JP6629015B2 - Floating structure - Google Patents

Description

  The present invention relates to a floating structure having a structure supported on water by buoyancy, such as an offshore power generation facility or an offshore storage facility.

  2. Description of the Related Art In recent years, a floating type floating structure has been proposed as a facility for offshore wind power generation, solar power generation, mining, production, storage, and the like of various resources (for example, see Patent Document 1 below).

  The floating structure described in Patent Literature 1 is used for offshore wind power generation, and has a windmill as an upper structure connected to the upper end of a columnar column. The column part is configured as a hollow buoyancy body, and the upper structure is designed to support the upper structure so as to be able to float on the water in an upright state. Such a floating body structure using a single vertically long buoyancy body Are classified as "spar type". Further, in the case of the floating body structure described in Patent Document 1, while a spar-type structure is used as a base, an upper hull having an outer hull as a buoyant body is provided on the outer periphery in the vicinity of a waterline of a column portion, and a weight is provided at a lower end. The lower hull is provided to improve the restoring force of the floating structure. The structure in which the buoyant body is expanded in the horizontal direction and the restoring force is secured by increasing the radius of the metacenter is a feature of the “Semi-Submersible (semi-submersible) type” floating body structure. The floating structure as described in (1) can be referred to as “advanced spar type”.

  In addition, there are various types of floating structures for offshore wind power generation, such as “pontoon type” and “TLP (Tension Leg Platform: tension mooring type)”. As a document describing a semi-sub type floating structure, there is, for example, Patent Document 2 below.

Japanese Patent Application Laid-Open No. 2015-9591 JP 2010-280301 A

Wagner, H .: Uber stoss- und gleitvorgange an der overflache von flussigkeiten, ZAMM, Band 12, Heft 4 (1932) 193-215 Marine Engineering Series (8) “Hull Structure Vibration”, Seisando Shoten 2013 P.S. 202-207 Chuang, S.L .: Investigation of impact of rigid and elastic bodies with water, NSRDC Report 3248 (1970)

  By the way, in the case of the floating structure as described in Patent Document 1, the upper hull is arranged near the waterline, and a part thereof is designed to be submerged in a stationary state. However, if a wave occurs on the water surface or the floating structure tilts due to wind load, etc., the horizontal brace, outer hull, overhang, etc. that constitute the upper hull will rise, and the bottom will be exposed on the water surface, and then the underwater There is a case that slamming that sinks in occurs. In addition, since the entry into the water is accompanied by an impact, there is a concern that the impact may shorten the life of the floating structure. Further, if the floating structure is made to have sufficient strength in consideration of the impact pressure due to the slamming, the production cost increases.

  In the case of a semi-sub type floating structure as described in Patent Document 2, a member that is located above the waterline and has a bottom surface extending along the horizontal direction is installed at a position as high as possible from the water surface, and from the water surface It is common to take the distance to the bottom sufficiently long to avoid slamming itself. However, in such a method, the center of gravity of the floating structure is increased, resulting in a decrease in the oscillating performance. In addition, a strength design for maintaining the structural strength against the oscillating is required, which also increases the manufacturing cost.

  The present invention has been made in view of the above circumstances, and has as its object to provide a floating structure capable of reducing the impact pressure due to slamming with a simple configuration.

The present invention is a floating structure that is used in a moored state and supports an upper structure on the water by buoyancy.When a slamming occurs , the lower surface of a member located near a waterline hits a water surface. The present invention relates to a floating structure having a convex portion having a cross-sectional shape narrowing downward.

  In the floating structure of the present invention, it is preferable that the projection has a triangular prism shape having one side surface along a horizontal plane and two other side surfaces projecting downward from the one side surface.

  In the floating structure of the present invention, it is preferable that each of the other two side surfaces is arranged at an angle of 20 degrees or more with respect to a horizontal plane.

  A floating body structure according to the present invention comprises a columnar column portion configured to connect an upper structure to an upper end portion to support on water, and an upper configured to protrude radially near a waterline of the column portion to generate buoyancy. A hull may be provided, and the projection may be provided on a lower surface of a member constituting the upper hull.

  The floating structure of the present invention can be a semi-sub type floating structure in which a plurality of floating structures extending in the vertical direction are connected in the horizontal direction.

  ADVANTAGE OF THE INVENTION According to the floating body structure of this invention, the outstanding effect that the impact pressure by slamming can be reduced with a simple structure can be produced.

It is a front view showing the first example of the present invention. It is a figure which shows the principal part of 1st Example of this invention, (A) is a figure equivalent to the IIA-IIA arrow of FIG. 1, (B) is a figure equivalent to the IIB-IIB arrow of FIG. 1, (C) is FIG. 2 is a front sectional view of a lower structure in FIG. 1. It is a schematic diagram explaining operation of the present invention. FIG. 3 is a conceptual diagram showing a Wagner model for explaining an impact pressure when an object lands on water. FIG. 3 is a diagram illustrating a relationship between an attack angle and an impact pressure coefficient when an object lands on water. It is a conceptual diagram explaining operation | movement of this invention, (A) is the model of the object created according to the structure of this invention, (B) is the state when this model lands, (C) is water immersion. 4 is a graph showing a coefficient of an impact pressure generated on a lower surface of an object at the time. (A)-(C) each show another form of the floating structure according to the first embodiment of the present invention, (A) and (B) are front views of the lower structure of the floating structure, and (C) is a positive view. It is sectional drawing. FIG. 6 is a front view showing a second embodiment of the present invention. FIG. 7 is a perspective view showing a lower structure of the second embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIGS. 1 and 2 show a first embodiment of the present invention. The basic structure is common to the advanced spar type floating structure described in Patent Document 1. As shown in FIG. 1, the floating structure 1 of the first embodiment is configured so that an upper structure 2 is connected to an upper end of a columnar column 3 and supported on water by buoyancy. An upper hull 4 is provided near the water line of the column 3 so as to project radially from the column 3, and a lower hull 5 is provided at a lower end of the column 3 so as to project radially from the column 3. Thus, the restoring force of the floating structure 1 is improved. Here, “near the waterline” means “a range where the water surface can reach during use”.

  The upper structure 2 is, for example, a wind turbine for wind power generation, and includes a support column 21, a nacelle 22, and a blade 23 as shown in FIG. The column 21 is erected on the column portion 3 via a connecting portion 31 provided at the upper end of the column portion 3, and the nacelle 22 has a generator (not shown) inside and generates electric power by rotation of the blade 23. ing. It should be noted that the upper structure 2 is not limited to the wind power generation equipment as illustrated here. For example, a solar power generation facility may be used, and as the upper structure 2, various facilities that can be installed on water, such as various observation facilities, communication facilities, lighting facilities, and mining facilities, are assumed.

  The column portion 3 is a substantially columnar buoyant body serving as a central axis of the advanced spar type floating body structure 1, and the inside thereof is formed as a cavity. A part of the cavity may be used as a ballast tank. In addition, a pump room (not shown) and a machine room (not shown) equipped with various control devices and power supply devices are provided as necessary.

  The upper hull 4 includes, as shown in FIGS. 1 and 2A and 2C, a center hull 41 connected to the column portion 3, a horizontal brace 42 extending radially from the center hull 41 in a horizontal direction, And an outer hull 43 disposed at the end of the horizontal brace 42. The center hull 41 is a member that connects the horizontal brace 42 to the column 3 and supports the entire upper hull 4 on the column 3. The horizontal brace 42 is a member that connects the center hull 41 and the outer hull 43, and is preferably arranged in a submerged portion below the waterline and configured to support its own weight by buoyancy. Further, the interior can be hollowed and used as a ballast tank.

  The outer hull 43 is a cuboid-shaped buoyancy body, surrounds the column portion 3 in a circumferential direction at a position away from the center axis, and increases the metacenter radius to secure the restoring force of the floating structure 1. The inside is used as a ballast tank. The shape is not limited to the rectangular parallelepiped shown here, but may be various shapes such as a sphere, a spheroid, and a column. A fixed gap is set between adjacent outer hulls 43, and the wave load is reduced by passing a wave through the gap, and a work boat or the like can easily access the vicinity of the center hull 41. I have.

  The lower hull 5 is a substantially disk-shaped or polygon-shaped weight disposed at the lower end of the column portion 3 as shown in FIG. The interior is, for example, radially divided into a plurality of spaces, and each space forms a ballast tank. In this way, by arranging the heavy hull 5 at the lower end of the column 3, the center of gravity of the floating structure 1 is lowered to keep the height of the center of gravity low, and at the same time, the plane formed by the lower hull 5 along the horizontal direction is formed. The resistance to vertical movement is increased, and vertical (Heaving), vertical (Pitching), and rolling (Rolling) are reduced.

  Further, the lower hull 5 may be provided with fins 51 as shown in FIGS. 1 and 2B. The fins 51 are provided on the upper surface of the lower hull 5 so as to form a plane extending in the vertical direction, and increase the drag force against the rotation of the floating structure 1 around the column portion 3 and reduce the bowing (Yawing). It has become.

  The floating structure 1 is moored on the seabed via a plurality of mooring lines 6 and stays in a predetermined sea area. The lower end of the mooring line 6 is fixed to the seabed, and the upper end is connected to a predetermined position of the floating structure 1. The connection position of the mooring line 6 to the floating structure 1 can be, for example, on the outer surface of the outer hull 43 as shown in FIG. As described above, when the mooring line 6 is connected to the column portion 3 as far as possible in the radial direction, the floating structure 1 is effective in increasing the resistance to the bowing of the bow which tends to rotate around the column portion 3. It is.

  In the first embodiment, as shown in FIGS. 1 and 2A and 2C, a convex portion 44 is provided on the lower surface of a member located near the waterline of the floating structure 1 to prevent slamming. I have.

In the example shown here, the convex portion 44 is configured as a triangular prism-shaped member provided on the lower surface of the outer hull 43 that forms the outer peripheral portion of the upper hull 4. The triangular prism forming the convex portion 44 is attached along a horizontal plane such that one side surface is in contact with the lower surface of the outer hull 43, and the other two side surfaces are arranged so as to project downward from the one side surface. As shown in FIG. 2 (C), the two side surfaces projecting downward form angles θ ₁ and θ ₂ with respect to a horizontal plane when the floating structure 1 is stationary. The angles θ ₁ and θ ₂ may be equal to each other or different from each other. However, it is preferable that each of the angles θ ₁ and θ ₂ is set to be equal to or more than 20 ° and equal to or less than 90 °. When one of the angles θ ₁ and θ ₂ is set to 90 °, the other is set to less than 90 °. In the example shown here, the angles θ ₁ and θ ₂ are each about 40 °. In this manner, the convex portion 44 is disposed on the lower surface of the outer hull 43 so as to have a cross-sectional shape narrowing downward.

  Next, the operation of the first embodiment will be described.

  FIG. 3 shows how slamming occurs when the floating structure 1 is used. When the advanced spar type floating structure 1 receives a load due to a wave or wind, pitching or rolling may occur around the center of gravity in the column portion 3 as shown by a solid line and an imaginary line in FIG. . At this time, the upper hull 4 arranged so as to surround the column portion 3 in the vicinity of the waterline, for example, at one point, one end is lifted up while the other end is sunk, and the one end that has been lifted up by the subsequent swingback The movement of sinking and lifting the other end is repeated. Then, when the shaking increases, slamming occurs, in which the member on one end side is exposed to the lower surface on the water surface, and is subsequently hit against the water surface by the subsequent shaking. At this time, a shock is applied to the components of the upper hull 4 from water.

  In the case of pitching or rolling, since the center of the rocking is located in the column portion 3, the movement of the upper hull 4 due to the rocking becomes larger as the position becomes more distant from the column portion 3 in the radial direction. For this reason, when slamming occurs, a particularly strong impact pressure is applied to a member (in this case, the outer hull 43) of the constituent members of the upper hull 4 that are separated from the column part 3.

Here, in general, when an object is hit against the water surface, the smaller the angle (attack angle) between the lower surface of the object and the water surface, the greater the impact applied to the object from water. FIG. 4 shows a Wagner model for explaining the magnitude of impact when an object lands on a still water surface (see Non-Patent Document 1). According to Wagner's theory, the maximum value (maximum impact pressure) p _max of the impact pressure applied from the water to the wedge-shaped object B entering at a velocity V toward the water surface is represented by the following equation [Equation 1].
^{_{p max = (1 + π 2}} / 4tan 2 β) × ρV 2/2
Given by β is the angle formed by the lower surface of the object B with respect to the water surface, that is, the attack angle, and ρ represents the density of water. According to this relational expression, the maximum impact pressure p _max is proportional to the square of the entry speed V of the object B with respect to the water surface and the density ρ of water, and the coefficient increases as the attack angle β increases. Hereinafter, this coefficient is referred to as an impact pressure coefficient K. That is,
[Equation 2]
_{K = p max × 2 / ρV} 2 = 1 + π 2 / 4tan 2 β
It is.

FIG. 5 is a graph showing the relationship between the attack angle β and the impact pressure coefficient K, and the dashed line represents the above-mentioned Wagner's theoretical formula (see Non-Patent Document 2). On the other hand, the solid line represents the relationship between the attack angle β and the impact pressure coefficient K experimentally shown by Chuang's research (see Non-Patent Document 3). According to Wagner's theoretical formula, when the attack angle β approaches zero, the impact pressure coefficient K or the maximum impact pressure p _max increases infinitely. It does not become infinity because it occurs and the impact is reduced. However, when the attack angle β is in the range of about 10 ° or more, Wagner's theoretical formula agrees well with Chuang's experimental value. In any case, basically, it can be said that the larger the attack angle β, the smaller the impact pressure coefficient K or the maximum impact pressure p _max becomes. In particular, when the attack angle β is about 20 ° or more, the maximum impact pressure p _max becomes remarkably large. This can be confirmed from the graph of FIG. Specifically, when the attack angle β is close to zero, the shock pressure coefficient K is about 200 to 300 according to Chuang's empirical formula, but when the attack angle β is 20 °, the shock pressure coefficient K is 20 to 300. It is reduced to about 30 and about 1/10.

In the case of the floating structure 1 according to the first embodiment, the lower surface of the outer hull 43 is provided with a convex portion 44 having a cross-sectional shape that is narrowed downward. A predetermined attack angle with respect to the water surface is ensured. That is, the angles θ ₁ and θ ₂ (see FIG. 2C) formed by the two side surfaces of the convex portion 44 projecting downward with respect to the horizontal plane substantially correspond to the attack angle β in FIG. Due to its own inclination, the actual attack angle deviates slightly from the angles θ ₁ and θ ₂ ).

FIG. 6 shows a result of performing a fluid analysis by creating a model simulating the structure around the convex portion 44 of the floating structure 1 on a computer in order to confirm the impact mitigation effect of the convex portion 44. I have. The model used for the analysis has a shape as shown in FIG. 6A, and a wedge-shaped convex portion is formed on the lower surface on one end side (left side in the figure) of a rectangular parallelepiped main body. This convex portion corresponds to the convex portion 44 of the floating structure 1, and the entire object including the convex portion corresponds to a part of the structure of the upper hull 4 including the convex portion 44 (FIGS. 1 and 2 ( C)). The angles θ ₁ and θ ₂ formed by the two side surfaces forming the convex portion of the object with respect to the horizontal plane are each about 40 °.

  As shown in FIG. 6 (B), such an object lands on the lower water surface in a state where the right side in the figure is relatively lower and the left side in the figure is relatively higher. Consider the case. That is, as shown in FIG. 3, in a state where slamming due to pitching or rolling has occurred in the floating structure 1, it is assumed that the movement close to the behavior shown by the outer hull 43 and the horizontal brace 42 located at one end of the upper hull 4. ing.

  FIG. 6C shows the result of analyzing the impact pressure applied to each part of the object in this case. The numerical values on the horizontal axis of the graph of FIG. 6C indicate the coordinates corresponding to the horizontal position of the object in FIG. 6B, and the position coordinate of the wedge-shaped vertex provided on the lower surface at one end is set to zero. The right side of the vertex is indicated by a plus value, and the left side is indicated by a minus value. The range of approximately minus 2 to plus 2 corresponds to a portion having a wedge shape, and the range of plus 2 to plus 8 corresponds to a portion having a flat bottom without a wedge shape. The vertical axis indicates the impact pressure coefficient K at each position of the object. The impact pressure coefficient K is approximately 16 at the flat lower surface of the plus 5 to the plus 8, whereas the wedge shape is formed on the lower surface. In the range of 2 to plus 2, it is around 3, which is reduced to about 1/5.

  As described above, the impact pressure coefficient K can be significantly reduced in the portion having the wedge shape formed on the lower surface as compared with the flat portion in which the wedge shape is not formed. As shown in FIG. 1, if the convex portion 44 is provided on the lower surface of the outer hull 43 of the floating structure 1, the shock applied to the outer hull 43 is greatly reduced even if slamming occurs due to shaking as shown in FIG. 3. Will be.

  In the case where the outer hull 43 is not provided with the convex portion 44, the entire lower surface of the outer hull 43 is instantaneously hit against the water surface when the outer hull 43 comes into contact with the water. In this case, the convex portion 44 will be submerged in the water for a certain period of time in order from the lower end, so that the force of the members constituting the upper hull 4 from the water surface per unit time is reduced.

  In the example shown in FIGS. 1 and 2, the impact pressure coefficient K does not decrease in the horizontal brace 42 because the horizontal brace 42 does not have the convex portion 44. However, in the case of slamming due to pitching or rolling as shown in FIG. 3, the speed at which the horizontal brace 42 located radially inside the outer hull 43 enters the water surface is lower than the speed at which the outer hull 43 rushes, so that the impact pressure is reduced. Even if the coefficient K is large, the impact pressure does not become so large. If the convex portion 44 has landed before the horizontal brace 42, the landing of the convex portion 44 reduces the speed of the entire upper hull 4 with respect to the water surface. The effect of reducing the speed of 42 and reducing the impact pressure can also be expected.

  Further, the convex portion 44 has an effect of not only reducing the impact due to the slamming, but also making it difficult to generate the slamming itself. Since the convex portion 44 projects into the submerged portion on the lower surface of the outer hull 43, the draft of the upper hull 4 is apparently deep. The slamming of the floating structure 1 occurs when the outer hull 43 and the convex portion 44 are lifted and the lower surface is exposed from the water surface with the occurrence of the shaking, but if the convex portion 44 protrudes from the lower surface of the outer hull 43. In addition, the amount of lifting required until the entire outer hull 43 and the convex portion 44 are exposed to the water surface becomes large, and slamming hardly occurs.

  Thus, by merely providing the convex portion 44 on the lower surface of the outer hull 43, it is possible to greatly reduce the impact at the time of slamming and at the same time, to suppress the slamming itself. If the projection 44 is formed as a triangular prism member as shown in FIGS. 1 and 2, it can be manufactured easily and inexpensively, and can be easily attached to the existing floating structure 1.

  The configuration of the floating structure 1 is not limited to the examples shown in FIGS. For example, as shown in FIG. 7A, a protrusion 45 may be provided on the outer periphery of the outer hull 43 as necessary. The projecting portion 45 is a flange projecting radially outward from the submerged portion on the outer periphery of the outer hull 43, forms a surface along the horizontal direction, and increases the drag generated due to the inclination of the floating structure 1, The shaking is reduced. The inside of the overhang portion 45 may be formed as a cavity and used as a ballast tank.

  Further, as a reinforcing material for supporting the outer hull 43, an oblique brace 7 and a middle brace 8 as shown in FIG. 7B may be provided. In the example shown here, the diagonal braces 7 are arranged such that the upper end is connected to the lower surface of the outer hull 43 and the lower end is connected to the upper surface of the central portion of the lower hull 5 and radially spreads upward as a whole. The middle brace 8 is arranged along the horizontal direction so as to connect the intermediate portions of the adjacent oblique braces 7. The arrangement and the number of the oblique braces 7 and the middle braces 8 are not limited to the example shown here. The diagonal brace 7 may be connected to, for example, the horizontal brace 42 or the column 3, and the middle brace 8 may be disposed in, for example, the vertical direction. Further, the inside of the oblique brace 7 or the middle brace 8 can be formed as a cavity and used as a ballast tank.

  And the installation position of the convex part 44 is not limited to the lower surface of the outer hull 43 as shown in FIG. 1, FIG. What is necessary is just to be attached to the lower surface of the member located in the vicinity of the waterline, for example, it can be attached to the lower surface of the horizontal brace 42, or if it has the overhang 45, it can be attached to the lower surface. Further, a convex portion 44 may be provided on the lower surface of each of the horizontal brace 42, the outer hull 43, and the overhang portion 45. Alternatively, it is conceivable to provide a deck or the like near the waterline of the column unit 3, but in that case, it may be attached to the lower surface of the deck. However, from the viewpoint of alleviating the impact due to slamming, it is effective to attach the column portion 3 to the lower surface of a member (that is, the outer hull 43 or the overhang portion 45) that is separated as far as possible in the radial direction.

  Note that the shape of the convex portion 44 is not limited to the triangular prism shape illustrated here. For example, it is configured as a quadrangular prism having a trapezoidal cross section, and of the two parallel surfaces forming the base of the trapezoid, the side forming the short side is directed downward, and the side forming the long side is the lower surface of the outer hull 43. It may be attached to. Alternatively, the apex may be directed downward, and the bottom surface may be formed in a shape such as a polygonal pyramid or a cone attached to the lower surface of the outer hull 43, or, for example, as a hemispherical member projecting downward from the lower surface of the outer hull 43 good. In addition, the convex portion 44 can take various shapes as long as it has a cross-sectional shape narrowing downward.

  The protrusion 44 may be hollow or solid, but when it is hollow, the internal cavity can be used as a ballast tank. When the inside of the member (the outer hull 43 in the examples shown in FIGS. 1 and 2) to which the protrusion 44 is attached is also formed as a cavity, the cavities inside both may be communicated.

  In the embodiments shown in FIGS. 1, 7A and 7B, the convex portion 44 is a member attached to the lower surface of the outer hull 43, but the outer hull 43 is formed integrally with the convex portion 44. May be. Alternatively, as shown in FIG. 7C, the outer hull 43 may have a cross-sectional shape that is narrowed downward so that the outer hull 43 itself also functions as the projection 44.

  When the protrusion 44 is provided on the overhang 45, the overhang 45 may be formed integrally with the protrusion 44, or the overhang 45 itself may have a cross section that narrows downward. It may be a shape having a shape.

  As described above, the first embodiment is a floating structure 1 that supports the upper structure 2 on the water by buoyancy, and is a member (the upper hull 4 or a member that constitutes the upper hull 4) located near the waterline. The outer hull 43 or the horizontal brace 42, the overhanging portion 45) is provided with a convex portion 44 having a cross-sectional shape that narrows downward, so that slamming occurs in a member located near the waterline. At this time, the impact pressure can be reduced by increasing the attack angle with respect to the water surface.

  In the first embodiment, since the convex portion 44 has a triangular prism shape having one side surface along the horizontal plane and the other two side surfaces projecting downward from the one side surface, It is possible to take measures against slamming with a simple configuration.

In the first embodiment, since the other two side surfaces are each disposed at an angle θ ₁ or θ ₂ of 20 degrees or more with respect to the horizontal plane, the impact pressure can be reduced more effectively. Can be.

  The floating structure 1 according to the first embodiment has a columnar column portion 3 configured to connect the upper structure 2 to an upper end portion and support it on water, and projects radially in the vicinity of a water line of the column portion 3. And the upper hull 4 configured to generate buoyancy. Since the convex portion 44 is provided on the lower surface of the member constituting the upper hull 4, the spar-type floating structure 1 is reliably prevented from slamming. It can be carried out.

  Therefore, according to the first embodiment, the impact pressure due to slamming can be reduced with a simple configuration.

  8 and 9 show a second embodiment of the present invention. Unlike the spar type (advanced spar type) floating structure 1 of the first embodiment (see FIGS. 1 and 2), the semi-sub type is shown in FIGS. A floating structure 100 of the type referred to is shown. Although the wind turbine 101 for power generation is provided as the upper structure, the wind turbine is not particularly limited to the wind turbine, and may be a solar power generation facility, various observation facilities, communication facilities, lighting facilities, mining facilities, and the like. good.

  In the floating structure 100 shown here, a plurality of floating bodies 102 extending in the vertical direction are connected to each other in the horizontal direction, and the upper structure 101 is connected to the upper part of the floating body 102 located at the center. Floating bodies 102 are connected to each other by an upper connecting member 103 that bridges the upper ends of the floating bodies 102 in the horizontal direction and a lower connecting member 104 that bridges the lower ends of the floating bodies 102 in the horizontal direction. In use, the upper connecting member 103 is located above the waterline, and the lower connecting member 104 is located in the submerged portion. Further, an oblique brace 105 is provided between the upper connecting member 103 and the lower connecting member 104 so as to obliquely bridge between the floating bodies 102, and the entire structure is reinforced. The upper surface of each floating body 102 and the upper connecting member 103 is configured as a flat deck 106, in which various devices are installed and a worker can pass.

  In the case of the second embodiment, a convex portion 107 is provided on the lower surface of the upper connecting member 103 to prevent slamming in the upper connecting member 103. The convex portion 107 is a triangular prism-shaped member similar to the convex portion 44 (see FIGS. 1 and 2) of the first embodiment, and is attached along a horizontal plane such that one side surface is in contact with the lower surface of the upper connecting member 103. And the other two sides are arranged so as to project downward from the one side. The two side surfaces projecting downward form predetermined angles with respect to a horizontal plane when the floating structure 100 is stationary. Each of the angles is preferably 20 ° or more and 90 ° or less, and in the example shown here, each is about 40 °.

  The operation of the convex portion 107 as a countermeasure against slamming is the same as that of the convex portion 44 of the first embodiment, and thus the description thereof is omitted (see FIGS. 3 to 6). In the case of the floating structure 100, a particularly great effect can be expected in terms of strength design. That is, in a general semi-sub type floating structure, a portion having a horizontal bottom surface such as a connecting member or a deck is installed at a position as high as possible from the water surface, and a distance from the water surface to the bottom surface (called an air gap). Is taken long enough to avoid slamming itself. In this case, it is necessary to maintain appropriate strength in order to cope with the deterioration of the rocking performance due to the high center of gravity. Here, when the convex structure 107 is provided as a countermeasure against slamming like the floating structure 100 of the second embodiment, it is not necessary to install the upper connecting member 103 or the deck 106 at a position higher than the water surface. Therefore, the center of gravity of the entire floating structure 100 can be lowered to improve the rocking performance, and the required strength can be reduced to reduce the cost for manufacturing.

  Here, the convex portion 107 is installed on the lower surface of the upper connecting member 103, but the mounting position of the convex portion 107 is not limited to this. For example, when it is assumed that slamming may occur in the diagonal brace 105 depending on the installation state of the floating structure 100, a projection 107 may be provided on the lower surface of the diagonal brace 105. Depending on the design of the floating structure 100, a deck or the like may be provided at an intermediate portion or the like of the floating body 102, in which case, a convex portion 107 may be provided on the lower surface of the deck. In addition, a convex portion 107 can be appropriately provided for a member or a portion which is located near the waterline and may cause slamming on the lower surface.

  As described above, the second embodiment is a floating structure 100 that supports the upper structure 101 on the water by buoyancy. The lower structure is provided on the lower surface of the member (the upper connecting member 103) located near the waterline. Since the convex portion 107 having the cross-sectional shape that narrows toward the water line is provided, when slamming occurs in the member located near the waterline, the attack angle to the water surface can be increased to reduce the impact pressure.

  In the second embodiment, the convex portion 107 has a triangular prism shape having one side surface along the horizontal plane and another two side surfaces projecting downward from the one side surface. It is possible to take measures against slamming with a simple configuration.

  In the second embodiment, the other two side surfaces are each disposed at an angle of 20 degrees or more with respect to the horizontal plane, so that the impact pressure can be more effectively reduced.

  The floating structure 100 of the second embodiment is a semi-sub type floating structure 100 formed by connecting a plurality of floating bodies 102 extending in the vertical direction to each other in the horizontal direction. Therefore, it is possible to reliably take measures against slamming.

  Therefore, according to the second embodiment, the impact pressure due to slamming can be reduced with a simple configuration.

  It should be noted that the floating structure of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Floating structure 2 Upper structure 3 Column part 4 Upper hull 44 Convex part 100 Floating structure 101 Upper structure 102 Floating body 107 Convex part

Claims (5)

A floating structure that is used in a moored state and supports the upper structure on the water by buoyancy.The lower surface of a member located near the waterline may have a lower surface so that it can land on the water surface when slamming occurs. A floating structure provided with a convex portion having a cross-sectional shape narrowing toward the bottom.   The floating structure according to claim 1, wherein the projection has a triangular prism shape including one side surface along a horizontal plane and two other side surfaces projecting downward from the one side surface.   The floating structure according to claim 2, wherein the other two side surfaces are each arranged at an angle of 20 degrees or more with respect to a horizontal plane.   The floating structure includes a columnar column portion configured to connect the upper structure to an upper end portion and supported on water, and an upper hull configured to protrude radially near a waterline of the column portion to generate buoyancy. The floating structure according to any one of claims 1 to 3, further comprising: a convex portion provided on a lower surface of a member constituting the upper hull.   The floating structure according to any one of claims 1 to 3, wherein the floating structure is a semi-sub type floating structure formed by connecting a plurality of floating structures extending in a vertical direction to each other in a horizontal direction.

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