JPH0549519B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a ship having a dome on the upper deck. In particular, the present invention relates to a ship having a dome on the upper deck. The present invention relates to a hull structure suitable for use in a liquefied gas carrier.

[Conventional technology]

BACKGROUND ART Conventionally, there has been a liquefied gas carrier that employs a tank cover having a hemispherical shell shape and a boneless structure, and the structure of the tank cover is shown in FIGS. 8 to 12. 8 is a cross-sectional view of the hull, FIG. 9 is a longitudinal sectional view of the hull, FIG. 10 is a top view of the hull, and FIG. 11 is a sectional view taken along the line aa of FIG. 10.

In order to isolate the liquefied gas tank 1 from the outside air and seawater, an expansion joint 4 is arranged in the ship's ship direction and the ship's width direction on a boneless tank cover 3 made of a hemispherical shell-like member provided on the upper deck 2. . The cross-sectional shape of the expansion joint 4 is as shown in FIG.
It has a rectangular closed cross section. When the tank cover 3 is forcibly deformed due to hull deformation, the expansion joint 4 absorbs the deformation and expands the tank cover 3.
This is provided for the purpose of preventing buckling of the tank cover 3 and high stress occurring in the joint between the tank cover 3 and the upper deck 2 by lowering the stress generated in the tank cover 3.

Conventional wisdom holds that structures such as the tank cover 3 that are greatly affected by hull deformation (for example, the superstructure of a car carrier) must be equipped with expansion joints such as this expansion joint in order to avoid the high stress caused by vertical bending deformation of the hull. It was thought to be natural to add a structure that would absorb the deformation. However, in the case of the tank cover 3 as a hemispherical shell-like member, the interference force acting between the hull and the tank cover 3 is greatest at the front, rear, left and right sides of the tank cover 3, and in addition, The expansion joint 4 has good elasticity in the width direction, but is very rigid in the longitudinal direction.
In the shaded areas in Figures 8 to 10, a very large interference force acts between the tank cover 3 and the upper deck 2, and in this actual ship, there are cracks and welds in the shaded areas of all ships of the same type. A rupture has occurred.

The annular upper deck portion of the upper deck 2 adjacent to the periphery of the circular opening does not have aggregates such as small bones or girders, and has a flexible structure with brackets.

Furthermore, as shown in FIG. 12, the transverse bulkhead 16 of a conventional ship has a structure in which it is stretched over almost the entire cross section of the ship, and as a result, the rigidity of the ship is large, making it difficult for the ship's side to absorb the interference force. It has a structure.

[Problem to be solved by the invention]

Conventionally, expansion joints have often been used in dome structures that are significantly affected by hull deformation, such as tank covers on liquefied gas carriers, but the problem with expansion joints is that they tend to have the disadvantages mentioned above. There is a point.

Therefore, if the structure does not have an expansion joint, the above-mentioned disadvantages will be eliminated, but in order to do so, it is necessary to absorb the relative deformation between the hull and the dome somewhere other than the expansion joint, which was conventionally absorbed by the expansion joint. , or to reduce the hull deformation itself.

The present invention allows relative deformation between the hull and the dome to be absorbed by the hull structure and the short cylindrical member.
The purpose is to provide a ship with a dome on the upper deck.

[Means to solve the problem]

In order to achieve the above-mentioned object, a ship having a dome on the upper deck of the present invention is provided with a dome installed between adjacent hull transverse bulkheads in the front and rear to cover an opening in the upper deck, and the dome is a rigid body. A short cylindrical member configured as a hemispherical shell-like structure connects a peripheral edge of the hemispherical shell-like member and a peripheral edge of the opening in the upper deck, and the transverse hull bulkhead has a large opening. It is characterized by being constructed as a flexible structure.

[Operation] In the above-described ship having a dome on the upper deck of the present invention, when a vertical bending moment acts on the hull,
The interference force between the hull and the dome caused by this moment is absorbed by the hull's transverse bulkhead, which has a flexible structure, as well as by the plate of the short cylindrical member itself, which is interposed between the dome and the periphery of the circular opening in the upper deck. Absorbed by bending.

〔Example〕

Hereinafter, a liquefied natural gas carrier (LNG ship) with a tank cover as an embodiment of the present invention is shown in the drawings.
To explain this, Figure 1 is a perspective view showing the main parts of the hull, Figure 2 is a cross-sectional view of the hull, Figure 3 is a longitudinal sectional view of the hull, and Figure 4 is a front view of the transverse bulkhead of the hull. Figure 5 is a longitudinal cross-sectional view of the center of the hull.
FIG. 6 is a perspective sectional view of the central part of the hull.

As shown in FIGS. 1 to 6, a spherical tank 1 for liquefied gas is placed above the foundation deck 5 through a cylindrical skirt 6 between the hull transverse bulkheads 16, 16 adjacent in the front and rear. A short cylindrical member 7 is provided on the upper deck 2 to protrude upward through the circular opening of the deck 2, and connects to the circular opening in order to cover the upper part of the tank 1 and isolate it from outside air and seawater. A tank cover 3 having a boneless structure as a rigid hemispherical shell-like member is joined via the tank cover 3 . The tank cover 3 is not provided with any expansion joints, and thus has a rigid structure.

On the other hand, as shown in FIGS. 4 and 6, the transverse bulkhead 16 in the hull has a flexible structure with a large opening 16' wide in the width direction of the ship.
Of these, the large openings 16' on both sides are provided inside the side ballast tank 10. In conventional ships, such a large opening 16' was not provided, and the side ballast tank 10 was divided into two tanks, front and rear, by a transverse bulkhead 16. In this embodiment, the transverse bulkhead 16 in the ballast tank 10 is
1, the tank 10 is a single tank with the front and rear integrated. The problem of safety in the event of flooding due to the provision of the large opening 16' is that each hold has a watertight plate 17, a horizontal bulkhead 16, a ballast tank wall 1
8, the problem is solved by separating the foundation deck 5 and the stole plate 19.

Further, an annular upper deck portion 20 having a flexible structure and having no aggregate as shown by diagonal lines in FIG. 1 is disposed in a portion of the upper deck 2 adjacent to the periphery of the circular opening. In addition, the code|symbol 9 in a figure shows a longitudinal bulkhead, 11 shows a cross deck part, and 12 shows a ship side outer plate.

With the above configuration, the vertical bending moment 8 is applied to the hull.
If the longitudinal bulkhead 9 and ballast tank 1
0 and the annular upper deck part 20 enclosed by the cross deck part 11 and the tank cover 3.Since the tank cover 3 has no expansion joint and the tank cover 3 itself is quite rigid, the part as a whole is It has great rigidity against bending moment 8. Furthermore, on the hull side, the annular upper deck portion 20
The amount of deformation 14 of the portion constituted by the tank cover 3 is as small as about 1/4 to 1/5.

At this time, the transverse bulkhead 16 deforms as shown by the dotted line in FIG. 4, absorbing the relative displacement between the hull and the tank cover 3. Further, the annular upper deck portion 20 also has a flexible structure without aggregate, so that it can contribute to absorbing relative deformation between the tank cover 3 and the hull.

In this way, the interference force between the hull and the tank cover 3 caused by the vertical bending moment 8 is absorbed by the hull structure, and the interference force between the tank cover 3 and the tank cover 3, which was the cause of damage in conventional ships, is absorbed by the hull structure. Upper deck 2
It is possible to drastically reduce the interference force acting on the joint 15 with the

In addition, by interposing the short cylindrical member 7 between the hemispherical shell member 3 and the upper deck 2, the short cylindrical member 7 absorbs the interference force from the cylindrical plate constituting the short cylindrical member 7. Bending the plate allows better absorption.

To further explain the effect of the short cylindrical member 7 with reference to FIGS. 7a, b, and c, when a vertical bending moment 8 as shown in FIG. 1 acts on the hull, the tank cover 3
tries to deform into an oval shape in the front-rear direction, so it deforms outward at the front and inward at the side, but since the short cylindrical member 7 has significantly lower bending rigidity than the tank cover 3, As shown by the broken line,
Bending deformation occurs, thereby making it possible to more effectively absorb relative deformation between the tank cover 3 and the hull side.

In this way, according to this liquefied gas carrier with a tank cover, the relative interference force between the hull and the tank cover 3 that occurs when the hull is deformed by the weight of cargo or waves is reduced by the short cylindrical member. 7, the annular upper deck 20, the transverse hull bulkhead 16, and other flexible hull structures.

In addition, the height of the short cylindrical member 7 is as follows in this embodiment:
The radius of the tank cover 3 is about 20m, whereas the radius is about 1.5m.

In order to confirm the effect of the above-mentioned embodiment of the present invention, a tank cover with a hemispherical shell shape without an expansion joint and a hull transverse bulkhead with a large opening was provided.
As shown in Figure 13, a numerical model of the LNG carrier's hull, tanks, and tank cover was created by taking out one hold length across the hull transverse bulkhead. The results of FEM (finite element method) analysis with a vertical bending moment of 650,000 ton・m (vessel design value) are shown below.

Looking at the vertical displacement of each part of the transverse bulkhead, the vertical displacement of the upper deck 2, second deck 22, and foundation deck 5 in the longitudinal section in the direction of FIG. As shown in FIG. 14, using each intersection between the deck deck 5 and the ship's side shell plating 12 as a reference point, as is clear from the figure, since the large opening 16' is provided, the hull transverse bulkhead 16 is deformed in-plane. The tank cover 3 becomes softer and rises around the center line as the tank cover 3 is displaced. The effective range and size of the large opening 16' is, as in this embodiment, an opening that covers almost the entire width of the hull, and its size is about 30% or more of the cross-sectional area of the hull. is good.

Next, in order to confirm the effect of reducing stress levels on the conventional structure, we created an FEM model of a tank cover as an example of the present invention shown in Fig. 15 and an FEM model of a tank cover with a conventional structure shown in Fig. 16. Analyzed. Two types of loads were used in the FEM analysis: (1) Hull vertical bending moment of 650,000 ton・m (hogging) (2) Tank cover internal pressure of 0.15 Kg/cm ² (positive pressure, gauge pressure). (Design value of LNG ship which is an embodiment of the present invention) As a result of FEM analysis, the value of stress generated at the base of expansion joint 4, which caused crack damage in the conventional structure, was As shown in Figure 17, the internal pressure becomes 79Kg/ ^mm2 .
For 0.5Kg/ ^cm2 , 26 as shown in Figure 18.
Kg/ ^mm2 . Furthermore, the stress value at the joint between the base of the tank cover 3 and the upper deck 2, which has conventionally caused cracks, is 31 kg/mm ² (first
Figure 9), and the internal pressure is 17Kg/mm ² (Figure 20).

In contrast, in the embodiment of the present invention, at the joint 15 between the short cylindrical member 7 and the upper deck 2, which corresponds to the above position, the internal pressure is 12 Kg/mm ² (Fig. The stress level is 4.2Kg/mm ² (Figure 22) compared to 0.15Kg/cm ² , which is a significant reduction in stress compared to the conventional structure.

The above-mentioned stress reduction effect of the present invention includes the hull transverse bulkhead 1
In addition to the effect of the large opening 16' of 6, the short cylindrical member 7
has the effect of absorbing the relative displacement between the tank cover 3 and the hull by deforming softly, but this is due to the above-mentioned
This is confirmed by the results of FEM analysis.

That is, in FIGS. 23 and 24,
By deforming the short cylindrical member 7 interposed between the tank cover 3 and the upper deck 2 in an out-of-plane direction, the relative displacement between the two is absorbed without generating high stress.

Above, a liquefied gas carrier with a tank cover has been described in detail as an embodiment of the present invention, but the present invention is not limited to the above-mentioned embodiment.
This method can be implemented on other ships in general that have a dome on the upper deck, and can also be implemented on, for example, a leisure barge that has a hemispherical ridge. In addition, the shape of the hemispherical shell member and short cylindrical member of the dome does not necessarily mean that it is strictly hemispherical or cylindrical; the dome may also be a polygonal pyramid that is close to a hemispherical shape (a knuckle line may occur). However, the short cylindrical member may have a conical shape.

〔Effect of the invention〕

As detailed above, according to the ship having a dome on the upper deck of the present invention, there is no need to provide an expansion joint on the dome, so that the joint between the dome and the hull, which conventionally occurs as a side effect of the joint, It is possible to eliminate damage to the expansion joint, and there is an advantage that the labor and cost required for manufacturing and installing the expansion joint can be significantly reduced.

[Brief explanation of drawings]

Figures 1 to 7 show a liquefied gas carrier with a tank cover as an embodiment of the present invention. Figure 1 is a perspective view of the main parts of the hull, Figure 2 is a cross-sectional view of the hull, and Figure 3 is a cross-sectional view of the hull. 4 is a front view of the transverse bulkhead of the hull, FIG. 5 is a vertical sectional view of the center of the hull, FIG. 6 is a perspective sectional view of the center of the hull, and FIG. 7a , b, and c are explanatory diagrams showing the action of the tank cover and the short cylindrical member;
Figure 2 shows a conventional liquefied gas carrier with a tank cover, Figure 8 is a cross-sectional view of the hull, Figure 9 is a longitudinal sectional view of the hull, Figure 10 is a top view of the hull, and Figure 11 is a cross-sectional view of the hull. A cross-sectional view of the expansion joint of the tank cover (a cross-sectional view taken along the line a-a in FIG. 10), FIG. 12 is a front view showing the transverse bulkhead of the hull, and
Figure 24 shows an FEM model of a liquefied gas carrier with a tank cover as an embodiment of the present invention and a conventional example, as well as analysis results thereof. The figure shows the vertical displacement of each part of the hull transverse bulkhead.
Figure 15 is the FEM model diagram of the tank cover, 1st
Figure 6 is a diagram of a conventional tank cover model, Figure 17 is a principal stress diagram due to the vertical bending moment of the hull generated at the base of the left-right expansion joint, Figure 18 is a principal stress diagram due to the internal pressure of the tank cover, and Figure 19 is its diagram. Figure 20 is a principal stress diagram due to the hull vertical bending moment occurring at the center of the hold at the base of the tank cover, Figure 20 is a principal stress diagram due to the internal pressure of the tank cover, and Figure 21 is a diagram showing the hull vertical bending occurring at the center of the hold of the short cylindrical part of an embodiment of the present invention. Fig. 22 is a principal stress diagram due to the internal pressure of the tank cover; Fig. 23 is a perspective view showing deformation due to a vertical bending moment of the hull that occurs at the center of the hold of the short cylindrical part of an embodiment of the present invention; Fig. 24 The figure is a perspective view showing deformation caused by a hull vertical bending moment that occurs on the center line side of the short cylindrical portion. 1... Spherical tank for liquefied gas, 2... Upper deck,
3... Tank cover, 4... Expansion joint, 5... Foundation deck, 6... Skirt, 7...
...Short cylindrical member, 8...Vertical bending moment, 9...
Longitudinal bulkhead, 10...Ballast tank, 11...Cross deck section, 12...Ship side outer plate, 13, 14...
... Deformation amount, 15 ... Joint, 16 ... Hull transverse bulkhead, 16' ... Large opening, 17 ... Watertight plate, 18
... Ballast tank wall, 19 ... Stole board,
20...Annular upper deck part, 21...Big bone, 22...
Second deck.

Claims (1)

[Claims] 1. A dome is installed between the front and rear hull transverse bulkheads to cover the opening of the upper deck, and the dome is configured as a hemispherical shell-like member with a rigid structure, and the dome is configured as a hemispherical shell-like member with a rigid structure, and the dome is connected to the peripheral edge of the hemispherical shell-like member. A ship having a dome on the upper deck, characterized in that a short cylindrical member is provided to connect the peripheral edge of the opening in the upper deck, and the hull transverse bulkhead is configured as a flexible structure having a large opening. .