JPH0234498A - Multi-point mooring method for floating type ocean structure - Google Patents

Abstract

PURPOSE:To absorb swinging of an ocean structure and eliminate excessive strain of ropes by providing rope guides and dampers actuating in the vertical direction on a floating ocean structure, and fixing one ends of a plurality of mooring ropes to anchors and the other ends to the dampers through the rope guides. CONSTITUTION:In a floating type ocean structure 11, fair-leaders 14 as rope guides and dampers 15 on which elastic force P actuates vertically are provided. One end of a mooring rope 20 is fixed to an anchor 19 at the sea bottom, and the other end is fixed to a flange 17a of the damper 15 through the fair-leader 14. Among the flanges 17a, 17b, 17c, elastic bodies such as rubber are arranged and provided. As for the damper 15, its strain and load are nearly proportional at small strain, but in the vicinity of rated load the strain is only increasing with nearly constant load. Consequently, as swinging of said structure is absorbed in the vicinity of rated load, mooring with multi-point mooring ropes can be performed even in the shallow sea territory.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a multi-point mooring system for floating marine structures, more specifically, a floating marine structure suitable for mooring floating marine structures in relatively shallow waters. This paper relates to a multi-point mooring system for offshore structures.

[Prior art]

Conventionally, as a method of holding a floating marine structure in a predetermined position, a method has been known in which one end of the mooring cable is fixed to an anchor laid on the seabed and the other end of the mooring line is attached to the floating marine structure, the so-called multi-point mooring method. It is being This method uses the load-displacement characteristics of the catenary curve formed by the weight of the mooring line itself to absorb steady external forces and the movement of the floating marine structure.
For example, it has been adopted as a mooring method in relatively deep waters, at a depth of 50 to 200 meters.

However, if this mooring method is adopted in relatively shallow waters of 50 m or less, even small movements of the floating marine structure will cause the catenary curve to become tortuous, resulting in abnormal tension acting on the mooring line and causing it to break. There is a fear of
Ta.

Under these circumstances, when mooring a floating marine structure in this shallow area, dolphin 2 is placed on the seabed as shown in Figure 7.
The dolphin 2 is used to moor the floating marine structure 4 via the damper 3, which is the so-called dolphin damper one-type method, or a sinker is attached to the mooring line 5 as shown in FIGS. 8(a) and 8(b). A multi-point mooring system is adopted in which a buoy 7 is attached to the mooring line 5 or a buoy 7 is attached to the mooring line 5.

[Problem to be solved by the invention]

However, in the above-mentioned mooring method for floating marine structures, the construction work is troublesome as the dolphin must be driven into the seabed each time, and in the multi-point mooring method using sinkers and buoys, The mooring ropes are complicated and economically disadvantageous.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems. , and a damper that generates elasticity in the vertical direction, one end of each mooring cable is fixed to an anchor provided on the seabed, and the other end of the mooring cable is attached to the damper via the cable guide. This is what I did.

The cable guide is constructed of a fairlead, for example, and is attached to a relatively bottom position of the floating marine structure, and the damper is attached to the upper part of the cable guide. That is, the mooring cable is guided vertically via the cable guide and attached to the damper.

[For production]

According to such a mooring method, when external force due to waves or wind acts on the floating marine structure and causes it to sway, a damper effect is generated and the mooring line is not strained.

〔Example〕

An embodiment of a multi-point mooring system for a floating marine structure according to the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 is a plan view of the floating marine structure 11, and FIG. 2 is a side view thereof. This floating marine structure 11 is composed of a platform 12 and a column 13, and is made to float on the sea surface due to the buoyancy of the column 13. A fairlead 14 is provided on the side of the column 13 as a rope guide, and this fairlead 14
A damper 15 is arranged on the platform 12 at the top of the.

As shown in FIGS. 3 and 4, this damper 15 is arranged in a recess hole 16 provided in the platform 12, and its structure includes a plurality of flanges 17a, 17.
A cylindrical elastic body 18 made of rubber or the like is arranged between b and 17c, and the elasticity P acts in the vertical direction.

One end of the mooring line 20 is attached to an anchor 19 provided on the seabed, and the other end of the mooring line 20 is guided vertically via a fairlead 14 to a flange 17a forming a damper 15.
attached to the back of the゛In the above configuration, if an external force such as waves acts on the floating marine structure 1 and causes it to sway, a tension F is generated in the mooring cable 20, and as a result,
The damper 15 is compressed as shown in FIG. An example of the load-strain curve of this damper 15 is shown in FIG. In other words, if we take the strain on the horizontal axis and the load on the vertical axis, the amount of strain and load will increase almost proportionally when the initial strain is in the range of "a", but when the load is near the rated value (in the range of "a") As shown in the range "b", the load remains almost constant and only the amount of strain increases. Therefore, the vibration of the floating marine structure 11 can be absorbed within this range of "b". Of course, since this damper 15 is attached to each mooring line 20, it is possible to absorb any vibration such as pitching, rolling, or yawing of the floating marine structure 1.

〔Effect of the invention〕

As is clear from the above description, according to the multi-point mooring method for floating marine structures according to the present invention, each mooring line 20 is attached to a damper provided on the platform 11 via a cable guide, and the floating structure is suspended by the damper effect. Since it is designed to absorb the vibrations of an offshore structure, mooring using multi-point mooring lines is possible even in relatively shallow waters below 50 meters in depth.

[Brief explanation of the drawing]

1 to 6 are explanatory diagrams of a multi-point mooring system for a floating marine structure according to the present invention, in which FIG. 1 is a plan view of the floating marine structure, FIG. 2 is a side view thereof, and FIG. FIG. 3 is an enlarged sectional view of part 2 in FIG. 2, and FIG. 4 is a view taken along the line IV--IV in FIG. 3. FIG. 5 is an explanatory diagram of the action of the damper, and FIG. 6 is a load-distortion curve diagram of the damper. FIGS. 7 and 8 show conventional mooring systems for floating marine structures; FIG. 7 is a dolphin type mooring system, and FIG. 8 is a multi-point mooring system. 1... tt4 bottom, 2... Dolphin, 3... Damper 4.11... Floating marine structure, 5... Mooring line, 6... Sinker, 7... Buoy, 12 ... Platform, 13... Column, 14... Fair league, 15... Damper 16... Recess hole, 17a
, 17b, 17c...flange, 18...elastic body, 19...anchor, 20...mooring rope.

Claims (1)

[Claims] A floating marine structure is provided with a plurality of cable guides and a damper that is provided on each cable guide and generates elasticity in the vertical direction, and one end of each mooring cable is fixed to an anchor provided on the seabed, A multi-point mooring system for a floating marine structure, characterized in that the other end of the mooring cable is attached to the damper via the cable guide.