering, and, in-particular, to an anti-motion structure of a column floater.

BACKGROUND

Bottom damping structure or damping plate (anti-motion structure) of a column floater (i.e., a straight cylinder type floating platform) is an annular structure, which surrounds the bottom and the outer periphery of the upright buoy or extended cylinder of a column floater. For some column floaters, such as SEVAN's cylindrical FPSO, partial fractures are arranged in the annular anti-motion structure to form an intermittent annular structure in order to install fairleads of mooring legs (usually 3 groups). The function of anti-motion structure is to increase added mass of entrained water, natural period and motion damping, and finally reduce the motion response of the platform and improve the motion performance of the platform. Therefore, it is called “anti-motion structure”. In a word, the anti-motion structure is a very important structural component of a column floater. According to the structural form of the radial cross section of the annular anti-motion structure, the anti-motion structure can be divided into three types: the first type is represented by SEVAN's cylindrical FPSO, its anti-motion structure is airtight box-shaped structure with a relatively small height, which is a part of the platform's seawater ballast compartment. The second type refers to the U-shaped and inverted U-shaped structure of the open plate structure proposed by the inventor. The third type refers to a higher-height closed box structure proposed by the inventor, and the damping holes which can be opened or closed are arranged in the roof plate and the floor plate of the box. When the platform is in the state of floating and wet towing, all damping holes are closed and the anti-motion structure becomes an airtight floating compartment, or the damping holes in the roof plate are closed and the damping holes in the floor plate are opened to form an air-float compartment, both of which can provide buoyancy and stability for the platform. During in-place condition (offshore production or survival conditions) of the platform, all damping holes are opened and seawater is filled inside, which makes the added mass of entrained water increase, but doesn't make the displacement of the platform increase (see PCT/CN2017/085052). The performance of heave motion of the column floater is the key point that must be paid special attention to. Compare the added mass of entrained water and viscous damping, the first type of anti-motion structure has the worst performance, in particular, the partial fractures of the anti-motion structure for installing fairlead makes the structure integrity be destroyed, in addition, as the area of horizontal projection decreases, the added mass of entrained water of the heave motion decreases accordingly; the second is the second type; and the optimal one is the third one. However, the third one also falls short in terms of how to increase viscous damping, and there is still much room for progress. After repeated analysis and calculation and experimental research found that a case in point where conventional cognition is hard to explain, in order to increase the add mass of the internal entrained water, under the condition that the outside diameter of the anti-motion structure remains unchanged, the height of the structure should be moderately increased, but the viscous damping of the platform oscillation is reduced. The question is how to increase the height of anti-motion structure moderately and increase viscous damping at the same time? What else can be done to increase viscous damping? Viscous damping is of great significance to effectively reduce the motion response of a column floater under once-in-a-century environmental conditions and improve the platform's motion performance.
For the above reasons, based on the results of the study, the inventor improved and optimized the above three types of anti-motion structure, and put forward a new concept of “edge extending lath”, and with help of the edge extending lath, the viscous damping of the platform and the add mass of the entrained water are increased. At same time, adopting groove instead of fracture for installing fairlead, forming a new form of anti-motion structure, finally overcome existing shortcomings of said three types of anti-motion structure, and further improve the motion performance of the platform.

SUMMARY

The invention discloses an anti-motion structure of a column floater, the anti-motion structure is an annular structure, which surrounds the bottom and outer periphery of the upright buoy or extended cylinder (collectively called “the buoy”) of a column floater, and an annular radial gap is set or optionally not set between them. The structure sketch of the radial cross section of the anti-motion structure is a rectangular or trapezoid box, which is watertight to be connected by an horizontal roof plate, an horizontal floor plate, an outer annular vertical plate and an inner annular vertical plate with each other, and besides, the annular box-typed structure is divided into a plurality of watertight compartments by a plurality of radial vertical partitions; At least one of the horizontal roof plate and/or the horizontal floor plate protrudes outward from the intersection between the horizontal roof plate and the outer annular vertical plate (i.e., the “outer corner line of the box”) to form an outer edge extending lath. Similarly, for the anti-motion structure with annular radial gap, an inner edge extending lath can also be provided as an option. In order to install fairleads of mooring legs on the lower part of the buoy of the column floater without destroying the integrity of the anti-motion structure, a U-shaped groove structure for installing the fairleads is arranged on the anti-motion structure's inner side adjacent to the buoy shell, and the groove structure shall not destroy the water tightness of the watertight compartment.
Both physical model experiment and computer model calculation show that in the motion process of the platform, the inner and outer edge extending laths which are set on the horizontal roof plate and the horizontal floor plate can change the local flow field, intensify the turbulence and dissipate energy of the local water body, thus significantly increasing the viscous damping of the platform motion and increasing the add mass of the entrained water. The groove structure is used to replace the current intermittent fracture structure, which is beneficial to increase the add mass of the entrained water and ensure the integrity of the structure. Compared with the current anti-motion structures, the viscous damping and the add mass of the entrained water of the anti-motion structure of the present invention are increased, so as to further improve the motion performance of the platform.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures described herein are for the purposes of interpretation only and are not intended in any way to limit the scope of the present invention to be disclosed.

FIG. 1 is the main schematic diagram and partial sectional view of the anti-motion structure of a column floater, showing the basic structure of the anti-motion structure and the connection with the buoy.

FIG. 2 is the enlarged diagram at I in FIG. 1, showing the structure diagram of the first type of outer edge extending lath.

FIG. 3 is a radial local section schematic diagram of the anti-motion structure, showing the second type of outer edge extending lath.

FIG. 4 is a radial local section schematic diagram of the anti-motion structure, showing the third type of outer edge extending lath.

FIG. 5 is a radial local section schematic diagram of the anti-motion structure, showing the fourth type of outer edge extending lath.

FIG. 6 is the radial local section schematic diagram of the anti-motion structure, showing the fifth type of outer edge extending lath.

FIG. 7 is a radial local section of another anti-motion structure of the present invention and a magnified view of the same part as that shown in FIG. 2.

DETAILED DESCRIPTION

The details of the invention can be understood more clearly in combination with the figures and the description of the embodiments of the present invention. However, the specific embodiment of the present invention described herein, only for the purpose of interpreting the present invention, cannot be construed in any way as a limitation of the present invention.
The invention discloses an anti-motion structure of a column floater (i.e., a straight cylinder floating platform). See FIG. 1, the column floater 1 is floating and positioned on a water surface 2; The column floater 1 comprises a topside 11, a buoy 12 at a water surface with an anti-motion structure 13; The buoy 12 comprises only an upright buoy or the upright buoy with extended cylinder, the extended cylinder comprises two forms of fixed extended cylinder and sliding extended cylinder; The anti-motion structure 13 is an annular structure, which surrounds the bottom and outer periphery of the buoy 12, and an annular radial gap 14 is set or optionally not set between them. See FIGS. 2 and 3, The anti-motion structure 13 comprises a roof plate 131, a floor plate 133 under the roof plate 131, an outer annular vertical plate 132 and an inner annular vertical plate 134 in between the outer annular vertical plate 132 and the buoy 12, and said four plates (131˜134) are watertight connected with each other to form an annular box structure with a rectangular or trapezoid radial cross section. (FIG. 1-7 show that the structure sketch of the anti-motion structure with rectangular typed radial crossing section, and the trapezoidal section is not shown.) Among them, the roof plate 131 and the floor plate 133 intersect with the outer annular vertical plate 132 respectively to form a roof outer corner line of the box (located on the outer edge of the roof of the box body) and a floor outer corner line of the box (located on the outer edge of the floor of the box body). The roof plate 131 and the floor plate 133 intersect with the inner annular vertical plate 134 respectively to form a roof inner corner line of the box (located on the inner edge of the roof of the box body) and a floor inner corner line of the box (located on the inner edge of the floor of box body), and i. e., forming four circles of closed corner lines. The radial vertical cross section of the box body of the anti-motion structure 13 shown in FIG. 1-7 is a rectangle, and the vertices of the four corners of the rectangle are respectively the points on the closed box corner line. The geometric figures of box corner line are also different with the different structural forms of the anti-motion structure 13. But in any case, the geometry centroid of each corner line is located on the vertical central axis of the buoy 12 and the anti-motion structure's box body is rotationally symmetric with the centroid (such as a round or regular polygon corner line), or the anti-motion structure's box body is symmetric anteroposterior and left-right with the axis of the rectangular coordinate system described the origin as the centroid (i.e., the vertical central axis of the buoy 12), such as an oval corner line or a closed geometric figure with parallel straight lines on the left and right sides and circular or broken line on the front and rear sides. The anti-motion structure 13 is connected with the buoy 12 of the column floater 1 by multiple radial vertical brackets (not shown in the attached figures). The box body is divided into several watertight compartments by a plurality of radial vertical partitions (not shown in the attached figures). The horizontal roof plate 131 and/or the horizontal floor plate 133 of each watertight compartment are provided with damping holes that can be opened and closed. By opening or closing the damping holes, the column floater 1 can be met the requirement under different working conditions: When the platform is under conditions of floating and wet towing, all the damping holes are closed, the watertight compartment of the anti-motion structure 13 becomes a closed buoyancy module, or the damping holes of the roof plate 131 are closed and the damping holes of floor plate 133 are opened at same time, the interior of the compartment is filled with air, and the watertight compartment of the anti-motion structure 13 becomes a closed gas-float compartment and buoyancy module. Both types of buoyancy module can provide buoyancy and stability for floating and wet towing of the platform. During in-place condition of the platform, the damping holes are opened (the best option is to open all damping holes) and the water from the sea is filled inside the anti-motion structure 13, which makes the added mass of inside entrained water increase, but doesn't make the displacement of the platform increase.
The fundamental difference between the present invention and PCT/CN2017/085052 is: at least one plate of roof plate 131 and floor plate 133 of the anti-motion structure 13 without annular radial gap 14 shall be provided with an outer edge extending lath respectively; The outer edge extending laths are roof edge extending lath 135 and floor edge extending lath 136. Refer to FIG. 1-7, showing the anti-motion structure 13 with annular radial gap 14, an outer edge extending lath and/or an inner edge extending lath are set separately or simultaneously on at least one plate of the roof plate 131 and/or the floor plate 133 of the anti-motion structure 13. The outer edge extending laths are roof outer edge extending lath 135 and floor outer edge extending lath 136, while the inner edge extending laths are roof inner edge extending lath and floor inner edge extending lath. The outer edge extending lath is a plate structure, which extends outward and/or upward and/or downward from the roof outer corner line and the floor outer corner line respectively. The roof outer edge extending lath 135 is formed on the roof plate 131 and the floor outer edge extending lath 136 is formed on the floor plate 133. The inner edge extending lath is a plate structure, which extends horizontally from the roof inner corner and/or the floor inner corner of the box to the direction of the buoy 12. The horizontal roof inner edge extending lath is formed on the roof plate 131, and the horizontal floor inner edge extending lath is formed on the floor plate 133. The inner edge extending lath shall not close the annular radial gap 14 (See FIG. 7).
As a practical embodiment, the anti-motion structure 13 is a circular or a regular polygon structure, and the four box corner lines correspond to a circular or a regular polygon. As another practicable embodiment, the shape of the inner wall (the inner annular vertical plate 134) and the outer wall (the outer annular vertical plate 132) of the annular anti-motion structure of the present invention is different. For example, the inner wall is a circular of ring plate or positive multilateral ring plate, and the roof inner corner line of the box and the floor inner corner line of the box are corresponding to a circular or regular polygon, and the outer wall is oval-shaped, and the roof outer corner line and the floor outer corner line of the box is an oval; or the outer wall is hetero-polygons-shaped, the roof outer corner lines and the floor outer corner line of the box is a closed geometric figures formed by parallel straight lines on the left and right sides and circular or broken lines on the front and rear sides, the dimensions in the left and right directions are smaller than those in the front and rear directions. Its advantage is that the requirements of width of drydock for platform construction of can be reduced.
Further, the roof outer edge extending lath 135 and the floor outer edge extending lath 136 are of annular plate structures. The end edge of roof outer edge extending lath 135 and the end edge of the floor outer edge extending lath 136 form a roof outer end edge line and a floor outer end edge line respectively. The geometric figures of said two end edge lines have the same centroid as the roof outer corner line and the floor outer corner line of the box, which is rotationally symmetric with the centroid or symmetric with the vertical central axis of the buoy 12 in direction of anteroposterior/left-right. Or, the roof outer edge extending lath 135 and the floor outer edge extending lath 136 are protruding to form a wall structure upward and downward respectively, and the upper edge and lower edge of the protruding edge extending lath wall structure form a circle of closed upper end edge line and a circle of closed lower end edge line respectively. The centroid of the geometry of said each end edge line is located in the vertical central axis of buoy 12 and equal to or similar to the geometry of the roof and floor corner lines of the box respectively; or the roof outer edge extending lath 135 and the floor outer edge extending lath 136 is an horizontal annular plate then folding and protruding upward or downward to form a wall structure respectively, and the end edge of the wall of the roof outer edge extending lath 135/the floor outer edge extending lath 136 forms a circle of closed roof/floor end edge line respectively. The centroid of the plane geometry of the circle of closed roof/floor end edge line is located in the vertical central axis of the buoy 12, which is similar to the plane geometry of the roof outer corner line of the box/the floor outer corner line of the box. Alternatively, the roof outer edge extending lath 135/the floor outer edge extending lath 136 consists of a horizontal annular plate structure plus a vertical ring wall structure protruding upward/downward respectively; and in such case, the roof outer edge extending lath 135 forms a circles of roof outer end edge line plus a circle of roof upper end edge line, and the floor outer edge extending lath 136 forms a circles of floor outer end edge line plus a circle of floor lower end edge line, i.e., both of the roof outer edge extending lath 135 and the floor outer edge extending lath 136 have two circles of end edge lines.
Further, roof outer edge extending lath 135 and floor outer edge extending lath 136 are single-layer plate structures (see FIGS. 1-7). For the convenience of description and understanding, the plate thickness of the edge extending lath structure is very small, and the plate thickness is ignored in the following description of the invention and regarded as “paper”. Therefore, as the edge extending lath with a convex structure extending up and down (see FIG. 3˜6), said convex structure of the roof outer edge extending lath 135 and the floor outer edge extending lath 136 will form an upright frustum cone wall or an upright cylindrical wall (see FIG. 3 and FIG. 5), or form a horizontal annular plate structure then folding and protruding upward or downward being a convex structure (see FIG. 4 and FIG. 6), said convex structure forms a circle of closed upper end edge line and a circle of closed lower end edge line, which centroid of the geometry is located in the vertical central axis of the buoy 12 and which geometry is equal to or similar to the geometry of the roof and floor corner lines of the box respectively. When the outer edge extending laths are as shown as FIGS. 1/2/7 being horizontal extension structures of the roof plate 131 and/or the floor plate 133, both of the roof outer edge extending lath 135 and the floor outer edge extending lath 136 are horizontal annular plates and each plate with only one closed circle outer end edge line (the inner edge line is merged with the outer box corner line).
Optionally, multiple damping holes can be set or not be set on the roof outer edge extending lath 135 and the floor outer edge extending lath 136.
The outer edge extending lath (i.e., the roof outer edge extending lath 135 and/or the floor outer edge extending lath 136) comprises six structural forms.
(1) The roof outer edge extending lath 135 or the floor outer edge extending lath 136, as horizontal annular plate structures, are the horizontal extension structures of the roof plate 131 or the floor plate 133 respectively, and the geometries of their outer end edge lines (i. e., the outer end edge line of the roof outer edge extending lath 135 and the outer edge line of the floor outer edge extending lath 136) have the same centroid as the geometries of the roof corner line of the box and the floor corner line of the box, and are rotationally symmetrical with the centroid, or anteroposterior and left-right symmetrical with the axes of the Cartesian coordinate system with the centroid as the origin, as shown in FIGS. 1, 2 and 7.
(2) The roof outer edge extending lath 135 is an inverted frustum-shaped wall structure with its upper dimension larger than its lower dimension, which lower end edge line coincides with the roof outer corner line of the box; and the floor outer edge extending lath 136 is a positive frustum-shaped wall structure with its upper dimension less than its lower dimension, which upper end edge line coincides with the floor outer corner line of the box, see FIG. 3.
(3) The roof outer edge extending lath 135 or the floor outer edge extending lath 136 is a horizontal annular plate as the extension structure of the roof plate 131 or the floor plate 133 (the extension distance is smaller), and then folded upward to form an inverted frustum-shaped wall structure with its upper dimension larger than its lower dimension or downward to form a positive frustum-shaped wall structure with its upper dimension less than its lower dimension respectively. The dimension of the lower edge line graph of the inverted frustum-shaped wall structure is larger than that of the roof outer corner line graph of the box, and said two graphs are similar figures with a common centroid; the dimension of the upper edge line graph of the positive frustum-shaped wall structure is larger than that of the floor outer corner graph of the box, and said two graphs are similar figures with a common centroid, see FIG. 4.
(4) The roof outer edge extending lath 135 is a vertical cylindrical wall structure by folding the horizontal roof plate 131 upward with a 90-degree angle on the roof outer corner line of the box, and the floor outer edge extending lath 136 is a vertical cylindrical wall structure by folding the horizontal floor plate 133 downward with a 90-degree angle on the floor outer corner line of the box; the lower edge line of the vertical cylindrical wall structure of the roof outer edge extending lath 135 coincides with the roof outer corner line of the box, and the upper edge line of the vertical cylindrical wall structure of the floor outer edge extending lath 136 coincides with the floor outer corner line of the box, see FIG. 5.
(5) The roof outer edge extending lath 135 or the floor outer edge extending lath 136 is a horizontal annular plate as the extension plate of the roof plate 131 or the floor plate 133 (the extension distance is smaller), and then connected with a vertical cylindrical wall structure by folding the horizontal extended plate upward or downward with a 90-degree angle respectively. The dimension of the lower edge line graph of the vertical cylindrical wall structure of the roof outer edge extending lath 135 is larger than that of the roof outer corner line graph of the box, and said two graphs are similar figures with a common centroid. The dimension of the upper edge line graph of the vertical cylindrical wall structure of the floor edge extending lath 136 is larger than that of the floor outer corner graph of the box, and said two graphs are similar figures with a common centroid, see FIG. 6.
(6) A combination of the above-mentioned two structural forms (1) and (4), the roof outer edge extending lath 135 or the floor outer edge extending lath 136 is a horizontal extension plate extending from the roof plate 131 or the floor plate 133, and at the same time, plus a vertical cylindrical wall structure connected upward to the roof outer corner line of the box or downward to the floor outer line of the box with a 90-degree angle from the horizontal extension plate; thus the roof outer edge extending lath 135 or the floor outer edge extending lath 136 both has two circles of end edge lines, i.e., a circle of roof outer end edge line plus a circle of roof upper end edge line, and a circle of floor outer end edge line plus a circle of floor lower end edge line respectively (not shown in the figures).
In order to understand the convex edge extending lath structure more clearly, taking the doughnut-shaped anti-motion structure with said third form of edge extending lath structure (the radial cross section is rectangular) as an example to give description: Under the above conditions, the four corner lines of the box of the anti-motion structure are all round, and the center of the four circles are located in the vertical central axis of buoy 12, the roof outer edge extending lath 135 or the floor outer edge extending lath 136 is formed by a horizontal extension plate of the roof plate 131 or the floor plate 133 firstly, and then folding the extension plate upward or downward as an inverted circular truncated cone with its upper diameter larger than its lower diameter or a positive circular truncated cone with its upper diameter less than its lower diameter respectively, and the lower diameter of the inverted circular truncated cone is larger than diameter of the circle of the roof outer corner line with a common circle center and the upper diameter of the positive circular truncated cone is larger than diameter of the circle of the floor outer corner line with a common circle center.
Although FIG. 1˜6 shows that the roof outer edge extending lath 135 and the floor outer edge extending lath 136 adopt a combination of the same structural form, the roof outer edge extending lath 135 and the floor outer edge extending lath 136 can adopt a different combination according to different demands. For example, the roof outer edge extending lath 135 adopts the second form of structure (shown in FIG. 3) and the floor outer edge extending lath 136 adopts the first form of structure (shown in FIG. 2), etc. The protruding size of the edge extending lath (the roof outer edge extending lath 135 and the floor outer edge extending lath 136) is smaller compared to the size of anti-motion structure 13. The specific size of the edge extending lath of plate structure, whether damping holes setting up on the edge plate or not, and the number and diameter of the damping holes should be determined and optimized by experiment and calculation.
For the anti-motion structure 13 with annular radial gap 14, as an optimized embodiment of the present invention, a horizontal annular plate is arranged on at least one annular part on the outer wall of buoy 12 which is the same as the elevation of the roof plate 131 and/or the floor plate 133, thus a buoy upper lath 121 and/or a buoy lower lath 122 (see FIG. 7) are formed with a gap between the buoy upper lath 121 and the roof inner edge extending lath and/or with a gap between the buoy lower lath 122 and the floor inner edge extending lath respectively to further increase the damping of heave motion. Another embodiment to increase the damping of the heave motion is presented below, for the anti-motion structure 13 with annular radial gap 14, at least one plate of the roof plate 131 and the floor plate 133 shall extend horizontally in the direction of buoy 12 from the roof inner corner line of the box and/or from the floor inner corner line of the box up to connecting the buoy 12 respectively to close the annular radial gap 14, and a plurality of damping holes are set up on the closing area of the gap, usually evenly distributed (not shown in the figures). In order to further increase damping, as an optimal embodiment, the upper gap between the roof inner edge extending lath and the buoy upper lath 121 and the lower gap between the floor inner edge extending lath and the buoy lower lath 122 should be dislocated as far as possible. For example, the upper gap is closer to the buoy 12 and the lower gap is closer to the inner annular vertical plate 134. Or further, adding a layer of horizontal interspace annular plate at the midpoint between the roof inner edge extending lath and the floor inner edge extending lath, which is mounted on the inner annular vertical plate 134 or on the outer wall of the buoy 12 and maintains a gap with the outer wall of the buoy 12 or with the inner annular vertical plate 134 (both called “middle gap”) respectively, thus making the upper gap, lower gap and middle gap dislocation of each other. The gap dislocation, especially the horizontal interspace annular plate can not only increase the viscous damping, but also lessen the mass reduction of the entrained water due to the gap between the anti-motion structure 13 and the buoy 12.
As a further optimal embodiment, said outer end edge line (the roof outer end edge line or the floor outer end edge line) can adopt a serrated line to replace a flat straight line or smooth arc line, that is, a serrated end edge with tooth convex and tooth concave to replace the straight or smooth curved end edge, and the tooth convex and the tooth concave have the same or different geometric figures. That is to say, when both roof outer edge extending lath 135 and floor outer edge extending lath 136 are horizontal annular plates, one of the roof outer end edge line and/or the floor outer end edge line is at least one continuous serrated line, and/or one of the roof inner end edge line and the floor inner end edge line is at least a continuous serrated line. The serrated edge on each tooth is usually described as a regular geometric figure, such as triangular tooth, rectangular or trapezoidal tooth; and the convex and concave shapes of triangular teeth are triangular, the convex and concave shapes of the rectangular teeth are rectangular, or the convex and concave shapes of the trapezoidal teeth are trapezoidal, and the convex and concave shapes of the s are a combination of triangle, rectangular and/or trapezoidal; Or the serrated edge on each tooth is an irregular geometric figure, of which the convex and concave shapes of the teeth are other figures different from triangle, rectangle or trapezoid. For example, for the roof outer edge extending lath 135 and the floor outer edge extending lath 136 with multiple damping holes, a notch from the end edge of the edge extending lath to each damping hole is set up to form a convex and concave of tooth.
As another further optimal embodiment, said roof upper end edge line or said floor lower end edge line can adopt a serrated line to replace a flat straight line or smooth arc line, that is, a serrated end edge with tooth convex and tooth concave to replace the straight or smooth curved end edge, and the tooth convex and the tooth concave have the same or different geometric figures. That is to say, when the roof outer edge extending lath 135 or the floor outer edge extending lath 136 extending up or down to form a closed circle roof upper end edge line or a closed floor circle lower end edge line, one of the roof upper end edge line and/or the floor lower end edge line is at least a continuous serrated line. The serrated edge on each tooth is usually described as a regular geometric figure, such as triangular tooth, rectangular or trapezoidal tooth; and the convex and concave shapes of the triangular teeth are triangular, the convex and concave shapes of the rectangular teeth are rectangular, or the convex and concave shapes of the trapezoidal teeth are trapezoidal, and the convex and concave shapes of the compound teeth are a combination of triangle, rectangular and/or trapezoidal; Or the serrated edge on each tooth is an irregular geometric figure, of which the convex and concave shapes of the teeth are other figures different from triangle, rectangle or trapezoid. For example, for the roof outer edge extending lath 135 and the floor outer edge extending lath 136 with multiple damping holes, a notch from the end edge of the edge extending lath to each damping hole is set up to form a convex and concave of tooth.
Compared with a straight or smooth curved end edge, the edge extending lath with an end edge line shaped the convex and concave of teeth will further increase the viscous damping of the platform motion.
As an optimized embodiment, for the roof outer edge extending lath 135 and/or the floor outer edge extending lath 136 of the anti-motion structure being horizontal annular plate, when the roof outer end edge line and the floor outer end edge line adopt serrated lines, or when the roof outer edge extending lath 135 and floor outer edge extending lath 136 are set up damping holes, a layer of horizontal interspace annular plate at the midpoint between the roof outer edge extending lath and the floor outer edge extending lath, namely middle outer edge extending lath, is mounted on the outer annular vertical plate 132, and the end edge of the middle outer edge extending lath is a straight and/or smooth curved edge line. The function of the middle outer edge extending lath is to reduce the loss of add mass of the entrained water of heave motion due to the serrated edges and/or damping holes of the roof outer edge extending lath 135 and floor outer edge extending lath 136.
In order to install fairleads of mooring legs at the lower part of the outer wall of the buoy 12 without destroying the integrity of the anti-motion structure and to increase the add mass of the entrained water, at the position on the inner side of anti-motion structure 13 adjacent to the buoy 12 and corresponding to the space for installing fairlead, a U-shaped fairlead groove is set up horizontally and up and down through the roof plate and the floor plate (not shown in the figures). The structure of said each U-shaped groove is as follows: the inner annular vertical plate 134 corresponding to the U-shaped groove covering area is shifted outwards (in the horizontal direction away from the buoy 12), and vertical baffles are installed on both sides of the U-shaped groove; the plate surface of the roof plate 131 and the floor plate 133 covered by the U-shaped groove are excised except that the U-shaped edge is retained to form a U-shaped plate edge extending lath. A total of 5 pieces of plates, i.e., said shifted inner annular vertical plate, said vertical baffles on both sides of the groove and said roof plate 131 and floor plate 133 taken some areas out, are watertight connected with each other. In other words, the water tightness of the watertight compartments of the anti-motion structure shall not be destroyed after the U-shaped fairlead groove been formed. The so-called U-shaped plate edge extending lath refers to the U-shaped edges of the horizontal roof plate 131 and the floor plate 133 protruding from the shifted part of the inner annular vertical plate and the vertical baffles on both sides of the groove. The U-shaped plate edge extending lath is good for viscous damping. The space of the groove must be capable of accommodating the fairlead mounted below the buoy 12 and ensuring necessary maintenance requirements. As a practical embodiment, the fairlead groove of the anti-motion structure 13 was broken as a fracture at the initial stage of construction, and after the fairlead guide groove been installed to the buoy 12, a water-tight box structure are installed to close the fracture to form a complete U-shaped fairlead groove.
The present invention overcomes the shortcomings of the current anti-motion structure of column floater, not only increases the add mass of the entrained water, but also increases the damping of motions, especially the damping of heave motion, at the same time ensures the integrity of anti-motion structure, and finally greatly improves the motion performance of the column floater.

Claims

1. An anti-motion structure of a column floater comprising:

an annular structure surrounding the bottom and outer periphery of the buoy of the column float, said annular structure comprises a roof plate, a floor plate with spacing below the roof plate, an outer annular vertical plate and an inner annular vertical plate spaced between the outer annular vertical plate and the buoy, and said roof plates, floor plate, outer annular vertical plate and inner annular vertical plate to be watertight connected with each other to form an annular box with rectangular or trapezoidal radial vertical cross section, and to form a total of four circles of corner lines along the box corners, i.e., a roof outer corner line of the box, a floor outer corner line of the box, a roof inner corner line of the box and a floor inner corner line of the box, wherein the centroid of each corner line of plane geometry is located in the vertical central axis of the buoy and the said annular box body is rotationally symmetric with the centroid, or symmetric anteroposterior and left-right with the vertical central axis of the buoy, and an annular radial gap is set or optionally not set between the anti-motion structure and the buoy;

wherein the anti-motion structure is connected with the buoy by multiple radial vertical brackets, and the box body is divided into several watertight compartments by a plurality of radial vertical partitions, the horizontal roof plate and/or the horizontal floor plate corresponding to each watertight compartment are provided with damping holes capable of being opened or closed; by opening of the damping holes in the horizontal roof plate and the horizontal floor plate, the compartments are filled with water introduced with sea, or by closing of the damping holes in the horizontal roof plate and the horizontal floor plate, a closed floating compartment is formed, or by closing of the damping holes in the horizontal roof plate and opening of the damping holes in the horizontal floor plate, a closed air floating compartment is formed, so as to meet requirements under different working conditions of the column floater;

wherein at least one of plates of the roof plate and/or the floor plate of the anti-motion structure without the annular radial gap shall be provided with an outer edge extending lath, i.e., roof outer edge extending lath and floor outer edge extending lath; and at least one of plates of the roof plate and the floor plate of the anti-motion structure with the annular radial gap shall be provided with an outer edge extending lath and an inner edge extending lath separately or simultaneously, said outer edge extending lath is the outer edge extending lath and the floor outer edge extending lath, and said inner edge extending lath is roof inner edge extending lath and floor inner edge extending lath;

wherein the outer edge extending lath is a plate structure, which extends outward and/or upward and downward from the roof outer corner line and the floor outer corner line respectively; the roof outer edge extending lath is formed on the roof plate and the floor outer edge extending lath is formed on the floor plate; the inner edge extending lath is a plate structure, which extends horizontally from the roof inner corner line and/or the floor inner corner line of the box to the direction of the buoy; the horizontal roof inner edge extending lath is formed on the roof plate, and the horizontal floor inner edge extending lath is formed on the floor plate; the inner edge extending lath shall not close the annular radial gap.

2. The anti-motion structure of column floater according to claim 1 comprising: the anti-motion structure is a circular or regular polygon structure, and the four box corner lines correspond to a circular or regular polygon;

or the shapes of the inner annular vertical plate and the outer annular vertical plate of the anti-motion are different, the inner annular vertical plate is circular or regular polygon and the roof inner corner line and the floor inner corner line of the box are circular or regular polygon accordingly, and the outer annular vertical plate is oval and the roof outer corner line and the floor outer corner line of the box are oval accordingly, or the outer annular vertical plate is hetero-polygon, the roof outer corner line and the floor outer corner line of the box are closed geometric figures with parallel straight lines on the left and right sides and circular or broken lines on the front and rear sides, its dimensions in the left and right directions are smaller than those in the front and rear directions.

3. The anti-motion structure of column floater according to claim 2 comprising: the roof outer edge extending lath and the floor outer edge extending lath are of horizontal annular structures, the edge of the roof outer edge extending lath and the edge of the floor outer edge extending lath forms a roof outer end edge line and a floor outer end edge line respectively; and the plane geometric figures of the roof outer edge line or the floor outer edge line has the same centroid as the roof outer box corner line and the floor outer box corner line and is rotationally symmetric to the centroid, or symmetric to the vertical central axis of the upright floater front-back and left-right;

or, the roof outer edge extending lath or the floor outer edge extending lath is a protruding wall structure upward or downward respectively, and the upper edge and the lower edge of each protruding edge extending lath wall structure form a circle of closed upper end edge line and a circle of closed lower end edge line respectively, which centroid is located in the vertical central axis of buoy and the geometry of said each end edge line is equal to or similar to the geometry of the roof and floor corner lines of the box respectively;

or the roof outer edge extending lath or the floor outer edge extending lath is an horizontal annular plate then folding and protruding upward or downward to form a wall respectively, and the end edge of the wall of the roof outer edge extending lath or of the floor outer edge extending lath forms a circle of closed roof end edge line or a circle of closed floor end edge line respectively, which centroid of the plane geometry is located on the vertical central axis of the buoy, and the plane geometry of the circle of closed roof end edge line or the circle of closed floor end edge line is similar to the plane geometry of the roof outer corner line of the box or similar to the plane geometry of the floor outer corner line of the box respectively.

4. The anti-motion structure of column floater according to claim 3 comprising: the roof outer edge extending lath or the floor outer edge extending lath is a horizontal annular plate structure, which is the horizontal and outward extension structure of the roof plate or the floor plate;

or the roof outer edge extending lath is an inverted frustum-shaped wall structure with its upper dimension larger than its lower dimension, which lower end edge line coincides with the roof outer corner line of the box; and the floor outer edge extending lath is a positive frustum-shaped wall structure with its upper dimension less than its lower dimension, which upper end edge line coincides with the floor outer corner line of the box; or the roof outer edge extending lath or the floor outer edge extending lath is a horizontal and outward extension structure of the roof plate or of the floor plate with limited extending distance, and then connected to an inverted frustum-shaped wall structure with its upper dimension larger than its lower dimension or to a positive frustum-shaped wall structure with its upper dimension less than its lower dimension respectively; at same time the dimension of the circle of closed lower end edge line graph of the inverted frustum-shaped wall structure is larger than that of the roof outer corner line graph of the box, and said two graphs are similar figures with a common centroid, and the dimension of the circle of closed upper end edge line graph of the positive frustum-shaped wall structure is larger than that of the floor outer corner graph of the box, and said two graphs are similar figures with a common centroid;

or the roof outer edge extending lath or the floor outer edge extending lath is a vertical cylindrical wall structure by folding the horizontal roof plate upward or the horizontal floor plate downward with a 90-degree angle on the roof or floor outer corner line of the box respectively; the lower edge line of the vertical cylindrical wall structure of the roof outer edge extending lath coincides with the roof outer corner line of the box, and the upper edge line of the vertical cylindrical wall structure of the floor outer edge extending lath coincides with the floor outer corner line of the box; or the roof outer edge extending lath or the floor outer edge extending lath is a horizontal and outward extension structures of the roof plate or of the floor plate with some extending distance, and then connected to a vertical cylindrical wall structure by folding the extension structure upward or downward with a 90-degree angle respectively; the dimension of the lower edge line of the vertical cylindrical wall structure of the roof outer edge extending lath is larger than the roof outer corner line of the box, and the dimension of the upper edge line of the vertical cylindrical wall structure of floor outer edge extending lath is larger than the floor outer corner line of the box, and said two graphs are similar figures with a common centroid.

5. The anti-motion structure of column floater according to claim 1 comprising: some damping holes are set up or optionally not set up on the roof outer edge extending lath and/or floor outer edge extending lath.

6. The anti-motion structure of column floater according to claim 5 comprising: for the anti-motion structure with annular radial gap, a horizontal annular plate is arranged on at least one part of the annular part on the outer wall of the buoy which is the same elevation as the roof plate and/or the floor plate, thus a buoy upper lath and/or a buoy lower lath are formed with a gap between the buoy upper lath and the roof inner edge extending lath and/or between the buoy lower lath and the floor inner edge extending lath.

7. The anti-motion structure of column floater according to claim 5 comprising: at least one of the roof plate and the floor plate of the anti-motion structure with the annular radial gap shall extend horizontally in the direction of the buoy from the roof inner corner line of the box and the floor inner corner line of the box up to connecting the buoy respectively to close the annular radial gap, and a plurality of damping holes are set up on the closing area the gap.

8. The anti-motion structure of column floater according to claim 1 comprising: a U-shaped fairlead groove is set up horizontally and up and down through the roof plate and the floor plate at the position on the inner side of anti-motion structure) adjacent to the buoy and corresponding to the space for installing fairlead, which shall be capable of accommodating and facilitating the maintenance of the fairlead mounted on the lower part of the outer wall of the buoy; the structure of said each U-shaped groove is as follows: the inner annular vertical plate corresponding to the U-shaped groove covering area is shifted outwards, and vertical baffles are installed on both sides of the U-shaped groove; the plate surface of the roof plate and the floor plate covered by the U-shaped groove are excised except that the U-shaped edge is retained to form a U-shaped plate edge extending lath; said shifted inner annular vertical plate, said vertical baffles on both sides of the groove and said roof plate and floor plate been taken some areas out are watertight connected to each other, and the water tightness of the watertight compartments of the anti-motion structure shall not be destroyed after the U-shaped fairlead groove been formed.

9. The anti-motion structure of column floater according to claim 3 comprising: when both roof outer edge extending lath and floor outer edge extending lath are horizontal annular plates, one of the roof outer end edge line and/or the floor outer end edge line is at least one continuous serrated line to form a serrated end edge, and/or one of the roof inner end edge line and/or the floor inner end edge line is at least a continuous serrated line to form a serrated end edge; when both roof outer edge extending lath and floor outer edge extending lath with a convex structure extending up and down to form a closed circle roof upper end edge line and a closed floor circle lower end edge line, at least one of the roof upper end edge line and/or the floor lower end edge line is a continuous serrated line to form a serrated end edge; said serrated end edge with tooth convex and tooth concave, which have the same or different geometric figures.

10. The anti-motion structure of column floater according to claim 9 comprising: said serrated edge on each tooth is triangular tooth, rectangular or trapezoidal tooth, and the shape of the convex and concave teeth of triangular teeth is triangular, the convex and concave shapes of the rectangular teeth are rectangular, the convex and concave shapes of the trapezoidal teeth are trapezoidal, and the convex and concave shapes of the compound shaped teeth are respectively a combination of triangle, rectangle or trapezoidal.

11. The anti-motion structure of column floater according to claim 3 comprising: the roof outer edge extending lath or the floor outer edge extending lath is a horizontal annular plate extending from the roof plate or the floor plate respectively, and at the same time, plus a vertical cylindrical wall structure connected upward to the roof outer corner line of the box or downward to the floor outer line of the box with a 90-degree angle from the horizontal extension plate; the roof outer edge extending lath or the floor outer edge extending lath simultaneously form a circle of roof outer end edge line plus a circle of roof upper end edge line, or a circle of floor outer end edge line plus a circle of floor lower end edge line respectively.

12. The anti-motion structure of column floater according to claim 4 comprising: for the roof outer edge extending lath and floor outer edge extending lath of anti-motion structure being horizontal annular plates, when the roof outer edge line and the floor outer edge line adopt serrated lines, or when the roof outer edge extending lath and the floor outer edge extending lath are provided with damping holes, a middle outer edge lath is arranged on the outer annular vertical plate equidistant from the roof outer box corner line and the floor outer box corner line, the middle outer edge lath is a horizontal annular plate structure, and its outer end edge is a straight and/or smooth curved edge.

13. The anti-motion structure of column floater according to claim 6 comprising: the upper gap between the roof inner edge extending lath and the buoy upper lath and the lower gap between the floor inner edge extending lath and the buoy lower lath should be dislocated as far as possible; or further, adding a layer of horizontal interspace annular plate at the midpoint between the roof inner edge extending lath and the floor inner edge extending lath, which is mounted on the inner annular vertical plate and maintains a middle gap with the outer wall of the buoy, or mounted on the outer wall of the buoy and maintains a middle gap with the inner annular vertical plate, thus the upper gap, the lower gap and the middle gap are dislocated with each other.