JP4022973B2 - Rolling reduction structure for floating structures - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure that reduces rolling caused by waves of a floating structure that is suspended in a coastal area such as the sea and used for various purposes.
[0002]
[Prior art]
In recent years, effective use of coastal areas has been considered, and large-scale convention facilities and parking lot facilities have been manufactured as pontoon-type floating structures, and these are being floated and installed.
[0003]
When trying to use such a coastal floating structure in the same way as a ground structure, it is necessary to minimize the fluctuation caused by waves. Although it is moored at the position by a large number of chains and wire ropes, the fact is that the oscillation due to waves cannot be effectively reduced by simply increasing the number of chains or wire ropes.
[0004]
In particular, in the floating structure in the coastal area, as shown in a plan view in FIG. 4, the force of the wave W in a substantially constant direction is often applied to the floating structure 2 moored on the quay 1 from the offshore side. Reduction of rolling R (rolling) due to the wave W is the biggest issue.
[0005]
Therefore, the applicant of the present invention has already filed an effective structure for reducing the rolling structure of a floating structure as Japanese Patent Application No. 3-19145. In the invention of this existing application, for example, schematically shown in FIG. Thus, it is proposed that the side 2x on the incident side of the wave W in the floating structure 2 provided as a box-shaped floating body (pontoon) is inclined toward the upstream side in the traveling direction of the wave W. .
[0006]
In fact, by adopting such a shape, it has been confirmed by a water tank test that the wave forcing moment and the roll amplitude with respect to the roll R of the floating structure 2 can be reduced and the roll R can be greatly reduced. Yes.
[0007]
[Problems to be solved by the invention]
However, since the roll R is reduced by changing the shape of the floating structure 2 itself in the conventional structure of the already filed application, the floating structure 2 has an asymmetric shape in the traveling direction of the wave W. Since extra buoyancy will increase on the incident side, there is a difficulty in maintaining and adjusting the neutrality of the floating structure 2, which causes a problem in that the arrangement of various devices on the upper surface is also restricted. there were.
[0008]
The present invention has been made in view of the above circumstances, and has a higher effect of reducing rolling than the conventional structure, and the rolling of the floating structure that can easily maintain and adjust the neutrality of the floating structure. It aims to provide a reduction structure.
[0009]
[Means for Solving the Problems]
The present invention, on the side of the incident side of the floating structure of the floating structure, an inclined plate inclined toward the upstream side in the wave traveling direction with the vicinity of the draft line as the upper end, and the lower end to the vicinity of the lower surface depth of the floating structure, A vibration-reducing hollow body comprising a bottom plate extending substantially horizontally from the lower end of the inclined plate toward the floating structure and having an opening formed at an appropriate position is attached to both ends of the inner space of the vibration- reducing hollow body. The invention relates to a structure for reducing a roll of a floating structure, which is characterized by being open to the outside.
[0010]
Thus, in this way, the overall shape of the floating structure including the anti-vibration hollow body is such that the side surface on the wave incident side of the floating structure itself is located upstream of the wave traveling direction as in the conventional structure. As a result, the wave forcing moment with respect to the roll is reduced, and the roll amplitude is also reduced.
[0011]
At this time, on the lower side of the bottom plate of the vibration-reducing hollow body, the water moves up and down by the incidence of the wave, but the water freely enters and exits the opening of the bottom plate. Buoyancy does not occur, and when water enters and exits the opening of the bottom plate, vortices are formed on the exit and exit side of the water, and a large damping force against rolling is generated.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0013]
1 to 3 show an example of an embodiment for carrying out the present invention, and the portions denoted by the same reference numerals as those in FIG. 5 represent the same items.
[0014]
As shown in FIGS. 1 and 2, in the present embodiment, the wave W of the floating structure 2 is formed on the side 2x on the incident side of the wave W with the vicinity of the draft line 3 (a demarcation line into which the floating structure enters the water) as an upper end. An inclined plate 4 that is inclined toward the upstream side in the traveling direction and has a lower end reaching the lower surface depth of the floating structure 2, and extends substantially horizontally from the lower end of the inclined plate 4 toward the floating structure 2 and the floating A vibration-reducing hollow body 7 comprising a bottom plate 6 having an opening 5 formed in the vicinity of the side 2x of the structure 2 on the incident side of the wave W is attached to the structure 2 from a horizontal direction substantially perpendicular to the traveling direction of the wave W. A triangular internal space 8 is formed as seen.
[0015]
Here, the internal space 8 of the vibration-reducing hollow body 7 extends in a horizontal direction substantially perpendicular to the traveling direction of the wave W, and both ends thereof are open to the outside. In this structure, water can freely enter and exit through the opening 5 so that the anti-vibration hollow body 7 itself does not generate buoyancy.
[0016]
Further, since the vibration reduction hollow body 7 is a plate assembly structure composed of the inclined plate 4 and the bottom plate 6, the weight increase due to the provision of the vibration reduction hollow body 7 is slight, and the vibration reduction hollow body 7 is attached. Compared with the previous floating structure 2, the amount of water discharged by the above-mentioned slight weight increment (the weight of water that the submerged part of the floating structure 2 excludes when the floating structure 2 floats in still water and maintains equilibrium: below the water surface The product of the volume of the floating structure 2 and the specific gravity of water is only increased.
[0017]
In the drawing, the upper end of the inclined plate 4 in the vibration-reducing hollow body 7 is aligned with the water line 3, but the upper end of the inclined plate 4 only needs to be positioned near the water line 3, for example, slightly below the water line 3. However, it is more effective that it is located above the waterline 3.
[0018]
Thus, in this way, the entire shape of the floating structure 2 including the anti-vibration hollow body 7 has the side surface 2x on the incident side of the wave W of the floating structure 2 itself as in the conventional structure. This is the same as that inclined toward the upstream side in the traveling direction, whereby the wave forcing moment with respect to the roll R is reduced and the roll amplitude is also reduced.
[0019]
At this time, water moves up and down by the incidence of the wave W on the lower side of the bottom plate 6 in the vibration-reducing hollow body 7, but the water freely enters and exits the opening 5 of the bottom plate 6. The oscillating hollow body 7 itself does not generate buoyancy, and when water enters and exits the opening 5 of the bottom plate 6, as shown by solid and broken arrows in FIG. A vortex is formed on the side and a large damping force against the roll R is generated.
[0020]
Therefore, according to the above embodiment, the wave forcing moment and the roll amplitude with respect to the roll R of the floating structure 2 can be reduced as in the conventional case by the outer shape formed by the vibration reducing hollow body 7, and the vibration reduction. Since the damping force by allowing water to enter and exit through the opening 5 of the bottom plate 6 of the hollow body 7 can also act synergistically, the effect of reducing the roll can be greatly improved compared to the conventional structure.
[0021]
Moreover, since the vibration reducing hollow body 7 is a plate assembly composed of the inclined plate 4 and the bottom plate 6, there is no extra buoyancy, and the weight increase due to the provision of the vibration reducing hollow body 7 can be negligible. Even if the overall shape of the floating structure 2 including the vibration-reducing hollow body 7 is asymmetric in the traveling direction of the wave W, the neutrality of the floating structure 2 can be easily maintained and adjusted. , The restrictions on the arrangement of various devices on the top surface can be greatly relaxed, and especially the existing floating structure 2 may cause particularly remarkable problems regarding neutral maintenance / adjustment and restrictions on the arrangement of various devices. And can be applied very easily.
[0022]
In addition, the rolling reduction structure of the floating structure of this invention is not limited only to the above-mentioned example, Of course, various changes can be added within the range which does not deviate from the summary of this invention.
[0023]
【The invention's effect】
According to the rolling reduction structure of the floating structure of the present invention described above, various excellent effects as described below can be obtained.
[0024]
(I) Due to the outer shape formed by the vibration reducing hollow body, the wave forcing moment and the vibration amplitude for the rolling of the floating structure can be reduced as in the conventional case, and through the opening of the bottom plate of the vibration reducing hollow body. Since the damping force caused by entering and exiting water can also act synergistically, the effect of reducing rolls can be greatly improved compared to the conventional structure.
[0025]
(II) The anti-vibration hollow body is a plate assembly composed of an inclined plate and a bottom plate, so that no extra buoyancy is generated and the weight increase due to the provision of the anti-vibration hollow body is negligible. Even if the overall shape of the floating structure, including the body, is asymmetrical in the direction of wave travel, the neutrality of the floating structure can be easily maintained and adjusted. Constraints on placement can be greatly relaxed, and it can be applied very easily to existing floating structures without incurring any significant problems related to neutral maintenance / adjustment and restrictions on the placement of various devices. it can.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing an example of an embodiment for carrying out the present invention.
FIG. 2 is a side view of FIG.
FIG. 3 is an enlarged view for explaining the movement of water entering and exiting the reduced vibration hollow body of FIG. 2;
FIG. 4 is a plan view showing an installation state of a floating structure in a coastal area.
FIG. 5 is a perspective view showing a conventional example.
[Explanation of symbols]
2 Floating structure 2x Side surface 3 on the incident side of the wave 3 Water line 4 Inclined plate 5 Opening 6 Bottom plate 7 Reduced hollow body R Rolling W wave

Claims (1)

A slanted plate inclined on the side of the floating structure where the wave is incident, with the vicinity of the waterline as the upper end and upstream in the direction of wave travel, and with the lower end reaching near the bottom surface depth of the floating structure; A vibration-reducing hollow body comprising a bottom plate extending substantially horizontally from the lower end toward the floating structure and having an opening formed at an appropriate position is attached, and both ends of the internal space of the vibration- reducing hollow body are opened to the outside. A rolling reduction structure for floating structures.

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