JP4490123B2 - Floating structure - Google Patents

Description

  The present invention relates to a floating structure used for ocean observation and ocean development, such as an ocean observation buoy, a weather observation buoy, or a floating oil production apparatus.

Various structures have been proposed to suppress the vibrations excited by waves in floating structures such as ocean observation buoys, meteorological observation buoys, or floating oil production equipment. (See Patent Document 1)
Fluctuations of floating structures are classified into translational movements (vertical shaking, horizontal shaking, forward / backward shaking) and rotational movements (longitudinal shaking, roll shaking, bow shaking) on ships, but ocean observation buoys installed in a fixed sea area. , Because weather observation buoys or floating oil production equipment, etc., do not need to distinguish between front and rear and left and right, the horizontal translation and forward and backward shaking are collectively referred to as horizontal translational shaking, and vertical and lateral shaking are collectively referred to as the horizontal axis. This will be described as rotational shaking. In addition, the bow swing which is the rotation around the vertical axis is not an important problem.

  As shown in FIG. 5 (A), a general floating body 1 has a relationship between the shape of the floating body and the shaking, and the simple floating body 1 follows up and down the waves, causing vertical shaking, horizontal translation shaking, and rotational shaking around the horizontal axis.

  5B, if the floating body 2 has an elongated shape in the vertical direction, the wave force in the vertical direction can be reduced and the vertical swing can be reduced, but the rotational swing around the horizontal axis cannot be reduced. Oil production equipment can reduce this rotational sway around the horizontal axis by making the floating body size sufficiently larger than the wave, but it is not efficient because it requires a large structural weight.

Furthermore, as shown in FIG. 5 (C), in the semi-submersible type floating body 3 formed by connecting the deck structure portion 3C to the submerged floating body structure 3A via the column 3B where the inundation line has an intermediate height, Although the vertical swing and the rotational swing around the horizontal axis can be reduced to some extent at the same time, it is necessary to combine a plurality of element floating bodies, and the structure becomes complicated and the construction cost is high.
JP-A-8-127387

  By the way, in relatively small floating structures such as ocean observation buoys and meteorological observation buoys, the natural period of the vertical oscillation and the rotation around the horizontal axis tends to be close to the period of waves in the installation sea area, and may be greatly shaken by resonance. There is. In observation buoys equipped with sensitive equipment, in particular, vertical and horizontal tilts are a problem, so it is necessary to suppress these fluctuations as much as possible.

  Here, the natural period of vertical swing and rotational swing around the horizontal axis varies depending on the shape and dimensions of the floating body, but it is extremely difficult to set each independently to an arbitrary natural period because they are related to each other. It was. In other words, if the shape is changed to change one of the natural periods, the other natural period that does not need to be changed also changes at the same time, and as a result, both cannot be set to a desired natural period. Have a problem.

  The present invention has been made in view of the above-described problems, and allows the natural periods of vertical and horizontal rotations to be set independently, and suppresses fluctuations excited by waves. An object of the present invention is to provide a floating structure.

The floating structure according to claim 1, which achieves the above object, has a disk shape that defines a natural period of rotational oscillation about a horizontal axis in the water below the floating body, having a larger planar projection outline than the floating body. A vibration suppression member whose maximum diameter is twice or more than that of the floating body is connected so as to be relatively unmovable at a predetermined interval via a connecting member, and a natural period of vertical vibration is defined at the approximate center of the vibration suppression member. The opening to be formed is formed with an opening larger than the size of the floating body .

Upset this configuration, the natural period of heave is a major factor the area of fluctuation suppression member, because the natural period of the horizontal axis rotary shaking determined the profile of fluctuation suppression member, largely due to change the size of the opening By changing the area of the entire restraining member, the natural period of the vertical swing can be set without greatly affecting the natural period of the rotational swing around the horizontal axis. In other words, the natural period of rotational swing around the horizontal axis can be set by the disk-shaped outer shape of the vibration suppression member, and the natural period of vertical swing can be set by the size of the opening, so that the rotational swing and vertical swing around the horizontal axis can be set. Can be set independently of each other.
In addition, the vibration suppressing member has a simple shape, and the area of the entire vibration suppressing member can be set by setting the size of the opening, and the natural period of rotational fluctuation about the horizontal axis can be arbitrarily set.
Further, the vibration suppressing member has a disc-shaped maximum diameter that is at least twice that of the floating body, and the opening is larger than the floating body. The period can be separated and independent from the natural period of the floating body to the large period side.

According to the floating structure according to claim 1, the natural period of the vertical swing is determined by the area of the vibration suppressing member as a large factor, and the natural period of the rotational swing around the horizontal axis is determined by the outer shape of the vibration suppressing member as a large factor. By changing the disk-shaped outer shape of the restraining member, the natural period of rotation fluctuation around the horizontal axis can be changed, and by changing the size of the opening , the natural period of rotation fluctuation around the horizontal axis is hardly changed. It is possible to change the natural period of vertical shaking. This makes it possible to independently set the natural period of the vertical oscillation and the rotational oscillation around the horizontal axis independently according to the wave period prevailing in the installation sea area, and to suppress the vibration excited by the wave. Accordingly, it is possible to construct a floating structure that is difficult to shake and stable.
In addition, since the vibration suppression member has a flat plate shape and the opening is formed at the approximate center thereof, the vibration suppression member has a simple shape, and the area of the entire vibration suppression member can be increased depending on the size of the opening. By setting, the natural period of rotational swing around the horizontal axis can be easily set. As a result, it is possible to configure a stable floating structure that is difficult to shake by arbitrarily setting the natural periods of vertical and horizontal rotations independently and independently.
In addition, the vibration suppression member has a disc-shaped maximum diameter that is more than twice that of the floating body and the opening is larger than the floating body, thereby separating the natural period of vertical shaking and the natural period of rotational shaking around the horizontal axis. It can be made independent and can be greatly displaced from the natural period of the floating body to the long period side, and a stable floating structure that is not easily shaken can be configured.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram of a configuration example of a floating structure to which the present invention is applied.
The illustrated floating structure 10 is a buoy for ocean observation and meteorological observation, and a lower floating body 12 as a rocking suppression member is provided on a lower side of an upper floating body 11 as a floating body by a connecting structural member 13 as a connecting member. Concatenated and integrated.

  The upper floating body 11 is a main body of the floating structure 10 in which an observation device or the like is accommodated, and has a disk shape with a predetermined volume.

The lower floating body 12 has a disk shape whose outer shape is larger than that of the upper floating body as shown in a plan view in FIG. 4, and a circular opening 12A as an open portion is formed at the center. Moreover, the thickness is formed as thin as possible within a range that maintains rigidity.

  The connecting structural member 13 includes a connecting bar 13A that connects the centers of the upper floating body 11 and the lower floating body 12, and a reinforcing wire 13B that connects the peripheral portions. The connecting bar 13A defines the distance between the upper floating body 11 and the lower floating body 12. In addition, the reinforcing wire 13B couples both. The connecting bar 13A is fixed to the edge of the opening 12A of the lower floating body 12 at the tip of the branched lower end, and the reinforcing wire 13B is stretched by connecting the outer periphery of the upper floating body 11 and the lower floating body 12, thereby reducing water resistance. The upper floating body 11 and the lower floating body 12 are coupled so as not to be relatively movable at a predetermined vertical interval by an extremely thin member (having a small horizontal projection area). Note that the connecting bar 13A may be a pipe-like member, and the reinforcing wire 13B is not limited to a wire but may be another member.

  And it is moored by the anchor 15 of the seabed via the mooring line 14, and is installed in a predetermined sea area.

  In the floating structure 10 having the above-described configuration, the natural period of the vibration caused by the waves (vertical swing and rotational swing around the horizontal axis) is correlated with the additional mass or additional moment of inertia acting on the lower floating body 12.

  That is, the natural period of the vertical swing of the floating body is generally expressed by the following formula.

  Further, the natural period of the rotational swing around the horizontal axis of the floating body is generally expressed by the following mathematical formula.

  As can be seen from these equations, when the added mass (m) or the added moment of inertia (i) is increased, the respective natural period (THN or TRN) is increased (long period). By setting a large value, the natural period can be shifted to the long period side.

  The major factor that determines the additional mass of vertical shaking: m is the overall area, while the additional moment of inertia of the rotational oscillation about the horizontal axis: the major factor that determines i is its peripheral area (that is, the outer diameter). is there. However, when the total area is increased and the added mass: m is increased, the peripheral area is necessarily increased, and the added moment of inertia: i is increased (and vice versa). Since the natural period of vertical swing and rotational swing around the horizontal axis is linked, it cannot be arbitrarily set individually.

  In this configuration, by appropriately setting the size of the opening 12A of the lower floating body 12, the additional moment of inertia of the vertical swing: m is arbitrarily set without significantly affecting the additional moment of inertia of the rotational swing about the horizontal axis: i. it can.

  That is, the outer diameter of the lower floating body 12 is set so that the natural period of the rotational swing around the horizontal axis is an arbitrary period sufficiently separated from the wave period of the installation sea area to the long period side (additional moment of inertia: i), By appropriately setting the size (area) of the opening 12A without changing the outer diameter, the natural area of the vertical swing of the entire area of the lower floating body 12 becomes an arbitrary period sufficiently separated from the wave period of the installation sea area ( (Additional mass: m), so that each natural period of rotation and vertical oscillation around the horizontal axis: TRN and THN are set independently from each other by sufficiently separating them from the wave period of the sea area. Is something that can be done.

  2 (A) and 2 (B), assuming a sea area where a wave with a period of 5 to 16 seconds is dominant, set the natural period of rotation around the horizontal axis: TRN and the natural period of vertical movement: THN independently. Then, the graph of the oscillation response characteristic with respect to the input wave in the configuration example in which the oscillation is suppressed is shown overlapping the comparative example.

  As shown in FIG. 2 (C), the outer diameter of the upper floating body 11 is D, the outer diameter of the lower floating body 12 is D2, the diameter of the opening 12A is D3, the thickness of the upper floating body 11 is h, and the total height. : L, and the dimensions of these parts are set to the numerical values shown in FIG. 2D, and the vibration response to the input wave is calculated. FIG. B) shows vertical shaking. In each graph, the horizontal axis represents the period, and the vertical axis represents the ratio of the fluctuation amount to the input wave (angle ratio or length ratio). The larger the vertical axis is, the larger the response to the input wave is, and the natural period in which the peak of the graph resonates.

  In Comparative Example 1, the lower floating body 12 has no opening, and the area (additional mass: m) is ideally set so that the natural period of vertical shaking is sufficiently separated from the wave period to the long period side (20 seconds). In Example 2, the outer diameter (additional moment of inertia: i) is ideally set so that there is no opening in the lower floating body 12 and the natural period of rotational fluctuation about the horizontal axis is sufficiently separated from the wave period to the long period side (28 seconds). It is a thing.

  As can be seen from these graphs, in Comparative Example 1, there is no problem with vertical shaking, but the natural period of rotational shaking around the horizontal axis overlaps with the wave period of the set sea area. On the other hand, in Comparative Example 2, there is no problem with rotational swing around the horizontal axis, but the natural period of the vertical swing is greatly displaced toward the long period side, and accordingly, the fluctuation overlaps with the wave period of the set sea area that occurs on the short period side. Secondary peaks (indicated by X in the figure) will increase. In other words, the vertical shaking causes an increase in the shaking even if the natural period is displaced too much to the long cycle side, and cannot be set to satisfy both the vertical shaking and the rotational shaking around the horizontal axis.

  Therefore, in the configuration of the present application, the lower floating body 12 is set to have the same outer shape as that of the comparative example 2 and the entire area is substantially equal to that of the comparative example 1 by the opening 12A. As a result, the vertical shake shows almost the same oscillation response characteristics as in Comparative Example 1, the secondary peak of the oscillation is small, and the rotational oscillation around the horizontal axis is slightly displaced to the short period side, so that the natural period becomes about 24 seconds. It can be set sufficiently away from the ocean wave cycle.

  In this way, by providing the opening 12A in the lower floating body 12 and appropriately setting the size thereof, the vibration response characteristic of the rotational swing around the horizontal axis can be changed without greatly affecting the vibration response characteristic of the vertical swing. Therefore, it is possible to make settings that suppress both up-and-down shaking and rotation around the horizontal axis.

  In particular, in a relatively small floating structure such as an ocean observation buoy or a weather observation buoy, the size of the lower floating body 12 is more than twice that of the upper floating body 11, and the size of the opening 12A is larger than the size of the upper floating body 11. By doing so, the natural period of the vertical swing and the natural period of the rotational swing around the horizontal axis can be separated and independently displaced from the natural period of the upper floating body 11 to the long period side, and the vibration suppressing effect is large and more preferable. .

  Note that the present invention is not limited to the above configuration example, and can be changed as appropriate. For example, the entire structure of the floating structure is composed of a connecting structural member 16 as a connecting member for connecting the upper floating body 11 and the lower floating body 12 as shown in FIG. The mooring line 14 may be coupled to the connecting member 16B by connecting the connecting member 16B to the connecting member 16B. Further, the lower floating body 12 is not limited to a donut shape as shown in FIG. 4A in which a circular opening 12A is formed in a circular outer diameter as in the above configuration example, and may be a polygonal shape. As in the lower floating body 12 ′ shown in FIG. 4 (B), the center may be opened (opened portion 12A ′) by combining the flat plates 12B.

It is a conceptual diagram of the example of 1 structure of the floating body structure to which this invention is applied. (A), (B) is a graph of the fluctuation response characteristic with respect to an input wave. (C), (D) is a chart of the setting conditions of FIG. It is a conceptual diagram of the other structural example of a floating body structure. It is a top view of a lower floating body. It is explanatory drawing of the floating body of a prior art example.

Explanation of symbols

10 Floating structure 11 Upper floating body (floating body)
12 Lower floating body (sway suppression member)
12A opening (opening)
13, 16 Connection structural material (connection member)

Claims (1)

A vibration suppressing member having a planar projection outer shape larger than that of the floating body and defining a natural period of rotational swing around the horizontal axis in the water below the floating body and having a maximum diameter twice or more that of the floating body. Are connected through a connecting member so as not to move relative to each other at a predetermined interval, and an opening for defining a natural period of vertical shaking is formed at an approximate size in the center of the vibration suppressing member so as to be larger than the floating body. floating structure, characterized by being composed Te.

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