JPS602237B2 - intermediate buoy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in intermediate piers used when mooring floating offshore structures, oil tankers, and other floating structures.

Figure 1 shows a conventional Qin chain mooring device. Here, 1' is a floating structure, 2' is a millet chain, 3' is an anchor or sinker, and 4' is the seabed. When mooring large structures or floating structures in shallow waters, this mooring system cannot maintain safety because the amount of potential energy stored in the mooring device due to the displacement of the structure is insufficient. Can not. A cable mooring device with an intermediate buoy as shown in FIG. 2 has been proposed to address such drawbacks. This is the first
A buoy 5' of an appropriate size is attached to the middle of the bare chain 2' shown in the figure. In this case, floating structure 1' and sinker 3
Even if the positional relationship with ′ is the same as that in Figure 1, the bare chain 2
′ becomes longer, and therefore the allowable displacement amount also becomes larger. On the other hand, since the horizontal displacement of the floating structure 1' is accompanied by the vertical displacement of the buoy 5', the resulting change in the tension of the mirror 2' becomes large, and the position holding performance as a mooring system is sufficient. In addition, the large allowable displacement (and the large tension of the cable chain) means that the amount of potential energy that can be stored in this mooring device is large. As described above, it is undeniable that the mirror mooring device with intermediate buoy is a device that covers the drawbacks of the mirror mooring device in all aspects. However, this conventional example has the following problems. FIGS. 3 and 4 show typical examples of the oscillation characteristics of a conventional box-shaped floating body.

In these figures, the axis is the ratio of the incident wavelength to the representative length of the floating body, and the vertical axis is the ratio of the amplitude of each component of vibration to the amplitude of the incident wave or the maximum wave slope. As can be seen from these figures, when the incident wavelength is comparable to or several times the length of the floating body, the floating body oscillates greatly. If the incident wavelength is longer than that, the amplitude of each component will be the same as the amplitude of the incident wave or the maximum wave slope, and the floating body will sway with the waves. Now, consider the moored floating structure shown in FIG.

The floating structure 1' sways greatly and this mooring device fully exhibits the effect described above when the incident wavelength is longer than the length of the floating structure 1'. ′ can be considered to be usually several tens of meters or more in length, so such a hot water bath can only occur as a result of a rare turbulent storm. In other cases, the incident wavelength is the floating structure 1
It is considered that the floating structure 1' hardly moves. However, the length of the intermediate buoy 5' is usually
The length of the intermediate buoy 5 is from a fraction to several tenths of the length of the floating structure 1', so even if the incident wave is so long that the floating structure 1' hardly moves as described above, the intermediate buoy 5 ' is considered to be upset.

The intermediate buoy 5' therefore oscillates itself in response to normally occurring short waves, and in the case of extremely rare large storms, as the floating structure 1' oscillates and pulls on the bare chain 2'. That is, since the intermediate buoy 5' oscillates under any sea conditions, the portion where it and the cable chain 2' meet is subjected to severe friction and rapidly wears out.
The present invention is intended to solve the above-mentioned problems, and has a structure in which at least two large planar floating bodies and the same A rod-shaped body that connects the two floating bodies vertically and whose horizontal cross section is sufficiently smaller than either of the two floating bodies, and a rod-shaped body that is attached to the two floating bodies to maintain the vertical position of the two floating bodies and whose water surface is approximately in the shape of the rod. An intermediate buoy characterized by comprising a ballast that submerges a lower floating body so as to be located in the center, and the present invention is configured as described above, so that the left-right buoyancy and vertical swing of the intermediate buoy are significantly small. Therefore, the wear of bare chains can be significantly reduced.

Next, an embodiment of the present invention will be described with reference to FIG.

In FIG. 5, reference numeral 2 denotes an elementary mirror, and intermediate buoy 10 is a cylindrical floating body 11 having a larger planar shape than a rod-shaped body 13, which will be described later.
A cylindrical floating body 12 is also provided below, and the floating body 11
Alternatively, they are connected by a cylinder 13 whose planar shape is smaller than any of the 12.

The floating bodies 11 and 12 are filled with concrete, earth, etc. to keep them in an upright position, and a swamp 14 is placed approximately in the center of the cylinder 13.
will come. The lower floating body 12 is provided with approximately 1,000 eye plates 15 for connecting the bare chains 2.

The material of the floating bodies 11 and 12 and the cylinder 13 may be iron plate or plastic.

Next, the effects of the above embodiment will be explained. The stability of the intermediate buoy 10 formed as described above is as shown in FIG. That is, the length of the cylinder 13 is h, and the length of the cylinder 13 is
If the entire length of 0 is defined as a day, then the vertical displacement is small.

In general, floating bodies with this shape have a small stability force in relation to their displacement, so the period for synchronizing the upper and lower bridges, side-to-side bridges, etc. is long, and when waves with a period shorter than the synchronization period occur, the floating body will not be able to sway. It has the characteristic of becoming smaller.

Therefore, it is important to design such a floating body so that it hardly sways under waves with a wavelength that is ten times as long as the length of the floating body.
As shown in the figure and the graph of FIG. 9, this is fully possible.
That is, according to the present invention, the conventional characteristics shown in FIG. 3 are improved correspondingly to those shown in FIG. 8, and those of FIG. 4 are improved correspondingly to those shown in FIG. 9. Therefore, by using such an intermediate buoy, it is possible to make the intermediate buoy hardly shaken by waves having a wavelength that causes the floating structure 1 to hardly sway.

On the other hand, if we consider the case where the floating structure 1 itself is shaken by a large storm, in this case the intermediate buoy 10 will be pulled by the bare chain 2 and will now be submerged under the water surface, and will jump out onto the water surface. exercise vigorously.

In this case, an important characteristic of the intermediate buoy 10 is that it has scales that store a large amount of potential energy through displacement. Since the intermediate buoy 10 having this shape has a large vertical volume, it can exhibit a large restoring force, and in this respect, it can exhibit the same performance as when a simple pontoon is used as an intermediate buoy.

As mentioned above, intermediate buoys of this shape hardly sway during normal times (only low waves with short wavelengths) and do not apply unnecessary loads to the bare chain 2, etc., so they can be installed at the initial stage forever. It has the characteristic of being able to be kept in the same perfect condition as when it was created.

FIG. 7 shows another second embodiment, which is effective if used when a larger size than the first embodiment is required, and the two pontoons 20 and 21 can be arranged vertically or diagonally in the textbook. The structure is such that they are connected by a pipe 22. The operation and effect are the same as in the first embodiment described above.

In addition, the weight of the ballast applied to this intermediate buoy is
It is only necessary to set it by taking into consideration the tensile force of the rod-shaped body 13, and it is sufficient to set it so that the normal water surface is located approximately at the center of the rod-shaped body 13 when the cable chain 2 is connected to the floating body 12 below.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams of conventional examples. Figure 1 is an example of mooring a floating body without an intermediate buoy, Figure 2 is an example of mooring a floating body with an intermediate buoy 5', and Figure 3 is a diagram of the conventional example. FIG. 4 is a graph showing the vertical vibration characteristics. FIG. 4 is a graph showing the horizontal (left and right) vibration characteristics. FIGS. 5 to 9 are diagrams relating to the intermediate buoy of the embodiments of the present invention, and FIG. 5 is the graph of the first embodiment. Fig. 6 is a graph showing the stability of the intermediate buoy in Fig. 5, and Fig. 8 is the first implementation corresponding to Fig. 3 of the follower example. The characteristic graph of the example intermediate buoy, FIG. 9, is a characteristic graph corresponding to FIG. 4, and FIG. 7 is a characteristic graph of the second embodiment. 2...Mirror mirror, 10...Intermediate buoy, 11,12.
...Floating body, 13...Cylinder, 14...
...Hatchling (water surface). Saba 1 illustration 2 illustrations 4 illustrations of dancing illustrations 7 illustrations 8 illustrations? figure

Claims (1)

[Claims] 1 In the intermediate buoy installed between the ropes connecting the floating structure and the anchor, there are at least two large planar floating bodies, and any of the above two floating bodies has a horizontal cross-sectional shape that connects the two floating bodies vertically. and a ballast attached to the two floating bodies to maintain the vertical positions of the two floating bodies and submerge the lower floating body so that the water surface is located approximately at the center of the rod-shaped bodies. An intermediate buoy characterized by: